Add branch docs publishing

Fix elixir test assertion for erlang >=OTP-24.1 (#11311 )
Fix logger translator with otp-24 (#11222 )
2023-05-30 11:41:49 +02:00 · 2021-10-14 16:43:34 +02:00 · 2021-08-31 23:46:27 +02:00 · 2021-08-31 19:27:51 +02:00 · 2021-06-01 11:43:49 +02:00 · 2021-03-16 12:25:59 +01:00
494 changed files with 22698 additions and 70768 deletions
@@ -12,21 +12,20 @@ test_template: &DEFAULT_TEST_SETTINGS
 test_freebsd_task:
  <<: *DEFAULT_TEST_SETTINGS

-  name: FreeBSD 13.0
+  name: FreeBSD 12.1
  alias: FreeBSD Stable

  freebsd_instance:
-    image_family: freebsd-13-0
+    image_family: freebsd-12-1
    cpu: 8
    memory: 7424Mi

  env:
    CHECK_REPRODUCIBLE: true
    LC_ALL: en_US.UTF-8
-    PATH: $PATH:/usr/local/lib/erlang24/bin

  install_script:
-    - pkg install -y erlang-runtime24 git gmake
+    - pkg install -y erlang git gmake
    - rm -rf .git
    - gmake compile

@@ -1,10 +1,9 @@
 [
  inputs: [
    "lib/*/{lib,unicode,test}/**/*.{ex,exs}",
-    "lib/*/*.exs",
-    "lib/ex_unit/examples/*.exs",
-    ".formatter.exs"
+    "lib/*/mix.exs"
  ],
+
  locals_without_parens: [
    # Formatter tests
    assert_format: 2,
@@ -14,6 +13,5 @@

    # Errors tests
    assert_eval_raise: 3
-  ],
-  normalize_bitstring_modifiers: false
+  ]
 ]
@@ -0,0 +1,20 @@
+### Precheck
+
+* Do not use the issue tracker for help or support (try Elixir Forum, Stack Overflow, IRC, etc.)
+* For proposing a new feature, please start a discussion on the Elixir Core mailing list: https://groups.google.com/group/elixir-lang-core
+* For bugs, do a quick search and make sure the bug has not yet been reported
+* Please disclose security vulnerabilities privately at elixir-security@googlegroups.com
+* Finally, be nice and have fun!
+
+### Environment
+
+* Elixir & Erlang/OTP versions (elixir --version): 
+* Operating system: 
+
+### Current behavior
+
+Include code samples, errors and stacktraces if appropriate.
+
+### Expected behavior
+
+A short description on how you expect the code to behave.
@@ -1,11 +0,0 @@
---
-blank_issues_enabled: true
-
-contact_links:
-  - name: Discuss proposals
-    url: https://groups.google.com/g/elixir-lang-core
-    about: Send proposals for new ideas to our mailing list
-
-  - name: Ask questions and support
-    url: https://elixirforum.com/
-    about: Ask questions, provide support and more on Elixir Forum
@@ -1,53 +0,0 @@
---
-name: Report an issue
-description:
-  Tell us about something that is not working the way we (probably) intend
-body:
-  - type: markdown
-    attributes:
-      value: >
-        Thank you for contributing to Elixir! :heart:
-
-
-        Please, do not use this form for guidance, questions or support.
-        Try instead in [Elixir Forum](https://elixirforum.com),
-        the [IRC Chat](https://web.libera.chat/#elixir),
-        [Stack Overflow](https://stackoverflow.com/questions/tagged/elixir),
-        [Slack](https://elixir-slackin.herokuapp.com),
-        [Discord](https://discord.gg/elixir) or in other online communities.
-
-  - type: textarea
-    id: elixir-and-otp-version
-    attributes:
-      label: Elixir and Erlang/OTP versions
-      description: Paste the output of `elixir --version` here.
-    validations:
-      required: true
-
-  - type: input
-    id: os
-    attributes:
-      label: Operating system
-      description: The operating system that this issue is happening on.
-    validations:
-      required: true
-
-  - type: textarea
-    id: current-behavior
-    attributes:
-      label: Current behavior
-      description: >
-        Include code samples, errors, and stacktraces if appropriate.
-
-
-        If reporting a bug, please include the reproducing steps.
-    validations:
-      required: true
-
-  - type: textarea
-    id: expected-behavior
-    attributes:
-      label: Expected behavior
-      description: A short description on how you expect the code to behave.
-    validations:
-      required: true
@@ -1,6 +0,0 @@
-version: 2
-updates:
-  - package-ecosystem: "github-actions"
-    directory: "/"
-    schedule:
-      interval: "weekly"
@@ -22,8 +22,8 @@ jobs:
      max-parallel: 1
      matrix:
        include:
-          - otp: 25
-            otp_version: '25.3'
+          - otp: 23
+            otp_version: '23.3'
            build_docs: build_docs
    runs-on: ubuntu-20.04
    steps:
@@ -8,35 +8,29 @@ env:
  ERLC_OPTS: "warnings_as_errors"
  LANG: C.UTF-8

-permissions:
-  contents: read
-
 jobs:
  test_linux:
-    name: Linux, ${{ matrix.otp_release }}, Ubuntu 20.04
+    name: Linux, ${{ matrix.otp_release }}, Ubuntu 16.04
+    continue-on-error: ${{ matrix.development }}
    strategy:
      fail-fast: false
      matrix:
+        otp_release: ['OTP-24.0', 'OTP-23.0', 'OTP-22.3', 'OTP-22.0', 'OTP-21.3.8', 'OTP-21.0']
+        development: [false]
        include:
-          - otp_release: OTP-25.0
-            otp_latest: true
-          - otp_release: OTP-24.3
-          - otp_release: OTP-24.0
-          - otp_release: OTP-23.3
-          - otp_release: OTP-23.0
          - otp_release: master
            development: true
          - otp_release: maint
            development: true
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-16.04
    steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v2
        with:
          fetch-depth: 50
      - name: Install Erlang/OTP
        run: |
          cd $RUNNER_TEMP
-          wget -O otp.tar.gz https://repo.hex.pm/builds/otp/ubuntu-20.04/${{ matrix.otp_release }}.tar.gz
+          wget -O otp.tar.gz https://repo.hex.pm/builds/otp/ubuntu-16.04/${{ matrix.otp_release }}.tar.gz
          mkdir -p otp
          tar zxf otp.tar.gz -C otp --strip-components=1
          otp/Install -minimal $(pwd)/otp
@@ -45,52 +39,34 @@ jobs:
        run: |
          rm -rf .git
          make compile
-          echo "$PWD/bin" >> $GITHUB_PATH
      - name: Build info
        run: bin/elixir --version
      - name: Check format
        run: make test_formatted && echo "All Elixir source code files are properly formatted."
-      - name: Run Dialyzer
+      - name: Dyalizer
        run: dialyzer -pa lib/elixir/ebin --build_plt --output_plt elixir.plt --apps lib/elixir/ebin/elixir.beam lib/elixir/ebin/Elixir.Kernel.beam
      - name: Erlang test suite
        run: make test_erlang
-        continue-on-error: ${{ matrix.development }}
      - name: Elixir test suite
        run: make test_elixir
-        continue-on-error: ${{ matrix.development }}
      - name: Check reproducible builds
        run: taskset 1 make check_reproducible
-        if: ${{ matrix.otp_latest }}
-      - name: Build docs
-        if: ${{ matrix.otp_latest }}
-        run: |
-          git config --global advice.detachedHead false
-          EX_DOC_LATEST_STABLE_VERSION=$(curl -s https://hex.pm/api/packages/ex_doc | jq --raw-output '.latest_stable_version')
-          for branch in main v${EX_DOC_LATEST_STABLE_VERSION}; do
-            echo "Building docs with ExDoc ${branch}"
-            cd ..
-            git clone https://github.com/elixir-lang/ex_doc.git --branch ${branch} --depth 1
-            cd ex_doc
-            ../elixir/bin/mix do local.rebar --force + local.hex --force + deps.get + compile
-            cd ../elixir/
-            make docs
-            rm -rf ../ex_doc/
-          done
+        if: matrix.otp_release == 'OTP-23.0'

  test_windows:
    name: Windows, OTP-${{ matrix.otp_release }}, Windows Server 2019
    strategy:
      matrix:
-        otp_release: ['23.3']
+        otp_release: ['22.0']
    runs-on: windows-2019
    steps:
      - name: Configure Git
        run: git config --global core.autocrlf input
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v2
        with:
          fetch-depth: 50
      - name: Cache Erlang/OTP package
-        uses: actions/cache@v3
+        uses: actions/cache@v2
        with:
          path: C:\Users\runneradmin\AppData\Local\Temp\chocolatey\erlang
          key: OTP-${{ matrix.otp_release }}-windows-2019
@@ -107,15 +83,13 @@ jobs:
      - name: Erlang test suite
        run: make --keep-going test_erlang
      - name: Elixir test suite
-        run: |
-          del c:/Windows/System32/drivers/etc/hosts
-          make --keep-going test_elixir
+        run: make --keep-going test_elixir

  check_posix_compliant:
    name: Check POSIX-compliant
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-16.04
    steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v2
        with:
          fetch-depth: 50
      - name: Install Shellcheck
@@ -1,72 +0,0 @@
-# #!/usr/bin/env elixir
-[tag] = System.argv()
-
-Mix.install([
-  {:req, "~> 0.2.1"},
-  {:jason, "~> 1.0"}
-])
-
-%{status: 200, body: release} =
-  Req.get!("https://api.github.com/repos/elixir-lang/elixir/releases/tags/#{tag}")
-
-if release["draft"] do
-  raise "cannot notify a draft release"
-end
-
-## Notify on elixir-lang-ann
-
-names_and_checksums =
-  for asset <- release["assets"],
-      name = asset["name"],
-      name =~ ~r/.sha\d+sum$/,
-      do: {name, Req.get!(asset["browser_download_url"]).body}
-
-line_items =
-  for {name, checksum_and_name} <- Enum.sort(names_and_checksums) do
-    [checksum | _] = String.split(checksum_and_name, " ")
-    root = Path.rootname(name)
-    "." <> type = Path.extname(name)
-    "  * #{root} - #{type} - #{checksum}\n"
-  end
-
-mail = %{
-  "From" => "jose.valim@dashbit.co",
-  "To" => "elixir-lang-ann@googlegroups.com",
-  "Subject" => "Elixir #{tag} released",
-  "HtmlBody" => "https://github.com/elixir-lang/elixir/releases/tag/#{tag}\n\n#{line_items}",
-  "MessageStream" => "outbound"
-}
-
-if System.get_env("DRYRUN") do
-  IO.puts("MAIL")
-  IO.inspect(mail)
-else
-  headers = %{
-    "X-Postmark-Server-Token" => System.fetch_env!("ELIXIR_LANG_ANN_TOKEN")
-  }
-
-  resp = Req.post!("https://api.postmarkapp.com/email", {:json, mail}, headers: headers)
-  IO.puts("#{resp.status} elixir-lang-ann\n#{inspect(resp.body)}")
-end
-
-## Notify on Elixir Forum
-
-post = %{
-  "title" => "Elixir #{tag} released",
-  "raw" => "https://github.com/elixir-lang/elixir/releases/tag/#{tag}\n\n#{release["body"]}",
-  # Elixir News
-  "category" => 28
-}
-
-if System.get_env("DRYRUN") do
-  IO.puts("POST")
-  IO.inspect(post)
-else
-  headers = %{
-    "api-key" => System.fetch_env!("ELIXIR_FORUM_TOKEN"),
-    "api-username" => "Elixir"
-  }
-
-  resp = Req.post!("https://elixirforum.com/posts.json", {:json, post}, headers: headers)
-  IO.puts("#{resp.status} Elixir Forum\n#{inspect(resp.body)}")
-end
@@ -1,28 +0,0 @@
-name: Notify
-
-on:
-  release:
-    types:
-      - published
-
-permissions:
-  contents: read
-
-jobs:
-  notify:
-    runs-on: ubuntu-20.04
-    name: Notify
-    steps:
-      - uses: actions/checkout@v3
-        with:
-          fetch-depth: 50
-      - uses: erlef/setup-beam@v1
-        with:
-          otp-version: '25.0'
-          elixir-version: '1.14.0'
-      - name: Run Elixir script
-        env:
-          ELIXIR_FORUM_TOKEN: ${{ secrets.ELIXIR_FORUM_TOKEN }}
-          ELIXIR_LANG_ANN_TOKEN: ${{ secrets.ELIXIR_LANG_ANN_TOKEN }}
-        run: |
-          elixir .github/workflows/notify.exs ${{ github.ref_name }}
@@ -1,96 +0,0 @@
-name: Release
-
-on:
-  push:
-    tags:
-      - v*
-
-env:
-  ELIXIR_OPTS: "--warnings-as-errors"
-  ERLC_OPTS: "warnings_as_errors"
-  LANG: C.UTF-8
-
-jobs:
-  create_draft_release:
-    permissions:
-      contents: write
-    runs-on: ubuntu-20.04
-    env:
-      GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-    steps:
-      - name: Create draft release
-        run: |
-          gh release create \
-            --repo ${{ github.repository }} \
-            --title ${{ github.ref_name }} \
-            --notes '' \
-            --draft \
-            ${{ github.ref_name }}
-  release_pre_built:
-    needs: create_draft_release
-    strategy:
-      fail-fast: true
-      matrix:
-        include:
-          - otp: 23
-            otp_version: 23.3
-          - otp: 24
-            otp_version: 24.3
-          - otp: 25
-            otp_version: 25.0
-            build_docs: build_docs
-    runs-on: ubuntu-20.04
-    steps:
-      - uses: actions/checkout@v3
-        with:
-          fetch-depth: 50
-      - uses: erlef/setup-beam@v1
-        with:
-          otp-version: ${{ matrix.otp_version }}
-          version-type: strict
-      - name: Build Elixir Release
-        run: |
-          make Precompiled.zip
-          mv Precompiled.zip elixir-otp-${{ matrix.otp }}.zip
-          shasum -a 1 elixir-otp-${{ matrix.otp }}.zip > elixir-otp-${{ matrix.otp }}.zip.sha1sum
-          shasum -a 256 elixir-otp-${{ matrix.otp }}.zip > elixir-otp-${{ matrix.otp }}.zip.sha256sum
-          echo "$PWD/bin" >> $GITHUB_PATH
-      - name: Upload Pre-built
-        env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-        run: |
-          gh release upload --clobber "${{ github.ref_name }}" \
-            elixir-otp-${{ matrix.otp }}.zip \
-            elixir-otp-${{ matrix.otp }}.zip.sha{1,256}sum
-      - name: Get latest stable ExDoc version
-        if: ${{ matrix.build_docs }}
-        run: |
-          EX_DOC_LATEST_STABLE_VERSION=$(curl -s https://hex.pm/api/packages/ex_doc | jq --raw-output '.latest_stable_version')
-          echo "EX_DOC_LATEST_STABLE_VERSION=${EX_DOC_LATEST_STABLE_VERSION}" >> $GITHUB_ENV
-      - uses: actions/checkout@v3
-        if: ${{ matrix.build_docs }}
-        with:
-          repository: elixir-lang/ex_doc
-          ref: v${{ env.EX_DOC_LATEST_STABLE_VERSION }}
-          path: ex_doc
-      - name: Build ex_doc
-        if: ${{ matrix.build_docs }}
-        run: |
-          mv ex_doc ../ex_doc
-          cd ../ex_doc
-          ../elixir/bin/mix do local.rebar --force + local.hex --force + deps.get + compile
-          cd ../elixir
-      - name: Build Docs
-        if: ${{ matrix.build_docs }}
-        run: |
-          make Docs.zip
-          shasum -a 1 Docs.zip > Docs.zip.sha1sum
-          shasum -a 256 Docs.zip > Docs.zip.sha256sum
-      - name: Upload Docs
-        if: ${{ matrix.build_docs }}
-        env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-        run: |
-          gh release upload --clobber "${{ github.ref_name }}" \
-            Docs.zip \
-            Docs.zip.sha{1,256}sum
@@ -40,7 +40,7 @@ runs:
      run: |
        mv ex_doc ../ex_doc
        cd ../ex_doc
-        ../elixir/bin/mix do local.rebar --force + local.hex --force + deps.get + compile
+        ../elixir/bin/mix do local.rebar --force, local.hex --force, deps.get, compile
        cd ../elixir
    - name: Build Docs
      if: ${{ inputs.build_docs }}
@@ -13,23 +13,17 @@ The goal of the Code of Conduct is to specify a baseline standard of behavior so
 These are the values Elixir developers should aspire to:

  * Be friendly and welcoming
-  * Be kind
+  * Be patient
    * Remember that people have varying communication styles and that not everyone is using their native language. (Meaning and tone can be lost in translation.)
-    * Interpret the arguments of others in good faith, do not seek to disagree.
-    * When we do disagree, try to understand why.
  * Be thoughtful
    * Productive communication requires effort. Think about how your words will be interpreted.
    * Remember that sometimes it is best to refrain entirely from commenting.
  * Be respectful
    * In particular, respect differences of opinion. It is important that we resolve disagreements and differing views constructively.
-  * Be constructive
-    * Avoid derailing: stay on topic; if you want to talk about something else, start a new conversation.
-    * Avoid unconstructive criticism: don't merely decry the current state of affairs; offer — or at least solicit — suggestions as to how things may be improved.
-    * Avoid harsh words and stern tone: we are all aligned towards the well-being of the community and the progress of the ecosystem. Harsh words exclude, demotivate, and lead to unnecessary conflict.
-    * Avoid snarking (pithy, unproductive, sniping comments).
-    * Avoid microaggressions (brief and commonplace verbal, behavioral and environmental indignities that communicate hostile, derogatory or negative slights and insults towards a project, person or group).
-  * Be responsible
-    * What you say and do matters. Take responsibility for your words and actions, including their consequences, whether intended or otherwise.
+  * Avoid destructive behavior
+    * Derailing: stay on topic; if you want to talk about something else, start a new conversation.
+    * Unconstructive criticism: don't merely decry the current state of affairs; offer (or at least solicit) suggestions as to how things may be improved.
+    * Snarking (pithy, unproductive, sniping comments).

 The following actions are explicitly forbidden:

@@ -47,11 +41,11 @@ Explicit enforcement of the Code of Conduct applies to the official mediums oper

 * The [official GitHub projects][1] and code reviews.
 * The official elixir-lang mailing lists.
-* The **[#elixir][2]** IRC channel on [Libera.Chat][3].
+* The **[#elixir-lang][2]** IRC channel on [Freenode][3].

 Other Elixir activities (such as conferences, meetups, and unofficial forums) are encouraged to adopt this Code of Conduct. Such groups must provide their own contact information.

-Project maintainers may block, remove, edit, or reject comments, commits, code, wiki edits, issues, and other contributions that are not aligned to this Code of Conduct.
+Project maintainers may remove, edit, or reject comments, commits, code, wiki edits, issues, and other contributions that are not aligned to this Code of Conduct.

 Instances of abusive, harassing, or otherwise unacceptable behavior may be reported by emailing: elixir-lang-conduct@googlegroups.com. All complaints will be reviewed and investigated and will result in a response that is deemed necessary and appropriate to the circumstances. **All reports will be kept confidential**.

@@ -59,8 +53,8 @@ Instances of abusive, harassing, or otherwise unacceptable behavior may be repor

 ## Acknowledgements

-This document was based on the Code of Conduct from the Go project (dated Sep/2021) and the Contributor Covenant (v1.4).
+This document was based on the Code of Conduct from the Go project with parts derived from Django's Code of Conduct, Rust's Code of Conduct and the Contributor Covenant.

 [1]: https://github.com/elixir-lang/
-[2]: https://web.libera.chat/#elixir
-[3]: https://libera.chat/
+[2]: https://webchat.freenode.net/?channels=#elixir-lang
+[3]: https://www.freenode.net
@@ -2,9 +2,7 @@ PREFIX ?= /usr/local
 TEST_FILES ?= "*_test.exs"
 SHARE_PREFIX ?= $(PREFIX)/share
 MAN_PREFIX ?= $(SHARE_PREFIX)/man
-CANONICAL := 1.14/
-CANONICAL ?= main/
-DOCS_FORMAT ?= html
+CANONICAL := v1.11/
 ELIXIRC := bin/elixirc --ignore-module-conflict $(ELIXIRC_OPTS)
 ERLC := erlc -I lib/elixir/include
 ERL_MAKE := if [ -n "$(ERLC_OPTS)" ]; then ERL_COMPILER_OPTIONS=$(ERLC_OPTS) erl -make; else erl -make; fi
@@ -29,9 +27,9 @@ SOURCE_DATE_EPOCH_FILE = $(SOURCE_DATE_EPOCH_PATH)/SOURCE_DATE_EPOCH
 #==> Functions

 define CHECK_ERLANG_RELEASE
-	erl -noshell -eval '{V,_} = string:to_integer(erlang:system_info(otp_release)), io:fwrite("~s", [is_integer(V) and (V >= 23)])' -s erlang halt | grep -q '^true'; \
+	erl -noshell -eval '{V,_} = string:to_integer(erlang:system_info(otp_release)), io:fwrite("~s", [is_integer(V) and (V >= 21)])' -s erlang halt | grep -q '^true'; \
 		if [ $$? != 0 ]; then \
-		  echo "At least Erlang/OTP 23.0 is required to build Elixir"; \
+		  echo "At least Erlang/OTP 21.0 is required to build Elixir"; \
 		  exit 1; \
 		fi
 endef
@@ -84,7 +82,7 @@ $(PARSER): lib/elixir/src/elixir_parser.yrl

 # Since Mix depends on EEx and EEx depends on Mix,
 # we first compile EEx without the .app file,
-# then Mix, and then compile EEx fully
+# then Mix and then compile EEx fully
 elixir: stdlib lib/eex/ebin/Elixir.EEx.beam mix ex_unit logger eex iex

 stdlib: $(KERNEL) VERSION
@@ -93,10 +91,10 @@ $(KERNEL): lib/elixir/lib/*.ex lib/elixir/lib/*/*.ex lib/elixir/lib/*/*/*.ex
 		echo "==> bootstrap (compile)"; \
 		$(ERL) -s elixir_compiler bootstrap -s erlang halt; \
 	fi
-	$(Q) "$(MAKE)" unicode
+	$(Q) $(MAKE) unicode
 	@ echo "==> elixir (compile)";
 	$(Q) cd lib/elixir && ../../$(ELIXIRC) "lib/**/*.ex" -o ebin;
-	$(Q) "$(MAKE)" app
+	$(Q) $(MAKE) app

 app: $(APP)
 $(APP): lib/elixir/src/elixir.app.src lib/elixir/ebin VERSION $(GENERATE_APP)
@@ -106,7 +104,7 @@ unicode: $(UNICODE)
 $(UNICODE): lib/elixir/unicode/*
 	@ echo "==> unicode (compile)";
 	$(Q) $(ELIXIRC) lib/elixir/unicode/unicode.ex -o lib/elixir/ebin;
-	$(Q) $(ELIXIRC) lib/elixir/unicode/security.ex -o lib/elixir/ebin;
+	$(Q) $(ELIXIRC) lib/elixir/unicode/properties.ex -o lib/elixir/ebin;
 	$(Q) $(ELIXIRC) lib/elixir/unicode/tokenizer.ex -o lib/elixir/ebin;

 $(eval $(call APP_TEMPLATE,ex_unit,ExUnit))
@@ -128,7 +126,7 @@ install: compile
 	$(Q) for file in "$(DESTDIR)$(PREFIX)"/$(LIBDIR)/elixir/bin/*; do \
 		ln -sf "../$(LIBDIR)/elixir/bin/$${file##*/}" "$(DESTDIR)$(PREFIX)/$(BINDIR)/"; \
 	done
-	"$(MAKE)" install_man
+	$(MAKE) install_man

 check_reproducible: compile
 	$(Q) echo "==> Checking for reproducible builds..."
@@ -146,7 +144,7 @@ check_reproducible: compile
 	$(Q) mv lib/iex/ebin/* lib/iex/tmp/ebin_reproducible/
 	$(Q) mv lib/logger/ebin/* lib/logger/tmp/ebin_reproducible/
 	$(Q) mv lib/mix/ebin/* lib/mix/tmp/ebin_reproducible/
-	SOURCE_DATE_EPOCH=$(call READ_SOURCE_DATE_EPOCH) "$(MAKE)" compile
+	SOURCE_DATE_EPOCH=$(call READ_SOURCE_DATE_EPOCH) $(MAKE) compile
 	$(Q) echo "Diffing..."
 	$(Q) bin/elixir lib/elixir/diff.exs lib/elixir/ebin/ lib/elixir/tmp/ebin_reproducible/
 	$(Q) bin/elixir lib/elixir/diff.exs lib/eex/ebin/ lib/eex/tmp/ebin_reproducible/
@@ -160,7 +158,7 @@ clean:
 	rm -rf ebin
 	rm -rf lib/*/ebin
 	rm -rf $(PARSER)
-	$(Q) "$(MAKE)" clean_residual_files
+	$(Q) $(MAKE) clean_residual_files

 clean_elixir:
 	$(Q) rm -f lib/*/ebin/Elixir.*.beam
@@ -173,14 +171,15 @@ clean_residual_files:
 	rm -rf lib/mix/test/fixtures/git_rebar/
 	rm -rf lib/mix/test/fixtures/git_repo/
 	rm -rf lib/mix/test/fixtures/git_sparse_repo/
-	rm -rf lib/mix/test/fixtures/archive/ebin/
 	rm -f erl_crash.dump
-	$(Q) "$(MAKE)" clean_man
+	$(Q) $(MAKE) clean_man

 #==> Documentation tasks

 LOGO_PATH = $(shell test -f ../docs/logo.png && echo "--logo ../docs/logo.png")
 SOURCE_REF = $(shell tag="$(call GIT_TAG)" revision="$(call GIT_REVISION)"; echo "$${tag:-$$revision}")
+
+DOCS_FORMAT = html
 DOCS_COMPILE = CANONICAL=$(CANONICAL) bin/elixir ../ex_doc/bin/ex_doc "$(1)" "$(VERSION)" "lib/$(2)/ebin" --main "$(3)" --source-url "https://github.com/elixir-lang/elixir" --source-ref "$(call SOURCE_REF)" $(call LOGO_PATH) --output doc/$(2) --canonical "https://hexdocs.pm/$(2)/$(CANONICAL)" --homepage-url "https://elixir-lang.org/docs.html" --formatter "$(DOCS_FORMAT)" $(4)
 DOCS_CONFIG = bin/elixir lib/elixir/scripts/docs_config.exs "$(1)"

@@ -235,9 +234,19 @@ Docs.zip: docs

 Precompiled.zip: build_man compile
 	rm -f Precompiled.zip
-	zip -9 -r Precompiled.zip bin CHANGELOG.md lib/*/ebin lib/*/lib LICENSE Makefile man NOTICE README.md VERSION
+	zip -9 -r Precompiled.zip bin CHANGELOG.md lib/*/ebin lib/*/lib LICENSE man NOTICE README.md VERSION
 	@ echo "Precompiled file created $(CURDIR)/Precompiled.zip"

+zips: Precompiled.zip Docs.zip
+	@ echo ""
+	@ echo "### Checksums"
+	@ echo ""
+	@ shasum -a 1 < Precompiled.zip | sed -e "s/-//" | xargs echo "  * Precompiled.zip SHA1:"
+	@ shasum -a 512 < Precompiled.zip | sed -e "s/-//" | xargs echo "  * Precompiled.zip SHA512:"
+	@ shasum -a 1 < Docs.zip | sed -e "s/-//" | xargs echo "  * Docs.zip SHA1:"
+	@ shasum -a 512 < Docs.zip | sed -e "s/-//" | xargs echo "  * Docs.zip SHA512:"
+	@ echo ""
+
 #==> Test tasks

 # If you modify this task, please update .cirrus.yml accordingly
@@ -276,7 +285,7 @@ $(TEST_EBIN)/%.beam: $(TEST_ERL)/%.erl
 	$(Q) mkdir -p $(TEST_EBIN)
 	$(Q) $(ERLC) -o $(TEST_EBIN) $<

-test_elixir: test_stdlib test_ex_unit test_logger test_eex test_iex test_mix
+test_elixir: test_stdlib test_ex_unit test_logger test_mix test_eex test_iex

 test_stdlib: compile
 	@ echo "==> elixir (ex_unit)"
@@ -294,7 +303,7 @@ PLT = .elixir.plt

 $(PLT):
 	@ echo "==> Building PLT with Elixir's dependencies..."
-	$(Q) dialyzer --output_plt $(PLT) --build_plt --apps erts kernel stdlib compiler syntax_tools parsetools tools ssl inets crypto runtime_tools ftp tftp mnesia public_key asn1 sasl
+	$(Q) dialyzer --output_plt $(PLT) --build_plt --apps erts kernel stdlib compiler syntax_tools parsetools tools ssl inets crypto runtime_tools ftp tftp mnesia public_key asn1 hipe sasl

 clean_plt:
 	$(Q) rm -f $(PLT)
@@ -333,4 +342,4 @@ install_man: build_man
 	$(Q) $(INSTALL_DATA) man/elixirc.1 $(DESTDIR)$(MAN_PREFIX)/man1
 	$(Q) $(INSTALL_DATA) man/iex.1     $(DESTDIR)$(MAN_PREFIX)/man1
 	$(Q) $(INSTALL_DATA) man/mix.1     $(DESTDIR)$(MAN_PREFIX)/man1
-	"$(MAKE)" clean_man
+	$(MAKE) clean_man
@@ -22,7 +22,6 @@ limitations under the License.
 == All other files

 Copyright 2012 Plataformatec
-Copyright 2021 The Elixir Team

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -1,7 +1,6 @@
-<img src="https://github.com/elixir-lang/elixir-lang.github.com/raw/main/images/logo/logo.png#gh-light-mode-only" width="200" alt="Elixir">
-<img src="https://github.com/elixir-lang/elixir-lang.github.com/raw/main/images/logo/logo-dark.png#gh-dark-mode-only" width="200" alt="Elixir">
+# ![Elixir](https://github.com/elixir-lang/elixir-lang.github.com/raw/master/images/logo/logo.png)

-[![CI](https://github.com/elixir-lang/elixir/workflows/CI/badge.svg?branch=main)](https://github.com/elixir-lang/elixir/actions?query=branch%3Amain+workflow%3ACI) [![Build status](https://api.cirrus-ci.com/github/elixir-lang/elixir.svg?branch=main)](https://cirrus-ci.com/github/elixir-lang/elixir)
+[![CI](https://github.com/elixir-lang/elixir/workflows/CI/badge.svg?branch=master)](https://github.com/elixir-lang/elixir/actions?query=branch%3Amaster+workflow%3ACI) [![Build status](https://api.cirrus-ci.com/github/elixir-lang/elixir.svg?branch=master)](https://cirrus-ci.com/github/elixir-lang/elixir)

 Elixir is a dynamic, functional language designed for building scalable
 and maintainable applications.
@@ -12,14 +11,11 @@ For more about Elixir, installation and documentation,
 ## Policies

 New releases are announced in the [announcement mailing list][8].
-You can subscribe by sending an email to elixir-lang-ann+subscribe@googlegroups.com
-and replying to the confirmation email.
+You can subscribe by sending an email to elixir-lang-ann+subscribe@googlegroups.com and replying to the confirmation email.

-All security releases [will be tagged with `[security]`][10]. For more
-information, please read our [Security Policy][9].
+All security releases [will be tagged with `[security]`][10]. For more information, please read our [Security Policy][9].

-All interactions in our official communication channels follow our
-[Code of Conduct][1].
+All interactions in our official communication channels follow our [Code of Conduct][1].

 ## Bug reports

@@ -27,56 +23,13 @@ For reporting bugs, [visit our issue tracker][2] and follow the steps
 for reporting a new issue. **Please disclose security vulnerabilities
 privately at elixir-security@googlegroups.com**.

-## Issues tracker management
-
-All currently open bugs related to the Elixir repository are listed
-in the issues tracker. The Elixir team uses the issues tracker to focus
-on *actionable items*, including planned enhancements in the short- and
-medium-term. We also do our best to label entries for clarity and to ease
-collaboration.
-
-Our *actionable item policy* has some important consequences, such as:
-
-  * Proposing new features as well as request for support, help, and
-    guidance must be done in their own spaces, detailed next.
-
-  * Issues where we have identified to be outside of Elixir scope,
-    such as a bug upstream, will be closed (and requested to be moved
-    elsewhere if appropriate).
-
-  * We actively close unrelated and non-actionable issues to keep the
-    issues tracker tidy. However, we may get things wrong from time to
-    time, so we are glad to revisit issues and reopen if necessary.
-
-Keep the tone positive and be kind! For more information, see the
-[Code of Conduct][1].
-
-### Proposing new features
-
-For proposing new features, please start a discussion in the
-[Elixir Core mailing list][3]. Keep in mind that it is your responsibility
-to argue and explain why a feature is useful and how it will impact the
-codebase and the community.
-
-Once a proposal is accepted, it will be added to [the issue tracker][2].
-Features and bug fixes that have already been merged and will be included
-in the next release are then "closed" and added to the [changelog][7].
-
-### Discussions, support, and help
-
-For general discussions, support, and help, please use many of the community
-spaces [listed on the sidebar of the Elixir website](https://elixir-lang.org/),
-such as forums, chat platforms, etc, where the wider community will be available
-to help you.
-
 ## Compiling from source

 For the many different ways to install Elixir,
 [see our installation instructions on the website](https://elixir-lang.org/install.html).
-However, if you want to contribute to Elixir, you will need to compile from source.
+To compile from source, you can follow the steps below.

-First, [install Erlang](https://elixir-lang.org/install.html#installing-erlang).
-After that, clone this repository to your machine, compile and test it:
+First, [install Erlang](https://elixir-lang.org/install.html#installing-erlang). Then clone this repository to your machine, compile and test it:

 ```sh
 git clone https://github.com/elixir-lang/elixir.git
@@ -88,13 +41,37 @@ make clean test
 [this article includes important notes for compiling Elixir from source
 on Windows](https://github.com/elixir-lang/elixir/wiki/Windows).

-In case you want to use this Elixir version as your system version,
-you need to add the `bin` directory to [your PATH environment variable](https://elixir-lang.org/install.html#setting-path-environment-variable).
-
 If Elixir fails to build (specifically when pulling in a new version via
 `git`), be sure to remove any previous build artifacts by running
 `make clean`, then `make test`.

+If tests pass, you can use Interactive Elixir by running `bin/iex` in your terminal.
+
+However, if tests fail, it is likely that you have an outdated Erlang/OTP version
+(Elixir requires Erlang/OTP 21.0 or later). You can check your Erlang/OTP version
+by calling `erl` in the command line. You will see some information similar to:
+
+    Erlang/OTP 21 [erts-9.0] [smp:2:2] [async-threads:10] [kernel-poll:false]
+
+If you have properly set up your dependencies and tests still fail,
+you may want to open up a bug report, as explained next.
+
+## Proposing new features
+
+For proposing new features, please start a discussion in the
+[Elixir Core mailing list][3]. Keep in mind that it is your responsibility
+to argue and explain why a feature is useful and how it will impact the
+codebase and the community.
+
+Once a proposal is accepted, it will be added to [the issue tracker][2].
+The issue tracker focuses on *actionable items* and it holds a list of
+upcoming enhancements and pending bugs. All entries in the tracker are
+tagged for clarity and to ease collaboration.
+
+Features and bug fixes that have already been merged and will be included
+in the next release are marked as "closed" in the issue tracker and are
+added to the [changelog][7].
+
 ## Contributing

 We welcome everyone to contribute to Elixir. To do so, there are a few
@@ -115,7 +92,7 @@ in applications inside the `lib` folder:

 You can run all tests in the root directory with `make test` and you can
 also run tests for a specific framework `make test_#{APPLICATION}`, for example,
-`make test_ex_unit`. If you just changed something in Elixir's standard
+`make test_ex_unit`. If you just changed something in the Elixir's standard
 library, you can run only that portion through `make test_stdlib`.

 If you are changing just one file, you can choose to compile and run tests only
@@ -127,12 +104,6 @@ bin/elixirc lib/elixir/lib/string.ex -o lib/elixir/ebin
 bin/elixir lib/elixir/test/elixir/string_test.exs
 ```

-You can also use the `LINE` env var to run a single test:
-
-```sh
-LINE=123 bin/elixir lib/elixir/test/elixir/string_test.exs
-````
-
 To recompile (including Erlang modules):

 ```sh
@@ -152,7 +123,7 @@ make clean_elixir compile

 Similarly, if you can't get Elixir to compile or the tests to pass after
 updating an existing checkout, run `make clean compile`. You can check
-[the official build status](https://github.com/elixir-lang/elixir/actions/workflows/ci.yml).
+[the official build status on Cirrus CI](https://cirrus-ci.com/github/elixir-lang/elixir).
 More tasks can be found by reading the [Makefile](Makefile).

 With tests running and passing, you are ready to contribute to Elixir and
@@ -160,9 +131,9 @@ With tests running and passing, you are ready to contribute to Elixir and
 We have saved some excellent pull requests we have received in the past in
 case you are looking for some examples:

-* [Implement Enum.member? - Pull request](https://github.com/elixir-lang/elixir/pull/992)
-* [Add String.valid? - Pull request](https://github.com/elixir-lang/elixir/pull/1058)
-* [Implement capture_io for ExUnit - Pull request](https://github.com/elixir-lang/elixir/pull/1059)
+* [Implement Enum.member? - Pull Request](https://github.com/elixir-lang/elixir/pull/992)
+* [Add String.valid? - Pull Request](https://github.com/elixir-lang/elixir/pull/1058)
+* [Implement capture_io for ExUnit - Pull Request](https://github.com/elixir-lang/elixir/pull/1059)

 ### Reviewing changes

@@ -171,12 +142,12 @@ We outline our process below to clarify the roles of everyone involved.

 All pull requests must be approved by two committers before being merged into
 the repository. If any changes are necessary, the team will leave appropriate
-comments requesting changes to the code. Unfortunately, we cannot guarantee a
+comments requesting changes to the code. Unfortunately we cannot guarantee a
 pull request will be merged, even when modifications are requested, as the Elixir
 team will re-evaluate the contribution as it changes.

 Committers may also push style changes directly to your branch. If you would
-rather manage all changes yourself, you can disable the "Allow edits from maintainers"
+rather manage all changes yourself, you can disable "Allow edits from maintainers"
 feature when submitting your pull request.

 The Elixir team may optionally assign someone to review a pull request.
@@ -195,8 +166,8 @@ to be installed and built alongside Elixir:

 ```sh
 # After cloning and compiling Elixir, in its parent directory:
-git clone https://github.com/elixir-lang/ex_doc.git
-cd ex_doc && ../elixir/bin/mix do deps.get + compile
+git clone git://github.com/elixir-lang/ex_doc.git
+cd ex_doc && ../elixir/bin/mix do deps.get, compile
 ```

 Now go back to Elixir's root directory and run:
@@ -219,13 +190,13 @@ and `mix` under the `doc` directory. If you are planning to contribute documenta
  * [Issue tracker][2]
  * [Changelog][7]
  * [Security Policy][9]
-  * **[#elixir][4]** on [Libera.Chat][5] IRC
+  * **[#elixir-lang][4]** on [Freenode][5] IRC

  [1]: CODE_OF_CONDUCT.md
  [2]: https://github.com/elixir-lang/elixir/issues
  [3]: https://groups.google.com/group/elixir-lang-core
-  [4]: https://web.libera.chat/#elixir
-  [5]: https://libera.chat
+  [4]: https://webchat.freenode.net/?channels=#elixir-lang
+  [5]: https://www.freenode.net
  [6]: https://elixir-lang.org/docs.html
  [7]: CHANGELOG.md
  [8]: https://groups.google.com/group/elixir-lang-ann
@@ -234,7 +205,7 @@ and `mix` under the `doc` directory. If you are planning to contribute documenta

 ## License

-"Elixir" and the Elixir logo are registered trademarks of The Elixir Team.
+"Elixir" and the Elixir logo are copyright (c) 2012 Plataformatec.

 Elixir source code is released under Apache License 2.0.

@@ -4,19 +4,25 @@

 1. Ensure you are running on the oldest supported Erlang version

-2. Update version in /VERSION, bin/elixir and bin/elixir.bat
+2. Update version in /VERSION

 3. Ensure /CHANGELOG.md is updated, versioned and add the current date

 4. Update "Compatibility and Deprecations" if a new OTP version is supported

-5. Commit changes above with title "Release vVERSION", generate a new tag, and push it
+5. Commit changes above with title "Release vVERSION" and generate a new tag

-6. Wait until GitHub Actions publish artifacts to the draft release and the CI is green
+6. Run `make clean test` to ensure all tests pass from scratch and the CI is green

-7. Copy the relevant bits from /CHANGELOG.md to the GitHub release and publish it
+7. Recompile an existing project (for example, Ecto) to ensure manifests can be upgraded

-8. Add the release to `elixir.csv` with the minimum supported OTP version (all releases), update `erlang.csv` to the latest supported OTP version, and `_data/elixir-versions.yml` (except for RCs) files in `elixir-lang/elixir-lang.github.com`
+8. Push branch and the new tag
+
+9. Publish new zips with `make zips`, upload `Precompiled.zip` and `Docs.zip` to GitHub Releases, and include SHAs+CHANGELOG
+
+10. Add the release to `elixir.csv` (all releases), update `erlang.csv` to the precompiled OTP version, and `_data/elixir-versions.yml` (except for RCs) files in `elixir-lang/elixir-lang.github.com`
+
+11. Send an e-mail to elixir-lang-ann@googlegroups.com with title "Elixir vVERSION released". The body should be a link to the Release page on GitHub and the checksums. If it is a security release, prefix the title with the `[security]` tag

 ## Creating a new vMAJOR.MINOR branch

@@ -26,24 +32,14 @@

 2. Update tables in /SECURITY.md and "Compatibility and Deprecations"

-3. Commit "Branch out vMAJOR.MINOR"
+3. Commit "Prepare vMAJOR.MINOR for release"

-### Back in main
+### Back in master

-1. Bump /VERSION file, bin/elixir and bin/elixir.bat
+1. Bump /VERSION file

 2. Start new /CHANGELOG.md

-3. Update tables in /SECURITY.md and in "Compatibility and Deprecations"
+3. Update tables in /SECURITY.md in "Compatibility and Deprecations"

 4. Commit "Start vMAJOR.MINOR+1"
-
-## Changing supported Erlang/OTP versions
-
-1. Update the table in Compatibility and Deprecations
-
-2. Update `otp_release` checks in /Makefile and `/lib/elixir/src/elixir.erl`
-
-3. Update CI workflows in `/.cirrus.yml`, `/.github/workflows/ci.yml`, and `/.github/workflows/releases.yml`
-
-4. Remove `otp_release` version checks that are no longer needed
@@ -4,19 +4,19 @@

 Elixir applies bug fixes only to the latest minor branch. Security patches are available for the last 5 minor branches:

-Elixir version | Support
-:------------- | :-----------------------------
-1.14           | Bug fixes and security patches
-1.13           | Security patches only
-1.12           | Security patches only
-1.11           | Security patches only
-1.10           | Security patches only
+| Elixir version | Support
+| -------------- | ------------------------------
+| 1.11           | Bug fixes and security patches
+| 1.10           | Security patches only
+| 1.9            | Security patches only
+| 1.8            | Security patches only
+| 1.7            | Security patches only

 ## Announcements

 New releases are announced in the read-only [announcements mailing list](https://groups.google.com/group/elixir-lang-ann). You can subscribe by sending an email to elixir-lang-ann+subscribe@googlegroups.com and replying to the confirmation email.

-Security notifications [will be tagged with `[security]`](https://groups.google.com/forum/#!searchin/elixir-lang-ann/%5Bsecurity%5D%7Csort:date).
+All security releases [will be tagged with `[security]`](https://groups.google.com/forum/#!searchin/elixir-lang-ann/%5Bsecurity%5D%7Csort:date).

 ## Reporting a vulnerability

@@ -1 +1 @@
-1.14.5
+1.11.4
@@ -1,22 +1,20 @@
 #!/bin/sh
 set -e

-ELIXIR_VERSION=1.14.5
-
-if [ $# -eq 0 ] || { [ $# -eq 1 ] && { [ "$1" = "--help" ] || [ "$1" = "-h" ]; }; }; then
+if [ $# -eq 0 ] || [ "$1" = "--help" ] || [ "$1" = "-h" ]; then
  cat <<USAGE >&2
 Usage: $(basename "$0") [options] [.exs file] [data]

 ## General options

  -e "COMMAND"                 Evaluates the given command (*)
-  -h, --help                   Prints this message (standalone)
+  -h, --help                   Prints this message and exits
  -r "FILE"                    Requires the given files/patterns (*)
-  -S SCRIPT                    Finds and executes the given script in \$PATH
+  -S SCRIPT                    Finds and executes the given script in \$PATH
  -pr "FILE"                   Requires the given files/patterns in parallel (*)
  -pa "PATH"                   Prepends the given path to Erlang code path (*)
  -pz "PATH"                   Appends the given path to Erlang code path (*)
-  -v, --version                Prints Erlang/OTP and Elixir versions (standalone)
+  -v, --version                Prints Elixir version and exits

  --app APP                    Starts the given app and its dependencies (*)
  --erl "SWITCHES"             Switches to be passed down to Erlang (*)
@@ -24,7 +22,6 @@ Usage: $(basename "$0") [options] [.exs file] [data]
  --logger-otp-reports BOOL    Enables or disables OTP reporting
  --logger-sasl-reports BOOL   Enables or disables SASL reporting
  --no-halt                    Does not halt the Erlang VM after execution
-  --short-version              Prints Elixir version (standalone)
  --werl                       Uses Erlang's Windows shell GUI (Windows only)

 Options given after the .exs file or -- are passed down to the executed code.
@@ -55,7 +52,6 @@ It will attempt to create PIPEDIR and LOGDIR if they don't exist.
 See run_erl to learn more. To reattach, run: to_erl PIPEDIR.

 ** Options marked with (*) can be given more than once.
-** Standalone options can't be combined with other options.
 USAGE
  exit 1
 fi
@@ -70,16 +66,11 @@ readlink_f () {
  fi
 }

-if [ $# -eq 1 ] && [ "$1" = "--short-version" ]; then
-  echo "$ELIXIR_VERSION"
-  exit 0
-fi
-
 # Stores static Erlang arguments and --erl (which is passed as is)
 ERL=""

 # Stores erl arguments preserving spaces/quotes (mimics an array)
-erl_set () {
+erl () {
  eval "E${E}=\$1"
  E=$((E + 1))
 }
@@ -100,29 +91,32 @@ LENGTH=$#
 set -- "$@" -extra

 while [ $I -le $LENGTH ]; do
-  # S counts to be shifted, C counts to be copied
-  S=0
-  C=0
+  S=1
  case "$1" in
    +iex)
-        C=1
+        set -- "$@" "$1"
        MODE="iex"
        ;;
    +elixirc)
-        C=1
+        set -- "$@" "$1"
        MODE="elixirc"
        ;;
-    -v|--no-halt|--no-pry)
-        C=1
+    -v|--no-halt)
+        set -- "$@" "$1"
        ;;
    -e|-r|-pr|-pa|-pz|--app|--eval|--remsh|--dot-iex)
-        C=2
+        S=2
+        set -- "$@" "$1" "$2"
        ;;
    --rpc-eval)
-        C=3
+        S=3
+        set -- "$@" "$1" "$2" "$3"
+        ;;
+    --detached)
+        echo "warning: the --detached option is deprecated" >&2
+        ERL="$ERL -detached"
        ;;
    --hidden)
-        S=1
        ERL="$ERL -hidden"
        ;;
    --logger-otp-reports)
@@ -143,34 +137,34 @@ while [ $I -le $LENGTH ]; do
        ;;
    --cookie)
        S=2
-        erl_set "-setcookie"
-        erl_set "$2"
+        erl "-setcookie"
+        erl "$2"
        ;;
    --sname|--name)
        S=2
-        erl_set "$(echo "$1" | cut -c 2-)"
-        erl_set "$2"
+        erl "$(echo "$1" | cut -c 2-)"
+        erl "$2"
        ;;
    --erl-config)
        S=2
-        erl_set "-config"
-        erl_set "$2"
+        erl "-config"
+        erl "$2"
        ;;
    --vm-args)
        S=2
-        erl_set "-args_file"
-        erl_set "$2"
+        erl "-args_file"
+        erl "$2"
        ;;
    --boot)
        S=2
-        erl_set "-boot"
-        erl_set "$2"
+        erl "-boot"
+        erl "$2"
        ;;
    --boot-var)
        S=3
-        erl_set "-boot_var"
-        erl_set "$2"
-        erl_set "$3"
+        erl "-boot_var"
+        erl "$2"
+        erl "$3"
        ;;
    --pipe-to)
        S=3
@@ -183,7 +177,6 @@ while [ $I -le $LENGTH ]; do
        fi
        ;;
    --werl)
-        S=1
        if [ "$OS" = "Windows_NT" ]; then ERL_EXEC="werl"; fi
        ;;
    *)
@@ -196,13 +189,6 @@ while [ $I -le $LENGTH ]; do
        ;;
  esac

-  while [ $I -le $LENGTH ] && [ $C -gt 0 ]; do
-    C=$((C - 1))
-    I=$((I + 1))
-    set -- "$@" "$1"
-    shift
-  done
-
  I=$((I + S))
  shift $S
 done
@@ -224,11 +210,7 @@ if [ "$OS" != "Windows_NT" ] && [ -z "$NO_COLOR" ]; then
  if test -t 1 -a -t 2; then ERL="-elixir ansi_enabled true $ERL"; fi
 fi

-# One MAY change ERTS_BIN= but you MUST NOT change
-# ERTS_BIN=$ERTS_BIN as it is handled by Elixir releases.
 ERTS_BIN=
-ERTS_BIN="$ERTS_BIN"
-
 set -- "$ERTS_BIN$ERL_EXEC" -pa "$SCRIPT_PATH"/../lib/*/ebin $ELIXIR_ERL_OPTIONS $ERL "$@"

 if [ -n "$RUN_ERL_PIPE" ]; then
@@ -1,14 +1,10 @@
@if defined ELIXIR_CLI_ECHO (@echo on) else (@echo off)
-
-set ELIXIR_VERSION=1.14.5
-
 setlocal enabledelayedexpansion
-if    ""%1""==""""                if ""%2""=="""" goto documentation
-if /I ""%1""==""--help""          if ""%2""=="""" goto documentation
-if /I ""%1""==""-h""              if ""%2""=="""" goto documentation
-if /I ""%1""==""/h""              if ""%2""=="""" goto documentation
-if    ""%1""==""/?""              if ""%2""=="""" goto documentation
-if /I ""%1""==""--short-version"" if ""%2""=="""" goto shortversion
+if    ""%1""==""""       goto documentation
+if /I ""%1""==""--help"" goto documentation
+if /I ""%1""==""-h""     goto documentation
+if /I ""%1""==""/h""     goto documentation
+if    ""%1""==""/?""     goto documentation
 goto parseopts

 :documentation
@@ -17,13 +13,13 @@ echo.
 echo ## General options
 echo.
 echo   -e "COMMAND"                 Evaluates the given command (*)
-echo   -h, --help                   Prints this message (standalone)
+echo   -h, --help                   Prints this message and exits
 echo   -r "FILE"                    Requires the given files/patterns (*)
 echo   -S SCRIPT                    Finds and executes the given script in $PATH
 echo   -pr "FILE"                   Requires the given files/patterns in parallel (*)
 echo   -pa "PATH"                   Prepends the given path to Erlang code path (*)
 echo   -pz "PATH"                   Appends the given path to Erlang code path (*)
-echo   -v, --version                Prints Erlang/OTP and Elixir versions (standalone)
+echo   -v, --version                Prints Elixir version and exits
 echo.
 echo   --app APP                    Starts the given app and its dependencies (*)
 echo   --erl "SWITCHES"             Switches to be passed down to Erlang (*)
@@ -31,7 +27,6 @@ echo   --eval "COMMAND"             Evaluates the given command, same as -e (*)
 echo   --logger-otp-reports BOOL    Enables or disables OTP reporting
 echo   --logger-sasl-reports BOOL   Enables or disables SASL reporting
 echo   --no-halt                    Does not halt the Erlang VM after execution
-echo   --short-version              Prints Elixir version (standalone)
 echo   --werl                       Uses Erlang's Windows shell GUI (Windows only)
 echo.
 echo Options given after the .exs file or -- are passed down to the executed code.
@@ -59,11 +54,6 @@ echo.
 echo --pipe-to is not supported on Windows. If set, Elixir won't boot.
 echo.
 echo ** Options marked with (*) can be given more than once.
-echo ** Standalone options can't be combined with other options.
-goto end
-
-:shortversion
-echo !ELIXIR_VERSION!
 goto end

 :parseopts
@@ -88,7 +78,6 @@ set SCRIPT_PATH=%~dp0

 rem Designates the path to the ERTS system
 set ERTS_BIN=
-set ERTS_BIN=!ERTS_BIN!

 rem Recursive loop called for each parameter that parses the cmd line parameters
 :startloop
@@ -110,21 +99,18 @@ if !par!=="+elixirc" (set parsElixir=!parsElixir! +elixirc && set runMode="elixi
 rem ******* EVAL PARAMETERS ************************
 if ""==!par:-e=! (
  set "VAR=%~1"
-  if not defined VAR (set VAR= )
  set parsElixir=!parsElixir! -e "!VAR:"=\"!"
  shift
  goto startloop
 )
 if ""==!par:--eval=! (
  set "VAR=%~1"
-  if not defined VAR (set VAR= )
  set parsElixir=!parsElixir! --eval "!VAR:"=\"!"
  shift
  goto startloop
 )
 if ""==!par:--rpc-eval=! (
  set "VAR=%~2"
-  if not defined VAR (set VAR= )
  set parsElixir=!parsElixir! --rpc-eval %1 "!VAR:"=\"!"
  shift
  shift
@@ -136,12 +122,10 @@ if ""==!par:-pr=!         (set "parsElixir=!parsElixir! -pr %1" && shift && goto
 if ""==!par:-pa=!         (set "parsElixir=!parsElixir! -pa %1" && shift && goto startloop)
 if ""==!par:-pz=!         (set "parsElixir=!parsElixir! -pz %1" && shift && goto startloop)
 if ""==!par:-v=!          (set "parsElixir=!parsElixir! -v" && goto startloop)
-if ""==!par:--version=!   (set "parsElixir=!parsElixir! --version" && goto startloop)
 if ""==!par:--app=!       (set "parsElixir=!parsElixir! --app %1" && shift && goto startloop)
 if ""==!par:--no-halt=!   (set "parsElixir=!parsElixir! --no-halt" && goto startloop)
 if ""==!par:--remsh=!     (set "parsElixir=!parsElixir! --remsh %1" && shift && goto startloop)
 if ""==!par:--dot-iex=!   (set "parsElixir=!parsElixir! --dot-iex %1" && shift && goto startloop)
-if ""==!par:--no-pry=!    (set "parsElixir=!parsElixir! --no-pry" && goto startloop)
 rem ******* ERLANG PARAMETERS **********************
 if ""==!par:--boot=!                (set "parsErlang=!parsErlang! -boot %1" && shift && goto startloop)
 if ""==!par:--boot-var=!            (set "parsErlang=!parsErlang! -boot_var %1 %2" && shift && shift && goto startloop)
@@ -175,19 +159,10 @@ if %errorlevel% == 0 (
 if not !runMode! == "iex" (
  set beforeExtra=-noshell -s elixir start_cli !beforeExtra!
 )
-if defined ELIXIR_CLI_DRY_RUN (
-   if defined useWerl (
-     echo start "" "!ERTS_BIN!werl.exe" !ext_libs! !ELIXIR_ERL_OPTIONS! !parsErlang! !beforeExtra! -extra !parsElixir!
-   ) else (
-     echo "!ERTS_BIN!erl.exe" !ext_libs! !ELIXIR_ERL_OPTIONS! !parsErlang! !beforeExtra! -extra !parsElixir!
-   )
+if defined useWerl (
+  start "" "!ERTS_BIN!werl.exe" !ext_libs! !ELIXIR_ERL_OPTIONS! !parsErlang! !beforeExtra! -extra !parsElixir!
 ) else (
-  if defined useWerl (
-    start "" "!ERTS_BIN!werl.exe" !ext_libs! !ELIXIR_ERL_OPTIONS! !parsErlang! !beforeExtra! -extra !parsElixir!
-  ) else (
-    "!ERTS_BIN!erl.exe" !ext_libs! !ELIXIR_ERL_OPTIONS! !parsErlang! !beforeExtra! -extra !parsElixir!
-  )
+  "!ERTS_BIN!erl.exe" !ext_libs! !ELIXIR_ERL_OPTIONS! !parsErlang! !beforeExtra! -extra !parsElixir!
 )
-exit /B %ERRORLEVEL%
 :end
-endlocal
+endlocal
@@ -7,14 +7,13 @@ Usage: $(basename "$0") [elixir switches] [compiler switches] [.ex files]

  -h, --help                Prints this message and exits
  -o                        The directory to output compiled files
-  -v, --version             Prints Elixir version and exits (standalone)
+  -v, --version             Prints Elixir version and exits

  --ignore-module-conflict  Does not emit warnings if a module was previously defined
  --no-debug-info           Does not attach debug info to compiled modules
  --no-docs                 Does not attach documentation to compiled modules
-  --profile time            Profile the time to compile modules
  --verbose                 Prints compilation status
-  --warnings-as-errors      Treats warnings as errors and return non-zero exit status
+  --warnings-as-errors      Treats warnings as errors and return non-zero exit code

 Options given after -- are passed down to the executed code.
 Options can be passed to the Erlang runtime using \$ELIXIR_ERL_OPTIONS.
@@ -14,16 +14,15 @@ goto run
 :documentation
 echo Usage: %~nx0 [elixir switches] [compiler switches] [.ex files]
 echo.
-echo   -h, --help                Prints this message and exits
 echo   -o                        The directory to output compiled files
-echo   -v, --version             Prints Elixir version and exits (standalone)
 echo.
+echo   --help, -h                Prints this message and exits
 echo   --ignore-module-conflict  Does not emit warnings if a module was previously defined
 echo   --no-debug-info           Does not attach debug info to compiled modules
 echo   --no-docs                 Does not attach documentation to compiled modules
-echo   --profile time            Profile the time to compile modules
 echo   --verbose                 Prints compilation status
-echo   --warnings-as-errors      Treats warnings as errors and returns non-zero exit status
+echo   --version, -v             Prints Elixir version and exits
+echo   --warnings-as-errors      Treats warnings as errors and returns non-zero exit code
 echo.
 echo ** Options given after -- are passed down to the executed code
 echo ** Options can be passed to the Erlang runtime using ELIXIR_ERL_OPTIONS
@@ -7,11 +7,9 @@ Usage: $(basename "$0") [options] [.exs file] [data]

 The following options are exclusive to IEx:

-  --dot-iex "FILE"    Evaluates FILE, line by line, to set up IEx' environment.
-                      Defaults to evaluating .iex.exs or ~/.iex.exs, if any exists.
-                      If FILE is empty, then no file will be loaded.
-  --remsh NAME        Connects to a node using a remote shell.
-  --no-pry            Doesn't start pry sessions when dbg/2 is called.
+  --dot-iex "PATH"    Overrides default .iex.exs file and uses path instead;
+                      path can be empty, then no file will be loaded
+  --remsh NAME        Connects to a node using a remote shell

 It accepts all other options listed by "elixir --help".
 USAGE
@@ -11,19 +11,17 @@ echo Usage: %~nx0 [options] [.exs file] [data]
 echo.
 echo The following options are exclusive to IEx:
 echo.
-echo   --dot-iex "FILE"    Evaluates FILE, line by line, to set up IEx' environment.
-echo                       Defaults to evaluating .iex.exs or ~/.iex.exs, if any exists.
-echo                       If FILE is empty, then no file will be loaded.
+echo   --dot-iex "PATH"    Overrides default .iex.exs file and uses path instead;
+echo                       path can be empty, then no file will be loaded
 echo   --remsh NAME        Connects to a node using a remote shell
 echo   --werl              Uses Erlang's Windows shell GUI (Windows only)
-echo   --no-pry            Doesn't start pry sessions when dbg/2 is called.
 echo.
 echo Set the IEX_WITH_WERL environment variable to always use werl.
 echo It accepts all other options listed by "elixir --help".
 goto end

 :run
-if defined IEX_WITH_WERL (set __ELIXIR_IEX_FLAGS=--werl) else (set __ELIXIR_IEX_FLAGS=)
+if defined IEX_WITH_WERL (@set __ELIXIR_IEX_FLAGS=--werl) else (set __ELIXIR_IEX_FLAGS=)
 call "%~dp0\elixir.bat" --no-halt --erl "-noshell -user Elixir.IEx.CLI" +iex %__ELIXIR_IEX_FLAGS% %*
 :end
 endlocal
@@ -9,19 +9,19 @@ end

 defmodule EEx do
  @moduledoc ~S"""
-  EEx stands for Embedded Elixir.
-
-  Embedded Elixir allows you to embed Elixir code inside a string
-  in a robust way.
+  EEx stands for Embedded Elixir. It allows you to embed
+  Elixir code inside a string in a robust way.

      iex> EEx.eval_string("foo <%= bar %>", bar: "baz")
      "foo baz"

-  This module provides three main APIs for you to use:
+  ## API
+
+  This module provides 3 main APIs for you to use:

    1. Evaluate a string (`eval_string/3`) or a file (`eval_file/3`)
       directly. This is the simplest API to use but also the
-       slowest, since the code is evaluated at runtime and not precompiled.
+       slowest, since the code is evaluated and not compiled before.

    2. Define a function from a string (`function_from_string/5`)
       or a file (`function_from_file/5`). This allows you to embed
@@ -34,48 +34,19 @@ defmodule EEx do
       above and is available to you if you want to provide your own
       ways of handling the compiled template.

-  The APIs above support several options, documented below. You may
-  also pass an engine which customizes how the EEx code is compiled.
-
  ## Options

-  All functions in this module, unless otherwise noted, accept EEx-related
-  options. They are:
+  All functions in this module accept EEx-related options.
+  They are:

    * `:file` - the file to be used in the template. Defaults to the given
-      file the template is read from or to `"nofile"` when compiling from a string.
-
-    * `:line` - the line to be used as the template start. Defaults to `1`.
-
+      file the template is read from or to "nofile" when compiling from a string.
+    * `:line` - the line to be used as the template start. Defaults to 1.
    * `:indentation` - (since v1.11.0) an integer added to the column after every
-      new line. Defaults to `0`.
-
+      new line. Defaults to 0.
    * `:engine` - the EEx engine to be used for compilation.
-
-    * `:trim` - if `true`, trims whitespace left and right of quotation as
-      long as at least one newline is present. All subsequent newlines and
-      spaces are removed but one newline is retained. Defaults to `false`.
-
-    * `:parser_options` - (since: 1.13.0) allow customizing the parsed code
-      that is generated. See `Code.string_to_quoted/2` for available options.
-      Note that the options `:file`, `:line` and `:column` are ignored if
-      passed in. Defaults to `Code.get_compiler_option(:parser_options)`
-      (which defaults to `[]` if not set).
-
-  ## Tags
-
-  EEx supports multiple tags, declared below:
-
-      <% Elixir expression: executes code but discards output %>
-      <%= Elixir expression: executes code and prints result %>
-      <%% EEx quotation: returns the contents inside the tag as is %>
-      <%!-- Comments: they are discarded from source --%>
-
-  EEx supports additional tags, that may be used by some engines,
-  but they do not have a meaning by default:
-
-      <%| ... %>
-      <%/ ... %>
+    * `:trim` - if true, trims whitespace left/right of quotation tags up until
+      newlines. At least one newline is retained. Defaults to false.

  ## Engine

@@ -85,10 +56,42 @@ defmodule EEx do
  By default, `EEx` uses the `EEx.SmartEngine` that provides some
  conveniences on top of the simple `EEx.Engine`.

-  ### `EEx.SmartEngine`
+  ### Tags

-  The smart engine uses EEx default rules and adds the `@` construct
-  for reading template assigns:
+  `EEx.SmartEngine` supports the following tags:
+
+      <% Elixir expression - inline with output %>
+      <%= Elixir expression - replace with result %>
+      <%% EEx quotation - returns the contents inside %>
+      <%# Comments - they are discarded from source %>
+
+  All expressions that output something to the template
+  **must** use the equals sign (`=`). Since everything in
+  Elixir is an expression, there are no exceptions for this rule.
+  For example, while some template languages would special-case
+  `if` clauses, they are treated the same in EEx and
+  also require `=` in order to have their result printed:
+
+      <%= if true do %>
+        It is obviously true
+      <% else %>
+        This will never appear
+      <% end %>
+
+  To escape an EEx expression in EEx use `<%% content %>`. For example:
+
+      <%%= x + 3 %>
+
+  will be rendered as `<%= x + 3 %>`.
+
+  Note that different engines may have different rules
+  for each tag. Other tags may be added in future versions.
+
+  ### Macros
+
+  `EEx.SmartEngine` also adds some macros to your template.
+  An example is the `@` macro which allows easy data access
+  in a template:

      iex> EEx.eval_string("<%= @foo %>", assigns: [foo: 1])
      "1"
@@ -101,26 +104,11 @@ defmodule EEx do
  required by the template is not specified at compilation time.
  """

-  @type line :: non_neg_integer
-  @type column :: non_neg_integer
-  @type marker :: '=' | '/' | '|' | ''
-  @type metadata :: %{column: column, line: line}
-  @type token ::
-          {:comment, charlist, metadata}
-          | {:text, charlist, metadata}
-          | {:expr | :start_expr | :middle_expr | :end_expr, marker, charlist, metadata}
-          | {:eof, metadata}
-
  @doc """
-  Generates a function definition from the given string.
+  Generates a function definition from the string.

-  The first argument is the kind of the generated function (`:def` or `:defp`).
-  The `name` argument is the name that the generated function will have.
-  `template` is the string containing the EEx template. `args` is a list of arguments
-  that the generated function will accept. They will be available inside the EEx
-  template.
-
-  The supported `options` are described [in the module docs](#module-options).
+  The kind (`:def` or `:defp`) must be given, the
+  function name, its arguments and the compilation options.

  ## Examples

@@ -132,11 +120,11 @@ defmodule EEx do
      "3"

  """
-  defmacro function_from_string(kind, name, template, args \\ [], options \\ []) do
+  defmacro function_from_string(kind, name, source, args \\ [], options \\ []) do
    quote bind_quoted: binding() do
      info = Keyword.merge([file: __ENV__.file, line: __ENV__.line], options)
      args = Enum.map(args, fn arg -> {arg, [line: info[:line]], nil} end)
-      compiled = EEx.compile_string(template, info)
+      compiled = EEx.compile_string(source, info)

      case kind do
        :def -> def unquote(name)(unquote_splicing(args)), do: unquote(compiled)
@@ -148,17 +136,12 @@ defmodule EEx do
  @doc """
  Generates a function definition from the file contents.

-  The first argument is the kind of the generated function (`:def` or `:defp`).
-  The `name` argument is the name that the generated function will have.
-  `file` is the path to the EEx template file. `args` is a list of arguments
-  that the generated function will accept. They will be available inside the EEx
-  template.
+  The kind (`:def` or `:defp`) must be given, the
+  function name, its arguments and the compilation options.

  This function is useful in case you have templates but
  you want to precompile inside a module for speed.

-  The supported `options` are described [in the module docs](#module-options).
-
  ## Examples

      # sample.eex
@@ -177,7 +160,7 @@ defmodule EEx do
  """
  defmacro function_from_file(kind, name, file, args \\ [], options \\ []) do
    quote bind_quoted: binding() do
-      info = Keyword.merge([file: IO.chardata_to_string(file), line: 1], options)
+      info = Keyword.merge(options, file: file, line: 1)
      args = Enum.map(args, fn arg -> {arg, [line: 1], nil} end)
      compiled = EEx.compile_file(file, info)

@@ -191,86 +174,34 @@ defmodule EEx do
  end

  @doc """
-  Gets a string `source` and generates a quoted expression
+  Gets a string `source` and generate a quoted expression
  that can be evaluated by Elixir or compiled to a function.
-
-  This is useful if you want to compile a EEx template into code and inject
-  that code somewhere or evaluate it at runtime.
-
-  The generated quoted code will use variables defined in the template that
-  will be taken from the context where the code is evaluated. If you
-  have a template such as `<%= a + b %>`, then the returned quoted code
-  will use the `a` and `b` variables in the context where it's evaluated. See
-  examples below.
-
-  The supported `options` are described [in the module docs](#module-options).
-
-  ## Examples
-
-      iex> quoted = EEx.compile_string("<%= a + b %>")
-      iex> {result, _bindings} = Code.eval_quoted(quoted, a: 1, b: 2)
-      iex> result
-      "3"
-
  """
  @spec compile_string(String.t(), keyword) :: Macro.t()
  def compile_string(source, options \\ []) when is_binary(source) and is_list(options) do
-    case tokenize(source, options) do
-      {:ok, tokens} ->
-        EEx.Compiler.compile(tokens, options)
-
-      {:error, message, %{column: column, line: line}} ->
-        file = options[:file] || "nofile"
-        raise EEx.SyntaxError, file: file, line: line, column: column, message: message
-    end
+    EEx.Compiler.compile(source, options)
  end

  @doc """
-  Gets a `filename` and generates a quoted expression
+  Gets a `filename` and generate a quoted expression
  that can be evaluated by Elixir or compiled to a function.
-
-  This is useful if you want to compile a EEx template into code and inject
-  that code somewhere or evaluate it at runtime.
-
-  The generated quoted code will use variables defined in the template that
-  will be taken from the context where the code is evaluated. If you
-  have a template such as `<%= a + b %>`, then the returned quoted code
-  will use the `a` and `b` variables in the context where it's evaluated. See
-  examples below.
-
-  The supported `options` are described [in the module docs](#module-options).
-
-  ## Examples
-
-      # sample.eex
-      <%= a + b %>
-
-      # In code:
-      quoted = EEx.compile_file("sample.eex")
-      {result, _bindings} = Code.eval_quoted(quoted, a: 1, b: 2)
-      result
-      #=> "3"
-
  """
-  @spec compile_file(Path.t(), keyword) :: Macro.t()
-  def compile_file(filename, options \\ []) when is_list(options) do
-    filename = IO.chardata_to_string(filename)
-    options = Keyword.merge([file: filename, line: 1], options)
+  @spec compile_file(String.t(), keyword) :: Macro.t()
+  def compile_file(filename, options \\ []) when is_binary(filename) and is_list(options) do
+    options = Keyword.merge(options, file: filename, line: 1)
    compile_string(File.read!(filename), options)
  end

  @doc """
  Gets a string `source` and evaluate the values using the `bindings`.

-  The supported `options` are described [in the module docs](#module-options).
-
  ## Examples

      iex> EEx.eval_string("foo <%= bar %>", bar: "baz")
      "foo baz"

  """
-  @spec eval_string(String.t(), keyword, keyword) :: String.t()
+  @spec eval_string(String.t(), keyword, keyword) :: any
  def eval_string(source, bindings \\ [], options \\ [])
      when is_binary(source) and is_list(bindings) and is_list(options) do
    compiled = compile_string(source, options)
@@ -280,64 +211,24 @@ defmodule EEx do
  @doc """
  Gets a `filename` and evaluate the values using the `bindings`.

-  The supported `options` are described [in the module docs](#module-options).
-
  ## Examples

      # sample.eex
      foo <%= bar %>

-      # IEx
+      # iex
      EEx.eval_file("sample.eex", bar: "baz")
      #=> "foo baz"

  """
-  @spec eval_file(Path.t(), keyword, keyword) :: String.t()
+  @spec eval_file(String.t(), keyword, keyword) :: any
  def eval_file(filename, bindings \\ [], options \\ [])
-      when is_list(bindings) and is_list(options) do
-    filename = IO.chardata_to_string(filename)
-    options = Keyword.put_new(options, :file, filename)
+      when is_binary(filename) and is_list(bindings) and is_list(options) do
+    options = Keyword.put(options, :file, filename)
    compiled = compile_file(filename, options)
    do_eval(compiled, bindings, options)
  end

-  @doc """
-  Tokenize the given contents according to the given options.
-
-  ## Options
-
-    * `:line` - An integer to start as line. Default is 1.
-    * `:column` - An integer to start as column. Default is 1.
-    * `:indentation` - An integer that indicates the indentation. Default is 0.
-    * `:trim` - Tells the tokenizer to either trim the content or not. Default is false.
-    * `:file` - Can be either a file or a string "nofile".
-
-  ## Examples
-
-      iex> EEx.tokenize('foo', line: 1, column: 1)
-      {:ok, [{:text, 'foo', %{column: 1, line: 1}}, {:eof, %{column: 4, line: 1}}]}
-
-  ## Result
-
-  It returns `{:ok, [token]}` where a token is one of:
-
-    * `{:text, content, %{column: column, line: line}}`
-    * `{:expr, marker, content, %{column: column, line: line}}`
-    * `{:start_expr, marker, content, %{column: column, line: line}}`
-    * `{:middle_expr, marker, content, %{column: column, line: line}}`
-    * `{:end_expr, marker, content, %{column: column, line: line}}`
-    * `{:eof, %{column: column, line: line}}`
-
-  Or `{:error, message, %{column: column, line: line}}` in case of errors.
-  Note new tokens may be added in the future.
-  """
-  @doc since: "1.14.0"
-  @spec tokenize(IO.chardata(), opts :: keyword) ::
-          {:ok, [token()]} | {:error, String.t(), metadata()}
-  def tokenize(contents, opts \\ []) do
-    EEx.Compiler.tokenize(contents, opts)
-  end
-
  ### Helpers

  defp do_eval(compiled, bindings, options) do
@@ -3,345 +3,63 @@ defmodule EEx.Compiler do

  # When changing this setting, don't forget to update the docs for EEx
  @default_engine EEx.SmartEngine
-  @h_spaces [?\s, ?\t]
-  @all_spaces [?\s, ?\t, ?\n, ?\r]
-
-  @doc """
-  Tokenize EEx contents.
-  """
-  def tokenize(contents, opts) when is_binary(contents) do
-    tokenize(String.to_charlist(contents), opts)
-  end
-
-  def tokenize(contents, opts) when is_list(contents) do
-    file = opts[:file] || "nofile"
-    line = opts[:line] || 1
-    trim = opts[:trim] || false
-    indentation = opts[:indentation] || 0
-    column = indentation + (opts[:column] || 1)
-
-    state = %{trim: trim, indentation: indentation, file: file}
-
-    {contents, line, column} =
-      (trim && trim_init(contents, line, column, state)) || {contents, line, column}
-
-    tokenize(contents, line, column, state, [{line, column}], [])
-  end
-
-  defp tokenize('<%%' ++ t, line, column, state, buffer, acc) do
-    tokenize(t, line, column + 3, state, [?%, ?< | buffer], acc)
-  end
-
-  defp tokenize('<%!--' ++ t, line, column, state, buffer, acc) do
-    case comment(t, line, column + 5, state, []) do
-      {:error, line, column, message} ->
-        {:error, message, %{line: line, column: column}}
-
-      {:ok, new_line, new_column, rest, comments} ->
-        token = {:comment, Enum.reverse(comments), %{line: line, column: column}}
-        trim_and_tokenize(rest, new_line, new_column, state, buffer, acc, &[token | &1])
-    end
-  end
-
-  # TODO: Deprecate this on Elixir v1.18
-  defp tokenize('<%#' ++ t, line, column, state, buffer, acc) do
-    case expr(t, line, column + 3, state, []) do
-      {:error, line, column, message} ->
-        {:error, message, %{line: line, column: column}}
-
-      {:ok, _, new_line, new_column, rest} ->
-        trim_and_tokenize(rest, new_line, new_column, state, buffer, acc, & &1)
-    end
-  end
-
-  defp tokenize('<%' ++ t, line, column, state, buffer, acc) do
-    {marker, t} = retrieve_marker(t)
-
-    case expr(t, line, column + 2 + length(marker), state, []) do
-      {:error, line, column, message} ->
-        {:error, message, %{line: line, column: column}}
-
-      {:ok, expr, new_line, new_column, rest} ->
-        {key, expr} =
-          case :elixir_tokenizer.tokenize(expr, 1, file: "eex", check_terminators: false) do
-            {:ok, _line, _column, warnings, tokens} ->
-              Enum.each(Enum.reverse(warnings), fn {location, file, msg} ->
-                :elixir_errors.erl_warn(location, file, msg)
-              end)
-
-              token_key(tokens, expr)
-
-            {:error, _, _, _, _} ->
-              {:expr, expr}
-          end
-
-        marker =
-          if key in [:middle_expr, :end_expr] and marker != '' do
-            message =
-              "unexpected beginning of EEx tag \"<%#{marker}\" on \"<%#{marker}#{expr}%>\", " <>
-                "please remove \"#{marker}\""
-
-            :elixir_errors.erl_warn({line, column}, state.file, message)
-            ''
-          else
-            marker
-          end
-
-        token = {key, marker, expr, %{line: line, column: column}}
-        trim_and_tokenize(rest, new_line, new_column, state, buffer, acc, &[token | &1])
-    end
-  end
-
-  defp tokenize('\n' ++ t, line, _column, state, buffer, acc) do
-    tokenize(t, line + 1, state.indentation + 1, state, [?\n | buffer], acc)
-  end
-
-  defp tokenize([h | t], line, column, state, buffer, acc) do
-    tokenize(t, line, column + 1, state, [h | buffer], acc)
-  end
-
-  defp tokenize([], line, column, _state, buffer, acc) do
-    eof = {:eof, %{line: line, column: column}}
-    {:ok, Enum.reverse([eof | tokenize_text(buffer, acc)])}
-  end
-
-  defp trim_and_tokenize(rest, line, column, state, buffer, acc, fun) do
-    {rest, line, column, buffer} = trim_if_needed(rest, line, column, state, buffer)
-
-    acc = tokenize_text(buffer, acc)
-    tokenize(rest, line, column, state, [{line, column}], fun.(acc))
-  end
-
-  # Retrieve marker for <%
-
-  defp retrieve_marker([marker | t]) when marker in [?=, ?/, ?|] do
-    {[marker], t}
-  end
-
-  defp retrieve_marker(t) do
-    {'', t}
-  end
-
-  # Tokenize a multi-line comment until we find --%>
-
-  defp comment([?-, ?-, ?%, ?> | t], line, column, _state, buffer) do
-    {:ok, line, column + 4, t, buffer}
-  end
-
-  defp comment('\n' ++ t, line, _column, state, buffer) do
-    comment(t, line + 1, state.indentation + 1, state, '\n' ++ buffer)
-  end
-
-  defp comment([head | t], line, column, state, buffer) do
-    comment(t, line, column + 1, state, [head | buffer])
-  end
-
-  defp comment([], line, column, _state, _buffer) do
-    {:error, line, column, "missing token '--%>'"}
-  end
-
-  # Tokenize an expression until we find %>
-
-  defp expr([?%, ?> | t], line, column, _state, buffer) do
-    {:ok, Enum.reverse(buffer), line, column + 2, t}
-  end
-
-  defp expr('\n' ++ t, line, _column, state, buffer) do
-    expr(t, line + 1, state.indentation + 1, state, [?\n | buffer])
-  end
-
-  defp expr([h | t], line, column, state, buffer) do
-    expr(t, line, column + 1, state, [h | buffer])
-  end
-
-  defp expr([], line, column, _state, _buffer) do
-    {:error, line, column, "missing token '%>'"}
-  end
-
-  # Receives tokens and check if it is a start, middle or an end token.
-  defp token_key(tokens, expr) do
-    case {tokens, tokens |> Enum.reverse() |> drop_eol()} do
-      {[{:end, _} | _], [{:do, _} | _]} ->
-        {:middle_expr, expr}
-
-      {_, [{:do, _} | _]} ->
-        {:start_expr, maybe_append_space(expr)}
-
-      {_, [{:block_identifier, _, _} | _]} ->
-        {:middle_expr, maybe_append_space(expr)}
-
-      {[{:end, _} | _], [{:stab_op, _, _} | _]} ->
-        {:middle_expr, expr}
-
-      {_, [{:stab_op, _, _} | reverse_tokens]} ->
-        fn_index = Enum.find_index(reverse_tokens, &match?({:fn, _}, &1)) || :infinity
-        end_index = Enum.find_index(reverse_tokens, &match?({:end, _}, &1)) || :infinity
-
-        if end_index > fn_index do
-          {:start_expr, expr}
-        else
-          {:middle_expr, expr}
-        end
-
-      {tokens, _} ->
-        case Enum.drop_while(tokens, &closing_bracket?/1) do
-          [{:end, _} | _] -> {:end_expr, expr}
-          _ -> {:expr, expr}
-        end
-    end
-  end
-
-  defp drop_eol([{:eol, _} | rest]), do: drop_eol(rest)
-  defp drop_eol(rest), do: rest
-
-  defp maybe_append_space([?\s]), do: [?\s]
-  defp maybe_append_space([h]), do: [h, ?\s]
-  defp maybe_append_space([h | t]), do: [h | maybe_append_space(t)]
-
-  defp closing_bracket?({closing, _}) when closing in ~w"( [ {"a, do: true
-  defp closing_bracket?(_), do: false
-
-  # Tokenize the buffered text by appending
-  # it to the given accumulator.
-
-  defp tokenize_text([{_line, _column}], acc) do
-    acc
-  end
-
-  defp tokenize_text(buffer, acc) do
-    [{line, column} | buffer] = Enum.reverse(buffer)
-    [{:text, buffer, %{line: line, column: column}} | acc]
-  end
-
-  ## Trim
-
-  defp trim_if_needed(rest, line, column, state, buffer) do
-    if state.trim do
-      buffer = trim_left(buffer, 0)
-      {rest, line, column} = trim_right(rest, line, column, 0, state)
-      {rest, line, column, buffer}
-    else
-      {rest, line, column, buffer}
-    end
-  end
-
-  defp trim_init([h | t], line, column, state) when h in @h_spaces,
-    do: trim_init(t, line, column + 1, state)
-
-  defp trim_init([?\r, ?\n | t], line, _column, state),
-    do: trim_init(t, line + 1, state.indentation + 1, state)
-
-  defp trim_init([?\n | t], line, _column, state),
-    do: trim_init(t, line + 1, state.indentation + 1, state)
-
-  defp trim_init([?<, ?% | _] = rest, line, column, _state),
-    do: {rest, line, column}
-
-  defp trim_init(_, _, _, _), do: false
-
-  defp trim_left(buffer, count) do
-    case trim_whitespace(buffer, 0) do
-      {[?\n, ?\r | rest], _} -> trim_left(rest, count + 1)
-      {[?\n | rest], _} -> trim_left(rest, count + 1)
-      _ when count > 0 -> [?\n | buffer]
-      _ -> buffer
-    end
-  end
-
-  defp trim_right(rest, line, column, last_column, state) do
-    case trim_whitespace(rest, column) do
-      {[?\r, ?\n | rest], column} ->
-        trim_right(rest, line + 1, state.indentation + 1, column + 1, state)
-
-      {[?\n | rest], column} ->
-        trim_right(rest, line + 1, state.indentation + 1, column, state)
-
-      {[], column} ->
-        {[], line, column}
-
-      _ when last_column > 0 ->
-        {[?\n | rest], line - 1, last_column}
-
-      _ ->
-        {rest, line, column}
-    end
-  end
-
-  defp trim_whitespace([h | t], column) when h in @h_spaces, do: trim_whitespace(t, column + 1)
-  defp trim_whitespace(list, column), do: {list, column}

  @doc """
  This is the compilation entry point. It glues the tokenizer
  and the engine together by handling the tokens and invoking
  the engine every time a full expression or text is received.
  """
-  @spec compile([EEx.token()], keyword) :: Macro.t()
-  def compile(tokens, opts) do
+  @spec compile(String.t(), keyword) :: Macro.t()
+  def compile(source, opts) when is_binary(source) and is_list(opts) do
    file = opts[:file] || "nofile"
    line = opts[:line] || 1
-    parser_options = opts[:parser_options] || Code.get_compiler_option(:parser_options)
-    engine = opts[:engine] || @default_engine
+    column = 1
+    indentation = opts[:indentation] || 0
+    trim = opts[:trim] || false
+    tokenizer_options = %{trim: trim, indentation: indentation}

-    state = %{
-      engine: engine,
-      file: file,
-      line: line,
-      quoted: [],
-      start_line: nil,
-      start_column: nil,
-      parser_options: parser_options
-    }
+    case EEx.Tokenizer.tokenize(source, line, column, tokenizer_options) do
+      {:ok, tokens} ->
+        state = %{
+          engine: opts[:engine] || @default_engine,
+          file: file,
+          line: line,
+          quoted: [],
+          start_line: nil,
+          start_column: nil,
+          parser_options: Code.get_compiler_option(:parser_options)
+        }

-    init = state.engine.init(opts)
-    generate_buffer(tokens, init, [], state)
-  end
+        init = state.engine.init(opts)
+        generate_buffer(tokens, init, [], state)

-  # Ignore tokens related to comment.
-  defp generate_buffer([{:comment, _chars, _meta} | rest], buffer, scope, state) do
-    generate_buffer(rest, buffer, scope, state)
+      {:error, line, column, message} ->
+        raise EEx.SyntaxError, file: file, line: line, column: column, message: message
+    end
  end

  # Generates the buffers by handling each expression from the tokenizer.
  # It returns Macro.t/0 or it raises.

-  defp generate_buffer([{:text, chars, meta} | rest], buffer, scope, state) do
-    buffer =
-      if function_exported?(state.engine, :handle_text, 3) do
-        meta = [line: meta.line, column: meta.column]
-        state.engine.handle_text(buffer, meta, IO.chardata_to_string(chars))
-      else
-        # TODO: Deprecate this branch on Elixir v1.18.
-        # We should most likely move this check to init to emit the deprecation once.
-        state.engine.handle_text(buffer, IO.chardata_to_string(chars))
-      end
-
+  defp generate_buffer([{:text, _line, _column, chars} | rest], buffer, scope, state) do
+    buffer = state.engine.handle_text(buffer, IO.chardata_to_string(chars))
    generate_buffer(rest, buffer, scope, state)
  end

-  defp generate_buffer([{:expr, mark, chars, meta} | rest], buffer, scope, state) do
-    options =
-      [file: state.file, line: meta.line, column: column(meta.column, mark)] ++
-        state.parser_options
-
+  defp generate_buffer([{:expr, line, column, mark, chars} | rest], buffer, scope, state) do
+    options = [file: state.file, line: line, column: column(column, mark)] ++ state.parser_options
    expr = Code.string_to_quoted!(chars, options)
    buffer = state.engine.handle_expr(buffer, IO.chardata_to_string(mark), expr)
    generate_buffer(rest, buffer, scope, state)
  end

  defp generate_buffer(
-         [{:start_expr, mark, chars, meta} | rest],
+         [{:start_expr, start_line, start_column, mark, chars} | rest],
         buffer,
         scope,
         state
       ) do
-    if mark == '' do
-      message =
-        "the contents of this expression won't be output unless the EEx block starts with \"<%=\""
-
-      :elixir_errors.erl_warn({meta.line, meta.column}, state.file, message)
-    end
-
-    {rest, line, contents} = look_ahead_middle(rest, meta.line, chars) || {rest, meta.line, chars}
+    {contents, line, rest} = look_ahead_middle(rest, start_line, chars)

    {contents, rest} =
      generate_buffer(
@@ -352,8 +70,8 @@ defmodule EEx.Compiler do
          state
          | quoted: [],
            line: line,
-            start_line: meta.line,
-            start_column: column(meta.column, mark)
+            start_line: start_line,
+            start_column: column(start_column, mark)
        }
      )

@@ -362,31 +80,47 @@ defmodule EEx.Compiler do
  end

  defp generate_buffer(
-         [{:middle_expr, '', chars, meta} | rest],
+         [{:middle_expr, line, _column, '', chars} | rest],
         buffer,
         [current | scope],
         state
       ) do
-    {wrapped, state} = wrap_expr(current, meta.line, buffer, chars, state)
-    state = %{state | line: meta.line}
+    {wrapped, state} = wrap_expr(current, line, buffer, chars, state)
+    state = %{state | line: line}
    generate_buffer(rest, state.engine.handle_begin(buffer), [wrapped | scope], state)
  end

-  defp generate_buffer([{:middle_expr, _, chars, meta} | _], _buffer, [], state) do
+  defp generate_buffer(
+         [{:middle_expr, line, column, modifier, chars} | t],
+         buffer,
+         [_ | _] = scope,
+         state
+       ) do
+    message =
+      "unexpected beginning of EEx tag \"<%#{modifier}\" on \"<%#{modifier}#{chars}%>\", " <>
+        "please remove \"#{modifier}\" accordingly"
+
+    :elixir_errors.erl_warn(line, state.file, message)
+    generate_buffer([{:middle_expr, line, column, '', chars} | t], buffer, scope, state)
+    # TODO: Make this an error on Elixir v2.0 since it accidentally worked previously.
+    # raise EEx.SyntaxError, message: message, file: state.file, line: line
+  end
+
+  defp generate_buffer([{:middle_expr, line, column, _, chars} | _], _buffer, [], state) do
    raise EEx.SyntaxError,
      message: "unexpected middle of expression <%#{chars}%>",
      file: state.file,
-      line: meta.line,
-      column: meta.column
+      line: line,
+      column: column
  end

  defp generate_buffer(
-         [{:end_expr, '', chars, meta} | rest],
+         [{:end_expr, line, _column, '', chars} | rest],
         buffer,
         [current | _],
         state
       ) do
-    {wrapped, state} = wrap_expr(current, meta.line, buffer, chars, state)
+    {wrapped, state} = wrap_expr(current, line, buffer, chars, state)
    column = state.start_column
    options = [file: state.file, line: state.start_line, column: column] ++ state.parser_options
    tuples = Code.string_to_quoted!(wrapped, options)
@@ -394,24 +128,40 @@ defmodule EEx.Compiler do
    {buffer, rest}
  end

-  defp generate_buffer([{:end_expr, _, chars, meta} | _], _buffer, [], state) do
+  defp generate_buffer(
+         [{:end_expr, line, column, modifier, chars} | t],
+         buffer,
+         [_ | _] = scope,
+         state
+       ) do
+    message =
+      "unexpected beginning of EEx tag \"<%#{modifier}\" on end of " <>
+        "expression \"<%#{modifier}#{chars}%>\", please remove \"#{modifier}\" accordingly"
+
+    :elixir_errors.erl_warn(line, state.file, message)
+    generate_buffer([{:end_expr, line, column, '', chars} | t], buffer, scope, state)
+    # TODO: Make this an error on Elixir v2.0 since it accidentally worked previously.
+    # raise EEx.SyntaxError, message: message, file: state.file, line: line, column: column
+  end
+
+  defp generate_buffer([{:end_expr, line, column, _, chars} | _], _buffer, [], state) do
    raise EEx.SyntaxError,
      message: "unexpected end of expression <%#{chars}%>",
      file: state.file,
-      line: meta.line,
-      column: meta.column
+      line: line,
+      column: column
  end

-  defp generate_buffer([{:eof, _meta}], buffer, [], state) do
+  defp generate_buffer([{:eof, _, _}], buffer, [], state) do
    state.engine.handle_body(buffer)
  end

-  defp generate_buffer([{:eof, meta}], _buffer, _scope, state) do
+  defp generate_buffer([{:eof, line, column}], _buffer, _scope, state) do
    raise EEx.SyntaxError,
      message: "unexpected end of string, expected a closing '<% end %>'",
      file: state.file,
-      line: meta.line,
-      column: meta.column
+      line: line,
+      column: column
  end

  # Creates a placeholder and wrap it inside the expression block
@@ -428,27 +178,28 @@ defmodule EEx.Compiler do

  # Look middle expressions that immediately follow a start_expr

-  defp look_ahead_middle([{:comment, _comment, _meta} | rest], start, contents),
-    do: look_ahead_middle(rest, start, contents)
-
-  defp look_ahead_middle([{:text, text, _meta} | rest], start, contents) do
+  defp look_ahead_middle(
+         [{:text, _, _, text}, {:middle_expr, line, _, _, chars} | rest] = tokens,
+         start,
+         contents
+       ) do
    if only_spaces?(text) do
-      look_ahead_middle(rest, start, contents ++ text)
+      {contents ++ text ++ chars, line, rest}
    else
-      nil
+      {contents, start, tokens}
    end
  end

-  defp look_ahead_middle([{:middle_expr, _, chars, meta} | rest], _start, contents) do
-    {rest, meta.line, contents ++ chars}
+  defp look_ahead_middle([{:middle_expr, line, _column, _, chars} | rest], _start, contents) do
+    {contents ++ chars, line, rest}
  end

-  defp look_ahead_middle(_tokens, _start, _contents) do
-    nil
+  defp look_ahead_middle(tokens, start, contents) do
+    {contents, start, tokens}
  end

  defp only_spaces?(chars) do
-    Enum.all?(chars, &(&1 in @all_spaces))
+    Enum.all?(chars, &(&1 in [?\s, ?\t, ?\r, ?\n]))
  end

  # Changes placeholder to real expression
@@ -4,8 +4,10 @@ defmodule EEx.Engine do

  An engine needs to implement all callbacks below.

-  This module also ships with a default engine implementation
-  you can delegate to. See `EEx.SmartEngine` as an example.
+  An engine may also `use EEx.Engine` to get the default behaviour
+  but this is not advised. In such cases, if any of the callbacks
+  are overridden, they must call `super()` to delegate to the
+  underlying `EEx.Engine`.
  """

  @type state :: term
@@ -29,8 +31,7 @@ defmodule EEx.Engine do

  It must return the updated state.
  """
-  @callback handle_text(state, [line: pos_integer, column: pos_integer], text :: String.t()) ::
-              state
+  @callback handle_text(state, text :: String.t()) :: state

  @doc """
  Called for the dynamic/code parts of a template.
@@ -68,7 +69,6 @@ defmodule EEx.Engine do
  @callback handle_end(state) :: Macro.t()

  @doc false
-  @deprecated "Use explicit delegation to EEx.Engine instead"
  defmacro __using__(_) do
    quote do
      @behaviour EEx.Engine
@@ -90,7 +90,7 @@ defmodule EEx.Engine do
      end

      def handle_text(state, text) do
-        EEx.Engine.handle_text(state, [], text)
+        EEx.Engine.handle_text(state, text)
      end

      def handle_expr(state, marker, expr) do
@@ -147,7 +147,7 @@ defmodule EEx.Engine do
    end
  end

-  @doc "Default implementation for `c:init/1`."
+  @doc false
  def init(_opts) do
    %{
      binary: [],
@@ -156,18 +156,18 @@ defmodule EEx.Engine do
    }
  end

-  @doc "Default implementation for `c:handle_begin/1`."
+  @doc false
  def handle_begin(state) do
    check_state!(state)
    %{state | binary: [], dynamic: []}
  end

-  @doc "Default implementation for `c:handle_end/1`."
+  @doc false
  def handle_end(quoted) do
    handle_body(quoted)
  end

-  @doc "Default implementation for `c:handle_body/1`."
+  @doc false
  def handle_body(state) do
    check_state!(state)
    %{binary: binary, dynamic: dynamic} = state
@@ -176,16 +176,14 @@ defmodule EEx.Engine do
    {:__block__, [], Enum.reverse(dynamic)}
  end

-  @doc "Default implementation for `c:handle_text/3`."
-  def handle_text(state, _meta, text) do
-    check_state!(state)
+  @doc false
+  def handle_text(state, text) do
    %{binary: binary} = state
    %{state | binary: [text | binary]}
  end

-  @doc "Default implementation for `c:handle_expr/3`."
+  @doc false
  def handle_expr(state, "=", ast) do
-    check_state!(state)
    %{binary: binary, dynamic: dynamic, vars_count: vars_count} = state
    var = Macro.var(:"arg#{vars_count}", __MODULE__)

@@ -33,26 +33,10 @@ defmodule EEx.SmartEngine do

  """

-  @behaviour EEx.Engine
+  use EEx.Engine

-  @impl true
-  defdelegate init(opts), to: EEx.Engine
-
-  @impl true
-  defdelegate handle_body(state), to: EEx.Engine
-
-  @impl true
-  defdelegate handle_begin(state), to: EEx.Engine
-
-  @impl true
-  defdelegate handle_end(state), to: EEx.Engine
-
-  @impl true
-  defdelegate handle_text(state, meta, text), to: EEx.Engine
-
-  @impl true
-  def handle_expr(state, marker, expr) do
+  def handle_expr(buffer, mark, expr) do
    expr = Macro.prewalk(expr, &EEx.Engine.handle_assign/1)
-    EEx.Engine.handle_expr(state, marker, expr)
+    super(buffer, mark, expr)
  end
 end
@@ -0,0 +1,234 @@
+defmodule EEx.Tokenizer do
+  @moduledoc false
+
+  @type content :: IO.chardata()
+  @type line :: non_neg_integer
+  @type column :: non_neg_integer
+  @type marker :: '=' | '/' | '|' | ''
+  @type token ::
+          {:text, line, column, content}
+          | {:expr | :start_expr | :middle_expr | :end_expr, line, column, marker, content}
+          | {:eof, line, column}
+
+  @spaces [?\s, ?\t]
+
+  @doc """
+  Tokenizes the given charlist or binary.
+
+  It returns {:ok, list} with the following tokens:
+
+    * `{:text, line, column, content}`
+    * `{:expr, line, column, marker, content}`
+    * `{:start_expr, line, column, marker, content}`
+    * `{:middle_expr, line, column, marker, content}`
+    * `{:end_expr, line, column, marker, content}`
+    * `{:eof, line, column}`
+
+  Or `{:error, line, column, message}` in case of errors.
+  """
+  @spec tokenize(binary | charlist, line, column, map) ::
+          {:ok, [token]} | {:error, line, column, String.t()}
+
+  def tokenize(bin, line, column, opts) when is_binary(bin) do
+    tokenize(String.to_charlist(bin), line, column, opts)
+  end
+
+  def tokenize(list, line, column, opts)
+      when is_list(list) and is_integer(line) and line >= 0 and is_integer(column) and column >= 0 do
+    column = opts.indentation + column
+
+    {list, line, column} =
+      (opts.trim && trim_init(list, line, column, opts)) || {list, line, column}
+
+    tokenize(list, line, column, opts, [{line, column}], [])
+  end
+
+  defp tokenize('<%%' ++ t, line, column, opts, buffer, acc) do
+    tokenize(t, line, column + 3, opts, [?%, ?< | buffer], acc)
+  end
+
+  defp tokenize('<%#' ++ t, line, column, opts, buffer, acc) do
+    case expr(t, line, column + 3, opts, []) do
+      {:error, _, _, _} = error ->
+        error
+
+      {:ok, _, new_line, new_column, rest} ->
+        {rest, new_line, new_column, buffer} =
+          trim_if_needed(rest, new_line, new_column, opts, buffer)
+
+        acc = tokenize_text(buffer, acc)
+        tokenize(rest, new_line, new_column, opts, [{new_line, new_column}], acc)
+    end
+  end
+
+  defp tokenize('<%' ++ t, line, column, opts, buffer, acc) do
+    {marker, t} = retrieve_marker(t)
+
+    case expr(t, line, column + 2 + length(marker), opts, []) do
+      {:error, _, _, _} = error ->
+        error
+
+      {:ok, expr, new_line, new_column, rest} ->
+        {key, expr} =
+          case :elixir_tokenizer.tokenize(expr, 1, file: "eex", check_terminators: false) do
+            {:ok, tokens} -> token_key(tokens, expr)
+            {:error, _, _, _} -> {:expr, expr}
+          end
+
+        {rest, new_line, new_column, buffer} =
+          trim_if_needed(rest, new_line, new_column, opts, buffer)
+
+        acc = tokenize_text(buffer, acc)
+        final = {key, line, column, marker, expr}
+        tokenize(rest, new_line, new_column, opts, [{new_line, new_column}], [final | acc])
+    end
+  end
+
+  defp tokenize('\n' ++ t, line, _column, opts, buffer, acc) do
+    tokenize(t, line + 1, opts.indentation + 1, opts, [?\n | buffer], acc)
+  end
+
+  defp tokenize([h | t], line, column, opts, buffer, acc) do
+    tokenize(t, line, column + 1, opts, [h | buffer], acc)
+  end
+
+  defp tokenize([], line, column, _opts, buffer, acc) do
+    eof = {:eof, line, column}
+    {:ok, Enum.reverse([eof | tokenize_text(buffer, acc)])}
+  end
+
+  # Retrieve marker for <%
+
+  defp retrieve_marker([marker | t]) when marker in [?=, ?/, ?|] do
+    {[marker], t}
+  end
+
+  defp retrieve_marker(t) do
+    {'', t}
+  end
+
+  # Tokenize an expression until we find %>
+
+  defp expr([?%, ?> | t], line, column, _opts, buffer) do
+    {:ok, Enum.reverse(buffer), line, column + 2, t}
+  end
+
+  defp expr('\n' ++ t, line, _column, opts, buffer) do
+    expr(t, line + 1, opts.indentation + 1, opts, [?\n | buffer])
+  end
+
+  defp expr([h | t], line, column, opts, buffer) do
+    expr(t, line, column + 1, opts, [h | buffer])
+  end
+
+  defp expr([], line, column, _opts, _buffer) do
+    {:error, line, column, "missing token '%>'"}
+  end
+
+  # Receives tokens and check if it is a start, middle or an end token.
+  defp token_key(tokens, expr) do
+    case {tokens, Enum.reverse(tokens)} do
+      {[{:end, _} | _], [{:do, _} | _]} ->
+        {:middle_expr, expr}
+
+      {_, [{:do, _} | _]} ->
+        {:start_expr, maybe_append_space(expr)}
+
+      {_, [{:block_identifier, _, _} | _]} ->
+        {:middle_expr, maybe_append_space(expr)}
+
+      {[{:end, _} | _], [{:stab_op, _, _} | _]} ->
+        {:middle_expr, expr}
+
+      {_, [{:stab_op, _, _} | reverse_tokens]} ->
+        fn_index = Enum.find_index(reverse_tokens, &match?({:fn, _}, &1)) || :infinity
+        end_index = Enum.find_index(reverse_tokens, &match?({:end, _}, &1)) || :infinity
+
+        if end_index > fn_index do
+          {:start_expr, expr}
+        else
+          {:middle_expr, expr}
+        end
+
+      {tokens, _} ->
+        case Enum.drop_while(tokens, &closing_bracket?/1) do
+          [{:end, _} | _] -> {:end_expr, expr}
+          _ -> {:expr, expr}
+        end
+    end
+  end
+
+  defp maybe_append_space([?\s]), do: [?\s]
+  defp maybe_append_space([h]), do: [h, ?\s]
+  defp maybe_append_space([h | t]), do: [h | maybe_append_space(t)]
+
+  defp closing_bracket?({closing, _}) when closing in ~w"( [ {"a, do: true
+  defp closing_bracket?(_), do: false
+
+  # Tokenize the buffered text by appending
+  # it to the given accumulator.
+
+  defp tokenize_text([{_line, _column}], acc) do
+    acc
+  end
+
+  defp tokenize_text(buffer, acc) do
+    [{line, column} | buffer] = Enum.reverse(buffer)
+    [{:text, line, column, buffer} | acc]
+  end
+
+  defp trim_if_needed(rest, line, column, opts, buffer) do
+    if opts.trim do
+      buffer = trim_left(buffer, 0)
+      {rest, line, column} = trim_right(rest, line, column, 0, opts)
+      {rest, line, column, buffer}
+    else
+      {rest, line, column, buffer}
+    end
+  end
+
+  defp trim_init([h | t], line, column, opts) when h in @spaces,
+    do: trim_init(t, line, column + 1, opts)
+
+  defp trim_init([?\r, ?\n | t], line, _column, opts),
+    do: trim_init(t, line + 1, opts.indentation + 1, opts)
+
+  defp trim_init([?\n | t], line, _column, opts),
+    do: trim_init(t, line + 1, opts.indentation + 1, opts)
+
+  defp trim_init([?<, ?% | _] = rest, line, column, _opts),
+    do: {rest, line, column}
+
+  defp trim_init(_, _, _, _), do: false
+
+  defp trim_left(buffer, count) do
+    case trim_whitespace(buffer, 0) do
+      {[?\n, ?\r | rest], _} -> trim_left(rest, count + 1)
+      {[?\n | rest], _} -> trim_left(rest, count + 1)
+      _ when count > 0 -> [?\n | buffer]
+      _ -> buffer
+    end
+  end
+
+  defp trim_right(rest, line, column, last_column, opts) do
+    case trim_whitespace(rest, column) do
+      {[?\r, ?\n | rest], column} ->
+        trim_right(rest, line + 1, opts.indentation + 1, column + 1, opts)
+
+      {[?\n | rest], column} ->
+        trim_right(rest, line + 1, opts.indentation + 1, column, opts)
+
+      {[], column} ->
+        {[], line, column}
+
+      _ when last_column > 0 ->
+        {[?\n | rest], line - 1, last_column}
+
+      _ ->
+        {rest, line, column}
+    end
+  end
+
+  defp trim_whitespace([h | t], column) when h in @spaces, do: trim_whitespace(t, column + 1)
+  defp trim_whitespace(list, column), do: {list, column}
+end
@@ -43,15 +43,6 @@ defmodule EEx.SmartEngineTest do
    assert_received :found
  end

-  test "error with unused \"do\" block without \"<%=\" modifier" do
-    stderr =
-      ExUnit.CaptureIO.capture_io(:stderr, fn ->
-        assert_eval("", "<% if true do %>I'm invisible!<% end %>", assigns: %{})
-      end)
-
-    assert stderr =~ "the contents of this expression won't be output"
-  end
-
  defp assert_eval(expected, actual, binding \\ []) do
    result = EEx.eval_string(actual, binding, file: __ENV__.file, engine: EEx.SmartEngine)
    assert result == expected
@@ -2,67 +2,41 @@ Code.require_file("../test_helper.exs", __DIR__)

 defmodule EEx.TokenizerTest do
  use ExUnit.Case, async: true
+  require EEx.Tokenizer, as: T

-  @opts [indentation: 0, trim: false]
+  @opts %{indentation: 0, trim: false}

  test "simple chars lists" do
-    assert EEx.tokenize('foo', @opts) ==
-             {:ok, [{:text, 'foo', %{column: 1, line: 1}}, {:eof, %{column: 4, line: 1}}]}
+    assert T.tokenize('foo', 1, 1, @opts) == {:ok, [{:text, 1, 1, 'foo'}, {:eof, 1, 4}]}
  end

  test "simple strings" do
-    assert EEx.tokenize("foo", @opts) ==
-             {:ok, [{:text, 'foo', %{column: 1, line: 1}}, {:eof, %{column: 4, line: 1}}]}
+    assert T.tokenize("foo", 1, 1, @opts) == {:ok, [{:text, 1, 1, 'foo'}, {:eof, 1, 4}]}
  end

  test "strings with embedded code" do
-    assert EEx.tokenize('foo <% bar %>', @opts) ==
-             {:ok,
-              [
-                {:text, 'foo ', %{column: 1, line: 1}},
-                {:expr, '', ' bar ', %{column: 5, line: 1}},
-                {:eof, %{column: 14, line: 1}}
-              ]}
+    assert T.tokenize('foo <% bar %>', 1, 1, @opts) ==
+             {:ok, [{:text, 1, 1, 'foo '}, {:expr, 1, 5, '', ' bar '}, {:eof, 1, 14}]}
  end

  test "strings with embedded equals code" do
-    assert EEx.tokenize('foo <%= bar %>', @opts) ==
-             {:ok,
-              [
-                {:text, 'foo ', %{column: 1, line: 1}},
-                {:expr, '=', ' bar ', %{column: 5, line: 1}},
-                {:eof, %{column: 15, line: 1}}
-              ]}
+    assert T.tokenize('foo <%= bar %>', 1, 1, @opts) ==
+             {:ok, [{:text, 1, 1, 'foo '}, {:expr, 1, 5, '=', ' bar '}, {:eof, 1, 15}]}
  end

  test "strings with embedded slash code" do
-    assert EEx.tokenize('foo <%/ bar %>', @opts) ==
-             {:ok,
-              [
-                {:text, 'foo ', %{column: 1, line: 1}},
-                {:expr, '/', ' bar ', %{column: 5, line: 1}},
-                {:eof, %{column: 15, line: 1}}
-              ]}
+    assert T.tokenize('foo <%/ bar %>', 1, 1, @opts) ==
+             {:ok, [{:text, 1, 1, 'foo '}, {:expr, 1, 5, '/', ' bar '}, {:eof, 1, 15}]}
  end

  test "strings with embedded pipe code" do
-    assert EEx.tokenize('foo <%| bar %>', @opts) ==
-             {:ok,
-              [
-                {:text, 'foo ', %{column: 1, line: 1}},
-                {:expr, '|', ' bar ', %{column: 5, line: 1}},
-                {:eof, %{column: 15, line: 1}}
-              ]}
+    assert T.tokenize('foo <%| bar %>', 1, 1, @opts) ==
+             {:ok, [{:text, 1, 1, 'foo '}, {:expr, 1, 5, '|', ' bar '}, {:eof, 1, 15}]}
  end

  test "strings with more than one line" do
-    assert EEx.tokenize('foo\n<%= bar %>', @opts) ==
-             {:ok,
-              [
-                {:text, 'foo\n', %{column: 1, line: 1}},
-                {:expr, '=', ' bar ', %{column: 1, line: 2}},
-                {:eof, %{column: 11, line: 2}}
-              ]}
+    assert T.tokenize('foo\n<%= bar %>', 1, 1, @opts) ==
+             {:ok, [{:text, 1, 1, 'foo\n'}, {:expr, 2, 1, '=', ' bar '}, {:eof, 2, 11}]}
  end

  test "strings with more than one line and expression with more than one line" do
@@ -74,235 +48,157 @@ defmodule EEx.TokenizerTest do
    '''

    exprs = [
-      {:text, 'foo ', %{column: 1, line: 1}},
-      {:expr, '=', ' bar\n\nbaz ', %{column: 5, line: 1}},
-      {:text, '\n', %{column: 7, line: 3}},
-      {:expr, '', ' foo ', %{column: 1, line: 4}},
-      {:text, '\n', %{column: 10, line: 4}},
-      {:eof, %{column: 1, line: 5}}
+      {:text, 1, 1, 'foo '},
+      {:expr, 1, 5, '=', ' bar\n\nbaz '},
+      {:text, 3, 7, '\n'},
+      {:expr, 4, 1, '', ' foo '},
+      {:text, 4, 10, '\n'},
+      {:eof, 5, 1}
    ]

-    assert EEx.tokenize(string, @opts) == {:ok, exprs}
+    assert T.tokenize(string, 1, 1, @opts) == {:ok, exprs}
  end

  test "quotation" do
-    assert EEx.tokenize('foo <%% true %>', @opts) ==
-             {:ok,
-              [
-                {:text, 'foo <% true %>', %{column: 1, line: 1}},
-                {:eof, %{column: 16, line: 1}}
-              ]}
+    assert T.tokenize('foo <%% true %>', 1, 1, @opts) ==
+             {:ok, [{:text, 1, 1, 'foo <% true %>'}, {:eof, 1, 16}]}
  end

-  test "quotation with do-end" do
-    assert EEx.tokenize('foo <%% true do %>bar<%% end %>', @opts) ==
-             {:ok,
-              [
-                {:text, 'foo <% true do %>bar<% end %>', %{column: 1, line: 1}},
-                {:eof, %{column: 32, line: 1}}
-              ]}
+  test "quotation with do/end" do
+    assert T.tokenize('foo <%% true do %>bar<%% end %>', 1, 1, @opts) ==
+             {:ok, [{:text, 1, 1, 'foo <% true do %>bar<% end %>'}, {:eof, 1, 32}]}
  end

  test "quotation with interpolation" do
    exprs = [
-      {:text, 'a <% b ', %{column: 1, line: 1}},
-      {:expr, '=', ' c ', %{column: 9, line: 1}},
-      {:text, ' ', %{column: 17, line: 1}},
-      {:expr, '=', ' d ', %{column: 18, line: 1}},
-      {:text, ' e %> f', %{column: 26, line: 1}},
-      {:eof, %{column: 33, line: 1}}
+      {:text, 1, 1, 'a <% b '},
+      {:expr, 1, 9, '=', ' c '},
+      {:text, 1, 17, ' '},
+      {:expr, 1, 18, '=', ' d '},
+      {:text, 1, 26, ' e %> f'},
+      {:eof, 1, 33}
    ]

-    assert EEx.tokenize('a <%% b <%= c %> <%= d %> e %> f', @opts) == {:ok, exprs}
+    assert T.tokenize('a <%% b <%= c %> <%= d %> e %> f', 1, 1, @opts) == {:ok, exprs}
  end

  test "improperly formatted quotation with interpolation" do
    exprs = [
-      {:text, '<%% a <%= b %> c %>', %{column: 1, line: 1}},
-      {:eof, %{column: 22, line: 1}}
+      {:text, 1, 1, '<%% a <%= b %> c %>'},
+      {:eof, 1, 22}
    ]

-    assert EEx.tokenize('<%%% a <%%= b %> c %>', @opts) == {:ok, exprs}
+    assert T.tokenize('<%%% a <%%= b %> c %>', 1, 1, @opts) == {:ok, exprs}
  end

-  test "EEx comments" do
+  test "eex comments" do
    exprs = [
-      {:text, 'foo ', %{column: 1, line: 1}},
-      {:eof, %{column: 16, line: 1}}
+      {:text, 1, 1, 'foo '},
+      {:eof, 1, 16}
    ]

-    assert EEx.tokenize('foo <%# true %>', @opts) == {:ok, exprs}
-
-    exprs = [
-      {:text, 'foo ', %{column: 1, line: 1}},
-      {:eof, %{column: 8, line: 2}}
-    ]
-
-    assert EEx.tokenize('foo <%#\ntrue %>', @opts) == {:ok, exprs}
+    assert T.tokenize('foo <%# true %>', 1, 1, @opts) == {:ok, exprs}
  end

-  test "EEx comments with do-end" do
+  test "eex comments with do/end" do
    exprs = [
-      {:text, 'foo ', %{column: 1, line: 1}},
-      {:text, 'bar', %{column: 19, line: 1}},
-      {:eof, %{column: 32, line: 1}}
+      {:text, 1, 1, 'foo '},
+      {:text, 1, 19, 'bar'},
+      {:eof, 1, 32}
    ]

-    assert EEx.tokenize('foo <%# true do %>bar<%# end %>', @opts) == {:ok, exprs}
+    assert T.tokenize('foo <%# true do %>bar<%# end %>', 1, 1, @opts) == {:ok, exprs}
  end

-  test "EEx comments inside do-end" do
+  test "elixir comments" do
    exprs = [
-      {:start_expr, '', ' if true do ', %{column: 1, line: 1}},
-      {:text, 'bar', %{column: 31, line: 1}},
-      {:end_expr, [], ' end ', %{column: 34, line: 1}},
-      {:eof, %{column: 43, line: 1}}
+      {:text, 1, 1, 'foo '},
+      {:expr, 1, 5, [], ' true # this is a boolean '},
+      {:eof, 1, 35}
    ]

-    assert EEx.tokenize('<% if true do %><%# comment %>bar<% end %>', @opts) == {:ok, exprs}
-
-    exprs = [
-      {:start_expr, [], ' case true do ', %{column: 1, line: 1}},
-      {:middle_expr, '', ' true -> ', %{column: 33, line: 1}},
-      {:text, 'bar', %{column: 46, line: 1}},
-      {:end_expr, [], ' end ', %{column: 49, line: 1}},
-      {:eof, %{column: 58, line: 1}}
-    ]
-
-    assert EEx.tokenize('<% case true do %><%# comment %><% true -> %>bar<% end %>', @opts) ==
-             {:ok, exprs}
+    assert T.tokenize('foo <% true # this is a boolean %>', 1, 1, @opts) == {:ok, exprs}
  end

-  test "EEx multi-line comments" do
+  test "elixir comments with do/end" do
    exprs = [
-      {:text, 'foo ', %{column: 1, line: 1}},
-      {:comment, ' true ', %{column: 5, line: 1}},
-      {:text, ' bar', %{column: 20, line: 1}},
-      {:eof, %{column: 24, line: 1}}
+      {:start_expr, 1, 1, [], ' if true do # startif '},
+      {:text, 1, 27, 'text'},
+      {:end_expr, 1, 31, [], ' end # closeif '},
+      {:eof, 1, 50}
    ]

-    assert EEx.tokenize('foo <%!-- true --%> bar', @opts) == {:ok, exprs}
-
-    exprs = [
-      {:text, 'foo ', %{column: 1, line: 1}},
-      {:comment, ' \ntrue\n ', %{column: 5, line: 1}},
-      {:text, ' bar', %{column: 6, line: 3}},
-      {:eof, %{column: 10, line: 3}}
-    ]
-
-    assert EEx.tokenize('foo <%!-- \ntrue\n --%> bar', @opts) == {:ok, exprs}
-
-    exprs = [
-      {:text, 'foo ', %{column: 1, line: 1}},
-      {:comment, ' <%= true %> ', %{column: 5, line: 1}},
-      {:text, ' bar', %{column: 27, line: 1}},
-      {:eof, %{column: 31, line: 1}}
-    ]
-
-    assert EEx.tokenize('foo <%!-- <%= true %> --%> bar', @opts) == {:ok, exprs}
-  end
-
-  test "Elixir comments" do
-    exprs = [
-      {:text, 'foo ', %{column: 1, line: 1}},
-      {:expr, [], ' true # this is a boolean ', %{column: 5, line: 1}},
-      {:eof, %{column: 35, line: 1}}
-    ]
-
-    assert EEx.tokenize('foo <% true # this is a boolean %>', @opts) == {:ok, exprs}
-  end
-
-  test "Elixir comments with do-end" do
-    exprs = [
-      {:start_expr, [], ' if true do # startif ', %{column: 1, line: 1}},
-      {:text, 'text', %{column: 27, line: 1}},
-      {:end_expr, [], ' end # closeif ', %{column: 31, line: 1}},
-      {:eof, %{column: 50, line: 1}}
-    ]
-
-    assert EEx.tokenize('<% if true do # startif %>text<% end # closeif %>', @opts) ==
+    assert T.tokenize('<% if true do # startif %>text<% end # closeif %>', 1, 1, @opts) ==
             {:ok, exprs}
  end

  test "strings with embedded do end" do
    exprs = [
-      {:text, 'foo ', %{column: 1, line: 1}},
-      {:start_expr, '', ' if true do ', %{column: 5, line: 1}},
-      {:text, 'bar', %{column: 21, line: 1}},
-      {:end_expr, '', ' end ', %{column: 24, line: 1}},
-      {:eof, %{column: 33, line: 1}}
+      {:text, 1, 1, 'foo '},
+      {:start_expr, 1, 5, '', ' if true do '},
+      {:text, 1, 21, 'bar'},
+      {:end_expr, 1, 24, '', ' end '},
+      {:eof, 1, 33}
    ]

-    assert EEx.tokenize('foo <% if true do %>bar<% end %>', @opts) == {:ok, exprs}
+    assert T.tokenize('foo <% if true do %>bar<% end %>', 1, 1, @opts) == {:ok, exprs}
  end

  test "strings with embedded -> end" do
    exprs = [
-      {:text, 'foo ', %{column: 1, line: 1}},
-      {:start_expr, '', ' cond do ', %{column: 5, line: 1}},
-      {:middle_expr, '', ' false -> ', %{column: 18, line: 1}},
-      {:text, 'bar', %{column: 32, line: 1}},
-      {:middle_expr, '', ' true -> ', %{column: 35, line: 1}},
-      {:text, 'baz', %{column: 48, line: 1}},
-      {:end_expr, '', ' end ', %{column: 51, line: 1}},
-      {:eof, %{column: 60, line: 1}}
+      {:text, 1, 1, 'foo '},
+      {:start_expr, 1, 5, '', ' cond do '},
+      {:middle_expr, 1, 18, '', ' false -> '},
+      {:text, 1, 32, 'bar'},
+      {:middle_expr, 1, 35, '', ' true -> '},
+      {:text, 1, 48, 'baz'},
+      {:end_expr, 1, 51, '', ' end '},
+      {:eof, 1, 60}
    ]

-    assert EEx.tokenize('foo <% cond do %><% false -> %>bar<% true -> %>baz<% end %>', @opts) ==
+    assert T.tokenize('foo <% cond do %><% false -> %>bar<% true -> %>baz<% end %>', 1, 1, @opts) ==
             {:ok, exprs}
  end

-  test "strings with fn-end with newline" do
+  test "strings with multiple callbacks" do
    exprs = [
-      {:start_expr, '=', ' a fn ->\n', %{column: 1, line: 1}},
-      {:text, 'foo', %{column: 3, line: 2}},
-      {:end_expr, [], ' end ', %{column: 6, line: 2}},
-      {:eof, %{column: 15, line: 2}}
+      {:start_expr, 1, 1, '=', ' a fn -> '},
+      {:text, 1, 15, 'foo'},
+      {:middle_expr, 1, 18, '', ' end, fn -> '},
+      {:text, 1, 34, 'bar'},
+      {:end_expr, 1, 37, '', ' end '},
+      {:eof, 1, 46}
    ]

-    assert EEx.tokenize('<%= a fn ->\n%>foo<% end %>', @opts) ==
+    assert T.tokenize('<%= a fn -> %>foo<% end, fn -> %>bar<% end %>', 1, 1, @opts) ==
             {:ok, exprs}
  end

-  test "strings with multiple fn-end" do
+  test "strings with callback followed by do block" do
    exprs = [
-      {:start_expr, '=', ' a fn -> ', %{column: 1, line: 1}},
-      {:text, 'foo', %{column: 15, line: 1}},
-      {:middle_expr, '', ' end, fn -> ', %{column: 18, line: 1}},
-      {:text, 'bar', %{column: 34, line: 1}},
-      {:end_expr, '', ' end ', %{column: 37, line: 1}},
-      {:eof, %{column: 46, line: 1}}
+      {:start_expr, 1, 1, '=', ' a fn -> '},
+      {:text, 1, 15, 'foo'},
+      {:middle_expr, 1, 18, '', ' end do '},
+      {:text, 1, 30, 'bar'},
+      {:end_expr, 1, 33, '', ' end '},
+      {:eof, 1, 42}
    ]

-    assert EEx.tokenize('<%= a fn -> %>foo<% end, fn -> %>bar<% end %>', @opts) ==
-             {:ok, exprs}
-  end
-
-  test "strings with fn-end followed by do block" do
-    exprs = [
-      {:start_expr, '=', ' a fn -> ', %{column: 1, line: 1}},
-      {:text, 'foo', %{column: 15, line: 1}},
-      {:middle_expr, '', ' end do ', %{column: 18, line: 1}},
-      {:text, 'bar', %{column: 30, line: 1}},
-      {:end_expr, '', ' end ', %{column: 33, line: 1}},
-      {:eof, %{column: 42, line: 1}}
-    ]
-
-    assert EEx.tokenize('<%= a fn -> %>foo<% end do %>bar<% end %>', @opts) == {:ok, exprs}
+    assert T.tokenize('<%= a fn -> %>foo<% end do %>bar<% end %>', 1, 1, @opts) == {:ok, exprs}
  end

  test "strings with embedded keywords blocks" do
    exprs = [
-      {:text, 'foo ', %{column: 1, line: 1}},
-      {:start_expr, '', ' if true do ', %{column: 5, line: 1}},
-      {:text, 'bar', %{column: 21, line: 1}},
-      {:middle_expr, '', ' else ', %{column: 24, line: 1}},
-      {:text, 'baz', %{column: 34, line: 1}},
-      {:end_expr, '', ' end ', %{column: 37, line: 1}},
-      {:eof, %{column: 46, line: 1}}
+      {:text, 1, 1, 'foo '},
+      {:start_expr, 1, 5, '', ' if true do '},
+      {:text, 1, 21, 'bar'},
+      {:middle_expr, 1, 24, '', ' else '},
+      {:text, 1, 34, 'baz'},
+      {:end_expr, 1, 37, '', ' end '},
+      {:eof, 1, 46}
    ]

-    assert EEx.tokenize('foo <% if true do %>bar<% else %>baz<% end %>', @opts) ==
+    assert T.tokenize('foo <% if true do %>bar<% else %>baz<% end %>', 1, 1, @opts) ==
             {:ok, exprs}
  end

@@ -310,61 +206,51 @@ defmodule EEx.TokenizerTest do
    template = '\t<%= if true do %> \n TRUE \n  <% else %>\n FALSE \n  <% end %>  \n\n  '

    exprs = [
-      {:start_expr, '=', ' if true do ', %{column: 2, line: 1}},
-      {:text, '\n TRUE \n', %{column: 20, line: 1}},
-      {:middle_expr, '', ' else ', %{column: 3, line: 3}},
-      {:text, '\n FALSE \n', %{column: 13, line: 3}},
-      {:end_expr, '', ' end ', %{column: 3, line: 5}},
-      {:eof, %{column: 3, line: 7}}
+      {:start_expr, 1, 2, '=', ' if true do '},
+      {:text, 1, 20, '\n TRUE \n'},
+      {:middle_expr, 3, 3, '', ' else '},
+      {:text, 3, 13, '\n FALSE \n'},
+      {:end_expr, 5, 3, '', ' end '},
+      {:eof, 7, 3}
    ]

-    assert EEx.tokenize(template, [trim: true] ++ @opts) == {:ok, exprs}
+    assert T.tokenize(template, 1, 1, %{@opts | trim: true}) == {:ok, exprs}
  end

  test "trim mode with comment" do
    exprs = [
-      {:text, '\n123', %{column: 19, line: 1}},
-      {:eof, %{column: 4, line: 2}}
+      {:text, 1, 19, '\n123'},
+      {:eof, 2, 4}
    ]

-    assert EEx.tokenize('  <%# comment %>  \n123', [trim: true] ++ @opts) == {:ok, exprs}
-  end
-
-  test "trim mode with multi-line comment" do
-    exprs = [
-      {:comment, ' comment ', %{column: 3, line: 1}},
-      {:text, '\n123', %{column: 23, line: 1}},
-      {:eof, %{column: 4, line: 2}}
-    ]
-
-    assert EEx.tokenize('  <%!-- comment --%>  \n123', [trim: true] ++ @opts) == {:ok, exprs}
+    assert T.tokenize('  <%# comment %>  \n123', 1, 1, %{@opts | trim: true}) == {:ok, exprs}
  end

  test "trim mode with CRLF" do
    exprs = [
-      {:text, '0\n', %{column: 1, line: 1}},
-      {:expr, '=', ' 12 ', %{column: 3, line: 2}},
-      {:text, '\n34', %{column: 15, line: 2}},
-      {:eof, %{column: 3, line: 3}}
+      {:text, 1, 1, '0\n'},
+      {:expr, 2, 3, '=', ' 12 '},
+      {:text, 2, 15, '\n34'},
+      {:eof, 3, 3}
    ]

-    assert EEx.tokenize('0\r\n  <%= 12 %>  \r\n34', [trim: true] ++ @opts) == {:ok, exprs}
+    assert T.tokenize('0\r\n  <%= 12 %>  \r\n34', 1, 1, %{@opts | trim: true}) == {:ok, exprs}
  end

  test "trim mode set to false" do
    exprs = [
-      {:text, ' ', %{column: 1, line: 1}},
-      {:expr, '=', ' 12 ', %{column: 2, line: 1}},
-      {:text, ' \n', %{column: 11, line: 1}},
-      {:eof, %{column: 1, line: 2}}
+      {:text, 1, 1, ' '},
+      {:expr, 1, 2, '=', ' 12 '},
+      {:text, 1, 11, ' \n'},
+      {:eof, 2, 1}
    ]

-    assert EEx.tokenize(' <%= 12 %> \n', [trim: false] ++ @opts) == {:ok, exprs}
+    assert T.tokenize(' <%= 12 %> \n', 1, 1, %{@opts | trim: false}) == {:ok, exprs}
  end

  test "trim mode no false positives" do
    assert_not_trimmed = fn x ->
-      assert EEx.tokenize(x, [trim: false] ++ @opts) == EEx.tokenize(x, @opts)
+      assert T.tokenize(x, 1, 1, %{@opts | trim: false}) == T.tokenize(x, 1, 1, @opts)
    end

    assert_not_trimmed.('foo <%= "bar" %>  ')
@@ -374,22 +260,12 @@ defmodule EEx.TokenizerTest do
  end

  test "returns error when there is start mark and no end mark" do
-    assert EEx.tokenize('foo <% :bar', @opts) ==
-             {:error, "missing token '%>'", %{column: 12, line: 1}}
-
-    assert EEx.tokenize('<%# true ', @opts) ==
-             {:error, "missing token '%>'", %{column: 10, line: 1}}
-
-    assert EEx.tokenize('<%!-- foo ', @opts) ==
-             {:error, "missing token '--%>'", %{column: 11, line: 1}}
+    assert T.tokenize('foo <% :bar', 1, 1, @opts) == {:error, 1, 12, "missing token '%>'"}
+    assert T.tokenize('<%# true ', 1, 1, @opts) == {:error, 1, 10, "missing token '%>'"}
  end

  test "marks invalid expressions as regular expressions" do
-    assert EEx.tokenize('<% 1 $ 2 %>', @opts) ==
-             {:ok,
-              [
-                {:expr, [], ' 1 $ 2 ', %{column: 1, line: 1}},
-                {:eof, %{column: 12, line: 1}}
-              ]}
+    assert T.tokenize('<% 1 $ 2 %>', 1, 1, @opts) ==
+             {:ok, [{:expr, 1, 1, [], ' 1 $ 2 '}, {:eof, 1, 12}]}
  end
 end
@@ -87,11 +87,7 @@ defmodule EExTest do
      expected = "123\n456\n789"
      assert_eval(expected, string, [], trim: true)

-      string = "<%= 123 %> \n\n456\n\n  <%= 789 %>"
-      expected = "123\n456\n789"
-      assert_eval(expected, string, [], trim: true)
-
-      string = "<%= 123 %> \n  \n456\n  \n  <%= 789 %>"
+      string = "<%= 123 %> \n  <%= 456 %>  \n  <%= 789 %>"
      expected = "123\n456\n789"
      assert_eval(expected, string, [], trim: true)

@@ -198,24 +194,6 @@ defmodule EExTest do
      assert_eval("foo baz", "foo <%= if false do %>bar<% else %>baz<% end %>")
    end

-    test "embedded code with comments in do end" do
-      assert_eval("foo bar", "foo <%= case true do %><%# comment %><% true -> %>bar<% end %>")
-
-      assert_eval(
-        "foo\n\nbar\n",
-        "foo\n<%= case true do %>\n<%# comment %>\n<% true -> %>\nbar\n<% end %>"
-      )
-    end
-
-    test "embedded code with multi-line comments in do end" do
-      assert_eval("foo bar", "foo <%= case true do %><%!-- comment --%><% true -> %>bar<% end %>")
-
-      assert_eval(
-        "foo\n\nbar\n",
-        "foo\n<%= case true do %>\n<%!-- comment --%>\n<% true -> %>\nbar\n<% end %>"
-      )
-    end
-
    test "embedded code with nested do end" do
      assert_eval("foo bar", "foo <%= if true do %><%= if true do %>bar<% end %><% end %>")
    end
@@ -233,11 +211,6 @@ defmodule EExTest do
        "<%= Enum.map([1, 2, 3], fn x -> %> <%= 100 + x %> <% end) %>"
      )

-      assert_eval(
-        " 101  102  103 ",
-        "<%= Enum.map([1, 2, 3], fn x ->\n%> <%= 100 + x %> <% end) %>"
-      )
-
      assert_eval(
        " 101  102  103 ",
        "<%= apply Enum, :map, [[1, 2, 3], fn x -> %> <%= 100 + x %> <% end] %>"
@@ -283,7 +256,7 @@ defmodule EExTest do
      assert_raise EEx.SyntaxError,
                   "nofile:1:18: unexpected middle of expression <% else %>",
                   fn ->
-                     EEx.compile_string("<%= if true %>foo<% else %>bar<% end %>")
+                     EEx.compile_string("<% if true %> foo<% else %>bar<% end %>")
                   end
    end

@@ -294,16 +267,16 @@ defmodule EExTest do
    end

    test "when start expression is found without an end expression" do
-      msg = "nofile:2:18: unexpected end of string, expected a closing '<% end %>'"
+      msg = "nofile:2:17: unexpected end of string, expected a closing '<% end %>'"

      assert_raise EEx.SyntaxError, msg, fn ->
-        EEx.compile_string("foo\n<%= if true do %>")
+        EEx.compile_string("foo\n<% if true do %>")
      end
    end

    test "when nested end expression is found without a start expression" do
-      assert_raise EEx.SyntaxError, "nofile:1:31: unexpected end of expression <% end %>", fn ->
-        EEx.compile_string("foo <%= if true do %><% end %><% end %>")
+      assert_raise EEx.SyntaxError, "nofile:1:30: unexpected end of expression <% end %>", fn ->
+        EEx.compile_string("foo <% if true do %><% end %><% end %>")
      end
    end

@@ -317,7 +290,7 @@ defmodule EExTest do
      assert ExUnit.CaptureIO.capture_io(:stderr, fn ->
               EEx.compile_string("foo <%= if true do %>true<% else %>false<%= end %>")
             end) =~
-               ~s[unexpected beginning of EEx tag \"<%=\" on \"<%= end %>\"]
+               ~s[unexpected beginning of EEx tag \"<%=\" on end of expression \"<%= end %>\"]
    end

    test "when trying to use marker '/' without implementation" do
@@ -551,7 +524,7 @@ defmodule EExTest do
       <% "a" in y -> %>
        Good
       <% true -> %>
-        <%= if true do %>true<% else %>false<% end %>
+        <% if true do %>true<% else %>false<% end %>
        Bad
      <% end %>
      """
@@ -596,6 +569,18 @@ defmodule EExTest do
  end

  describe "buffers" do
+    test "unused buffers are kept out" do
+      string = """
+      <%= 123 %>
+      <% if true do %>
+        <%= 456 %>
+      <% end %>
+      <%= 789 %>
+      """
+
+      assert_eval("123\n\n789\n", string)
+    end
+
    test "inside comprehensions" do
      string = """
      <%= for _name <- packages || [] do %>
@@ -633,24 +618,6 @@ defmodule EExTest do
      assert EExTest.Compiled.__info__(:attributes)[:external_resource] ==
               [Path.join(__DIR__, "fixtures/eex_template_with_bindings.eex")]
    end
-
-    test "supports t:Path.t() paths" do
-      filename = to_charlist(Path.join(__DIR__, "fixtures/eex_template_with_bindings.eex"))
-      result = EEx.eval_file(filename, bar: 1)
-      assert_normalized_newline_equal("foo 1\n", result)
-    end
-
-    assert_raise EEx.SyntaxError, "my_file.eex:1:12: missing token '%>'", fn ->
-      EEx.compile_string("foo <%= bar", file: "my_file.eex")
-    end
-
-    test "supports overriding file and line through options" do
-      filename = Path.join(__DIR__, "fixtures/eex_template_with_syntax_error.eex")
-
-      assert_raise EEx.SyntaxError, "my_file.eex:11:1: missing token '%>'", fn ->
-        EEx.eval_file(filename, _bindings = [], file: "my_file.eex", line: 10)
-      end
-    end
  end

  describe "precompiled" do
@@ -696,8 +663,8 @@ defmodule EExTest do
      buffer <> ":END"
    end

-    def handle_text(buffer, meta, text) do
-      buffer <> ":TEXT-#{meta[:line]}-#{meta[:column]}(#{String.trim(text)})"
+    def handle_text(buffer, text) do
+      buffer <> ":TEXT(#{String.trim(text)})"
    end

    def handle_expr(buffer, "/", expr) do
@@ -715,16 +682,16 @@ defmodule EExTest do

  describe "custom engines" do
    test "text" do
-      assert_eval("BODY(INIT:TEXT-1-1(foo))", "foo", [], engine: TestEngine)
+      assert_eval("BODY(INIT:TEXT(foo))", "foo", [], engine: TestEngine)
    end

    test "custom marker" do
-      assert_eval("BODY(INIT:TEXT-1-1(foo):DIV(:bar))", "foo <%/ :bar %>", [], engine: TestEngine)
+      assert_eval("BODY(INIT:TEXT(foo):DIV(:bar))", "foo <%/ :bar %>", [], engine: TestEngine)
    end

    test "begin/end" do
      assert_eval(
-        ~s[BODY(INIT:TEXT-1-1(foo):EQUAL(if do\n  "BEGIN:TEXT-1-17(this):END"\nelse\n  "BEGIN:TEXT-1-31(that):END"\nend))],
+        ~s[BODY(INIT:TEXT(foo):EQUAL(if do\n  "BEGIN:TEXT(this):END"\nelse\n  "BEGIN:TEXT(that):END"\nend))],
        "foo <%= if do %>this<% else %>that<% end %>",
        [],
        engine: TestEngine
@@ -741,16 +708,6 @@ defmodule EExTest do
    end
  end

-  describe "parser options" do
-    test "customizes parsed code" do
-      atoms_encoder = fn "not_jose", _ -> {:ok, :jose} end
-
-      assert_eval("valid", "<%= not_jose %>", [jose: "valid"],
-        parser_options: [static_atoms_encoder: atoms_encoder]
-      )
-    end
-  end
-
  defp assert_eval(expected, actual, binding \\ [], opts \\ []) do
    opts = Keyword.merge([file: __ENV__.file, engine: opts[:engine] || EEx.Engine], opts)
    result = EEx.eval_string(actual, binding, opts)
@@ -1 +0,0 @@
-foo <%= bar
@@ -1,8 +1 @@
-{line_exclude, line_include} =
-  if line = System.get_env("LINE"), do: {[:test], [line: line]}, else: {[], []}
-
-ExUnit.start(
-  trace: !!System.get_env("TRACE"),
-  include: line_include,
-  exclude: line_exclude
-)
+ExUnit.start(trace: "--trace" in System.argv())
@@ -7,7 +7,7 @@ defmodule Access do

  `Access` supports keyword lists (`Keyword`) and maps (`Map`) out
  of the box. Keywords supports only atoms keys, keys for maps can
-  be of any type. Both return `nil` if the key does not exist:
+  be of any type. Both returns `nil` if the key does not exist:

      iex> keywords = [a: 1, b: 2]
      iex> keywords[:a]
@@ -47,11 +47,12 @@ defmodule Access do
  > `map[key]`, if your map is made of predefined atom keys,
  > you should prefer to access those atom keys with `map.key`
  > instead of `map[key]`, as `map.key` will raise if the key
-  > is missing (which is not supposed to happen if the keys are
-  > predefined). Similarly, since structs are maps and structs
-  > have predefined keys, they only allow the `struct.key`
-  > syntax and they do not allow the `struct[key]` access syntax.
-  > See the `Map` module for more information.
+  > is missing. This is important because, if a map has a predefined
+  > set of keys and a key is missing, it is most likely a bug
+  > in your software or a typo on the key name. For this reason,
+  > because structs are predefined in nature, they only allow
+  > the `struct.key` syntax and they do not allow the `struct[key]`
+  > access syntax. See the `Map` module for more information.

  ## Nested data structures

@@ -94,19 +95,21 @@ defmodule Access do

  @type container :: keyword | struct | map
  @type nil_container :: nil
-  @type t :: container | nil_container | any
+  @type any_container :: any
+  @type t :: container | nil_container | any_container
  @type key :: any
  @type value :: any

-  @type get_fun(data) ::
-          (:get, data, (term -> term) -> new_data :: container)
+  @type get_fun(data, get_value) ::
+          (:get, data, (term -> term) ->
+             {get_value, new_data :: container})

-  @type get_and_update_fun(data, current_value) ::
+  @type get_and_update_fun(data, get_value) ::
          (:get_and_update, data, (term -> term) ->
-             {current_value, new_data :: container} | :pop)
+             {get_value, new_data :: container} | :pop)

-  @type access_fun(data, current_value) ::
-          get_fun(data) | get_and_update_fun(data, current_value)
+  @type access_fun(data, get_value) ::
+          get_fun(data, get_value) | get_and_update_fun(data, get_value)

  @doc """
  Invoked in order to access the value stored under `key` in the given term `term`.
@@ -132,16 +135,16 @@ defmodule Access do

  The implementation of this callback should invoke `fun` with the value under
  `key` in the passed structure `data`, or with `nil` if `key` is not present in it.
-  This function must return either `{current_value, new_value}` or `:pop`.
+  This function must return either `{get_value, update_value}` or `:pop`.

-  If the passed function returns `{current_value, new_value}`,
-  the return value of this callback should be `{current_value, new_data}`, where:
+  If the passed function returns `{get_value, update_value}`,
+  the return value of this callback should be `{get_value, new_data}`, where:

-    * `current_value` is the retrieved value (which can be operated on before being returned)
+    * `get_value` is the retrieved value (which can be operated on before being returned)

-    * `new_value` is the new value to be stored under `key`
+    * `update_value` is the new value to be stored under `key`

-    * `new_data` is `data` after updating the value of `key` with `new_value`.
+    * `new_data` is `data` after updating the value of `key` with `update_value`.

  If the passed function returns `:pop`, the return value of this callback
  must be `{value, new_data}` where `value` is the value under `key`
@@ -150,9 +153,8 @@ defmodule Access do
  See the implementations of `Map.get_and_update/3` or `Keyword.get_and_update/3`
  for more examples.
  """
-  @callback get_and_update(data, key, (value | nil -> {current_value, new_value :: value} | :pop)) ::
-              {current_value, new_data :: data}
-            when current_value: value, data: container
+  @callback get_and_update(data, key, (value -> {get_value, value} | :pop)) :: {get_value, data}
+            when get_value: var, data: container | any_container

  @doc """
  Invoked to "pop" the value under `key` out of the given data structure.
@@ -166,18 +168,14 @@ defmodule Access do

  See the implementations for `Map.pop/3` or `Keyword.pop/3` for more examples.
  """
-  @callback pop(data, key) :: {value, data} when data: container
+  @callback pop(data, key) :: {value, data} when data: container | any_container

  defmacrop raise_undefined_behaviour(exception, module, top) do
    quote do
      exception =
        case __STACKTRACE__ do
          [unquote(top) | _] ->
-            reason =
-              "#{inspect(unquote(module))} does not implement the Access behaviour. " <>
-                "If you are using get_in/put_in/update_in, you can specify the field " <>
-                "to be accessed using Access.key!/1"
-
+            reason = "#{inspect(unquote(module))} does not implement the Access behaviour"
            %{unquote(exception) | reason: reason}

          _ ->
@@ -323,9 +321,9 @@ defmodule Access do
  a struct that implements the `Access` behaviour).

  The `fun` argument receives the value of `key` (or `nil` if `key` is not
-  present in `container`) and must return a two-element tuple `{current_value, new_value}`:
-  the "get" value `current_value` (the retrieved value, which can be operated on before
-  being returned) and the new value to be stored under `key` (`new_value`).
+  present in `container`) and must return a two-element tuple `{get_value, update_value}`:
+  the "get" value `get_value` (the retrieved value, which can be operated on before
+  being returned) and the new value to be stored under `key` (`update_value`).
  `fun` may also return `:pop`, which means the current value
  should be removed from the container and returned.

@@ -340,9 +338,8 @@ defmodule Access do
      {1, [a: 2]}

  """
-  @spec get_and_update(data, key, (value | nil -> {current_value, new_value :: value} | :pop)) ::
-          {current_value, new_data :: data}
-        when current_value: var, data: container
+  @spec get_and_update(data, key, (value -> {get_value, value} | :pop)) :: {get_value, data}
+        when get_value: var, data: container
  def get_and_update(container, key, fun)

  def get_and_update(%module{} = container, key, fun) do
@@ -425,7 +422,7 @@ defmodule Access do
  The returned function uses the default value if the key does not exist.
  This can be used to specify defaults and safely traverse missing keys:

-      iex> get_in(%{}, [Access.key(:user, %{}), Access.key(:name, "meg")])
+      iex> get_in(%{}, [Access.key(:user, %{name: "meg"}), Access.key(:name)])
      "meg"

  Such is also useful when using update functions, allowing us to introduce
@@ -448,11 +445,14 @@ defmodule Access do

  An error is raised if the accessed structure is not a map or a struct:

+      iex> get_in(nil, [Access.key(:foo)])
+      ** (BadMapError) expected a map, got: nil
+
      iex> get_in([], [Access.key(:foo)])
      ** (BadMapError) expected a map, got: []

  """
-  @spec key(key, term) :: access_fun(data :: struct | map, current_value :: term)
+  @spec key(key, term) :: access_fun(data :: struct | map, get_value :: term)
  def key(key, default \\ nil) do
    fn
      :get, data, next ->
@@ -496,7 +496,7 @@ defmodule Access do
      ** (RuntimeError) Access.key!/1 expected a map/struct, got: []

  """
-  @spec key!(key) :: access_fun(data :: struct | map, current_value :: term)
+  @spec key!(key) :: access_fun(data :: struct | map, get_value :: term)
  def key!(key) do
    fn
      :get, %{} = data, next ->
@@ -544,7 +544,7 @@ defmodule Access do
      ** (RuntimeError) Access.elem/1 expected a tuple, got: %{}

  """
-  @spec elem(non_neg_integer) :: access_fun(data :: tuple, current_value :: term)
+  @spec elem(non_neg_integer) :: access_fun(data :: tuple, get_value :: term)
  def elem(index) when is_integer(index) and index >= 0 do
    pos = index + 1

@@ -598,7 +598,7 @@ defmodule Access do
      ** (RuntimeError) Access.all/0 expected a list, got: %{}

  """
-  @spec all() :: access_fun(data :: list, current_value :: list)
+  @spec all() :: access_fun(data :: list, get_value :: list)
  def all() do
    &all/3
  end
@@ -673,7 +673,7 @@ defmodule Access do
      ** (RuntimeError) Access.at/1 expected a list, got: %{}

  """
-  @spec at(integer) :: access_fun(data :: list, current_value :: term)
+  @spec at(integer) :: access_fun(data :: list, get_value :: term)
  def at(index) when is_integer(index) do
    fn op, data, next -> at(op, data, index, next) end
  end
@@ -727,8 +727,7 @@ defmodule Access do
      ** (Enum.OutOfBoundsError) out of bounds error

  """
-  @doc since: "1.11.0"
-  @spec at!(integer) :: access_fun(data :: list, current_value :: term)
+  @spec at!(integer) :: access_fun(data :: list, get_value :: term)
  def at!(index) when is_integer(index) do
    fn op, data, next -> at!(op, data, index, next) end
  end
@@ -795,7 +794,7 @@ defmodule Access do

  """
  @doc since: "1.6.0"
-  @spec filter((term -> boolean)) :: access_fun(data :: list, current_value :: list)
+  @spec filter((term -> boolean)) :: access_fun(data :: list, get_value :: list)
  def filter(func) when is_function(func) do
    fn op, data, next -> filter(op, data, func, next) end
  end
@@ -829,118 +828,4 @@ defmodule Access do
  defp get_and_update_filter([], _func, _next, updates, gets) do
    {:lists.reverse(gets), :lists.reverse(updates)}
  end
-
-  @doc ~S"""
-  Returns a function that accesses all items of a list that are within the provided range.
-
-  The range will be normalized following the same rules from `Enum.slice/2`.
-
-  The returned function is typically passed as an accessor to `Kernel.get_in/2`,
-  `Kernel.get_and_update_in/3`, and friends.
-
-  ## Examples
-
-      iex> list = [%{name: "john", salary: 10}, %{name: "francine", salary: 30}, %{name: "vitor", salary: 25}]
-      iex> get_in(list, [Access.slice(1..2), :name])
-      ["francine", "vitor"]
-      iex> get_and_update_in(list, [Access.slice(1..3//2), :name], fn prev ->
-      ...>   {prev, String.upcase(prev)}
-      ...> end)
-      {["francine"], [%{name: "john", salary: 10}, %{name: "FRANCINE", salary: 30}, %{name: "vitor", salary: 25}]}
-
-  `slice/1` can also be used to pop elements out of a list or
-  a key inside of a list:
-
-      iex> list = [%{name: "john", salary: 10}, %{name: "francine", salary: 30}, %{name: "vitor", salary: 25}]
-      iex> pop_in(list, [Access.slice(-2..-1)])
-      {[%{name: "francine", salary: 30}, %{name: "vitor", salary: 25}], [%{name: "john", salary: 10}]}
-      iex> pop_in(list, [Access.slice(-2..-1), :name])
-      {["francine", "vitor"], [%{name: "john", salary: 10}, %{salary: 30}, %{salary: 25}]}
-
-  When no match is found, an empty list is returned and the update function is never called
-
-      iex> list = [%{name: "john", salary: 10}, %{name: "francine", salary: 30}, %{name: "vitor", salary: 25}]
-      iex> get_in(list, [Access.slice(5..10//2), :name])
-      []
-      iex> get_and_update_in(list, [Access.slice(5..10//2), :name], fn prev ->
-      ...>   {prev, String.upcase(prev)}
-      ...> end)
-      {[], [%{name: "john", salary: 10}, %{name: "francine", salary: 30}, %{name: "vitor", salary: 25}]}
-
-  An error is raised if the accessed structure is not a list:
-
-      iex> get_in(%{}, [Access.slice(2..10//3)])
-      ** (ArgumentError) Access.slice/1 expected a list, got: %{}
-
-  An error is raised if the step of the range is negative:
-
-      iex> get_in([], [Access.slice(2..10//-1)])
-      ** (ArgumentError) Access.slice/1 does not accept ranges with negative steps, got: 2..10//-1
-
-  """
-  @doc since: "1.14"
-  @spec slice(Range.t()) :: access_fun(data :: list, current_value :: list)
-  def slice(%Range{} = range) do
-    if range.step > 0 do
-      fn op, data, next -> slice(op, data, range, next) end
-    else
-      raise ArgumentError,
-            "Access.slice/1 does not accept ranges with negative steps, got: #{inspect(range)}"
-    end
-  end
-
-  defp slice(:get, data, %Range{} = range, next) when is_list(data) do
-    data
-    |> Enum.slice(range)
-    |> Enum.map(next)
-  end
-
-  defp slice(:get_and_update, data, range, next) when is_list(data) do
-    range = normalize_range(range, data)
-
-    if range.first > range.last do
-      {[], data}
-    else
-      get_and_update_slice(data, range, next, [], [], 0)
-    end
-  end
-
-  defp slice(_op, data, _range, _next) do
-    raise ArgumentError, "Access.slice/1 expected a list, got: #{inspect(data)}"
-  end
-
-  defp normalize_range(%Range{first: first, last: last, step: step}, list)
-       when first < 0 or last < 0 do
-    count = length(list)
-    first = if first >= 0, do: first, else: Kernel.max(first + count, 0)
-    last = if last >= 0, do: last, else: last + count
-    Range.new(first, last, step)
-  end
-
-  defp normalize_range(range, _list), do: range
-
-  defp get_and_update_slice([head | rest], range, next, updates, gets, index) do
-    if index in range do
-      case next.(head) do
-        :pop ->
-          get_and_update_slice(rest, range, next, updates, [head | gets], index + 1)
-
-        {get, update} ->
-          get_and_update_slice(
-            rest,
-            range,
-            next,
-            [update | updates],
-            [get | gets],
-            index + 1
-          )
-      end
-    else
-      get_and_update_slice(rest, range, next, [head | updates], gets, index + 1)
-    end
-  end
-
-  defp get_and_update_slice([], _range, _next, updates, gets, _index) do
-    {:lists.reverse(gets), :lists.reverse(updates)}
-  end
 end
@@ -241,7 +241,7 @@ defmodule Agent do
  and the start function will return `{:error, :timeout}`.

  If the `:debug` option is present, the corresponding function in the
-  [`:sys` module](`:sys`) will be invoked.
+  [`:sys` module](http://www.erlang.org/doc/man/sys.html) will be invoked.

  If the `:spawn_opt` option is present, its value will be passed as options
  to the underlying process as in `Process.spawn/4`.
@@ -42,32 +42,18 @@ defmodule Application do
      end

  In Mix projects, the environment of the application and its dependencies can
-  be overridden via the `config/config.exs` and `config/runtime.exs` files. The
-  former is loaded at build-time, before your code compiles, and the latter at
-  runtime, just before your app starts. For example, someone using your application
-  can override its `:db_host` environment variable as follows:
+  be overridden via the `config/config.exs` file. For example, someone using
+  your application can override its `:db_host` environment variable as follows:

      import Config
      config :my_app, :db_host, "db.local"

-  See the "Configuration" section in the `Mix` module for more information.
  You can also change the application environment dynamically by using functions
-  such as `put_env/3` and `delete_env/2`.
+  such as `put_env/3` and `delete_env/2`. However, as a rule of thumb, each application
+  is responsible for its own environment. Please do not use the functions in this
+  module for directly accessing or modifying the environment of other applications.

-  > Note: The config files `config/config.exs` and `config/runtime.exs`
-  > are rarely used by libraries. Libraries typically define their environment
-  > in the `def application` function of their `mix.exs`. Configuration files
-  > are rather used by applications to configure their libraries.
-
-  > Note: Each application is responsible for its own environment. Do not
-  > use the functions in this module for directly accessing or modifying
-  > the environment of other applications. Whenever you change the application
-  > environment, Elixir's build tool will only recompile the files that
-  > belong to that application. So if you read the application environment
-  > of another application, there is a chance you will be depending on
-  > outdated configuration, as your file won't be recompiled as it changes.
-
-  ## Compile-time environment
+  ### Compile-time environment

  In the previous example, we read the application environment at runtime:

@@ -85,48 +71,36 @@ defmodule Application do
  will only be read when `MyApp.DBClient` effectively starts. While reading
  the application environment at runtime is the preferred approach, in some
  rare occasions you may want to use the application environment to configure
-  the compilation of a certain project. However, if you try to access
-  `Application.fetch_env!/2` outside of a function:
+  the compilation of a certain project. This is often done by calling `get_env/3`
+  outside of a function:

      defmodule MyApp.DBClient do
-        @db_host Application.fetch_env!(:my_app, :db_host)
+        @db_host Application.get_env(:my_app, :db_host, "db.local")

        def start_link() do
          SomeLib.DBClient.start_link(host: @db_host)
        end
      end

-  You might see warnings and errors:
+  This approach has one big limitation: if you change the value of the
+  application environment after the code is compiled, the value used at
+  runtime is not going to change! For example, if your `config/runtime.exs`
+  has:

-      warning: Application.fetch_env!/2 is discouraged in the module body,
-      use Application.compile_env/3 instead
-        iex:3: MyApp.DBClient
+      config :my_app, :db_host, "db.production"

-      ** (ArgumentError) could not fetch application environment :db_host
-      for application :my_app because the application was not loaded nor
-      configured
+  This value will have no effect as the code was compiled to connect to "db.local",
+  which is mostly likely unavailable in the production environment.

-  This happens because, when defining modules, the application environment
-  is not yet available. Luckily, the warning tells us how to solve this
-  issue, by using `Application.compile_env/3` instead:
+  For those reasons, reading the application environment at runtime should be the
+  first choice. However, if you really have to read the application environment
+  during compilation, we recommend you to use `compile_env/3` instead:

-      defmodule MyApp.DBClient do
-        @db_host Application.compile_env(:my_app, :db_host, "db.local")
+      @db_host Application.compile_env(:my_app, :db_host, "db.local")

-        def start_link() do
-          SomeLib.DBClient.start_link(host: @db_host)
-        end
-      end
-
-  The difference here is that `compile_env` expects the default value to be
-  given as an argument, instead of using the `def application` function of
-  your `mix.exs`. Furthermore, by using `compile_env/3`, tools like Mix will
-  store the values used during compilation and compare the compilation values
-  with the runtime values whenever your system starts, raising an error in
-  case they differ.
-
-  In any case, compile-time environments should be avoided. Whenever possible,
-  reading the application environment at runtime should be the first choice.
+  By using `compile_env/3`, tools like Mix will store the values used during
+  compilation and compare the compilation values with the runtime values whenever
+  your system starts, raising an error in case they differ.

  ## The application callback module

@@ -189,7 +163,7 @@ defmodule Application do
  In the sections above, we have configured an application in the
  `application/0` section of the `mix.exs` file. Ultimately, Mix will use
  this configuration to create an [*application resource
-  file*](https://www.erlang.org/doc/man/application.html), which is a file called
+  file*](http://erlang.org/doc/man/app.html), which is a file called
  `APP_NAME.app`. For example, the application resource file of the OTP
  application `ex_unit` is called `ex_unit.app`.

@@ -293,10 +267,11 @@ defmodule Application do
  ## Further information

  For further details on applications please check the documentation of the
-  [`:application` Erlang module](`:application`), and the
-  [Applications](https://www.erlang.org/doc/design_principles/applications.html)
+  [`application`](http://www.erlang.org/doc/man/application.html) Erlang module,
+  and the
+  [Applications](http://www.erlang.org/doc/design_principles/applications.html)
  section of the [OTP Design Principles User's
-  Guide](https://www.erlang.org/doc/design_principles/users_guide.html).
+  Guide](http://erlang.org/doc/design_principles/users_guide.html).
  """

  @doc """
@@ -411,7 +386,6 @@ defmodule Application do
    :maxT,
    :registered,
    :included_applications,
-    :optional_applications,
    :applications,
    :mod,
    :start_phases
@@ -525,34 +499,21 @@ defmodule Application do
  Giving a path is useful to let Elixir know that only certain paths
  in a large configuration are compile time dependent.
  """
+  # TODO: Warn on v1.14 if get_env/fetch_env/fetch_env! is used at compile time instead of compile_env
  @doc since: "1.10.0"
  @spec compile_env(app, key | list, value) :: value
-  defmacro compile_env(app, key_or_path, default \\ nil) do
+  defmacro compile_env(app, key_or_path, default \\ nil) when is_atom(app) do
    if __CALLER__.function do
      raise "Application.compile_env/3 cannot be called inside functions, only in the module body"
    end

-    key_or_path = Macro.expand_literals(key_or_path, %{__CALLER__ | function: {:__info__, 1}})
-
    quote do
-      Application.compile_env(__ENV__, unquote(app), unquote(key_or_path), unquote(default))
+      Application.__compile_env__(unquote(app), unquote(key_or_path), unquote(default), __ENV__)
    end
  end

-  @doc """
-  Reads the application environment at compilation time from a macro.
-
-  Typically, developers will use `compile_env/3`. This function must
-  only be invoked from macros which aim to read the compilation environment
-  dynamically.
-
-  It expects a `Macro.Env` as first argument, where the `Macro.Env` is
-  typically the `__CALLER__` in a macro. It raises if `Macro.Env` comes
-  from a function.
-  """
-  @doc since: "1.14.0"
-  @spec compile_env(Macro.Env.t(), app, key | list, value) :: value
-  def compile_env(%Macro.Env{} = env, app, key_or_path, default) do
+  @doc false
+  def __compile_env__(app, key_or_path, default, env) do
    case fetch_compile_env(app, key_or_path, env) do
      {:ok, value} -> value
      :error -> default
@@ -567,33 +528,18 @@ defmodule Application do
  """
  @doc since: "1.10.0"
  @spec compile_env!(app, key | list) :: value
-  defmacro compile_env!(app, key_or_path) do
+  defmacro compile_env!(app, key_or_path) when is_atom(app) do
    if __CALLER__.function do
      raise "Application.compile_env!/2 cannot be called inside functions, only in the module body"
    end

-    key_or_path = Macro.expand_literals(key_or_path, %{__CALLER__ | function: {:__info__, 1}})
-
    quote do
-      Application.compile_env!(__ENV__, unquote(app), unquote(key_or_path))
+      Application.__compile_env__!(unquote(app), unquote(key_or_path), __ENV__)
    end
  end

-  @doc """
-  Reads the application environment at compilation time from a macro
-  or raises.
-
-  Typically, developers will use `compile_env!/2`. This function must
-  only be invoked from macros which aim to read the compilation environment
-  dynamically.
-
-  It expects a `Macro.Env` as first argument, where the `Macro.Env` is
-  typically the `__CALLER__` in a macro. It raises if `Macro.Env` comes
-  from a function.
-  """
-  @doc since: "1.14.0"
-  @spec compile_env!(Macro.Env.t(), app, key | list) :: value
-  def compile_env!(%Macro.Env{} = env, app, key_or_path) do
+  @doc false
+  def __compile_env__!(app, key_or_path, env) do
    case fetch_compile_env(app, key_or_path, env) do
      {:ok, value} ->
        value
@@ -605,9 +551,8 @@ defmodule Application do
    end
  end

-  defp fetch_compile_env(app, key, env) when is_atom(key) do
-    fetch_compile_env(app, key, [], env)
-  end
+  defp fetch_compile_env(app, key, env) when is_atom(key),
+    do: fetch_compile_env(app, key, [], env)

  defp fetch_compile_env(app, [key | paths], env) when is_atom(key),
    do: fetch_compile_env(app, key, paths, env)
@@ -632,13 +577,14 @@ defmodule Application do
  If the configuration parameter does not exist, the function returns the
  `default` value.

-  > **Important:** you must use this function to read only your own application
-  > environment. Do not read the environment of other applications.
+  **Important:** if you are reading the application environment at compilation
+  time, for example, inside the module definition instead of inside of a
+  function, see `compile_env/3` instead.

-  > **Important:** if you are writing a library to be used by other developers,
-  > it is generally recommended to avoid the application environment, as the
-  > application environment is effectively a global storage. For more information,
-  > read our [library guidelines](library-guidelines.md).
+  **Important:** if you are writing a library to be used by other developers,
+  it is generally recommended to avoid the application environment, as the
+  application environment is effectively a global storage. For more information,
+  read our [library guidelines](library-guidelines.md).

  ## Examples

@@ -665,18 +611,10 @@ defmodule Application do

  Our database engine used by `:my_app` needs to know what databases exist, and
  what the database configurations are. The database engine can make a call to
-  `Application.get_env(:my_app, :my_app_databases, [])` to retrieve the list of
-  databases (specified by module names).
-
-  The engine can then traverse each repository in the list and call
-  `Application.get_env(:my_app, Databases.RepoOne)` and so forth to retrieve the
-  configuration of each one. In this case, each configuration will be a keyword
-  list, so you can use the functions in the `Keyword` module or even the `Access`
-  module to traverse it, for example:
-
-      config = Application.get_env(:my_app, Databases.RepoOne)
-      config[:ip]
-
+  `get_env(:my_app, :my_app_databases)` to retrieve the list of databases (specified
+  by module names). Our database engine can then traverse each repository in the
+  list and then call `get_env(:my_app, Databases.RepoOne)` and so forth to retrieve
+  the configuration of each one.
  """
  @spec get_env(app, key, value) :: value
  def get_env(app, key, default \\ nil) when is_atom(app) do
@@ -688,14 +626,6 @@ defmodule Application do
  Returns the value for `key` in `app`'s environment in a tuple.

  If the configuration parameter does not exist, the function returns `:error`.
-
-  > **Important:** you must use this function to read only your own application
-  > environment. Do not read the environment of other applications.
-
-  > **Important:** if you are writing a library to be used by other developers,
-  > it is generally recommended to avoid the application environment, as the
-  > application environment is effectively a global storage. For more information,
-  > read our [library guidelines](library-guidelines.md).
  """
  @spec fetch_env(app, key) :: {:ok, value} | :error
  def fetch_env(app, key) when is_atom(app) do
@@ -712,13 +642,9 @@ defmodule Application do

  If the configuration parameter does not exist, raises `ArgumentError`.

-  > **Important:** you must use this function to read only your own application
-  > environment. Do not read the environment of other applications.
-
-  > **Important:** if you are writing a library to be used by other developers,
-  > it is generally recommended to avoid the application environment, as the
-  > application environment is effectively a global storage. For more information,
-  > read our [library guidelines](library-guidelines.md).
+  **Important:** if you are reading the application environment at compilation
+  time, for example, inside the module definition instead of inside of a
+  function, see `compile_env!/2` instead.
  """
  @spec fetch_env!(app, key) :: value
  def fetch_env!(app, key) when is_atom(app) do
@@ -768,6 +694,9 @@ defmodule Application do
    :application.set_env(app, key, value, opts)
  end

+  # TODO: Remove this once we support Erlang/OTP 22+ exclusively.
+  @compile {:no_warn_undefined, {:application, :set_env, 2}}
+
  @doc """
  Puts the environment for multiple apps at the same time.

@@ -776,14 +705,28 @@ defmodule Application do
    * have the same application listed more than once
    * have the same key inside the same application listed more than once

-  If those conditions are not met, it will raise.
+  If those conditions are not met, the behaviour is undefined
+  (on Erlang/OTP 21 and earlier) or will raise (on Erlang/OTP 22
+  and later).

  It receives the same options as `put_env/4`. Returns `:ok`.
  """
  @doc since: "1.9.0"
  @spec put_all_env([{app, [{key, value}]}], timeout: timeout, persistent: boolean) :: :ok
  def put_all_env(config, opts \\ []) when is_list(config) and is_list(opts) do
-    :application.set_env(config, opts)
+    # TODO: Remove function exported? check when we require Erlang/OTP 22+
+    if function_exported?(:application, :set_env, 2) do
+      :application.set_env(config, opts)
+    else
+      for app_keyword <- config,
+          {app, keyword} = app_keyword,
+          key_value <- keyword,
+          {key, value} = key_value do
+        :application.set_env(app, key, value, opts)
+      end
+
+      :ok
+    end
  end

  @doc """
@@ -800,7 +743,6 @@ defmodule Application do
  defp maybe_warn_on_app_env_key(_app, key) when is_atom(key),
    do: :ok

-  # TODO: Remove this deprecation warning on 2.0+ and allow list lookups as in compile_env.
  defp maybe_warn_on_app_env_key(app, key) do
    message = "passing non-atom as application env key is deprecated, got: #{inspect(key)}"
    IO.warn_once({Application, :key, app, key}, message, _stacktrace_drop_levels = 2)
@@ -824,7 +766,7 @@ defmodule Application do
  @doc """
  Ensures the given `app` is loaded.

-  Same as `load/1` but returns `:ok` if the application was already
+  Same as `load/2` but returns `:ok` if the application was already
  loaded.
  """
  @doc since: "1.10.0"
@@ -945,7 +887,7 @@ defmodule Application do
      #=> "bar-123"

  For more information on code paths, check the `Code` module in
-  Elixir and also Erlang's [`:code` module](`:code`).
+  Elixir and also Erlang's [`:code` module](http://www.erlang.org/doc/man/code.html).
  """
  @spec app_dir(app) :: String.t()
  def app_dir(app) when is_atom(app) do
@@ -56,7 +56,7 @@ defmodule Atom do
  """
  @spec to_string(atom) :: String.t()
  def to_string(atom) do
-    :erlang.atom_to_binary(atom)
+    :erlang.atom_to_binary(atom, :utf8)
  end

  @doc """
@@ -4,7 +4,7 @@ defmodule Behaviour do

  This module is deprecated. Instead of `defcallback/1` and
  `defmacrocallback/1`, the `@callback` and `@macrocallback`
-  module attributes can be used respectively. See the
+  module attributes can be used (respectively). See the
  documentation for `Module` for more information on these
  attributes.

@@ -17,7 +17,6 @@ defmodule Behaviour do
  @doc """
  Defines a function callback according to the given type specification.
  """
-  @deprecated "Use the @callback module attribute instead"
  defmacro defcallback(spec) do
    do_defcallback(:def, split_spec(spec, quote(do: term)))
  end
@@ -25,7 +24,6 @@ defmodule Behaviour do
  @doc """
  Defines a macro callback according to the given type specification.
  """
-  @deprecated "Use the @macrocallback module attribute instead"
  defmacro defmacrocallback(spec) do
    do_defcallback(:defmacro, split_spec(spec, quote(do: Macro.t())))
  end
@@ -3,11 +3,31 @@ defmodule Bitwise do
  A set of functions that perform calculations on bits.

  All bitwise functions work only on integers; otherwise an
-  `ArithmeticError` is raised. The functions `band/2`,
-  `bor/2`, `bsl/2`, and `bsr/2` also have operators,
-  respectively: `&&&/2`, `|||/2`, `<<</2`, and `>>>/2`.
+  `ArithmeticError` is raised.

-  ## Guards
+  The functions in this module come in two flavors: named or
+  operators. For example:
+
+      iex> use Bitwise
+      iex> bnot(1) # named
+      -2
+      iex> 1 &&& 1 # operator
+      1
+
+  If you prefer to use only operators or skip them, you can
+  pass the following options:
+
+    * `:only_operators` - includes only operators
+    * `:skip_operators` - skips operators
+
+  For example:
+
+      iex> use Bitwise, only_operators: true
+      iex> 1 &&& 1
+      1
+
+  When invoked with no options, `use Bitwise` is equivalent
+  to `import Bitwise`.

  All bitwise functions can be used in guards:

@@ -22,7 +42,6 @@ defmodule Bitwise do
  """

  @doc false
-  @deprecated "import Bitwise instead"
  defmacro __using__(options) do
    except =
      cond do
@@ -30,7 +49,7 @@ defmodule Bitwise do
          [bnot: 1, band: 2, bor: 2, bxor: 2, bsl: 2, bsr: 2]

        Keyword.get(options, :skip_operators) ->
-          ["~~~": 1, &&&: 2, |||: 2, "^^^": 2, <<<: 2, >>>: 2]
+          [~~~: 1, &&&: 2, |||: 2, ^^^: 2, <<<: 2, >>>: 2]

        true ->
          []
@@ -61,8 +80,25 @@ defmodule Bitwise do
    :erlang.bnot(expr)
  end

-  @doc false
-  def unquote(:"~~~")(expr) do
+  @doc """
+  Bitwise NOT unary operator.
+
+  Calculates the bitwise NOT of the argument.
+
+  Allowed in guard tests. Inlined by the compiler.
+
+  ## Examples
+
+      iex> ~~~2
+      -3
+
+      iex> ~~~2 &&& 3
+      1
+
+  """
+  @doc guard: true
+  @spec ~~~integer :: integer
+  def ~~~expr do
    :erlang.bnot(expr)
  end

@@ -155,8 +191,22 @@ defmodule Bitwise do
    :erlang.bxor(left, right)
  end

-  @doc false
-  def unquote(:"^^^")(left, right) do
+  @doc """
+  Bitwise XOR operator.
+
+  Calculates the bitwise XOR of its arguments.
+
+  Allowed in guard tests. Inlined by the compiler.
+
+  ## Examples
+
+      iex> 9 ^^^ 3
+      10
+
+  """
+  @doc guard: true
+  @spec integer ^^^ integer :: integer
+  def left ^^^ right do
    :erlang.bxor(left, right)
  end

@@ -57,7 +57,7 @@ defmodule Calendar do
  representing the microseconds to external format. If the precision is 0,
  it means microseconds must be skipped.
  """
-  @type microsecond :: {value :: non_neg_integer, precision :: non_neg_integer}
+  @type microsecond :: {non_neg_integer, non_neg_integer}

  @typedoc "A calendar implementation"
  @type calendar :: module
@@ -189,7 +189,7 @@ defmodule Calendar do
  @doc """
  Calculates the year and era from the given `year`.
  """
-  @callback year_of_era(year, month, day) :: {year, era}
+  @callback year_of_era(year) :: {year, era}

  @doc """
  Calculates the day and era from the given `year`, `month`, and `day`.
@@ -365,7 +365,7 @@ defmodule Calendar do
  """
  @doc since: "1.8.0"
  @spec put_time_zone_database(time_zone_database()) :: :ok
-  def put_time_zone_database(database) when is_atom(database) do
+  def put_time_zone_database(database) do
    Application.put_env(:elixir, :time_zone_database, database)
  end

@@ -375,7 +375,7 @@ defmodule Calendar do
  @doc since: "1.8.0"
  @spec get_time_zone_database() :: time_zone_database()
  def get_time_zone_database() do
-    Application.fetch_env!(:elixir, :time_zone_database)
+    Application.get_env(:elixir, :time_zone_database, Calendar.UTCOnlyTimeZoneDatabase)
  end

  @doc """
@@ -453,7 +453,7 @@ defmodule Calendar do
  b      | Abbreviated month name                                                  | Jan
  B      | Full month name                                                         | January
  c      | Preferred date+time representation                                      | 2018-10-17 12:34:56
-  d      | Day of the month                                                        | 01, 31
+  d      | Day of the month                                                        | 01, 12
  f      | Microseconds *(does not support width and padding modifiers)*           | 000000, 999999, 0123
  H      | Hour using a 24-hour clock                                              | 00, 23
  I      | Hour using a 12-hour clock                                              | 01, 12
@@ -485,9 +485,6 @@ defmodule Calendar do
      iex> Calendar.strftime(~U[2019-08-26 13:52:06.0Z], "%a, %B %d %Y")
      "Mon, August 26 2019"

-      iex> Calendar.strftime(~U[2020-04-02 13:52:06.0Z], "%B %-d, %Y")
-      "April 2, 2020"
-
      iex> Calendar.strftime(~U[2019-08-26 13:52:06.0Z], "%c")
      "2019-08-26 13:52:06"

@@ -544,8 +541,8 @@ defmodule Calendar do
    parse_modifiers(rest, width, "", parser_data)
  end

-  defp parse_modifiers("0" <> rest, nil, nil, parser_data) do
-    parse_modifiers(rest, nil, ?0, parser_data)
+  defp parse_modifiers("0" <> rest, width, nil, parser_data) do
+    parse_modifiers(rest, width, ?0, parser_data)
  end

  defp parse_modifiers("_" <> rest, width, nil, parser_data) do
@@ -791,14 +788,7 @@ defmodule Calendar do

  # Year
  defp format_modifiers("Y" <> rest, width, pad, datetime, format_options, acc) do
-    {sign, year} =
-      if datetime.year < 0 do
-        {?-, -datetime.year}
-      else
-        {[], datetime.year}
-      end
-
-    result = [sign | year |> Integer.to_string() |> pad_leading(width, pad)]
+    result = datetime.year |> Integer.to_string() |> pad_leading(width, pad)
    parse(rest, datetime, format_options, [result | acc])
  end

@@ -4,7 +4,7 @@ defmodule Date do

  The Date struct contains the fields year, month, day and calendar.
  New dates can be built with the `new/3` function or using the
-  `~D` (see `sigil_D/2`) sigil:
+  `~D` (see `Kernel.sigil_D/2`) sigil:

      iex> ~D[2000-01-01]
      ~D[2000-01-01]
@@ -31,12 +31,7 @@ defmodule Date do

  Comparisons in Elixir using `==/2`, `>/2`, `</2` and similar are structural
  and based on the `Date` struct fields. For proper comparison between
-  dates, use the `compare/2` function. The existence of the `compare/2`
-  function in this module also allows using `Enum.min/2` and `Enum.max/2`
-  functions to get the minimum and maximum date of an `Enum`. For example:
-
-      iex>  Enum.min([~D[2017-03-31], ~D[2017-04-01]], Date)
-      ~D[2017-03-31]
+  dates, use the `compare/2` function.

  ## Using epochs

@@ -77,21 +72,19 @@ defmodule Date do
  ## Examples

      iex> Date.range(~D[1999-01-01], ~D[2000-01-01])
-      Date.range(~D[1999-01-01], ~D[2000-01-01])
+      #DateRange<~D[1999-01-01], ~D[2000-01-01]>

  A range of dates implements the `Enumerable` protocol, which means
  functions in the `Enum` module can be used to work with
  ranges:

      iex> range = Date.range(~D[2001-01-01], ~D[2002-01-01])
-      iex> range
-      Date.range(~D[2001-01-01], ~D[2002-01-01])
      iex> Enum.count(range)
      366
-      iex> ~D[2001-02-01] in range
+      iex> Enum.member?(range, ~D[2001-02-01])
      true
-      iex> Enum.take(range, 3)
-      [~D[2001-01-01], ~D[2001-01-02], ~D[2001-01-03]]
+      iex> Enum.reduce(range, 0, fn _date, acc -> acc - 1 end)
+      -366

  """
  @doc since: "1.5.0"
@@ -99,61 +92,19 @@ defmodule Date do
  def range(%{calendar: calendar} = first, %{calendar: calendar} = last) do
    {first_days, _} = to_iso_days(first)
    {last_days, _} = to_iso_days(last)
-    # TODO: Deprecate inferring a range with a step of -1 on Elixir v1.16
-    step = if first_days <= last_days, do: 1, else: -1
-    range(first, first_days, last, last_days, calendar, step)
-  end

-  def range(%{calendar: _, year: _, month: _, day: _}, %{calendar: _, year: _, month: _, day: _}) do
-    raise ArgumentError, "both dates must have matching calendars"
-  end
-
-  @doc """
-  Returns a range of dates with a step.
-
-  ## Examples
-
-      iex> range = Date.range(~D[2001-01-01], ~D[2002-01-01], 2)
-      iex> range
-      Date.range(~D[2001-01-01], ~D[2002-01-01], 2)
-      iex> Enum.count(range)
-      183
-      iex> ~D[2001-01-03] in range
-      true
-      iex> Enum.take(range, 3)
-      [~D[2001-01-01], ~D[2001-01-03], ~D[2001-01-05]]
-
-  """
-  @doc since: "1.12.0"
-  @spec range(Calendar.date(), Calendar.date(), step :: pos_integer | neg_integer) ::
-          Date.Range.t()
-  def range(%{calendar: calendar} = first, %{calendar: calendar} = last, step)
-      when is_integer(step) and step != 0 do
-    {first_days, _} = to_iso_days(first)
-    {last_days, _} = to_iso_days(last)
-    range(first, first_days, last, last_days, calendar, step)
-  end
-
-  def range(
-        %{calendar: _, year: _, month: _, day: _} = first,
-        %{calendar: _, year: _, month: _, day: _} = last,
-        step
-      ) do
-    raise ArgumentError,
-          "both dates must have matching calendar and the step must be a " <>
-            "non-zero integer, got: #{inspect(first)}, #{inspect(last)}, #{step}"
-  end
-
-  defp range(first, first_days, last, last_days, calendar, step) do
    %Date.Range{
      first: %Date{calendar: calendar, year: first.year, month: first.month, day: first.day},
      last: %Date{calendar: calendar, year: last.year, month: last.month, day: last.day},
      first_in_iso_days: first_days,
-      last_in_iso_days: last_days,
-      step: step
+      last_in_iso_days: last_days
    }
  end

+  def range(%{calendar: _, year: _, month: _, day: _}, %{calendar: _, year: _, month: _, day: _}) do
+    raise ArgumentError, "both dates must have matching calendars"
+  end
+
  @doc """
  Returns the current date in UTC.

@@ -322,7 +273,7 @@ defmodule Date do

  @doc """
  Parses the extended "Dates" format described by
-  [ISO 8601:2019](https://en.wikipedia.org/wiki/ISO_8601).
+  [ISO 8601:2004](https://en.wikipedia.org/wiki/ISO_8601).

  The year parsed by this function is limited to four digits.

@@ -347,7 +298,7 @@ defmodule Date do

  @doc """
  Parses the extended "Dates" format described by
-  [ISO 8601:2019](https://en.wikipedia.org/wiki/ISO_8601).
+  [ISO 8601:2004](https://en.wikipedia.org/wiki/ISO_8601).

  Raises if the format is invalid.

@@ -372,7 +323,7 @@ defmodule Date do

  @doc """
  Converts the given `date` to
-  [ISO 8601:2019](https://en.wikipedia.org/wiki/ISO_8601).
+  [ISO 8601:2004](https://en.wikipedia.org/wiki/ISO_8601).

  By default, `Date.to_iso8601/2` returns dates formatted in the "extended"
  format, for human readability. It also supports the "basic" format through passing the `:basic` option.
@@ -549,8 +500,8 @@ defmodule Date do
    end
  end

-  def compare(%{calendar: calendar1} = date1, %{calendar: calendar2} = date2) do
-    if Calendar.compatible_calendars?(calendar1, calendar2) do
+  def compare(date1, date2) do
+    if Calendar.compatible_calendars?(date1.calendar, date2.calendar) do
      case {to_iso_days(date1), to_iso_days(date2)} do
        {first, second} when first > second -> :gt
        {first, second} when first < second -> :lt
@@ -708,12 +659,11 @@ defmodule Date do
    end
  end

-  @doc false
-  def to_iso_days(%{calendar: Calendar.ISO, year: year, month: month, day: day}) do
+  defp to_iso_days(%{calendar: Calendar.ISO, year: year, month: month, day: day}) do
    {Calendar.ISO.date_to_iso_days(year, month, day), {0, 86_400_000_000}}
  end

-  def to_iso_days(%{calendar: calendar, year: year, month: month, day: day}) do
+  defp to_iso_days(%{calendar: calendar, year: year, month: month, day: day}) do
    calendar.naive_datetime_to_iso_days(year, month, day, 0, 0, 0, {0, 0})
  end

@@ -837,6 +787,8 @@ defmodule Date do
      ~D[2020-07-05]
      iex> Date.end_of_week(~D[2020-07-06], :sunday)
      ~D[2020-07-11]
+      iex> Date.end_of_week(~D[2020-07-06], :sunday)
+      ~D[2020-07-11]
      iex> Date.end_of_week(~D[2020-07-06], :saturday)
      ~D[2020-07-10]
      iex> Date.end_of_week(~N[2020-07-11 01:23:45])
@@ -948,14 +900,8 @@ defmodule Date do
  @spec year_of_era(Calendar.date()) :: {Calendar.year(), non_neg_integer()}
  def year_of_era(date)

-  def year_of_era(%{calendar: calendar, year: year, month: month, day: day}) do
-    # TODO: Remove me on 1.17
-    # The behaviour implementation already warns on missing callback.
-    if function_exported?(calendar, :year_of_era, 3) do
-      calendar.year_of_era(year, month, day)
-    else
-      calendar.year_of_era(year)
-    end
+  def year_of_era(%{calendar: calendar, year: year}) do
+    calendar.year_of_era(year)
  end

  @doc """
@@ -997,8 +943,6 @@ defmodule Date do
  """
  @doc since: "1.11.0"
  @spec beginning_of_month(Calendar.date()) :: t()
-  def beginning_of_month(date)
-
  def beginning_of_month(%{year: year, month: month, calendar: calendar}) do
    %Date{year: year, month: month, day: 1, calendar: calendar}
  end
@@ -1018,8 +962,6 @@ defmodule Date do
  """
  @doc since: "1.11.0"
  @spec end_of_month(Calendar.date()) :: t()
-  def end_of_month(date)
-
  def end_of_month(%{year: year, month: month, calendar: calendar} = date) do
    day = Date.days_in_month(date)
    %Date{year: year, month: month, day: day, calendar: calendar}
@@ -2,13 +2,12 @@ defmodule Date.Range do
  @moduledoc """
  Returns an inclusive range between dates.

-  Ranges must be created with the `Date.range/2` or `Date.range/3` function.
+  Ranges must be created with the `Date.range/2` function.

  The following fields are public:

    * `:first` - the initial date on the range
    * `:last` - the last date on the range
-    * `:step` - (since v1.12.0) the step

  The remaining fields are private and should not be accessed.
  """
@@ -16,134 +15,99 @@ defmodule Date.Range do
  @type t :: %__MODULE__{
          first: Date.t(),
          last: Date.t(),
-          first_in_iso_days: days(),
-          last_in_iso_days: days(),
-          step: pos_integer | neg_integer
+          first_in_iso_days: iso_days(),
+          last_in_iso_days: iso_days()
        }

-  @typep days() :: integer()
+  @typep iso_days() :: Calendar.iso_days()

-  @enforce_keys [:first, :last, :first_in_iso_days, :last_in_iso_days, :step]
-  defstruct [:first, :last, :first_in_iso_days, :last_in_iso_days, :step]
+  defstruct [:first, :last, :first_in_iso_days, :last_in_iso_days]

  defimpl Enumerable do
-    def member?(
-          %Date.Range{
-            first: %{calendar: calendar},
-            first_in_iso_days: first_days,
-            last_in_iso_days: last_days,
-            step: step
-          } = range,
-          %Date{calendar: calendar} = date
-        ) do
-      {days, _} = Date.to_iso_days(date)
+    def member?(%{first: %{calendar: calendar}} = range, %Date{calendar: calendar} = date) do
+      %{
+        first: first,
+        last: last,
+        first_in_iso_days: first_in_iso_days,
+        last_in_iso_days: last_in_iso_days
+      } = range

-      cond do
-        empty?(range) ->
-          {:ok, false}
+      %{year: first_year, month: first_month, day: first_day} = first
+      %{year: last_year, month: last_month, day: last_day} = last
+      %{year: year, month: month, day: day} = date
+      first = {first_year, first_month, first_day}
+      last = {last_year, last_month, last_day}
+      date = {year, month, day}

-        first_days <= last_days ->
-          {:ok, first_days <= days and days <= last_days and rem(days - first_days, step) == 0}
-
-        true ->
-          {:ok, last_days <= days and days <= first_days and rem(days - first_days, step) == 0}
+      if first_in_iso_days <= last_in_iso_days do
+        {:ok, date >= first and date <= last}
+      else
+        {:ok, date >= last and date <= first}
      end
    end

-    def member?(%Date.Range{step: _}, _) do
+    def member?(_, _) do
      {:ok, false}
    end

-    # TODO: Remove me on v2.0
-    def member?(
-          %{__struct__: Date.Range, first_in_iso_days: first_days, last_in_iso_days: last_days} =
-            date_range,
-          date
-        ) do
-      step = if first_days <= last_days, do: 1, else: -1
-      member?(Map.put(date_range, :step, step), date)
+    def count(%{first_in_iso_days: first, last_in_iso_days: last}) do
+      {:ok, abs(first - last) + 1}
    end

-    def count(range) do
-      {:ok, size(range)}
+    def slice(range) do
+      %{
+        first_in_iso_days: first,
+        last_in_iso_days: last,
+        first: %{calendar: calendar}
+      } = range
+
+      if first <= last do
+        {:ok, last - first + 1, &slice_asc(first + &1, &2, calendar)}
+      else
+        {:ok, first - last + 1, &slice_desc(first - &1, &2, calendar)}
+      end
    end

-    def slice(
-          %Date.Range{
-            first_in_iso_days: first,
-            first: %{calendar: calendar},
-            step: step
-          } = range
-        ) do
-      {:ok, size(range), &slice(first + &1 * step, step + &3 - 1, &2, calendar)}
+    defp slice_asc(current, 1, calendar), do: [date_from_iso_days(current, calendar)]
+
+    defp slice_asc(current, remaining, calendar) do
+      [date_from_iso_days(current, calendar) | slice_asc(current + 1, remaining - 1, calendar)]
    end

-    # TODO: Remove me on v2.0
-    def slice(
-          %{__struct__: Date.Range, first_in_iso_days: first_days, last_in_iso_days: last_days} =
-            date_range
-        ) do
-      step = if first_days <= last_days, do: 1, else: -1
-      slice(Map.put(date_range, :step, step))
+    defp slice_desc(current, 1, calendar), do: [date_from_iso_days(current, calendar)]
+
+    defp slice_desc(current, remaining, calendar) do
+      [date_from_iso_days(current, calendar) | slice_desc(current - 1, remaining - 1, calendar)]
    end

-    defp slice(current, _step, 1, calendar) do
-      [date_from_iso_days(current, calendar)]
+    def reduce(range, acc, fun) do
+      %{
+        first_in_iso_days: first_in_iso_days,
+        last_in_iso_days: last_in_iso_days,
+        first: %{calendar: calendar}
+      } = range
+
+      up? = first_in_iso_days <= last_in_iso_days
+      reduce(first_in_iso_days, last_in_iso_days, acc, fun, calendar, up?)
    end

-    defp slice(current, step, remaining, calendar) do
-      [
-        date_from_iso_days(current, calendar)
-        | slice(current + step, step, remaining - 1, calendar)
-      ]
-    end
-
-    def reduce(
-          %Date.Range{
-            first_in_iso_days: first_days,
-            last_in_iso_days: last_days,
-            first: %{calendar: calendar},
-            step: step
-          },
-          acc,
-          fun
-        ) do
-      reduce(first_days, last_days, acc, fun, step, calendar)
-    end
-
-    # TODO: Remove me on v2.0
-    def reduce(
-          %{__struct__: Date.Range, first_in_iso_days: first_days, last_in_iso_days: last_days} =
-            date_range,
-          acc,
-          fun
-        ) do
-      step = if first_days <= last_days, do: 1, else: -1
-      reduce(Map.put(date_range, :step, step), acc, fun)
-    end
-
-    defp reduce(_first_days, _last_days, {:halt, acc}, _fun, _step, _calendar) do
+    defp reduce(_x, _y, {:halt, acc}, _fun, _calendar, _up?) do
      {:halted, acc}
    end

-    defp reduce(first_days, last_days, {:suspend, acc}, fun, step, calendar) do
-      {:suspended, acc, &reduce(first_days, last_days, &1, fun, step, calendar)}
+    defp reduce(x, y, {:suspend, acc}, fun, calendar, up?) do
+      {:suspended, acc, &reduce(x, y, &1, fun, calendar, up?)}
    end

-    defp reduce(first_days, last_days, {:cont, acc}, fun, step, calendar)
-         when step > 0 and first_days <= last_days
-         when step < 0 and first_days >= last_days do
-      reduce(
-        first_days + step,
-        last_days,
-        fun.(date_from_iso_days(first_days, calendar), acc),
-        fun,
-        step,
-        calendar
-      )
+    defp reduce(x, y, {:cont, acc}, fun, calendar, up? = true) when x <= y do
+      reduce(x + 1, y, fun.(date_from_iso_days(x, calendar), acc), fun, calendar, up?)
    end

-    defp reduce(_, _, {:cont, acc}, _fun, _step, _calendar) do
+    defp reduce(x, y, {:cont, acc}, fun, calendar, up? = false) when x >= y do
+      reduce(x - 1, y, fun.(date_from_iso_days(x, calendar), acc), fun, calendar, up?)
+    end
+
+    defp reduce(_, _, {:cont, acc}, _fun, _calendar, _up) do
      {:done, acc}
    end

@@ -158,70 +122,11 @@ defmodule Date.Range do

      %Date{year: year, month: month, day: day, calendar: calendar}
    end
-
-    defp size(%Date.Range{first_in_iso_days: first_days, last_in_iso_days: last_days, step: step})
-         when step > 0 and first_days > last_days,
-         do: 0
-
-    defp size(%Date.Range{first_in_iso_days: first_days, last_in_iso_days: last_days, step: step})
-         when step < 0 and first_days < last_days,
-         do: 0
-
-    defp size(%Date.Range{first_in_iso_days: first_days, last_in_iso_days: last_days, step: step}),
-      do: abs(div(last_days - first_days, step)) + 1
-
-    # TODO: Remove me on v2.0
-    defp size(
-           %{__struct__: Date.Range, first_in_iso_days: first_days, last_in_iso_days: last_days} =
-             date_range
-         ) do
-      step = if first_days <= last_days, do: 1, else: -1
-      size(Map.put(date_range, :step, step))
-    end
-
-    defp empty?(%Date.Range{
-           first_in_iso_days: first_days,
-           last_in_iso_days: last_days,
-           step: step
-         })
-         when step > 0 and first_days > last_days,
-         do: true
-
-    defp empty?(%Date.Range{
-           first_in_iso_days: first_days,
-           last_in_iso_days: last_days,
-           step: step
-         })
-         when step < 0 and first_days < last_days,
-         do: true
-
-    defp empty?(%Date.Range{step: _}), do: false
-
-    # TODO: Remove me on v2.0
-    defp empty?(
-           %{__struct__: Date.Range, first_in_iso_days: first_days, last_in_iso_days: last_days} =
-             date_range
-         ) do
-      step = if first_days <= last_days, do: 1, else: -1
-      empty?(Map.put(date_range, :step, step))
-    end
  end

  defimpl Inspect do
-    import Kernel, except: [inspect: 2]
-
-    def inspect(%Date.Range{first: first, last: last, step: 1}, _) do
-      "Date.range(" <> inspect(first) <> ", " <> inspect(last) <> ")"
-    end
-
-    def inspect(%Date.Range{first: first, last: last, step: step}, _) do
-      "Date.range(" <> inspect(first) <> ", " <> inspect(last) <> ", #{step})"
-    end
-
-    # TODO: Remove me on v2.0
-    def inspect(%{__struct__: Date.Range, first: first, last: last} = date_range, opts) do
-      step = if first <= last, do: 1, else: -1
-      inspect(Map.put(date_range, :step, step), opts)
+    def inspect(%Date.Range{first: first, last: last}, _) do
+      "#DateRange<" <> inspect(first) <> ", " <> inspect(last) <> ">"
    end
  end
 end
@@ -2,24 +2,15 @@ defmodule DateTime do
  @moduledoc """
  A datetime implementation with a time zone.

-  This datetime can be seen as a snapshot of a date and time
-  at a given time zone. For such purposes, it also includes both
-  UTC and Standard offsets, as well as the zone abbreviation
-  field used exclusively for formatting purposes. Note future
-  datetimes are not necessarily guaranteed to exist, as time
-  zones may change any time in the future due to geopolitical
-  reasons. See the "Datetimes as snapshots" section for more
-  information.
+  This datetime can be seen as an ephemeral snapshot
+  of a datetime at a given time zone. For such purposes,
+  it also includes both UTC and Standard offsets, as
+  well as the zone abbreviation field used exclusively
+  for formatting purposes.

  Remember, comparisons in Elixir using `==/2`, `>/2`, `</2` and friends
  are structural and based on the DateTime struct fields. For proper
-  comparison between datetimes, use the `compare/2` function. The
-  existence of the `compare/2` function in this module also allows
-  using `Enum.min/2` and `Enum.max/2` functions to get the minimum and
-  maximum datetime of an `Enum`. For example:
-
-      iex> Enum.min([~U[2022-01-12 00:01:00.00Z], ~U[2021-01-12 00:01:00.00Z]], DateTime)
-      ~U[2021-01-12 00:01:00.00Z]
+  comparison between datetimes, use the `compare/2` function.

  Developers should avoid creating the `DateTime` struct directly
  and instead rely on the functions provided by this module as
@@ -34,74 +25,22 @@ defmodule DateTime do
  datetimes and returns `{:error, :utc_only_time_zone_database}`
  for any other time zone.

-  Other time zone databases can also be configured. Here are some
-  available options and libraries:
+  Other time zone databases can also be configured. For example,
+  two of the available options are:

-    * [`tz`](https://github.com/mathieuprog/tz)
-    * [`tzdata`](https://github.com/lau/tzdata)
-    * [`zoneinfo`](https://github.com/smartrent/zoneinfo) -
-      recommended for embedded devices
+    * [`tz`](https://hexdocs.pm/tz/)
+    * [`tzdata`](https://hexdocs.pm/tzdata/)

  To use them, first make sure it is added as a dependency in `mix.exs`.
  It can then be configured either via configuration:

-      config :elixir, :time_zone_database, Tz.TimeZoneDatabase
+      config :elixir, :time_zone_database, Tzdata.TimeZoneDatabase

  or by calling `Calendar.put_time_zone_database/1`:

-      Calendar.put_time_zone_database(Tz.TimeZoneDatabase)
+      Calendar.put_time_zone_database(Tzdata.TimeZoneDatabase)

  See the proper names in the library installation instructions.
-
-  ## Datetimes as snapshots
-
-  In the first section, we described datetimes as a "snapshot of
-  a date and time at a given time zone". To understand precisely
-  what we mean, let's see an example.
-
-  Imagine someone in Poland wants to schedule a meeting with someone
-  in Brazil in the next year. The meeting will happen at 2:30 AM
-  in the Polish time zone. At what time will the meeting happen in
-  Brazil?
-
-  You can consult the time zone database today, one year before,
-  using the API in this module and it will give you an answer that
-  is valid right now. However, this answer may not be valid in the
-  future. Why? Because both Brazil and Poland may change their timezone
-  rules, ultimately affecting the result. For example, a country may
-  choose to enter or abandon "Daylight Saving Time", which is a
-  process where we adjust the clock one hour forward or one hour
-  back once per year. Whenener the rules change, the exact instant
-  that 2:30 AM in Polish time will be in Brazil may change.
-
-  In other words, whenever working with future DateTimes, there is
-  no guarantee the results you get will always be correct, until
-  the event actually happens. Therefore, when you ask for a future
-  time, the answers you get are a snapshot that reflects the current
-  state of the time zone rules. For datetimes in the past, this is
-  not a problem, because time zone rules do not change for past
-  events.
-
-  To make matters worse, it may be that the 2:30 AM in Polish time
-  does not actually even exist or it is ambiguous. If a certain
-  time zone observes "Daylight Saving Time", they will move their
-  clock forward once a year. When this happens, there is a whole
-  hour that does not exist. Then, when they move the clock back,
-  there is a certain hour that will happen twice. So if you want
-  to schedule a meeting when this shift back happens, you would
-  need to explicitly say which of the 2:30 AM you precisely mean.
-  Applications that are date and time sensitive, need to take
-  these scenarios into account and correctly communicate them to
-  users.
-
-  The good news is: Elixir contains all of the building blocks
-  necessary to tackle those problems. The default timezone database
-  used by Elixir, `Calendar.UTCOnlyTimeZoneDatabase`, only works
-  with UTC, which does not observe those issues. Once you bring
-  a proper time zone database, the functions in this module will
-  query the database and return the relevant information. For
-  example, look at how `DateTime.new/4` returns different results
-  based on the scenarios described in this section.
  """

  @enforce_keys [:year, :month, :day, :hour, :minute, :second] ++
@@ -143,9 +82,6 @@ defmodule DateTime do
  @doc """
  Returns the current datetime in UTC.

-  If you want the current time in Unix seconds,
-  use `System.os_time/1` instead.
-
  ## Examples

      iex> datetime = DateTime.utc_now()
@@ -173,9 +109,8 @@ defmodule DateTime do
      {:ok, ~U[2016-05-24 13:26:08.003Z]}

  When the datetime is ambiguous - for instance during changing from summer
-  to winter time - the two possible valid datetimes are returned in a tuple.
-  The first datetime is also the one which comes first chronologically, while
-  the second one comes last.
+  to winter time - the two possible valid datetimes are returned. First the one
+  that happens first, then the one that happens after.

      iex> {:ambiguous, first_dt, second_dt} = DateTime.new(~D[2018-10-28], ~T[02:30:00], "Europe/Copenhagen", FakeTimeZoneDatabase)
      iex> first_dt
@@ -204,7 +139,7 @@ defmodule DateTime do
  @doc since: "1.11.0"
  @spec new(Date.t(), Time.t(), Calendar.time_zone(), Calendar.time_zone_database()) ::
          {:ok, t}
-          | {:ambiguous, first_datetime :: t, second_datetime :: t}
+          | {:ambiguous, t, t}
          | {:gap, t, t}
          | {:error,
             :incompatible_calendars | :time_zone_not_found | :utc_only_time_zone_database}
@@ -305,7 +240,9 @@ defmodule DateTime do

      {:error, reason} ->
        raise ArgumentError,
-              "cannot build datetime with #{inspect(date)} and #{inspect(time)}, reason: #{inspect(reason)}"
+              "cannot build datetime with #{inspect(date)} and #{inspect(time)}, reason: #{
+                inspect(reason)
+              }"
    end
  end

@@ -429,9 +366,8 @@ defmodule DateTime do
      {:ok, ~U[2016-05-24 13:26:08.003Z]}

  When the datetime is ambiguous - for instance during changing from summer
-  to winter time - the two possible valid datetimes are returned in a tuple.
-  The first datetime is also the one which comes first chronologically, while
-  the second one comes last.
+  to winter time - the two possible valid datetimes are returned. First the one
+  that happens first, then the one that happens after.

      iex> {:ambiguous, first_dt, second_dt} = DateTime.from_naive(~N[2018-10-28 02:30:00], "Europe/Copenhagen", FakeTimeZoneDatabase)
      iex> first_dt
@@ -482,7 +418,7 @@ defmodule DateTime do
          Calendar.time_zone_database()
        ) ::
          {:ok, t}
-          | {:ambiguous, first_datetime :: t, second_datetime :: t}
+          | {:ambiguous, t, t}
          | {:gap, t, t}
          | {:error,
             :incompatible_calendars | :time_zone_not_found | :utc_only_time_zone_database}
@@ -514,7 +450,7 @@ defmodule DateTime do
        # we get the last microsecond just before.
        before_naive =
          first_period_until_wall
-          |> Map.replace!(:microsecond, {999_999, 6})
+          |> Map.put(:microsecond, {999_999, 6})
          |> NaiveDateTime.add(-1)

        after_naive = second_period_from_wall
@@ -817,6 +753,10 @@ defmodule DateTime do
  It will return the integer with the given unit,
  according to `System.convert_time_unit/3`.

+  If you want to get the current time in Unix seconds,
+  do not do `DateTime.utc_now() |> DateTime.to_unix()`.
+  Simply call `System.os_time(:second)` instead.
+
  ## Examples

      iex> 1_464_096_368 |> DateTime.from_unix!() |> DateTime.to_unix()
@@ -861,8 +801,6 @@ defmodule DateTime do

  """
  @spec to_naive(Calendar.datetime()) :: NaiveDateTime.t()
-  def to_naive(datetime)
-
  def to_naive(%{
        calendar: calendar,
        year: year,
@@ -902,8 +840,6 @@ defmodule DateTime do

  """
  @spec to_date(Calendar.datetime()) :: Date.t()
-  def to_date(datetime)
-
  def to_date(%{
        year: year,
        month: month,
@@ -934,8 +870,6 @@ defmodule DateTime do

  """
  @spec to_time(Calendar.datetime()) :: Time.t()
-  def to_time(datetime)
-
  def to_time(%{
        year: _,
        month: _,
@@ -958,14 +892,13 @@ defmodule DateTime do

  @doc """
  Converts the given datetime to
-  [ISO 8601:2019](https://en.wikipedia.org/wiki/ISO_8601) format.
+  [ISO 8601:2004](https://en.wikipedia.org/wiki/ISO_8601) format.

  By default, `DateTime.to_iso8601/2` returns datetimes formatted in the "extended"
  format, for human readability. It also supports the "basic" format through passing the `:basic` option.

  Only supports converting datetimes which are in the ISO calendar,
  attempting to convert datetimes from other calendars will raise.
-  You can also optionally specify an offset for the formatted string.

  WARNING: the ISO 8601 datetime format does not contain the time zone nor
  its abbreviation, which means information is lost when converting to such
@@ -997,31 +930,11 @@ defmodule DateTime do
      iex> DateTime.to_iso8601(dt, :basic)
      "20000229T230007-0400"

-      iex> dt = %DateTime{year: 2000, month: 2, day: 29, zone_abbr: "AMT",
-      ...>                hour: 23, minute: 0, second: 7, microsecond: {0, 0},
-      ...>                utc_offset: -14400, std_offset: 0, time_zone: "America/Manaus"}
-      iex> DateTime.to_iso8601(dt, :extended, 3600)
-      "2000-03-01T04:00:07+01:00"
-
-      iex> dt = %DateTime{year: 2000, month: 2, day: 29, zone_abbr: "AMT",
-      ...>                hour: 23, minute: 0, second: 7, microsecond: {0, 0},
-      ...>                utc_offset: -14400, std_offset: 0, time_zone: "America/Manaus"}
-      iex> DateTime.to_iso8601(dt, :extended, 0)
-      "2000-03-01T03:00:07+00:00"
-
-      iex> dt = %DateTime{year: 2000, month: 3, day: 01, zone_abbr: "UTC",
-      ...>                hour: 03, minute: 0, second: 7, microsecond: {0, 0},
-      ...>                utc_offset: 0, std_offset: 0, time_zone: "Etc/UTC"}
-      iex> DateTime.to_iso8601(dt, :extended, 0)
-      "2000-03-01T03:00:07Z"
-
-      iex> {:ok, dt, offset} = DateTime.from_iso8601("2000-03-01T03:00:07Z")
-      iex> "2000-03-01T03:00:07Z" = DateTime.to_iso8601(dt, :extended, offset)
  """
-  @spec to_iso8601(Calendar.datetime(), :basic | :extended, nil | integer()) :: String.t()
-  def to_iso8601(datetime, format \\ :extended, offset \\ nil)
+  @spec to_iso8601(Calendar.datetime(), :extended | :basic) :: String.t()
+  def to_iso8601(datetime, format \\ :extended)

-  def to_iso8601(%{calendar: Calendar.ISO} = datetime, format, nil)
+  def to_iso8601(%{calendar: Calendar.ISO} = datetime, format)
      when format in [:extended, :basic] do
    %{
      year: year,
@@ -1036,56 +949,21 @@ defmodule DateTime do
      std_offset: std_offset
    } = datetime

-    datetime_to_string(year, month, day, hour, minute, second, microsecond, format) <>
+    Calendar.ISO.date_to_string(year, month, day, format) <>
+      "T" <>
+      Calendar.ISO.time_to_string(hour, minute, second, microsecond, format) <>
      Calendar.ISO.offset_to_string(utc_offset, std_offset, time_zone, format)
  end

-  def to_iso8601(
-        %{calendar: Calendar.ISO, microsecond: {_, precision}, time_zone: "Etc/UTC"} = datetime,
-        format,
-        0
-      )
-      when format in [:extended, :basic] do
-    {year, month, day, hour, minute, second, {microsecond, _}} = shift_by_offset(datetime, 0)
-
-    datetime_to_string(year, month, day, hour, minute, second, {microsecond, precision}, format) <>
-      "Z"
-  end
-
-  def to_iso8601(%{calendar: Calendar.ISO} = datetime, format, offset)
-      when format in [:extended, :basic] do
-    {_, precision} = datetime.microsecond
-    {year, month, day, hour, minute, second, {microsecond, _}} = shift_by_offset(datetime, offset)
-
-    datetime_to_string(year, month, day, hour, minute, second, {microsecond, precision}, format) <>
-      Calendar.ISO.offset_to_string(offset, 0, nil, format)
-  end
-
-  def to_iso8601(%{calendar: _} = datetime, format, offset) when format in [:extended, :basic] do
+  def to_iso8601(%{calendar: _} = datetime, format) when format in [:extended, :basic] do
    datetime
    |> convert!(Calendar.ISO)
-    |> to_iso8601(format, offset)
-  end
-
-  defp shift_by_offset(%{calendar: calendar} = datetime, offset) do
-    total_offset = datetime.utc_offset + datetime.std_offset
-
-    datetime
-    |> to_iso_days()
-    # Subtract total original offset in order to get UTC and add the new offset
-    |> Calendar.ISO.add_day_fraction_to_iso_days(offset - total_offset, 86400)
-    |> calendar.naive_datetime_from_iso_days()
-  end
-
-  defp datetime_to_string(year, month, day, hour, minute, second, microsecond, format) do
-    Calendar.ISO.date_to_string(year, month, day, format) <>
-      "T" <>
-      Calendar.ISO.time_to_string(hour, minute, second, microsecond, format)
+    |> to_iso8601(format)
  end

  @doc """
  Parses the extended "Date and time of day" format described by
-  [ISO 8601:2019](https://en.wikipedia.org/wiki/ISO_8601).
+  [ISO 8601:2004](https://en.wikipedia.org/wiki/ISO_8601).

  Since ISO 8601 does not include the proper time zone, the given
  string will be converted to UTC and its offset in seconds will be
@@ -1095,6 +973,9 @@ defmodule DateTime do
  As specified in the standard, the separator "T" may be omitted if
  desired as there is no ambiguity within this function.

+  The year parsed by this function is limited to four digits and,
+  while ISO 8601 allows datetimes to specify 24:00:00 as the zero
+  hour of the next day, this notation is not supported by Elixir.
  Note leap seconds are not supported by the built-in Calendar.ISO.

  ## Examples
@@ -1119,10 +1000,6 @@ defmodule DateTime do
      iex> datetime
      ~U[-2015-01-23 21:20:07.123Z]

-      iex> {:ok, datetime, 9000} = DateTime.from_iso8601("20150123T235007.123+0230", :basic)
-      iex> datetime
-      ~U[2015-01-23 21:20:07.123Z]
-
      iex> DateTime.from_iso8601("2015-01-23P23:50:07")
      {:error, :invalid_format}
      iex> DateTime.from_iso8601("2015-01-23T23:50:07")
@@ -1136,37 +1013,11 @@ defmodule DateTime do

  """
  @doc since: "1.4.0"
-  @spec from_iso8601(String.t(), Calendar.calendar(), :extended | :basic) ::
+  @spec from_iso8601(String.t(), Calendar.calendar()) ::
          {:ok, t, Calendar.utc_offset()} | {:error, atom}
-
-  def from_iso8601(string, format_or_calendar \\ Calendar.ISO)
-
-  def from_iso8601(string, format) when format in [:basic, :extended] do
-    from_iso8601(string, Calendar.ISO, format)
-  end
-
-  def from_iso8601(string, calendar) when is_atom(calendar) do
-    from_iso8601(string, calendar, :extended)
-  end
-
-  @doc """
-  Converts to ISO8601 specifying both a calendar and a mode.
-
-  See `from_iso8601/2` for more information.
-
-  ## Examples
-
-      iex> {:ok, datetime, 9000} = DateTime.from_iso8601("2015-01-23T23:50:07,123+02:30", Calendar.ISO, :extended)
-      iex> datetime
-      ~U[2015-01-23 21:20:07.123Z]
-
-      iex> {:ok, datetime, 9000} = DateTime.from_iso8601("20150123T235007.123+0230", Calendar.ISO, :basic)
-      iex> datetime
-      ~U[2015-01-23 21:20:07.123Z]
-  """
-  def from_iso8601(string, calendar, format) do
+  def from_iso8601(string, calendar \\ Calendar.ISO) do
    with {:ok, {year, month, day, hour, minute, second, microsecond}, offset} <-
-           Calendar.ISO.parse_utc_datetime(string, format) do
+           Calendar.ISO.parse_utc_datetime(string) do
      datetime = %DateTime{
        year: year,
        month: month,
@@ -1387,11 +1238,12 @@ defmodule DateTime do
  @doc """
  Subtracts `datetime2` from `datetime1`.

-  The answer can be returned in any `:day`, `:hour`, `:minute`, or any `unit`
-  available from `t:System.time_unit/0`. The unit is measured according to
-  `Calendar.ISO` and defaults to `:second`.
+  The answer can be returned in any `unit` available from `t:System.time_unit/0`.

-  Fractional results are not supported and are truncated.
+  Leap seconds are not taken into account.
+
+  This function returns the difference in seconds where seconds are measured
+  according to `Calendar.ISO`.

  ## Examples

@@ -1405,36 +1257,14 @@ defmodule DateTime do
      18000
      iex> DateTime.diff(dt2, dt1)
      -18000
-      iex> DateTime.diff(dt1, dt2, :hour)
-      5
-      iex> DateTime.diff(dt2, dt1, :hour)
-      -5

  """
  @doc since: "1.5.0"
-  @spec diff(
-          Calendar.datetime(),
-          Calendar.datetime(),
-          :day | :hour | :minute | System.time_unit()
-        ) :: integer()
-  def diff(datetime1, datetime2, unit \\ :second)
-
-  def diff(datetime1, datetime2, :day) do
-    diff(datetime1, datetime2, :second) |> div(86400)
-  end
-
-  def diff(datetime1, datetime2, :hour) do
-    diff(datetime1, datetime2, :second) |> div(3600)
-  end
-
-  def diff(datetime1, datetime2, :minute) do
-    diff(datetime1, datetime2, :second) |> div(60)
-  end
-
+  @spec diff(Calendar.datetime(), Calendar.datetime(), System.time_unit()) :: integer()
  def diff(
        %{utc_offset: utc_offset1, std_offset: std_offset1} = datetime1,
        %{utc_offset: utc_offset2, std_offset: std_offset2} = datetime2,
-        unit
+        unit \\ :second
      ) do
    naive_diff =
      (datetime1 |> to_iso_days() |> Calendar.ISO.iso_days_to_unit(unit)) -
@@ -1447,30 +1277,15 @@ defmodule DateTime do
  @doc """
  Adds a specified amount of time to a `DateTime`.

-  Accepts an `amount_to_add` in any `unit`. `unit` can be `:day`,
-  `:hour`, `:minute`, `:second` or any subsecond precision from
-  `t:System.time_unit/0`. It defaults to `:second`. Negative values
-  will move backwards in time.
+  Accepts an `amount_to_add` in any `unit` available from `t:System.time_unit/0`.
+  Negative values will move backwards in time.

-  This function always consider the unit to be computed according
-  to the `Calendar.ISO`.
+  Takes changes such as summer time/DST into account. This means that adding time
+  can cause the wall time to "go backwards" during "fall back" during autumn.
+  Adding just a few seconds to a datetime just before "spring forward" can cause wall
+  time to increase by more than an hour.

-  This function uses relies on a contiguous representation of time,
-  ignoring the wall time and timezone changes. For example, if you add
-  one day when there are summer time/daylight saving time changes,
-  it will also change the time forward or backward by one hour,
-  so the ellapsed time is precisely 24 hours. Similarly, adding just
-  a few seconds to a datetime just before "spring forward" can cause
-  wall time to increase by more than an hour.
-
-  While this means this function is precise in terms of ellapsed time,
-  its result may be misleading in certain use cases. For example, if a
-  user requests a meeting to happen every day at 15:00 and you use this
-  function to compute all future meetings by adding day after day, this
-  function may change the meeting time to 14:00 or 16:00 if there are
-  changes to the current timezone. Computing of recurring datetimes is
-  not currently supported in Elixir's standard library but it is available
-  by third-party libraries.
+  Fractional second precision stays the same in a similar way to `NaiveDateTime.add/2`.

  ### Examples

@@ -1481,33 +1296,15 @@ defmodule DateTime do
      iex> DateTime.add(~U[2018-11-15 10:00:00Z], 3600, :second)
      ~U[2018-11-15 11:00:00Z]

-  When adding 3 seconds just before "spring forward" we go from 1:59:59 to 3:00:02:
+  When adding 3 seconds just before "spring forward" we go from 1:59:59 to 3:00:02

      iex> dt = DateTime.from_naive!(~N[2019-03-31 01:59:59.123], "Europe/Copenhagen", FakeTimeZoneDatabase)
      iex> dt |> DateTime.add(3, :second, FakeTimeZoneDatabase)
      #DateTime<2019-03-31 03:00:02.123+02:00 CEST Europe/Copenhagen>

-  When adding 1 day during "spring forward", the hour also changes:
-
-      iex> dt = DateTime.from_naive!(~N[2019-03-31 01:00:00], "Europe/Copenhagen", FakeTimeZoneDatabase)
-      iex> dt |> DateTime.add(1, :day, FakeTimeZoneDatabase)
-      #DateTime<2019-04-01 02:00:00+02:00 CEST Europe/Copenhagen>
-
-  This operation merges the precision of the naive date time with the given unit:
-
-      iex> result = DateTime.add(~U[2014-10-02 00:29:10Z], 21, :millisecond)
-      ~U[2014-10-02 00:29:10.021Z]
-      iex> result.microsecond
-      {21000, 3}
-
  """
  @doc since: "1.8.0"
-  @spec add(
-          Calendar.datetime(),
-          integer,
-          :day | :hour | :minute | System.time_unit(),
-          Calendar.time_zone_database()
-        ) ::
+  @spec add(Calendar.datetime(), integer, System.time_unit(), Calendar.time_zone_database()) ::
          t()
  def add(
        datetime,
@@ -1515,20 +1312,7 @@ defmodule DateTime do
        unit \\ :second,
        time_zone_database \\ Calendar.get_time_zone_database()
      )
-
-  def add(datetime, amount_to_add, :day, time_zone_database) when is_integer(amount_to_add) do
-    add(datetime, amount_to_add * 86400, :second, time_zone_database)
-  end
-
-  def add(datetime, amount_to_add, :hour, time_zone_database) when is_integer(amount_to_add) do
-    add(datetime, amount_to_add * 3600, :second, time_zone_database)
-  end
-
-  def add(datetime, amount_to_add, :minute, time_zone_database) when is_integer(amount_to_add) do
-    add(datetime, amount_to_add * 60, :second, time_zone_database)
-  end
-
-  def add(datetime, amount_to_add, unit, time_zone_database) when is_integer(amount_to_add) do
+      when is_integer(amount_to_add) do
    %{
      utc_offset: utc_offset,
      std_offset: std_offset,
@@ -1536,15 +1320,8 @@ defmodule DateTime do
      microsecond: {_, precision}
    } = datetime

-    if not is_integer(unit) and
-         unit not in ~w(second millisecond microsecond nanosecond)a do
-      raise ArgumentError,
-            "unsupported time unit. Expected :day, :hour, :minute, :second, :millisecond, :microsecond, :nanosecond, or a positive integer, got #{inspect(unit)}"
-    end
-
    ppd = System.convert_time_unit(86400, :second, unit)
    total_offset = System.convert_time_unit(utc_offset + std_offset, :second, unit)
-    precision = max(Calendar.ISO.time_unit_to_precision(unit), precision)

    result =
      datetime
@@ -1,127 +1,22 @@
 defmodule Calendar.ISO do
  @moduledoc """
-  The default calendar implementation, a Gregorian calendar following ISO 8601.
+  A calendar implementation that follows to ISO 8601.

-  This calendar implements a proleptic Gregorian calendar and
+  This calendar implements the proleptic Gregorian calendar and
  is therefore compatible with the calendar used in most countries
  today. The proleptic means the Gregorian rules for leap years are
  applied for all time, consequently the dates give different results
  before the year 1583 from when the Gregorian calendar was adopted.

-  ## ISO 8601 compliance
-
-  The ISO 8601 specification is feature-rich, but allows applications
-  to selectively implement most parts of it. The choices Elixir makes
-  are catalogued below.
-
-  ### Features
-
-  The standard library supports a minimal set of possible ISO 8601 features.
-  Specifically, the parser only supports calendar dates and does not support
-  ordinal and week formats.
-
-  By default Elixir only parses extended-formatted date/times. You can opt-in
-  to parse basic-formatted date/times.
-
-  `NaiveDateTime.to_iso8601/2` and `DateTime.to_iso8601/2` allow you to produce
-  either basic or extended formatted strings, and `Calendar.strftime/2` allows
-  you to format datetimes however else you desire.
-
-  Elixir does not support reduced accuracy formats (for example, a date without
-  the day component) nor decimal precisions in the lowest component (such as
-  `10:01:25,5`). No functions exist to parse ISO 8601 durations or time intervals.
-
-  #### Examples
-
-  Elixir expects the extended format by default when parsing:
-
-      iex> Calendar.ISO.parse_naive_datetime("2015-01-23T23:50:07")
-      {:ok, {2015, 1, 23, 23, 50, 7, {0, 0}}}
-      iex> Calendar.ISO.parse_naive_datetime("20150123T235007")
-      {:error, :invalid_format}
-
-  Parsing can be restricted to basic if desired:
-
-      iex> Calendar.ISO.parse_naive_datetime("20150123T235007Z", :basic)
-      {:ok, {2015, 1, 23, 23, 50, 7, {0, 0}}}
-      iex> Calendar.ISO.parse_naive_datetime("20150123T235007Z", :extended)
-      {:error, :invalid_format}
-
-  Only calendar dates are supported in parsing; ordinal and week dates are not.
-
-      iex> Calendar.ISO.parse_date("2015-04-15")
-      {:ok, {2015, 4, 15}}
-      iex> Calendar.ISO.parse_date("2015-105")
-      {:error, :invalid_format}
-      iex> Calendar.ISO.parse_date("2015-W16")
-      {:error, :invalid_format}
-      iex> Calendar.ISO.parse_date("2015-W016-3")
-      {:error, :invalid_format}
-
-  Years, months, days, hours, minutes, and seconds must be fully specified:
-
-      iex> Calendar.ISO.parse_date("2015-04-15")
-      {:ok, {2015, 4, 15}}
-      iex> Calendar.ISO.parse_date("2015-04")
-      {:error, :invalid_format}
-      iex> Calendar.ISO.parse_date("2015")
-      {:error, :invalid_format}
-
-      iex> Calendar.ISO.parse_time("23:50:07.0123456")
-      {:ok, {23, 50, 7, {12345, 6}}}
-      iex> Calendar.ISO.parse_time("23:50:07")
-      {:ok, {23, 50, 7, {0, 0}}}
-      iex> Calendar.ISO.parse_time("23:50")
-      {:error, :invalid_format}
-      iex> Calendar.ISO.parse_time("23")
-      {:error, :invalid_format}
-
-  ### Extensions
-
-  The parser and formatter adopt one ISO 8601 extension: extended year notation.
-
-  This allows dates to be prefixed with a `+` or `-` sign, extending the range of
-  expressible years from the default (`0000..9999`) to `-9999..9999`. Elixir still
-  restricts years in this format to four digits.
-
-  #### Examples
-
-      iex> Calendar.ISO.parse_date("-2015-01-23")
-      {:ok, {-2015, 1, 23}}
-      iex> Calendar.ISO.parse_date("+2015-01-23")
-      {:ok, {2015, 1, 23}}
-
-      iex> Calendar.ISO.parse_naive_datetime("-2015-01-23 23:50:07")
-      {:ok, {-2015, 1, 23, 23, 50, 7, {0, 0}}}
-      iex> Calendar.ISO.parse_naive_datetime("+2015-01-23 23:50:07")
-      {:ok, {2015, 1, 23, 23, 50, 7, {0, 0}}}
-
-      iex> Calendar.ISO.parse_utc_datetime("-2015-01-23 23:50:07Z")
-      {:ok, {-2015, 1, 23, 23, 50, 7, {0, 0}}, 0}
-      iex> Calendar.ISO.parse_utc_datetime("+2015-01-23 23:50:07Z")
-      {:ok, {2015, 1, 23, 23, 50, 7, {0, 0}}, 0}
-
-  ### Additions
-
-  ISO 8601 does not allow a whitespace instead of `T` as a separator
-  between date and times, both when parsing and formatting.
-  This is a common enough representation, Elixir allows it during parsing.
-
-  The formatting of dates in `NaiveDateTime.to_iso8601/1` and `DateTime.to_iso8601/1`
-  do produce specification-compliant string representations using the `T` separator.
-
-  #### Examples
-
-      iex> Calendar.ISO.parse_naive_datetime("2015-01-23 23:50:07.0123456")
-      {:ok, {2015, 1, 23, 23, 50, 7, {12345, 6}}}
-      iex> Calendar.ISO.parse_naive_datetime("2015-01-23T23:50:07.0123456")
-      {:ok, {2015, 1, 23, 23, 50, 7, {12345, 6}}}
-
-      iex> Calendar.ISO.parse_utc_datetime("2015-01-23 23:50:07.0123456Z")
-      {:ok, {2015, 1, 23, 23, 50, 7, {12345, 6}}, 0}
-      iex> Calendar.ISO.parse_utc_datetime("2015-01-23T23:50:07.0123456Z")
-      {:ok, {2015, 1, 23, 23, 50, 7, {12345, 6}}, 0}
+  Given this is the default calendar used by Elixir, it has one
+  difference compared to the ISO8601 specification in that it allows
+  a whitespace instead of `T` as a seperator between date and times
+  both when parsing and formatting. Strict formatting can be done
+  by using the `to_iso8601` found in `NaiveDateTime` and `DateTime`.

+  Note that while ISO 8601 allows times and datetimes to specify
+  24:00:00 as the zero hour of the next day, this notation is not
+  supported by Elixir.
  """

  @behaviour Calendar
@@ -131,8 +26,6 @@ defmodule Calendar.ISO do
  unix_end = 315_569_519_999_999_999 - @unix_epoch * 1_000_000
  @unix_range_microseconds unix_start..unix_end

-  defguardp is_format(term) when term in [:basic, :extended]
-
  @typedoc """
  "Before the Current Era" or "Before the Common Era" (BCE), for those years less than `1`.
  """
@@ -158,8 +51,6 @@ defmodule Calendar.ISO do
  @type minute :: 0..59
  @type second :: 0..59
  @type weekday :: :monday | :tuesday | :wednesday | :thursday | :friday | :saturday | :sunday
-  @type utc_offset :: integer
-  @type format :: :basic | :extended

  @typedoc """
  Microseconds with stored precision.
@@ -187,10 +78,7 @@ defmodule Calendar.ISO do
  @microseconds_per_second 1_000_000
  @parts_per_day @seconds_per_day * @microseconds_per_second

-  @datetime_seps [?\s, ?T]
-  @ext_date_sep ?-
-  @ext_time_sep ?:
-
+  @sep [?\s, ?T]
  @days_per_nonleap_year 365
  @days_per_leap_year 366

@@ -199,11 +87,10 @@ defmodule Calendar.ISO do
  # on ~D[0001-01-01] which is 366 days later.
  @iso_epoch 366

-  [match_basic_date, match_ext_date, guard_date, read_date] =
+  [match_date, guard_date, read_date] =
    quote do
      [
-        <<y1, y2, y3, y4, m1, m2, d1, d2>>,
-        <<y1, y2, y3, y4, @ext_date_sep, m1, m2, @ext_date_sep, d1, d2>>,
+        <<y1, y2, y3, y4, ?-, m1, m2, ?-, d1, d2>>,
        y1 >= ?0 and y1 <= ?9 and y2 >= ?0 and y2 <= ?9 and y3 >= ?0 and y3 <= ?9 and y4 >= ?0 and
          y4 <= ?9 and m1 >= ?0 and m1 <= ?9 and m2 >= ?0 and m2 <= ?9 and d1 >= ?0 and d1 <= ?9 and
          d2 >= ?0 and d2 <= ?9,
@@ -215,11 +102,10 @@ defmodule Calendar.ISO do
      ]
    end

-  [match_basic_time, match_ext_time, guard_time, read_time] =
+  [match_time, guard_time, read_time] =
    quote do
      [
-        <<h1, h2, i1, i2, s1, s2>>,
-        <<h1, h2, @ext_time_sep, i1, i2, @ext_time_sep, s1, s2>>,
+        <<h1, h2, ?:, i1, i2, ?:, s1, s2>>,
        h1 >= ?0 and h1 <= ?9 and h2 >= ?0 and h2 <= ?9 and i1 >= ?0 and i1 <= ?9 and i2 >= ?0 and
          i2 <= ?9 and s1 >= ?0 and s1 <= ?9 and s2 >= ?0 and s2 <= ?9,
        {
@@ -248,87 +134,49 @@ defmodule Calendar.ISO do
  defguardp is_std_offset(offset) when is_integer(offset)

  @doc """
-  Converts a `t:System.time_unit/0` to precision.
-
-  Integer-based time units always get maximum precision.
-  """
-  def time_unit_to_precision(:nanosecond), do: 6
-  def time_unit_to_precision(:microsecond), do: 6
-  def time_unit_to_precision(:millisecond), do: 3
-  def time_unit_to_precision(:second), do: 0
-  def time_unit_to_precision(_), do: 6
-
-  @doc """
-  Parses a time `string` in the `:extended` format.
-
-  For more information on supported strings, see how this
-  module implements [ISO 8601](#module-iso-8601-compliance).
+  Parses a time string.

  ## Examples

      iex> Calendar.ISO.parse_time("23:50:07")
      {:ok, {23, 50, 7, {0, 0}}}
-
      iex> Calendar.ISO.parse_time("23:50:07Z")
      {:ok, {23, 50, 7, {0, 0}}}
      iex> Calendar.ISO.parse_time("T23:50:07Z")
      {:ok, {23, 50, 7, {0, 0}}}

+      iex> Calendar.ISO.parse_time("23:50:07,0123456")
+      {:ok, {23, 50, 7, {12345, 6}}}
+      iex> Calendar.ISO.parse_time("23:50:07.0123456")
+      {:ok, {23, 50, 7, {12345, 6}}}
+      iex> Calendar.ISO.parse_time("23:50:07.123Z")
+      {:ok, {23, 50, 7, {123000, 3}}}
+
+      iex> Calendar.ISO.parse_time("2015:01:23 23-50-07")
+      {:error, :invalid_format}
+      iex> Calendar.ISO.parse_time("23:50:07A")
+      {:error, :invalid_format}
+      iex> Calendar.ISO.parse_time("23:50:07.")
+      {:error, :invalid_format}
+      iex> Calendar.ISO.parse_time("23:50:61")
+      {:error, :invalid_time}
+
  """
  @doc since: "1.10.0"
  @impl true
-  @spec parse_time(String.t()) ::
-          {:ok, {hour, minute, second, microsecond}}
-          | {:error, atom}
+  def parse_time("T" <> string) when is_binary(string),
+    do: do_parse_time(string)
+
  def parse_time(string) when is_binary(string),
-    do: parse_time(string, :extended)
+    do: do_parse_time(string)

-  @doc """
-  Parses a time `string` according to a given `format`.
-
-  The `format` can either be `:basic` or `:extended`.
-
-  For more information on supported strings, see how this
-  module implements [ISO 8601](#module-iso-8601-compliance).
-
-  ## Examples
-
-      iex> Calendar.ISO.parse_time("235007", :basic)
-      {:ok, {23, 50, 7, {0, 0}}}
-      iex> Calendar.ISO.parse_time("235007", :extended)
-      {:error, :invalid_format}
-
-  """
-  @doc since: "1.12.0"
-  @spec parse_time(String.t(), format) ::
-          {:ok, {hour, minute, second, microsecond}}
-          | {:error, atom}
-  def parse_time(string, format) when is_binary(string) and is_format(format) do
-    case string do
-      "T" <> rest -> do_parse_time(rest, format)
-      _ -> do_parse_time(string, format)
-    end
-  end
-
-  defp do_parse_time(<<unquote(match_basic_time), rest::binary>>, :basic)
-       when unquote(guard_time) do
-    {hour, minute, second} = unquote(read_time)
-    parse_formatted_time(hour, minute, second, rest)
-  end
-
-  defp do_parse_time(<<unquote(match_ext_time), rest::binary>>, :extended)
-       when unquote(guard_time) do
-    {hour, minute, second} = unquote(read_time)
-    parse_formatted_time(hour, minute, second, rest)
-  end
-
-  defp do_parse_time(_, _) do
-    {:error, :invalid_format}
-  end
-
-  defp parse_formatted_time(hour, minute, second, rest) do
-    with {microsecond, rest} <- parse_microsecond(rest),
+  defp do_parse_time(string) do
+    with <<unquote(match_time), rest::binary>> <- string,
+         true <- unquote(guard_time),
+         {microsecond, rest} <- parse_microsecond(rest),
         {_offset, ""} <- parse_offset(rest) do
+      {hour, minute, second} = unquote(read_time)
+
      if valid_time?(hour, minute, second, microsecond) do
        {:ok, {hour, minute, second, microsecond}}
      else
@@ -340,16 +188,14 @@ defmodule Calendar.ISO do
  end

  @doc """
-  Parses a date `string` in the `:extended` format.
-
-  For more information on supported strings, see how this
-  module implements [ISO 8601](#module-iso-8601-compliance).
+  Parses a date string.

  ## Examples

      iex> Calendar.ISO.parse_date("2015-01-23")
      {:ok, {2015, 1, 23}}
-
+      iex> Calendar.ISO.parse_date("-2015-01-23")
+      {:ok, {-2015, 1, 23}}
      iex> Calendar.ISO.parse_date("2015:01:23")
      {:error, :invalid_format}
      iex> Calendar.ISO.parse_date("2015-01-32")
@@ -358,160 +204,91 @@ defmodule Calendar.ISO do
  """
  @doc since: "1.10.0"
  @impl true
-  @spec parse_date(String.t()) ::
-          {:ok, {year, month, day}}
-          | {:error, atom}
+  def parse_date("-" <> string) when is_binary(string),
+    do: parse_date(string, -1)
+
  def parse_date(string) when is_binary(string),
-    do: parse_date(string, :extended)
+    do: parse_date(string, 1)

-  @doc """
-  Parses a date `string` according to a given `format`.
+  defp parse_date(string, multiplier) do
+    with unquote(match_date) <- string, true <- unquote(guard_date) do
+      {year, month, day} = unquote(read_date)
+      year = multiplier * year

-  The `format` can either be `:basic` or `:extended`.
-
-  For more information on supported strings, see how this
-  module implements [ISO 8601](#module-iso-8601-compliance).
-
-  ## Examples
-
-      iex> Calendar.ISO.parse_date("20150123", :basic)
-      {:ok, {2015, 1, 23}}
-      iex> Calendar.ISO.parse_date("20150123", :extended)
-      {:error, :invalid_format}
-
-  """
-  @doc since: "1.12.0"
-  @spec parse_date(String.t(), format) ::
-          {:ok, {year, month, day}}
-          | {:error, atom}
-  def parse_date(string, format) when is_binary(string) and is_format(format),
-    do: parse_date_guarded(string, format)
-
-  defp parse_date_guarded("-" <> string, format),
-    do: do_parse_date(string, -1, format)
-
-  defp parse_date_guarded("+" <> string, format),
-    do: do_parse_date(string, 1, format)
-
-  defp parse_date_guarded(string, format),
-    do: do_parse_date(string, 1, format)
-
-  defp do_parse_date(unquote(match_basic_date), multiplier, :basic) when unquote(guard_date) do
-    {year, month, day} = unquote(read_date)
-    parse_formatted_date(year, month, day, multiplier)
-  end
-
-  defp do_parse_date(unquote(match_ext_date), multiplier, :extended) when unquote(guard_date) do
-    {year, month, day} = unquote(read_date)
-    parse_formatted_date(year, month, day, multiplier)
-  end
-
-  defp do_parse_date(_, _, _) do
-    {:error, :invalid_format}
-  end
-
-  defp parse_formatted_date(year, month, day, multiplier) do
-    year = multiplier * year
-
-    if valid_date?(year, month, day) do
-      {:ok, {year, month, day}}
+      if valid_date?(year, month, day) do
+        {:ok, {year, month, day}}
+      else
+        {:error, :invalid_date}
+      end
    else
-      {:error, :invalid_date}
+      _ ->
+        {:error, :invalid_format}
    end
  end

  @doc """
-  Parses a naive datetime `string` in the `:extended` format.
-
-  For more information on supported strings, see how this
-  module implements [ISO 8601](#module-iso-8601-compliance).
+  Parses a naive datetime string.

  ## Examples

      iex> Calendar.ISO.parse_naive_datetime("2015-01-23 23:50:07")
      {:ok, {2015, 1, 23, 23, 50, 7, {0, 0}}}
-      iex> Calendar.ISO.parse_naive_datetime("2015-01-23 23:50:07Z")
+      iex> Calendar.ISO.parse_naive_datetime("2015-01-23T23:50:07")
      {:ok, {2015, 1, 23, 23, 50, 7, {0, 0}}}
-      iex> Calendar.ISO.parse_naive_datetime("2015-01-23 23:50:07-02:30")
+      iex> Calendar.ISO.parse_naive_datetime("2015-01-23T23:50:07Z")
      {:ok, {2015, 1, 23, 23, 50, 7, {0, 0}}}

      iex> Calendar.ISO.parse_naive_datetime("2015-01-23 23:50:07.0")
      {:ok, {2015, 1, 23, 23, 50, 7, {0, 1}}}
      iex> Calendar.ISO.parse_naive_datetime("2015-01-23 23:50:07,0123456")
      {:ok, {2015, 1, 23, 23, 50, 7, {12345, 6}}}
+      iex> Calendar.ISO.parse_naive_datetime("2015-01-23 23:50:07.0123456")
+      {:ok, {2015, 1, 23, 23, 50, 7, {12345, 6}}}
+      iex> Calendar.ISO.parse_naive_datetime("2015-01-23T23:50:07.123Z")
+      {:ok, {2015, 1, 23, 23, 50, 7, {123000, 3}}}
+
+      iex> Calendar.ISO.parse_naive_datetime("2015-01-23P23:50:07")
+      {:error, :invalid_format}
+      iex> Calendar.ISO.parse_naive_datetime("2015:01:23 23-50-07")
+      {:error, :invalid_format}
+      iex> Calendar.ISO.parse_naive_datetime("2015-01-23 23:50:07A")
+      {:error, :invalid_format}
+      iex> Calendar.ISO.parse_naive_datetime("2015-01-23 23:50:61")
+      {:error, :invalid_time}
+      iex> Calendar.ISO.parse_naive_datetime("2015-01-32 23:50:07")
+      {:error, :invalid_date}
+
+      iex> Calendar.ISO.parse_naive_datetime("2015-01-23T23:50:07.123+02:30")
+      {:ok, {2015, 1, 23, 23, 50, 7, {123000, 3}}}
+      iex> Calendar.ISO.parse_naive_datetime("2015-01-23T23:50:07.123+00:00")
+      {:ok, {2015, 1, 23, 23, 50, 7, {123000, 3}}}
+      iex> Calendar.ISO.parse_naive_datetime("2015-01-23T23:50:07.123-02:30")
+      {:ok, {2015, 1, 23, 23, 50, 7, {123000, 3}}}
+      iex> Calendar.ISO.parse_naive_datetime("2015-01-23T23:50:07.123-00:00")
+      {:error, :invalid_format}
+      iex> Calendar.ISO.parse_naive_datetime("2015-01-23T23:50:07.123-00:60")
+      {:error, :invalid_format}
+      iex> Calendar.ISO.parse_naive_datetime("2015-01-23T23:50:07.123-24:00")
+      {:error, :invalid_format}

  """
  @doc since: "1.10.0"
  @impl true
-  @spec parse_naive_datetime(String.t()) ::
-          {:ok, {year, month, day, hour, minute, second, microsecond}}
-          | {:error, atom}
+  def parse_naive_datetime("-" <> string) when is_binary(string),
+    do: parse_naive_datetime(string, -1)
+
  def parse_naive_datetime(string) when is_binary(string),
-    do: parse_naive_datetime(string, :extended)
+    do: parse_naive_datetime(string, 1)

-  @doc """
-  Parses a naive datetime `string` according to a given `format`.
-
-  The `format` can either be `:basic` or `:extended`.
-
-  For more information on supported strings, see how this
-  module implements [ISO 8601](#module-iso-8601-compliance).
-
-  ## Examples
-
-      iex> Calendar.ISO.parse_naive_datetime("20150123 235007", :basic)
-      {:ok, {2015, 1, 23, 23, 50, 7, {0, 0}}}
-      iex> Calendar.ISO.parse_naive_datetime("20150123 235007", :extended)
-      {:error, :invalid_format}
-
-  """
-  @doc since: "1.12.0"
-  @spec parse_naive_datetime(String.t(), format) ::
-          {:ok, {year, month, day, hour, minute, second, microsecond}}
-          | {:error, atom}
-  def parse_naive_datetime(string, format) when is_binary(string) and is_format(format),
-    do: parse_naive_datetime_guarded(string, format)
-
-  defp parse_naive_datetime_guarded("-" <> string, format),
-    do: do_parse_naive_datetime(string, -1, format)
-
-  defp parse_naive_datetime_guarded("+" <> string, format),
-    do: do_parse_naive_datetime(string, 1, format)
-
-  defp parse_naive_datetime_guarded(string, format),
-    do: do_parse_naive_datetime(string, 1, format)
-
-  defp do_parse_naive_datetime(
-         <<unquote(match_basic_date), datetime_sep, unquote(match_basic_time), rest::binary>>,
-         multiplier,
-         :basic
-       )
-       when unquote(guard_date) and datetime_sep in @datetime_seps and unquote(guard_time) do
-    {year, month, day} = unquote(read_date)
-    {hour, minute, second} = unquote(read_time)
-    parse_formatted_naive_datetime(year, month, day, hour, minute, second, rest, multiplier)
-  end
-
-  defp do_parse_naive_datetime(
-         <<unquote(match_ext_date), datetime_sep, unquote(match_ext_time), rest::binary>>,
-         multiplier,
-         :extended
-       )
-       when unquote(guard_date) and datetime_sep in @datetime_seps and unquote(guard_time) do
-    {year, month, day} = unquote(read_date)
-    {hour, minute, second} = unquote(read_time)
-    parse_formatted_naive_datetime(year, month, day, hour, minute, second, rest, multiplier)
-  end
-
-  defp do_parse_naive_datetime(_, _, _) do
-    {:error, :invalid_format}
-  end
-
-  defp parse_formatted_naive_datetime(year, month, day, hour, minute, second, rest, multiplier) do
-    year = multiplier * year
-
-    with {microsecond, rest} <- parse_microsecond(rest),
+  defp parse_naive_datetime(string, multiplier) do
+    with <<unquote(match_date), sep, unquote(match_time), rest::binary>> <- string,
+         true <- unquote(guard_date) and sep in @sep and unquote(guard_time),
+         {microsecond, rest} <- parse_microsecond(rest),
         {_offset, ""} <- parse_offset(rest) do
+      {year, month, day} = unquote(read_date)
+      {hour, minute, second} = unquote(read_time)
+      year = multiplier * year
+
      cond do
        not valid_date?(year, month, day) ->
          {:error, :invalid_date}
@@ -528,94 +305,54 @@ defmodule Calendar.ISO do
  end

  @doc """
-  Parses a UTC datetime `string` in the `:extended` format.
-
-  For more information on supported strings, see how this
-  module implements [ISO 8601](#module-iso-8601-compliance).
+  Parses a UTC datetime string.

  ## Examples

-      iex> Calendar.ISO.parse_utc_datetime("2015-01-23 23:50:07Z")
+      iex> Calendar.ISO.parse_utc_datetime("2015-01-23T23:50:07Z")
      {:ok, {2015, 1, 23, 23, 50, 7, {0, 0}}, 0}

-      iex> Calendar.ISO.parse_utc_datetime("2015-01-23 23:50:07+02:30")
-      {:ok, {2015, 1, 23, 21, 20, 7, {0, 0}}, 9000}
+      iex> Calendar.ISO.parse_utc_datetime("2015-01-23T23:50:07.123+02:30")
+      {:ok, {2015, 1, 23, 21, 20, 7, {123000, 3}}, 9000}

-      iex> Calendar.ISO.parse_utc_datetime("2015-01-23 23:50:07")
+      iex> Calendar.ISO.parse_utc_datetime("2015-01-23T23:50:07,123+02:30")
+      {:ok, {2015, 1, 23, 21, 20, 7, {123000, 3}}, 9000}
+
+      iex> Calendar.ISO.parse_utc_datetime("-2015-01-23T23:50:07Z")
+      {:ok, {-2015, 1, 23, 23, 50, 7, {0, 0}}, 0}
+
+      iex> Calendar.ISO.parse_utc_datetime("-2015-01-23T23:50:07,123+02:30")
+      {:ok, {-2015, 1, 23, 21, 20, 7, {123000, 3}}, 9000}
+
+      iex> Calendar.ISO.parse_utc_datetime("2015-01-23P23:50:07")
+      {:error, :invalid_format}
+      iex> Calendar.ISO.parse_utc_datetime("2015-01-23T23:50:07")
      {:error, :missing_offset}
+      iex> Calendar.ISO.parse_utc_datetime("2015-01-23 23:50:61")
+      {:error, :invalid_time}
+      iex> Calendar.ISO.parse_utc_datetime("2015-01-32 23:50:07")
+      {:error, :invalid_date}
+      iex> Calendar.ISO.parse_utc_datetime("2015-01-23T23:50:07.123-00:00")
+      {:error, :invalid_format}

  """
  @doc since: "1.10.0"
  @impl true
-  @spec parse_utc_datetime(String.t()) ::
-          {:ok, {year, month, day, hour, minute, second, microsecond}, utc_offset}
-          | {:error, atom}
+  def parse_utc_datetime("-" <> string) when is_binary(string),
+    do: parse_utc_datetime(string, -1)
+
  def parse_utc_datetime(string) when is_binary(string),
-    do: parse_utc_datetime(string, :extended)
+    do: parse_utc_datetime(string, 1)

-  @doc """
-  Parses a UTC datetime `string` according to a given `format`.
-
-  The `format` can either be `:basic` or `:extended`.
-
-  For more information on supported strings, see how this
-  module implements [ISO 8601](#module-iso-8601-compliance).
-
-  ## Examples
-
-      iex> Calendar.ISO.parse_utc_datetime("20150123 235007Z", :basic)
-      {:ok, {2015, 1, 23, 23, 50, 7, {0, 0}}, 0}
-      iex> Calendar.ISO.parse_utc_datetime("20150123 235007Z", :extended)
-      {:error, :invalid_format}
-
-  """
-  @doc since: "1.12.0"
-  @spec parse_utc_datetime(String.t(), format) ::
-          {:ok, {year, month, day, hour, minute, second, microsecond}, utc_offset}
-          | {:error, atom}
-  def parse_utc_datetime(string, format) when is_binary(string) and is_format(format),
-    do: parse_utc_datetime_guarded(string, format)
-
-  defp parse_utc_datetime_guarded("-" <> string, format),
-    do: do_parse_utc_datetime(string, -1, format)
-
-  defp parse_utc_datetime_guarded("+" <> string, format),
-    do: do_parse_utc_datetime(string, 1, format)
-
-  defp parse_utc_datetime_guarded(string, format),
-    do: do_parse_utc_datetime(string, 1, format)
-
-  defp do_parse_utc_datetime(
-         <<unquote(match_basic_date), datetime_sep, unquote(match_basic_time), rest::binary>>,
-         multiplier,
-         :basic
-       )
-       when unquote(guard_date) and datetime_sep in @datetime_seps and unquote(guard_time) do
-    {year, month, day} = unquote(read_date)
-    {hour, minute, second} = unquote(read_time)
-    parse_formatted_utc_datetime(year, month, day, hour, minute, second, rest, multiplier)
-  end
-
-  defp do_parse_utc_datetime(
-         <<unquote(match_ext_date), datetime_sep, unquote(match_ext_time), rest::binary>>,
-         multiplier,
-         :extended
-       )
-       when unquote(guard_date) and datetime_sep in @datetime_seps and unquote(guard_time) do
-    {year, month, day} = unquote(read_date)
-    {hour, minute, second} = unquote(read_time)
-    parse_formatted_utc_datetime(year, month, day, hour, minute, second, rest, multiplier)
-  end
-
-  defp do_parse_utc_datetime(_, _, _) do
-    {:error, :invalid_format}
-  end
-
-  defp parse_formatted_utc_datetime(year, month, day, hour, minute, second, rest, multiplier) do
-    year = multiplier * year
-
-    with {microsecond, rest} <- parse_microsecond(rest),
+  defp parse_utc_datetime(string, multiplier) do
+    with <<unquote(match_date), sep, unquote(match_time), rest::binary>> <- string,
+         true <- unquote(guard_date) and sep in @sep and unquote(guard_time),
+         {microsecond, rest} <- parse_microsecond(rest),
         {offset, ""} <- parse_offset(rest) do
+      {year, month, day} = unquote(read_date)
+      {hour, minute, second} = unquote(read_time)
+      year = multiplier * year
+
      cond do
        not valid_date?(year, month, day) ->
          {:error, :invalid_date}
@@ -645,7 +382,8 @@ defmodule Calendar.ISO do
          {:ok, {year, month, day, hour, minute, second, microsecond}, offset}
      end
    else
-      _ -> {:error, :invalid_format}
+      _ ->
+        {:error, :invalid_format}
    end
  end

@@ -1034,33 +772,14 @@ defmodule Calendar.ISO do
  """
  @doc since: "1.8.0"
  @spec year_of_era(year) :: {1..10000, era}
-  def year_of_era(year) when is_year_CE(year), do: {year, 1}
-  def year_of_era(year) when is_year_BCE(year), do: {abs(year) + 1, 0}
-
-  @doc """
-  Calendar callback to compute the year and era from the
-  given `year`, `month` and `day`.
-
-  In the ISO calendar, the new year coincides with the new era,
-  so the `month` and `day` arguments are discarded. If you only
-  have the year available, you can `year_of_era/1` instead.
-
-  ## Examples
-
-      iex> Calendar.ISO.year_of_era(1, 1, 1)
-      {1, 1}
-      iex> Calendar.ISO.year_of_era(2018, 12, 1)
-      {2018, 1}
-      iex> Calendar.ISO.year_of_era(0, 1, 1)
-      {1, 0}
-      iex> Calendar.ISO.year_of_era(-1, 12, 1)
-      {2, 0}
-
-  """
-  @doc since: "1.13.0"
  @impl true
-  @spec year_of_era(year, month, day) :: {1..10000, era}
-  def year_of_era(year, _month, _day), do: year_of_era(year)
+  def year_of_era(year) when is_year_CE(year) do
+    {year, 1}
+  end
+
+  def year_of_era(year) when is_year_BCE(year) do
+    {abs(year) + 1, 0}
+  end

  @doc """
  Calculates the day and era from the given `year`, `month`, and `day`.
@@ -1356,7 +1075,9 @@ defmodule Calendar.ISO do
  @doc """
  Determines if the date given is valid according to the proleptic Gregorian calendar.

-  Leap seconds are not supported by the built-in Calendar.ISO.
+  Note that while ISO 8601 allows times to specify 24:00:00 as the
+  zero hour of the next day, this notation is not supported by Elixir.
+  Leap seconds are not supported as well by the built-in Calendar.ISO.

  ## Examples

@@ -5,7 +5,7 @@ defmodule NaiveDateTime do
  The NaiveDateTime struct contains the fields year, month, day, hour,
  minute, second, microsecond and calendar. New naive datetimes can be
  built with the `new/2` and `new/8` functions or using the
-  `~N` (see `sigil_N/2`) sigil:
+  `~N` (see `Kernel.sigil_N/2`) sigil:

      iex> ~N[2000-01-01 23:00:07]
      ~N[2000-01-01 23:00:07]
@@ -36,18 +36,12 @@ defmodule NaiveDateTime do

  Comparisons in Elixir using `==/2`, `>/2`, `</2` and similar are structural
  and based on the `NaiveDateTime` struct fields. For proper comparison
-  between naive datetimes, use the `compare/2` function. The existence of the
-  `compare/2` function in this module also allows using `Enum.min/2` and
-  `Enum.max/2` functions to get the minimum and maximum naive datetime of an
-  `Enum`. For example:
-
-      iex> Enum.min([~N[2020-01-01 23:00:07], ~N[2000-01-01 23:00:07]], NaiveDateTime)
-      ~N[2000-01-01 23:00:07]
+  between naive datetimes, use the `compare/2` function.

  ## Using epochs

-  The `add/3` and `diff/3` functions can be used for computing date
-  times or retrieving the number of seconds between instants.
+  The `add/3` and `diff/3` functions can be used for computing with
+  date times or retrieving the number of seconds between instants.
  For example, if there is an interest in computing the number of
  seconds from the Unix epoch (1970-01-01 00:00:00):

@@ -356,17 +350,11 @@ defmodule NaiveDateTime do
  @doc """
  Adds a specified amount of time to a `NaiveDateTime`.

-  Accepts an `amount_to_add` in any `unit`. `unit` can be `:day`,
-  `:hour`, `:minute`, `:second` or any subsecond precision from
-  `t:System.time_unit/0`. It defaults to `:second`. Negative values
-  will move backwards in time.
-
-  This function always considers the unit to be computed according to the `Calendar.ISO`.
+  Accepts an `amount_to_add` in any `unit` available from `t:System.time_unit/0`.
+  Negative values will move backwards in time.

  ## Examples

-  It uses seconds by default:
-
      # adds seconds by default
      iex> NaiveDateTime.add(~N[2014-10-02 00:29:10], 2)
      ~N[2014-10-02 00:29:12]
@@ -375,28 +363,18 @@ defmodule NaiveDateTime do
      iex> NaiveDateTime.add(~N[2014-10-02 00:29:10], -2)
      ~N[2014-10-02 00:29:08]

-  It can also work with subsecond precisions:
-
+      # can work with other units
      iex> NaiveDateTime.add(~N[2014-10-02 00:29:10], 2_000, :millisecond)
-      ~N[2014-10-02 00:29:12.000]
+      ~N[2014-10-02 00:29:12]

-  As well as days/hours/minutes:
+      # keeps the same precision
+      iex> NaiveDateTime.add(~N[2014-10-02 00:29:10.021], 21, :second)
+      ~N[2014-10-02 00:29:31.021]

-      iex> NaiveDateTime.add(~N[2015-02-28 00:29:10], 2, :day)
-      ~N[2015-03-02 00:29:10]
-      iex> NaiveDateTime.add(~N[2015-02-28 00:29:10], 36, :hour)
-      ~N[2015-03-01 12:29:10]
-      iex> NaiveDateTime.add(~N[2015-02-28 00:29:10], 60, :minute)
-      ~N[2015-02-28 01:29:10]
-
-  This operation merges the precision of the naive date time with the given unit:
-
-      iex> result = NaiveDateTime.add(~N[2014-10-02 00:29:10], 21, :millisecond)
-      ~N[2014-10-02 00:29:10.021]
-      iex> result.microsecond
-      {21000, 3}
-
-  Operations on top of gregorian seconds or the Unix epoch are optimized:
+      # changes below the precision will not be visible
+      iex> hidden = NaiveDateTime.add(~N[2014-10-02 00:29:10], 21, :millisecond)
+      iex> hidden.microsecond # ~N[2014-10-02 00:29:10]
+      {21000, 0}

      # from Gregorian seconds
      iex> NaiveDateTime.add(~N[0000-01-01 00:00:00], 63_579_428_950)
@@ -413,29 +391,14 @@ defmodule NaiveDateTime do

  """
  @doc since: "1.4.0"
-  @spec add(Calendar.naive_datetime(), integer, :day | :hour | :minute | System.time_unit()) :: t
-  def add(naive_datetime, amount_to_add, unit \\ :second)
-
-  def add(naive_datetime, amount_to_add, :day) when is_integer(amount_to_add) do
-    add(naive_datetime, amount_to_add * 86400, :second)
-  end
-
-  def add(naive_datetime, amount_to_add, :hour) when is_integer(amount_to_add) do
-    add(naive_datetime, amount_to_add * 3600, :second)
-  end
-
-  def add(naive_datetime, amount_to_add, :minute) when is_integer(amount_to_add) do
-    add(naive_datetime, amount_to_add * 60, :second)
-  end
-
+  @spec add(Calendar.naive_datetime(), integer, System.time_unit()) :: t
  def add(
        %{microsecond: {_, precision}, calendar: calendar} = naive_datetime,
        amount_to_add,
-        unit
+        unit \\ :second
      )
      when is_integer(amount_to_add) do
    ppd = System.convert_time_unit(86400, :second, unit)
-    precision = max(Calendar.ISO.time_unit_to_precision(unit), precision)

    naive_datetime
    |> to_iso_days()
@@ -446,11 +409,10 @@ defmodule NaiveDateTime do
  @doc """
  Subtracts `naive_datetime2` from `naive_datetime1`.

-  The answer can be returned in any `:day`, `:hour`, `:minute`, or any `unit`
-  available from `t:System.time_unit/0`. The unit is measured according to
-  `Calendar.ISO` and defaults to `:second`.
+  The answer can be returned in any `unit` available from `t:System.time_unit/0`.

-  Fractional results are not supported and are truncated.
+  This function returns the difference in seconds where seconds are measured
+  according to `Calendar.ISO`.

  ## Examples

@@ -458,57 +420,24 @@ defmodule NaiveDateTime do
      2
      iex> NaiveDateTime.diff(~N[2014-10-02 00:29:12], ~N[2014-10-02 00:29:10], :microsecond)
      2_000_000
-
-      iex> NaiveDateTime.diff(~N[2014-10-02 00:29:10.042], ~N[2014-10-02 00:29:10.021])
-      0
      iex> NaiveDateTime.diff(~N[2014-10-02 00:29:10.042], ~N[2014-10-02 00:29:10.021], :millisecond)
      21
-
      iex> NaiveDateTime.diff(~N[2014-10-02 00:29:10], ~N[2014-10-02 00:29:12])
      -2
      iex> NaiveDateTime.diff(~N[-0001-10-02 00:29:10], ~N[-0001-10-02 00:29:12])
      -2

-  It can also compute the difference in days, hours, or minutes:
-
-      iex> NaiveDateTime.diff(~N[2014-10-10 00:29:10], ~N[2014-10-02 00:29:10], :day)
-      8
-      iex> NaiveDateTime.diff(~N[2014-10-02 12:29:10], ~N[2014-10-02 00:29:10], :hour)
-      12
-      iex> NaiveDateTime.diff(~N[2014-10-02 00:39:10], ~N[2014-10-02 00:29:10], :minute)
-      10
-
-  But it also rounds incomplete days to zero:
-
-      iex> NaiveDateTime.diff(~N[2014-10-10 00:29:09], ~N[2014-10-02 00:29:10], :day)
-      7
+      # to Gregorian seconds
+      iex> NaiveDateTime.diff(~N[2014-10-02 00:29:10], ~N[0000-01-01 00:00:00])
+      63579428950

  """
  @doc since: "1.4.0"
-  @spec diff(
-          Calendar.naive_datetime(),
-          Calendar.naive_datetime(),
-          :day | :hour | :minute | System.time_unit()
-        ) :: integer
-
-  def diff(naive_datetime1, naive_datetime2, unit \\ :second)
-
-  def diff(naive_datetime1, naive_datetime2, :day) do
-    diff(naive_datetime1, naive_datetime2, :second) |> div(86400)
-  end
-
-  def diff(naive_datetime1, naive_datetime2, :hour) do
-    diff(naive_datetime1, naive_datetime2, :second) |> div(3600)
-  end
-
-  def diff(naive_datetime1, naive_datetime2, :minute) do
-    diff(naive_datetime1, naive_datetime2, :second) |> div(60)
-  end
-
+  @spec diff(Calendar.naive_datetime(), Calendar.naive_datetime(), System.time_unit()) :: integer
  def diff(
        %{calendar: calendar1} = naive_datetime1,
        %{calendar: calendar2} = naive_datetime2,
-        unit
+        unit \\ :second
      ) do
    if not Calendar.compatible_calendars?(calendar1, calendar2) do
      raise ArgumentError,
@@ -669,7 +598,7 @@ defmodule NaiveDateTime do

  @doc """
  Parses the extended "Date and time of day" format described by
-  [ISO 8601:2019](https://en.wikipedia.org/wiki/ISO_8601).
+  [ISO 8601:2004](https://en.wikipedia.org/wiki/ISO_8601).

  Time zone offset may be included in the string but they will be
  simply discarded as such information is not included in naive date
@@ -678,6 +607,9 @@ defmodule NaiveDateTime do
  As specified in the standard, the separator "T" may be omitted if
  desired as there is no ambiguity within this function.

+  The year parsed by this function is limited to four digits and,
+  while ISO 8601 allows datetimes to specify 24:00:00 as the zero
+  hour of the next day, this notation is not supported by Elixir.
  Note leap seconds are not supported by the built-in Calendar.ISO.

  ## Examples
@@ -744,7 +676,7 @@ defmodule NaiveDateTime do

  @doc """
  Parses the extended "Date and time of day" format described by
-  [ISO 8601:2019](https://en.wikipedia.org/wiki/ISO_8601).
+  [ISO 8601:2004](https://en.wikipedia.org/wiki/ISO_8601).

  Raises if the format is invalid.

@@ -772,7 +704,7 @@ defmodule NaiveDateTime do

  @doc """
  Converts the given naive datetime to
-  [ISO 8601:2019](https://en.wikipedia.org/wiki/ISO_8601).
+  [ISO 8601:2004](https://en.wikipedia.org/wiki/ISO_8601).

  By default, `NaiveDateTime.to_iso8601/2` returns naive datetimes formatted in the "extended"
  format, for human readability. It also supports the "basic" format through passing the `:basic` option.
@@ -4,7 +4,7 @@ defmodule Time do

  The Time struct contains the fields hour, minute, second and microseconds.
  New times can be built with the `new/4` function or using the
-  `~T` (see `sigil_T/2`) sigil:
+  `~T` (see `Kernel.sigil_T/2`) sigil:

      iex> ~T[23:00:07.001]
      ~T[23:00:07.001]
@@ -31,12 +31,7 @@ defmodule Time do

  Comparisons in Elixir using `==/2`, `>/2`, `</2` and similar are structural
  and based on the `Time` struct fields. For proper comparison between
-  times, use the `compare/2` function. The existence of the `compare/2`
-  function in this module also allows using `Enum.min/2` and `Enum.max/2`
-  functions to get the minimum and maximum time of an `Enum`. For example:
-
-      iex> Enum.min([~T[23:00:07.001], ~T[10:00:07.001]], Time)
-      ~T[10:00:07.001]
+  times, use the `compare/2` function.
  """

  @enforce_keys [:hour, :minute, :second]
@@ -216,7 +211,7 @@ defmodule Time do

  @doc """
  Parses the extended "Local time" format described by
-  [ISO 8601:2019](https://en.wikipedia.org/wiki/ISO_8601).
+  [ISO 8601:2004](https://en.wikipedia.org/wiki/ISO_8601).

  Time zone offset may be included in the string but they will be
  simply discarded as such information is not included in times.
@@ -224,6 +219,12 @@ defmodule Time do
  As specified in the standard, the separator "T" may be omitted if
  desired as there is no ambiguity within this function.

+  Time representations with reduced accuracy are not supported.
+
+  Note that while ISO 8601 allows times to specify 24:00:00 as the
+  zero hour of the next day, this notation is not supported by Elixir.
+  Leap seconds are not supported as well by the built-in Calendar.ISO.
+
  ## Examples

      iex> Time.from_iso8601("23:50:07")
@@ -262,7 +263,7 @@ defmodule Time do

  @doc """
  Parses the extended "Local time" format described by
-  [ISO 8601:2019](https://en.wikipedia.org/wiki/ISO_8601).
+  [ISO 8601:2004](https://en.wikipedia.org/wiki/ISO_8601).

  Raises if the format is invalid.

@@ -289,7 +290,7 @@ defmodule Time do

  @doc """
  Converts the given time to
-  [ISO 8601:2019](https://en.wikipedia.org/wiki/ISO_8601).
+  [ISO 8601:2004](https://en.wikipedia.org/wiki/ISO_8601).

  By default, `Time.to_iso8601/2` returns times formatted in the "extended"
  format, for human readability. It also supports the "basic" format through
@@ -454,15 +455,10 @@ defmodule Time do
  end

  @doc """
-  Adds the `amount_to_add` of `unit`s to the given `time`.
+  Adds the `number` of `unit`s to the given `time`.

-  Accepts an `amount_to_add` in any `unit`. `unit` can be `:day`,
-  `:hour`, `:minute`, `:second` or any subsecond precision from
-  `t:System.time_unit/0`. It defaults to `:second`. Negative values
-  will move backwards in time.
-
-  This function always consider the unit to be computed according
-  to the `Calendar.ISO`.
+  This function accepts the `number` measured according to `Calendar.ISO`.
+  The time is returned in the same calendar as it was given in.

  Note the result value represents the time of day, meaning that it is cyclic,
  for instance, it will never go over 24 hours for the ISO calendar.
@@ -470,64 +466,30 @@ defmodule Time do
  ## Examples

      iex> Time.add(~T[10:00:00], 27000)
-      ~T[17:30:00]
+      ~T[17:30:00.000000]
      iex> Time.add(~T[11:00:00.005], 2400)
-      ~T[11:40:00.005]
-      iex> Time.add(~T[00:00:00.000], 86_399_999, :millisecond)
-      ~T[23:59:59.999]
-
-  Negative values are allowed:
-
-      iex> Time.add(~T[23:00:00], -60)
-      ~T[22:59:00]
-
-  Note that the time is cyclic:
-
+      ~T[11:40:00.005000]
+      iex> Time.add(~T[00:00:00], 86_399_999, :millisecond)
+      ~T[23:59:59.999000]
      iex> Time.add(~T[17:10:05], 86400)
-      ~T[17:10:05]
-
-  Hours and minutes are also supported:
-
-      iex> Time.add(~T[17:10:05], 2, :hour)
-      ~T[19:10:05]
-      iex> Time.add(~T[17:10:05], 30, :minute)
-      ~T[17:40:05]
-
-  This operation merges the precision of the time with the given unit:
-
-      iex> result = Time.add(~T[00:29:10], 21, :millisecond)
-      ~T[00:29:10.021]
-      iex> result.microsecond
-      {21000, 3}
+      ~T[17:10:05.000000]
+      iex> Time.add(~T[23:00:00], -60)
+      ~T[22:59:00.000000]

  """
  @doc since: "1.6.0"
-  @spec add(Calendar.time(), integer, :hour | :minute | System.time_unit()) :: t
-  def add(time, amount_to_add, unit \\ :second)
-
-  def add(time, amount_to_add, :hour) when is_integer(amount_to_add) do
-    add(time, amount_to_add * 3600, :second)
-  end
-
-  def add(time, amount_to_add, :minute) when is_integer(amount_to_add) do
-    add(time, amount_to_add * 60, :second)
-  end
-
-  def add(%{calendar: calendar, microsecond: {_, precision}} = time, amount_to_add, unit)
-      when is_integer(amount_to_add) do
-    amount_to_add = System.convert_time_unit(amount_to_add, unit, :microsecond)
-    total = time_to_microseconds(time) + amount_to_add
+  @spec add(Calendar.time(), integer, System.time_unit()) :: t
+  def add(%{calendar: calendar} = time, number, unit \\ :second) when is_integer(number) do
+    number = System.convert_time_unit(number, unit, :microsecond)
+    total = time_to_microseconds(time) + number
    parts = Integer.mod(total, @parts_per_day)
-    precision = max(Calendar.ISO.time_unit_to_precision(unit), precision)
-
-    {hour, minute, second, {microsecond, _}} =
-      calendar.time_from_day_fraction({parts, @parts_per_day})
+    {hour, minute, second, microsecond} = calendar.time_from_day_fraction({parts, @parts_per_day})

    %Time{
      hour: hour,
      minute: minute,
      second: second,
-      microsecond: {microsecond, precision},
+      microsecond: microsecond,
      calendar: calendar
    }
  end
@@ -694,12 +656,12 @@ defmodule Time do
  additional information about a date or time zone is ignored when calculating
  the difference.

-  The answer can be returned in any `:hour`, `:minute`, `:second` or any
-  subsecond `unit` available from `t:System.time_unit/0`. If the first time
-  value is earlier than the second, a negative number is returned.
+  The answer can be returned in any `unit` available from
+  `t:System.time_unit/0`. If the first time value is earlier than
+  the second, a negative number is returned.

-  The unit is measured according to `Calendar.ISO` and defaults to `:second`.
-  Fractional results are not supported and are truncated.
+  This function returns the difference in seconds where seconds
+  are measured according to `Calendar.ISO`.

  ## Examples

@@ -720,38 +682,25 @@ defmodule Time do
      iex> Time.diff(~T[00:29:10], ~T[00:29:12], :microsecond)
      -2_000_000

-      iex> Time.diff(~T[02:29:10], ~T[00:29:10], :hour)
-      2
-      iex> Time.diff(~T[02:29:10], ~T[00:29:11], :hour)
-      1
-
  """
  @doc since: "1.5.0"
-  @spec diff(Calendar.time(), Calendar.time(), :hour | :minute | System.time_unit()) :: integer
+  @spec diff(Calendar.time(), Calendar.time(), System.time_unit()) :: integer
  def diff(time1, time2, unit \\ :second)

-  def diff(time1, time2, :hour) do
-    diff(time1, time2, :second) |> div(3600)
-  end
-
-  def diff(time1, time2, :minute) do
-    diff(time1, time2, :second) |> div(60)
-  end
-
  def diff(
        %{
          calendar: Calendar.ISO,
          hour: hour1,
          minute: minute1,
          second: second1,
-          microsecond: {microsecond1, _}
+          microsecond: {microsecond1, @parts_per_day}
        },
        %{
          calendar: Calendar.ISO,
          hour: hour2,
          minute: minute2,
          second: second2,
-          microsecond: {microsecond2, _}
+          microsecond: {microsecond2, @parts_per_day}
        },
        unit
      ) do
@@ -14,7 +14,7 @@ defmodule Code.Identifier do
  def unary_op(op) do
    cond do
      op in [:&] -> {:non_associative, 90}
-      op in [:!, :^, :not, :+, :-, :"~~~"] -> {:non_associative, 300}
+      op in [:!, :^, :not, :+, :-, :~~~] -> {:non_associative, 300}
      op in [:@] -> {:non_associative, 320}
      true -> :error
    end
@@ -37,23 +37,163 @@ defmodule Code.Identifier do
      op in [:"::"] -> {:right, 60}
      op in [:|] -> {:right, 70}
      op in [:=] -> {:right, 100}
-      op in [:||, :|||, :or] -> {:left, 120}
-      op in [:&&, :&&&, :and] -> {:left, 130}
-      op in [:==, :!=, :=~, :===, :!==] -> {:left, 140}
-      op in [:<, :<=, :>=, :>] -> {:left, 150}
-      op in [:|>, :<<<, :>>>, :<~, :~>, :<<~, :~>>, :<~>, :"<|>"] -> {:left, 160}
-      op in [:in] -> {:left, 170}
-      op in [:"^^^"] -> {:left, 180}
-      op in [:"//"] -> {:right, 190}
+      op in [:||, :|||, :or] -> {:left, 130}
+      op in [:&&, :&&&, :and] -> {:left, 140}
+      op in [:==, :!=, :=~, :===, :!==] -> {:left, 150}
+      op in [:<, :<=, :>=, :>] -> {:left, 160}
+      op in [:|>, :<<<, :>>>, :<~, :~>, :<<~, :~>>, :<~>, :<|>] -> {:left, 170}
+      op in [:in] -> {:left, 180}
+      op in [:^^^] -> {:left, 190}
      op in [:++, :--, :.., :<>, :+++, :---] -> {:right, 200}
      op in [:+, :-] -> {:left, 210}
      op in [:*, :/] -> {:left, 220}
-      op in [:**] -> {:left, 230}
      op in [:.] -> {:left, 310}
      true -> :error
    end
  end

+  @doc """
+  Classifies the given atom into one of the following categories:
+
+    * `:alias` - a valid Elixir alias, like `Foo`, `Foo.Bar` and so on
+
+    * `:callable_local` - an atom that can be used as a local call;
+      this category includes identifiers like `:foo`
+
+    * `:callable_operator` - all callable operators, such as `:<>`. Note
+      operators such as `:..` are not callable because of ambiguity
+
+    * `:not_atomable` - callable operators that must be wrapped in quotes when
+      defined as an atom. For example, `::` must be written as `:"::"` to avoid
+      the ambiguity between the atom and the keyword identifier
+
+    * `:not_callable` - an atom that cannot be used as a function call after the
+      `.` operator (for example, `:<<>>` is not callable because `Foo.<<>>` is a
+      syntax error); this category includes atoms like `:Foo`, since they are
+      valid identifiers but they need quotes to be used in function calls
+      (`Foo."Bar"`)
+
+    * `:other` - any other atom (these are usually escaped when inspected, like
+      `:"foo and bar"`)
+
+  """
+  def classify(atom) when is_atom(atom) do
+    charlist = Atom.to_charlist(atom)
+
+    cond do
+      atom in [:%, :%{}, :{}, :<<>>, :..., :.., :., :->] ->
+        :not_callable
+
+      atom in [:"::"] ->
+        :not_atomable
+
+      unary_op(atom) != :error or binary_op(atom) != :error ->
+        :callable_operator
+
+      valid_alias?(charlist) ->
+        :alias
+
+      true ->
+        case :elixir_config.get(:identifier_tokenizer, String.Tokenizer).tokenize(charlist) do
+          {kind, _acc, [], _, _, special} ->
+            if kind == :identifier and not :lists.member(?@, special) do
+              :callable_local
+            else
+              :not_callable
+            end
+
+          _ ->
+            :other
+        end
+    end
+  end
+
+  defp valid_alias?('Elixir' ++ rest), do: valid_alias_piece?(rest)
+  defp valid_alias?(_other), do: false
+
+  defp valid_alias_piece?([?., char | rest]) when char >= ?A and char <= ?Z,
+    do: valid_alias_piece?(trim_leading_while_valid_identifier(rest))
+
+  defp valid_alias_piece?([]), do: true
+  defp valid_alias_piece?(_other), do: false
+
+  defp trim_leading_while_valid_identifier([char | rest])
+       when char >= ?a and char <= ?z
+       when char >= ?A and char <= ?Z
+       when char >= ?0 and char <= ?9
+       when char == ?_ do
+    trim_leading_while_valid_identifier(rest)
+  end
+
+  defp trim_leading_while_valid_identifier(other) do
+    other
+  end
+
+  @doc """
+  Inspects the identifier as an atom.
+  """
+  def inspect_as_atom(atom) when is_nil(atom) or is_boolean(atom) do
+    Atom.to_string(atom)
+  end
+
+  def inspect_as_atom(atom) when is_atom(atom) do
+    binary = Atom.to_string(atom)
+
+    case classify(atom) do
+      :alias ->
+        case binary do
+          binary when binary in ["Elixir", "Elixir.Elixir"] -> binary
+          "Elixir.Elixir." <> _rest -> binary
+          "Elixir." <> rest -> rest
+        end
+
+      type when type in [:callable_local, :callable_operator, :not_callable] ->
+        ":" <> binary
+
+      _ ->
+        {escaped, _} = escape(binary, ?")
+        IO.iodata_to_binary([?:, ?", escaped, ?"])
+    end
+  end
+
+  @doc """
+  Inspects the given identifier as a key.
+  """
+  def inspect_as_key(atom) when is_atom(atom) do
+    binary = Atom.to_string(atom)
+
+    case classify(atom) do
+      type when type in [:callable_local, :callable_operator, :not_callable] ->
+        IO.iodata_to_binary([binary, ?:])
+
+      _ ->
+        {escaped, _} = escape(binary, ?")
+        IO.iodata_to_binary([?", escaped, ?", ?:])
+    end
+  end
+
+  @doc """
+  Inspects the given identifier as a function name.
+  """
+  def inspect_as_function(atom) when is_atom(atom) do
+    binary = Atom.to_string(atom)
+
+    case classify(atom) do
+      type when type in [:callable_local, :callable_operator, :not_atomable] ->
+        binary
+
+      type ->
+        escaped =
+          if type in [:not_callable, :alias] do
+            binary
+          else
+            elem(escape(binary, ?"), 0)
+          end
+
+        IO.iodata_to_binary([?", escaped, ?"])
+    end
+  end
+
  @doc """
  Extracts the name and arity of the parent from the anonymous function identifier.
  """
@@ -71,12 +211,8 @@ defmodule Code.Identifier do
  @doc """
  Escapes the given identifier.
  """
-  @spec escape(binary(), char() | nil, :infinity | non_neg_integer, (char() -> iolist() | false)) ::
-          {escaped :: iolist(), remaining :: binary()}
-  def escape(binary, char, limit \\ :infinity, fun \\ &escape_map/1)
-      when ((char in 0..0x10FFFF or is_nil(char)) and limit == :infinity) or
-             (is_integer(limit) and limit >= 0) do
-    escape(binary, char, limit, [], fun)
+  def escape(other, char, count \\ :infinity, fun \\ &escape_map/1) do
+    escape(other, char, count, [], fun)
  end

  defp escape(<<_, _::binary>> = binary, _char, 0, acc, _fun) do
@@ -1,600 +0,0 @@
-defmodule Code.Normalizer do
-  @moduledoc false
-
-  defguard is_literal(x)
-           when is_integer(x) or
-                  is_float(x) or
-                  is_binary(x) or
-                  is_atom(x)
-
-  @doc """
-  Wraps literals in the quoted expression to conform to the AST format expected
-  by the formatter.
-  """
-  def normalize(quoted, opts \\ []) do
-    line = Keyword.get(opts, :line, nil)
-    escape = Keyword.get(opts, :escape, true)
-    locals_without_parens = Keyword.get(opts, :locals_without_parens, [])
-
-    state = %{
-      escape: escape,
-      parent_meta: [line: line],
-      locals_without_parens: locals_without_parens ++ Code.Formatter.locals_without_parens()
-    }
-
-    do_normalize(quoted, state)
-  end
-
-  # Wrapped literals should receive the block meta
-  defp do_normalize({:__block__, meta, [literal]}, state)
-       when not is_tuple(literal) or tuple_size(literal) == 2 do
-    normalize_literal(literal, meta, state)
-  end
-
-  # Only normalize the first argument of an alias if it's not an atom
-  defp do_normalize({:__aliases__, meta, [first | rest]}, state) when not is_atom(first) do
-    meta = patch_meta_line(meta, state.parent_meta)
-    first = do_normalize(first, %{state | parent_meta: meta})
-    {:__aliases__, meta, [first | rest]}
-  end
-
-  defp do_normalize({:__aliases__, _, _} = quoted, _state) do
-    quoted
-  end
-
-  # Skip captured arguments like &1
-  defp do_normalize({:&, meta, [term]}, state) when is_integer(term) do
-    meta = patch_meta_line(meta, state.parent_meta)
-    {:&, meta, [term]}
-  end
-
-  # Ranges
-  defp do_normalize(left..right//step, state) do
-    left = do_normalize(left, state)
-    right = do_normalize(right, state)
-    meta = meta_line(state)
-
-    if step == 1 do
-      {:.., meta, [left, right]}
-    else
-      step = do_normalize(step, state)
-      {:"..//", meta, [left, right, step]}
-    end
-  end
-
-  # Bit containers
-  defp do_normalize({:<<>>, _, args} = quoted, state) when is_list(args) do
-    normalize_bitstring(quoted, state)
-  end
-
-  # Atoms with interpolations
-  defp do_normalize(
-         {{:., dot_meta, [:erlang, :binary_to_atom]}, call_meta,
-          [{:<<>>, _, parts} = string, :utf8]},
-         state
-       )
-       when is_list(parts) do
-    dot_meta = patch_meta_line(dot_meta, state.parent_meta)
-    call_meta = patch_meta_line(call_meta, dot_meta)
-
-    utf8 =
-      if parts == [] or binary_interpolated?(parts) do
-        # a non-normalized :utf8 atom signals an atom interpolation
-        :utf8
-      else
-        normalize_literal(:utf8, [], state)
-      end
-
-    string =
-      if state.escape do
-        normalize_bitstring(string, state, true)
-      else
-        normalize_bitstring(string, state)
-      end
-
-    {{:., dot_meta, [:erlang, :binary_to_atom]}, call_meta, [string, utf8]}
-  end
-
-  # Charlists with interpolations
-  defp do_normalize({{:., dot_meta, [List, :to_charlist]}, call_meta, [parts]} = quoted, state) do
-    if list_interpolated?(parts) do
-      parts =
-        Enum.map(parts, fn
-          {{:., part_dot_meta, [Kernel, :to_string]}, part_call_meta, args} ->
-            args = normalize_args(args, state)
-
-            {{:., part_dot_meta, [Kernel, :to_string]}, part_call_meta, args}
-
-          part when is_binary(part) ->
-            if state.escape do
-              maybe_escape_literal(part, state)
-            else
-              part
-            end
-        end)
-
-      {{:., dot_meta, [List, :to_charlist]}, call_meta, [parts]}
-    else
-      normalize_call(quoted, state)
-    end
-  end
-
-  # Don't normalize the `Access` atom in access syntax
-  defp do_normalize({:., meta, [Access, :get]}, state) do
-    meta = patch_meta_line(meta, state.parent_meta)
-    {:., meta, [Access, :get]}
-  end
-
-  # Only normalize the left side of the dot operator
-  # The right hand side is an atom in the AST but it's not an atom literal, so
-  # it should not be wrapped
-  defp do_normalize({:., meta, [left, right]}, state) do
-    meta = patch_meta_line(meta, state.parent_meta)
-
-    left = do_normalize(left, %{state | parent_meta: meta})
-
-    {:., meta, [left, right]}
-  end
-
-  # A list of left to right arrows is not considered as a list literal, so it's not wrapped
-  defp do_normalize([{:->, _, [_ | _]} | _] = quoted, state) do
-    normalize_args(quoted, state)
-  end
-
-  # left -> right
-  defp do_normalize({:->, meta, [left, right]}, state) do
-    meta = patch_meta_line(meta, state.parent_meta)
-
-    left = normalize_args(left, %{state | parent_meta: meta})
-    right = do_normalize(right, %{state | parent_meta: meta})
-    {:->, meta, [left, right]}
-  end
-
-  # Maps
-  defp do_normalize({:%{}, meta, args}, state) when is_list(args) do
-    meta =
-      if meta == [] do
-        line = state.parent_meta[:line]
-        [line: line, closing: [line: line]]
-      else
-        meta
-      end
-
-    state = %{state | parent_meta: meta}
-
-    args =
-      case args do
-        [{:|, pipe_meta, [left, right]}] ->
-          left = do_normalize(left, state)
-          right = normalize_map_args(right, state)
-          [{:|, pipe_meta, [left, right]}]
-
-        [{_, _, _} = call] ->
-          [do_normalize(call, state)]
-
-        args ->
-          normalize_map_args(args, state)
-      end
-
-    {:%{}, meta, args}
-  end
-
-  # Sigils
-  defp do_normalize({sigil, meta, [{:<<>>, _, args} = string, modifiers]} = quoted, state)
-       when is_list(args) and is_atom(sigil) do
-    case Atom.to_string(sigil) do
-      <<"sigil_", _name>> ->
-        meta =
-          meta
-          |> patch_meta_line(state.parent_meta)
-          |> Keyword.put_new(:delimiter, "\"")
-
-        {sigil, meta, [do_normalize(string, %{state | parent_meta: meta}), modifiers]}
-
-      _ ->
-        normalize_call(quoted, state)
-    end
-  end
-
-  # Tuples
-  defp do_normalize({:{}, meta, args} = quoted, state) when is_list(args) do
-    {last_arg, args} = List.pop_at(args, -1)
-
-    if args != [] and match?([_ | _], last_arg) and keyword?(last_arg) do
-      args = normalize_args(args, state)
-      kw_list = normalize_kw_args(last_arg, state, true)
-      {:{}, meta, args ++ kw_list}
-    else
-      normalize_call(quoted, state)
-    end
-  end
-
-  # Module attributes
-  defp do_normalize({:@, meta, [{name, name_meta, [value]}]}, state) do
-    value =
-      cond do
-        keyword?(value) and value != [] ->
-          normalize_kw_args(value, state, true)
-
-        is_list(value) ->
-          normalize_literal(value, meta, state)
-
-        true ->
-          do_normalize(value, state)
-      end
-
-    {:@, meta, [{name, name_meta, [value]}]}
-  end
-
-  # Regular blocks
-  defp do_normalize({:__block__, meta, args}, state) when is_list(args) do
-    {:__block__, meta, normalize_args(args, state)}
-  end
-
-  # Calls
-  defp do_normalize({_, _, args} = quoted, state) when is_list(args) do
-    normalize_call(quoted, state)
-  end
-
-  # Vars
-  defp do_normalize({_, _, context} = quoted, _state) when is_atom(context) do
-    quoted
-  end
-
-  # Literals
-  defp do_normalize(quoted, state) do
-    normalize_literal(quoted, [], state)
-  end
-
-  # Numbers
-  defp normalize_literal(number, meta, state) when is_number(number) do
-    meta =
-      meta
-      |> Keyword.put_new(:token, inspect(number))
-      |> patch_meta_line(state.parent_meta)
-
-    {:__block__, meta, [number]}
-  end
-
-  # Atom, Strings
-  defp normalize_literal(literal, meta, state) when is_atom(literal) or is_binary(literal) do
-    meta = patch_meta_line(meta, state.parent_meta)
-    literal = maybe_escape_literal(literal, state)
-
-    if is_atom(literal) and Macro.classify_atom(literal) == :alias and
-         is_nil(meta[:delimiter]) do
-      segments =
-        case Atom.to_string(literal) do
-          "Elixir" ->
-            [:"Elixir"]
-
-          "Elixir." <> segments ->
-            segments
-            |> String.split(".")
-            |> Enum.map(&String.to_atom/1)
-        end
-
-      {:__aliases__, meta, segments}
-    else
-      {:__block__, meta, [literal]}
-    end
-  end
-
-  # 2-tuples
-  defp normalize_literal({left, right}, meta, state) do
-    meta = patch_meta_line(meta, state.parent_meta)
-    state = %{state | parent_meta: meta}
-
-    if match?([_ | _], right) and keyword?(right) do
-      {:__block__, meta, [{do_normalize(left, state), normalize_kw_args(right, state, true)}]}
-    else
-      {:__block__, meta, [{do_normalize(left, state), do_normalize(right, state)}]}
-    end
-  end
-
-  # Lists
-  defp normalize_literal(list, meta, state) when is_list(list) do
-    if list != [] and List.ascii_printable?(list) do
-      # It's a charlist
-      list =
-        if state.escape do
-          {string, _} = Code.Identifier.escape(IO.chardata_to_string(list), nil)
-          IO.iodata_to_binary(string) |> to_charlist()
-        else
-          list
-        end
-
-      meta =
-        meta
-        |> Keyword.put_new(:delimiter, "'")
-        |> patch_meta_line(state.parent_meta)
-
-      {:__block__, meta, [list]}
-    else
-      meta =
-        if line = state.parent_meta[:line] do
-          meta
-          |> Keyword.put_new(:closing, line: line)
-          |> patch_meta_line(state.parent_meta)
-        else
-          meta
-        end
-
-      {:__block__, meta, [normalize_kw_args(list, state, false)]}
-    end
-  end
-
-  # Probably an invalid value, wrap it and send it upstream
-  defp normalize_literal(quoted, meta, _state) do
-    {:__block__, meta, [quoted]}
-  end
-
-  defp normalize_call({form, meta, args}, state) do
-    meta = patch_meta_line(meta, state.parent_meta)
-    arity = length(args)
-
-    # Only normalize the form if it's a qualified call
-    form =
-      if is_atom(form) do
-        form
-      else
-        do_normalize(form, %{state | parent_meta: meta})
-      end
-
-    meta =
-      if is_nil(meta[:no_parens]) and is_nil(meta[:closing]) and is_nil(meta[:do]) and
-           not Code.Formatter.local_without_parens?(form, arity, state.locals_without_parens) do
-        [closing: [line: meta[:line]]] ++ meta
-      else
-        meta
-      end
-
-    cond do
-      Keyword.has_key?(meta, :do) or match?([{{:__block__, _, [:do]}, _} | _], List.last(args)) ->
-        # def foo do :ok end
-        # def foo, do: :ok
-        normalize_kw_blocks(form, meta, args, state)
-
-      match?([{:do, _} | _], List.last(args)) ->
-        # Non normalized kw blocks
-        line = state.parent_meta[:line]
-        meta = meta ++ [do: [line: line], end: [line: line]]
-        normalize_kw_blocks(form, meta, args, state)
-
-      allow_keyword?(form, arity) ->
-        args = normalize_args(args, %{state | parent_meta: meta})
-        {last_arg, leading_args} = List.pop_at(args, -1, [])
-
-        last_args =
-          case last_arg do
-            {:__block__, _, [[{{:__block__, key_meta, _}, _} | _]] = last_args} ->
-              if key_meta[:format] == :keyword do
-                last_args
-              else
-                [last_arg]
-              end
-
-            [] ->
-              []
-
-            _ ->
-              [last_arg]
-          end
-
-        {form, meta, leading_args ++ last_args}
-
-      true ->
-        args = normalize_args(args, %{state | parent_meta: meta})
-        {form, meta, args}
-    end
-  end
-
-  defp allow_keyword?(:when, 2), do: true
-  defp allow_keyword?(:{}, _), do: false
-  defp allow_keyword?(op, arity), do: not is_atom(op) or not Macro.operator?(op, arity)
-
-  defp normalize_bitstring({:<<>>, meta, parts}, state, escape_interpolation \\ false) do
-    meta = patch_meta_line(meta, state.parent_meta)
-
-    parts =
-      if binary_interpolated?(parts) do
-        normalize_interpolation_parts(parts, %{state | parent_meta: meta}, escape_interpolation)
-      else
-        state = %{state | parent_meta: meta}
-
-        Enum.map(parts, fn part ->
-          with {:"::", meta, [left, _]} <- part,
-               true <- meta[:inferred_bitstring_spec] do
-            do_normalize(left, state)
-          else
-            _ -> do_normalize(part, state)
-          end
-        end)
-      end
-
-    {:<<>>, meta, parts}
-  end
-
-  defp normalize_interpolation_parts(parts, state, escape_interpolation) do
-    Enum.map(parts, fn
-      {:"::", interpolation_meta,
-       [
-         {{:., dot_meta, [Kernel, :to_string]}, middle_meta, [middle]},
-         {:binary, binary_meta, context}
-       ]} ->
-        middle = do_normalize(middle, %{state | parent_meta: dot_meta})
-
-        {:"::", interpolation_meta,
-         [
-           {{:., dot_meta, [Kernel, :to_string]}, middle_meta, [middle]},
-           {:binary, binary_meta, context}
-         ]}
-
-      part ->
-        if escape_interpolation do
-          maybe_escape_literal(part, state)
-        else
-          part
-        end
-    end)
-  end
-
-  defp normalize_map_args(args, state) do
-    Enum.map(normalize_kw_args(args, state, false), fn
-      {:__block__, _, [{_, _} = pair]} -> pair
-      pair -> pair
-    end)
-  end
-
-  defp normalize_kw_blocks(form, meta, args, state) do
-    {kw_blocks, leading_args} = List.pop_at(args, -1)
-
-    kw_blocks =
-      Enum.map(kw_blocks, fn {tag, block} ->
-        block = do_normalize(block, %{state | parent_meta: meta})
-
-        block =
-          case block do
-            {_, _, [[{:->, _, _} | _] = block]} -> block
-            block -> block
-          end
-
-        # Only wrap the tag if it isn't already wrapped
-        tag =
-          case tag do
-            {:__block__, _, _} -> tag
-            _ -> {:__block__, [line: meta[:line]], [tag]}
-          end
-
-        {tag, block}
-      end)
-
-    leading_args = normalize_args(leading_args, %{state | parent_meta: meta})
-    {form, meta, leading_args ++ [kw_blocks]}
-  end
-
-  defp normalize_kw_args(elems, state, keyword?)
-
-  defp normalize_kw_args(
-         [{{:__block__, key_meta, [key]}, value} = first | rest] = current,
-         state,
-         keyword?
-       )
-       when is_atom(key) do
-    keyword? = keyword? or keyword?(current)
-
-    first =
-      if key_meta[:format] == :keyword and not keyword? do
-        key_meta = Keyword.delete(key_meta, :format)
-        line = key_meta[:line] || meta_line(state)
-        {:__block__, [line: line], [{{:__block__, key_meta, [key]}, value}]}
-      else
-        first
-      end
-
-    [first | normalize_kw_args(rest, state, keyword?)]
-  end
-
-  defp normalize_kw_args([{left, right} | rest] = current, state, keyword?) do
-    keyword? = keyword? or keyword?(current)
-
-    left =
-      if keyword? do
-        meta = [format: :keyword] ++ meta_line(state)
-        {:__block__, meta, [maybe_escape_literal(left, state)]}
-      else
-        do_normalize(left, state)
-      end
-
-    right = do_normalize(right, state)
-
-    pair =
-      with {:__block__, meta, _} <- left,
-           :keyword <- meta[:format] do
-        {left, right}
-      else
-        _ -> {:__block__, meta_line(state), [{left, right}]}
-      end
-
-    [pair | normalize_kw_args(rest, state, keyword?)]
-  end
-
-  defp normalize_kw_args([first | rest], state, keyword?) do
-    [do_normalize(first, state) | normalize_kw_args(rest, state, keyword?)]
-  end
-
-  defp normalize_kw_args([], _state, _keyword?) do
-    []
-  end
-
-  defp normalize_args(args, state) do
-    Enum.map(args, &do_normalize(&1, state))
-  end
-
-  defp maybe_escape_literal(string, %{escape: true}) when is_binary(string) do
-    {string, _} = Code.Identifier.escape(string, nil)
-    IO.iodata_to_binary(string)
-  end
-
-  defp maybe_escape_literal(atom, %{escape: true} = state) when is_atom(atom) do
-    atom
-    |> Atom.to_string()
-    |> maybe_escape_literal(state)
-    |> String.to_atom()
-  end
-
-  defp maybe_escape_literal(term, _) do
-    term
-  end
-
-  defp binary_interpolated?(parts) do
-    Enum.all?(parts, fn
-      {:"::", _, [{{:., _, [Kernel, :to_string]}, _, [_]}, {:binary, _, _}]} -> true
-      binary when is_binary(binary) -> true
-      _ -> false
-    end)
-  end
-
-  defp list_interpolated?(parts) do
-    Enum.all?(parts, fn
-      {{:., _, [Kernel, :to_string]}, _, [_]} -> true
-      binary when is_binary(binary) -> true
-      _ -> false
-    end)
-  end
-
-  defp patch_meta_line(meta, parent_meta) do
-    with nil <- meta[:line],
-         line when is_integer(line) <- parent_meta[:line] do
-      [line: line] ++ meta
-    else
-      _ -> meta
-    end
-  end
-
-  defp meta_line(state) do
-    if line = state.parent_meta[:line] do
-      [line: line]
-    else
-      []
-    end
-  end
-
-  defp keyword?([{{:__block__, key_meta, [key]}, _} | rest]) when is_atom(key) do
-    if key_meta[:format] == :keyword do
-      keyword?(rest)
-    else
-      false
-    end
-  end
-
-  defp keyword?([{key, _value} | rest]) when is_atom(key) do
-    case Atom.to_charlist(key) do
-      'Elixir.' ++ _ -> false
-      _ -> keyword?(rest)
-    end
-  end
-
-  defp keyword?([]), do: true
-  defp keyword?(_other), do: false
-end
@@ -7,9 +7,9 @@ defmodule Code.Typespec do
  @spec spec_to_quoted(atom, tuple) :: {atom, keyword, [Macro.t()]}
  def spec_to_quoted(name, spec)

-  def spec_to_quoted(name, {:type, anno, :fun, [{:type, _, :product, args}, result]})
+  def spec_to_quoted(name, {:type, line, :fun, [{:type, _, :product, args}, result]})
      when is_atom(name) do
-    meta = meta(anno)
+    meta = [line: line]
    body = {name, meta, Enum.map(args, &typespec_to_quoted/1)}

    vars =
@@ -27,13 +27,11 @@ defmodule Code.Typespec do
    end
  end

-  def spec_to_quoted(name, {:type, anno, :fun, []}) when is_atom(name) do
-    meta = meta(anno)
-    {:"::", meta, [{name, meta, []}, quote(do: term)]}
+  def spec_to_quoted(name, {:type, line, :fun, []}) when is_atom(name) do
+    {:"::", [line: line], [{name, [line: line], []}, quote(do: term)]}
  end

-  def spec_to_quoted(name, {:type, anno, :bounded_fun, [type, constrs]}) when is_atom(name) do
-    meta = meta(anno)
+  def spec_to_quoted(name, {:type, line, :bounded_fun, [type, constrs]}) when is_atom(name) do
    {:type, _, :fun, [{:type, _, :product, args}, result]} = type

    guards =
@@ -41,6 +39,7 @@ defmodule Code.Typespec do
        {erl_to_ex_var(var), typespec_to_quoted(type)}
      end

+    meta = [line: line]
    ignore_vars = Keyword.keys(guards)

    vars =
@@ -53,7 +52,7 @@ defmodule Code.Typespec do
    args = for arg <- args, do: typespec_to_quoted(arg)

    when_args = [
-      {:"::", meta, [{name, meta, args}, typespec_to_quoted(result)]},
+      {:"::", meta, [{name, [line: line], args}, typespec_to_quoted(result)]},
      guards ++ vars
    ]

@@ -174,11 +173,9 @@ defmodule Code.Typespec do
  end

  defp get_module_and_beam(module) when is_atom(module) do
-    with {^module, beam, _filename} <- :code.get_object_code(module),
-         {:ok, ^module} <- beam |> :beam_lib.info() |> Keyword.fetch(:module) do
-      {module, beam}
-    else
-      _ -> :error
+    case :code.get_object_code(module) do
+      {^module, beam, _filename} -> {module, beam}
+      :error -> :error
    end
  end

@@ -191,27 +188,27 @@ defmodule Code.Typespec do

  ## To AST conversion

-  defp collect_vars({:ann_type, _anno, args}) when is_list(args) do
+  defp collect_vars({:ann_type, _line, args}) when is_list(args) do
    []
  end

-  defp collect_vars({:type, _anno, _kind, args}) when is_list(args) do
+  defp collect_vars({:type, _line, _kind, args}) when is_list(args) do
    Enum.flat_map(args, &collect_vars/1)
  end

-  defp collect_vars({:remote_type, _anno, args}) when is_list(args) do
+  defp collect_vars({:remote_type, _line, args}) when is_list(args) do
    Enum.flat_map(args, &collect_vars/1)
  end

-  defp collect_vars({:typed_record_field, _anno, type}) do
+  defp collect_vars({:typed_record_field, _line, type}) do
    collect_vars(type)
  end

-  defp collect_vars({:paren_type, _anno, [type]}) do
+  defp collect_vars({:paren_type, _line, [type]}) do
    collect_vars(type)
  end

-  defp collect_vars({:var, _anno, var}) do
+  defp collect_vars({:var, _line, var}) do
    [erl_to_ex_var(var)]
  end

@@ -219,48 +216,48 @@ defmodule Code.Typespec do
    []
  end

-  defp typespec_to_quoted({:user_type, anno, name, args}) do
+  defp typespec_to_quoted({:user_type, line, name, args}) do
    args = for arg <- args, do: typespec_to_quoted(arg)
-    {name, meta(anno), args}
+    {name, [line: line], args}
  end

-  defp typespec_to_quoted({:type, anno, :tuple, :any}) do
-    {:tuple, meta(anno), []}
+  defp typespec_to_quoted({:type, line, :tuple, :any}) do
+    {:tuple, [line: line], []}
  end

-  defp typespec_to_quoted({:type, anno, :tuple, args}) do
+  defp typespec_to_quoted({:type, line, :tuple, args}) do
    args = for arg <- args, do: typespec_to_quoted(arg)
-    {:{}, meta(anno), args}
+    {:{}, [line: line], args}
  end

-  defp typespec_to_quoted({:type, _anno, :list, [{:type, _, :union, unions} = arg]}) do
+  defp typespec_to_quoted({:type, _line, :list, [{:type, _, :union, unions} = arg]}) do
    case unpack_typespec_kw(unions, []) do
      {:ok, ast} -> ast
      :error -> [typespec_to_quoted(arg)]
    end
  end

-  defp typespec_to_quoted({:type, anno, :list, []}) do
-    {:list, meta(anno), []}
+  defp typespec_to_quoted({:type, line, :list, []}) do
+    {:list, [line: line], []}
  end

-  defp typespec_to_quoted({:type, _anno, :list, [arg]}) do
+  defp typespec_to_quoted({:type, _line, :list, [arg]}) do
    [typespec_to_quoted(arg)]
  end

-  defp typespec_to_quoted({:type, anno, :nonempty_list, []}) do
-    [{:..., meta(anno), nil}]
+  defp typespec_to_quoted({:type, line, :nonempty_list, []}) do
+    [{:..., [line: line], nil}]
  end

-  defp typespec_to_quoted({:type, anno, :nonempty_list, [arg]}) do
-    [typespec_to_quoted(arg), {:..., meta(anno), nil}]
+  defp typespec_to_quoted({:type, line, :nonempty_list, [arg]}) do
+    [typespec_to_quoted(arg), {:..., [line: line], nil}]
  end

-  defp typespec_to_quoted({:type, anno, :map, :any}) do
-    {:map, meta(anno), []}
+  defp typespec_to_quoted({:type, line, :map, :any}) do
+    {:map, [line: line], []}
  end

-  defp typespec_to_quoted({:type, anno, :map, fields}) do
+  defp typespec_to_quoted({:type, line, :map, fields}) do
    fields =
      Enum.map(fields, fn
        {:type, _, :map_field_assoc, :any} ->
@@ -278,17 +275,16 @@ defmodule Code.Typespec do

    case List.keytake(fields, :__struct__, 0) do
      {{:__struct__, struct}, fields_pruned} when is_atom(struct) and struct != nil ->
-        map_pruned = {:%{}, meta(anno), fields_pruned}
-        {:%, meta(anno), [struct, map_pruned]}
+        map_pruned = {:%{}, [line: line], fields_pruned}
+        {:%, [line: line], [struct, map_pruned]}

      _ ->
-        {:%{}, meta(anno), fields}
+        {:%{}, [line: line], fields}
    end
  end

-  defp typespec_to_quoted({:type, anno, :binary, [arg1, arg2]}) do
+  defp typespec_to_quoted({:type, line, :binary, [arg1, arg2]}) do
    [arg1, arg2] = for arg <- [arg1, arg2], do: typespec_to_quoted(arg)
-    line = meta(anno)[:line]

    case {typespec_to_quoted(arg1), typespec_to_quoted(arg2)} do
      {arg1, 0} ->
@@ -302,57 +298,57 @@ defmodule Code.Typespec do
    end
  end

-  defp typespec_to_quoted({:type, anno, :union, args}) do
+  defp typespec_to_quoted({:type, line, :union, args}) do
    args = for arg <- args, do: typespec_to_quoted(arg)
-    Enum.reduce(Enum.reverse(args), fn arg, expr -> {:|, meta(anno), [arg, expr]} end)
+    Enum.reduce(Enum.reverse(args), fn arg, expr -> {:|, [line: line], [arg, expr]} end)
  end

-  defp typespec_to_quoted({:type, anno, :fun, [{:type, _, :product, args}, result]}) do
+  defp typespec_to_quoted({:type, line, :fun, [{:type, _, :product, args}, result]}) do
    args = for arg <- args, do: typespec_to_quoted(arg)
-    [{:->, meta(anno), [args, typespec_to_quoted(result)]}]
+    [{:->, [line: line], [args, typespec_to_quoted(result)]}]
  end

-  defp typespec_to_quoted({:type, anno, :fun, [args, result]}) do
-    [{:->, meta(anno), [[typespec_to_quoted(args)], typespec_to_quoted(result)]}]
+  defp typespec_to_quoted({:type, line, :fun, [args, result]}) do
+    [{:->, [line: line], [[typespec_to_quoted(args)], typespec_to_quoted(result)]}]
  end

-  defp typespec_to_quoted({:type, anno, :fun, []}) do
-    typespec_to_quoted({:type, anno, :fun, [{:type, anno, :any}, {:type, anno, :any, []}]})
+  defp typespec_to_quoted({:type, line, :fun, []}) do
+    typespec_to_quoted({:type, line, :fun, [{:type, line, :any}, {:type, line, :any, []}]})
  end

-  defp typespec_to_quoted({:type, anno, :range, [left, right]}) do
-    {:.., meta(anno), [typespec_to_quoted(left), typespec_to_quoted(right)]}
+  defp typespec_to_quoted({:type, line, :range, [left, right]}) do
+    {:.., [line: line], [typespec_to_quoted(left), typespec_to_quoted(right)]}
  end

-  defp typespec_to_quoted({:type, _anno, nil, []}) do
+  defp typespec_to_quoted({:type, _line, nil, []}) do
    []
  end

-  defp typespec_to_quoted({:type, anno, name, args}) do
+  defp typespec_to_quoted({:type, line, name, args}) do
    args = for arg <- args, do: typespec_to_quoted(arg)
-    {name, meta(anno), args}
+    {name, [line: line], args}
  end

-  defp typespec_to_quoted({:var, anno, var}) do
-    {erl_to_ex_var(var), meta(anno), nil}
+  defp typespec_to_quoted({:var, line, var}) do
+    {erl_to_ex_var(var), [line: line], nil}
  end

-  defp typespec_to_quoted({:op, anno, op, arg}) do
-    {op, meta(anno), [typespec_to_quoted(arg)]}
+  defp typespec_to_quoted({:op, line, op, arg}) do
+    {op, [line: line], [typespec_to_quoted(arg)]}
  end

-  defp typespec_to_quoted({:remote_type, anno, [mod, name, args]}) do
-    remote_type(anno, mod, name, args)
+  defp typespec_to_quoted({:remote_type, line, [mod, name, args]}) do
+    remote_type(line, mod, name, args)
  end

-  defp typespec_to_quoted({:ann_type, anno, [var, type]}) do
-    {:"::", meta(anno), [typespec_to_quoted(var), typespec_to_quoted(type)]}
+  defp typespec_to_quoted({:ann_type, line, [var, type]}) do
+    {:"::", [line: line], [typespec_to_quoted(var), typespec_to_quoted(type)]}
  end

  defp typespec_to_quoted(
-         {:typed_record_field, {:record_field, anno1, {:atom, anno2, name}}, type}
+         {:typed_record_field, {:record_field, line, {:atom, line1, name}}, type}
       ) do
-    typespec_to_quoted({:ann_type, anno1, [{:var, anno2, name}, type]})
+    typespec_to_quoted({:ann_type, line, [{:var, line1, name}, type]})
  end

  defp typespec_to_quoted({:type, _, :any}) do
@@ -363,7 +359,7 @@ defmodule Code.Typespec do
    typespec_to_quoted(type)
  end

-  defp typespec_to_quoted({type, _anno, atom}) when is_atom(type) do
+  defp typespec_to_quoted({type, _line, atom}) when is_atom(type) do
    atom
  end

@@ -371,30 +367,30 @@ defmodule Code.Typespec do

  ## Helpers

-  defp remote_type(anno, {:atom, _, :elixir}, {:atom, _, :charlist}, []) do
-    typespec_to_quoted({:type, anno, :charlist, []})
+  defp remote_type(line, {:atom, _, :elixir}, {:atom, _, :charlist}, []) do
+    typespec_to_quoted({:type, line, :charlist, []})
  end

-  defp remote_type(anno, {:atom, _, :elixir}, {:atom, _, :nonempty_charlist}, []) do
-    typespec_to_quoted({:type, anno, :nonempty_charlist, []})
+  defp remote_type(line, {:atom, _, :elixir}, {:atom, _, :nonempty_charlist}, []) do
+    typespec_to_quoted({:type, line, :nonempty_charlist, []})
  end

-  defp remote_type(anno, {:atom, _, :elixir}, {:atom, _, :struct}, []) do
-    typespec_to_quoted({:type, anno, :struct, []})
+  defp remote_type(line, {:atom, _, :elixir}, {:atom, _, :struct}, []) do
+    typespec_to_quoted({:type, line, :struct, []})
  end

-  defp remote_type(anno, {:atom, _, :elixir}, {:atom, _, :as_boolean}, [arg]) do
-    typespec_to_quoted({:type, anno, :as_boolean, [arg]})
+  defp remote_type(line, {:atom, _, :elixir}, {:atom, _, :as_boolean}, [arg]) do
+    typespec_to_quoted({:type, line, :as_boolean, [arg]})
  end

-  defp remote_type(anno, {:atom, _, :elixir}, {:atom, _, :keyword}, args) do
-    typespec_to_quoted({:type, anno, :keyword, args})
+  defp remote_type(line, {:atom, _, :elixir}, {:atom, _, :keyword}, args) do
+    typespec_to_quoted({:type, line, :keyword, args})
  end

-  defp remote_type(anno, mod, name, args) do
+  defp remote_type(line, mod, name, args) do
    args = for arg <- args, do: typespec_to_quoted(arg)
-    dot = {:., meta(anno), [typespec_to_quoted(mod), typespec_to_quoted(name)]}
-    {dot, meta(anno), args}
+    dot = {:., [line: line], [typespec_to_quoted(mod), typespec_to_quoted(name)]}
+    {dot, [line: line], args}
  end

  defp erl_to_ex_var(var) do
@@ -418,6 +414,4 @@ defmodule Code.Typespec do
  defp unpack_typespec_kw(_, _acc) do
    :error
  end
-
-  defp meta(anno), do: [line: :erl_anno.line(anno)]
 end
@@ -17,8 +17,8 @@ defprotocol Collectable do

  This design is intentional. `Enumerable` was designed to support infinite
  collections, resources and other structures with fixed shape. For example,
-  it doesn't make sense to insert values into a `Range`, as it has a
-  fixed shape where only the range limits and step are stored.
+  it doesn't make sense to insert values into a range, as it has a fixed
+  shape where just the range limits are stored.

  The `Collectable` module was designed to fill the gap left by the
  `Enumerable` protocol. `Collectable.into/1` can be seen as the opposite of
@@ -27,44 +27,32 @@ defprotocol Collectable do

  ## Examples

-  To show how to manually use the `Collectable` protocol, let's play with a
-  simplified implementation for `MapSet`.
+  To show how to manually use the `Collectable` protocol, let's play with its
+  implementation for `MapSet`.

      iex> {initial_acc, collector_fun} = Collectable.into(MapSet.new())
      iex> updated_acc = Enum.reduce([1, 2, 3], initial_acc, fn elem, acc ->
      ...>   collector_fun.(acc, {:cont, elem})
      ...> end)
      iex> collector_fun.(updated_acc, :done)
-      MapSet.new([1, 2, 3])
+      #MapSet<[1, 2, 3]>

  To show how the protocol can be implemented, we can again look at the
-  simplified implementation for `MapSet`. In this implementation "collecting" elements
+  implementation for `MapSet`. In this implementation "collecting" elements
  simply means inserting them in the set through `MapSet.put/2`.

      defimpl Collectable, for: MapSet do
-        def into(map_set) do
+        def into(original) do
          collector_fun = fn
-            map_set_acc, {:cont, elem} ->
-              MapSet.put(map_set_acc, elem)
-
-            map_set_acc, :done ->
-              map_set_acc
-
-            _map_set_acc, :halt ->
-              :ok
+            set, {:cont, elem} -> MapSet.put(set, elem)
+            set, :done -> set
+            _set, :halt -> :ok
          end

-          initial_acc = map_set
-
-          {initial_acc, collector_fun}
+          {original, collector_fun}
        end
      end

-  So now we can call `Enum.into/2`:
-
-      iex> Enum.into([1, 2, 3], MapSet.new())
-      MapSet.new([1, 2, 3])
-
  """

  @type command :: {:cont, term} | :done | :halt
@@ -72,11 +60,8 @@ defprotocol Collectable do
  @doc """
  Returns an initial accumulator and a "collector" function.

-  Receives a `collectable` which can be used as the initial accumulator that will
-  be passed to the function.
-
-  The collector function receives a term and a command and injects the term into
-  the collectable accumulator on every `{:cont, term}` command.
+  The returned function receives a term and a command and injects the term into
+  the collectable on every `{:cont, term}` command.

  `:done` is passed as a command when no further values will be injected. This
  is useful when there's a need to close resources or normalizing values. A
@@ -88,17 +73,16 @@ defprotocol Collectable do
  For examples on how to use the `Collectable` protocol and `into/1` see the
  module documentation.
  """
-  @spec into(t) :: {initial_acc :: term, collector :: (term, command -> t | term)}
+  @spec into(t) :: {term, (term, command -> t | term)}
  def into(collectable)
 end

 defimpl Collectable, for: List do
-  def into(list) do
-    # TODO: Change the behaviour so the into always comes last on Elixir v2.0
-    if list != [] do
+  def into(original) do
+    if original != [] do
      IO.warn(
        "the Collectable protocol is deprecated for non-empty lists. The behaviour of " <>
-          "Enum.into/2 and \"for\" comprehensions with an :into option is incorrect " <>
+          "things like Enum.into/2 or \"for\" comprehensions with an :into option is incorrect " <>
          "when collecting into non-empty lists. If you're collecting into a non-empty keyword " <>
          "list, consider using Keyword.merge/2 instead. If you're collecting into a non-empty " <>
          "list, consider concatenating the two lists with the ++ operator."
@@ -106,14 +90,9 @@ defimpl Collectable, for: List do
    end

    fun = fn
-      list_acc, {:cont, elem} ->
-        [elem | list_acc]
-
-      list_acc, :done ->
-        list ++ :lists.reverse(list_acc)
-
-      _list_acc, :halt ->
-        :ok
+      list, {:cont, x} -> [x | list]
+      list, :done -> original ++ :lists.reverse(list)
+      _, :halt -> :ok
    end

    {[], fun}
@@ -121,7 +100,7 @@ defimpl Collectable, for: List do
 end

 defimpl Collectable, for: BitString do
-  def into(binary) when is_binary(binary) do
+  def into(original) when is_binary(original) do
    fun = fn
      acc, {:cont, x} when is_binary(x) and is_list(acc) ->
        [acc | x]
@@ -138,14 +117,14 @@ defimpl Collectable, for: BitString do
      acc, :done ->
        IO.iodata_to_binary(acc)

-      __acc, :halt ->
+      _, :halt ->
        :ok
    end

-    {[binary], fun}
+    {[original], fun}
  end

-  def into(bitstring) do
+  def into(original) when is_bitstring(original) do
    fun = fn
      acc, {:cont, x} when is_bitstring(x) ->
        <<acc::bitstring, x::bitstring>>
@@ -153,27 +132,22 @@ defimpl Collectable, for: BitString do
      acc, :done ->
        acc

-      _acc, :halt ->
+      _, :halt ->
        :ok
    end

-    {bitstring, fun}
+    {original, fun}
  end
 end

 defimpl Collectable, for: Map do
-  def into(map) do
+  def into(original) do
    fun = fn
-      map_acc, {:cont, {key, value}} ->
-        Map.put(map_acc, key, value)
-
-      map_acc, :done ->
-        map_acc
-
-      _map_acc, :halt ->
-        :ok
+      map, {:cont, {k, v}} -> Map.put(map, k, v)
+      map, :done -> map
+      _, :halt -> :ok
    end

-    {map, fun}
+    {original, fun}
  end
 end
@@ -16,8 +16,7 @@ defmodule Config do
      import_config "#{config_env()}.exs"

  `import Config` will import the functions `config/2`, `config/3`
-  `config_env/0`, `config_target/0`, and `import_config/1`
-  to help you manage your configuration.
+  and `import_config/1` to help you manage your configuration.

  `config/2` and `config/3` are used to define key-value configuration
  for a given application. Once Mix starts, it will automatically
@@ -34,12 +33,10 @@ defmodule Config do
  `Config` also provides a low-level API for evaluating and reading
  configuration, under the `Config.Reader` module.

-  > **Important:** if you are writing a library to be used by other developers,
-  > it is generally recommended to avoid the application environment, as the
-  > application environment is effectively a global storage. Also note that
-  > the `config/config.exs` of a library is not evaluated when the library is
-  > used as a dependency, as configuration is always meant to configure the
-  > current project. For more information, read our [library guidelines](library-guidelines.md).
+  **Important:** if you are writing a library to be used by other developers,
+  it is generally recommended to avoid the application environment, as the
+  application environment is effectively a global storage. For more information,
+  read our [library guidelines](library-guidelines.md).

  ## Migrating from `use Mix.Config`

@@ -62,27 +59,7 @@ defmodule Config do
        import_config config
      end

-  The last step is to replace all `Mix.env()` calls in the config files with `config_env()`.
-
-  Keep in mind you must also avoid using `Mix.env()` inside your project files.
-  To check the environment at _runtime_, you may add a configuration key:
-
-      # config.exs
-      ...
-      config :my_app, env: config_env()
-
-  Then, in other scripts and modules, you may get the environment with
-  `Application.fetch_env!/2`:
-
-      # router.exs
-      ...
-      if Application.fetch_env!(:my_app, :env) == :prod do
-        ...
-      end
-
-  The only files where you may access functions from the `Mix` module are
-  the `mix.exs` file and inside custom Mix tasks, which always within the
-  `Mix.Tasks` namespace.
+  The last step is to replace all `Mix.env()` calls by `config_env()`.

  ## config/runtime.exs

@@ -95,7 +72,7 @@ defmodule Config do
  @config_key {__MODULE__, :config}
  @imports_key {__MODULE__, :imports}

-  defp get_opts!(), do: Process.get(@opts_key) || raise_improper_use!()
+  defp get_opts!(), do: Process.get(@opts_key)
  defp put_opts(value), do: Process.put(@opts_key, value)
  defp delete_opts(), do: Process.delete(@opts_key)

@@ -122,9 +99,8 @@ defmodule Config do

  The given `opts` are merged into the existing configuration
  for the given `root_key`. Conflicting keys are overridden by the
-  ones specified in `opts`, unless they are keywords, which are
-  deep merged recursively. For example, the application configuration
-  below
+  ones specified in `opts`. For example, the application
+  configuration below

      config :logger,
        level: :warn,
@@ -159,30 +135,21 @@ defmodule Config do

  The given `opts` are merged into the existing values for `key`
  in the given `root_key`. Conflicting keys are overridden by the
-  ones specified in `opts`, unless they are keywords, which are
-  deep merged recursively. For example, the application configuration
-  below
+  ones specified in `opts`. For example, the application
+  configuration below

      config :ecto, Repo,
        log_level: :warn,
-        adapter: Ecto.Adapters.Postgres,
-        metadata: [read_only: true]
+        adapter: Ecto.Adapters.Postgres

      config :ecto, Repo,
        log_level: :info,
-        pool_size: 10,
-        metadata: [replica: true]
+        pool_size: 10

  will have a final value of the configuration for the `Repo`
  key in the `:ecto` application of:

-      Application.get_env(:ecto, Repo)
-      #=> [
-      #=>   log_level: :info,
-      #=>   pool_size: 10,
-      #=>   adapter: Ecto.Adapters.Postgres,
-      #=>   metadata: [read_only: true, replica: true]
-      #=> ]
+      [log_level: :info, pool_size: 10, adapter: Ecto.Adapters.Postgres]

  """
  @doc since: "1.9.0"
@@ -321,6 +288,8 @@ defmodule Config do
        :ok
    end

+    # TODO: Emit a warning if Mix.env() is found in said files in Elixir v1.15.
+    # Note this won't be a deprecation warning as it will always be emitted.
    Code.eval_string(contents, [], file: file)
  end

@@ -11,55 +11,18 @@ defmodule Config.Provider do
  the file system. For more information on runtime configuration,
  see `mix release`.

-  ## Multiple config files
+  ## Sample config provider

-  One common use of config providers is to specify multiple
-  configuration files in a release. Elixir ships with one provider,
-  called `Config.Reader`, which is capable of handling Elixir's
-  built-in config files.
-
-  For example, imagine you want to list some basic configuration
-  on Mix's built-in `config/runtime.exs` file, but you also want
-  to support additional configuration files. To do so, you can add
-  this inside the `def project` portion of  your `mix.exs`:
-
-      releases: [
-        demo: [
-          config_providers: [
-            {Config.Reader, {:system, "RELEASE_ROOT", "/extra_config.exs"}}
-          ]
-        ]
-      ]
-
-  You can place this `extra_config.exs` file in your release in
-  multiple ways:
-
-    1. If it is available on the host when assembling the release,
-      you can place it on "rel/overlays/extra_config.exs" and it
-      will be automatically copied to the release root
-
-    2. If it is available on the target during deployment, you can
-      simply copy it to the release root as a step in your deployment
-
-  Now once the system boots, it will load both `config/runtime.exs`
-  and `extra_config.exs` early in the boot process. You can learn
-  more options on `Config.Reader`.
-
-  ## Custom config provider
-
-  You can also implement custom config providers, similar to how
-  `Config.Reader` works. For example, imagine you need to load
-  some configuration from a JSON file and load that into the system.
-  Said configuration provider would look like:
+  For example, imagine you need to load some configuration from
+  a JSON file and load that into the system. Said configuration
+  provider would look like:

      defmodule JSONConfigProvider do
        @behaviour Config.Provider

        # Let's pass the path to the JSON file as config
-        @impl true
        def init(path) when is_binary(path), do: path

-        @impl true
        def load(config, path) do
          # We need to start any app we may depend on.
          {:ok, _} = Application.ensure_all_started(:jason)
@@ -76,17 +39,19 @@ defmodule Config.Provider do
        end
      end

-  Then, when specifying your release, you can specify the provider in
+  Then when specifying your release, you can specify the provider in
  the release configuration:

      releases: [
        demo: [
-          config_providers: [
-            {JSONConfigProvider, "/etc/config.json"}
-          ]
+          # ...,
+          config_providers: [{JSONConfigProvider, "/etc/config.json"}]
        ]
      ]

+  Now once the system boots, it will invoke the provider early in
+  the boot process, save the merged configuration to the disk, and
+  reboot the system with the new values in place.
  """

  @type config :: keyword
@@ -128,7 +93,7 @@ defmodule Config.Provider do
  Loads configuration (typically during system boot).

  It receives the current `config` and the `state` returned by
-  `c:init/1`. Then, you typically read the extra configuration
+  `c:init/1`. Then you typically read the extra configuration
  from an external source and merge it into the received `config`.
  Merging should be done with `Config.Reader.merge/2`, as it
  performs deep merge. It should return the updated config.
@@ -230,6 +195,7 @@ defmodule Config.Provider do
  end

  defp boot_providers(path, provider, reboot_config, reboot_fun) do
+    validate_no_cyclic_boot!(path)
    original_config = read_config!(path)

    config =
@@ -341,7 +307,8 @@ defmodule Config.Provider do
  defp restart_and_sleep() do
    mode = Application.get_env(:elixir, @reboot_mode_key)

-    if mode in [:embedded, :interactive] do
+    # TODO: Remove otp_release check once we require Erlang/OTP 23+
+    if :erlang.system_info(:otp_release) >= '23' and mode in [:embedded, :interactive] do
      :init.restart(mode: mode)
    else
      :init.restart()
@@ -353,6 +320,14 @@ defmodule Config.Provider do
  defp booted_value(%{prune_runtime_sys_config_after_boot: true}, path), do: {:booted, path}
  defp booted_value(%{prune_runtime_sys_config_after_boot: false}, _path), do: {:booted, nil}

+  defp validate_no_cyclic_boot!(path) do
+    if System.get_env("ELIXIR_CONFIG_PROVIDER_BOOTED") do
+      bad_path_abort("Got infinite loop when running Config.Provider", path)
+    else
+      System.put_env("ELIXIR_CONFIG_PROVIDER_BOOTED", "1")
+    end
+  end
+
  defp read_config!(path) do
    case :file.consult(path) do
      {:ok, [inner]} ->
@@ -409,7 +384,7 @@ defmodule Config.Provider do
  end

  defp abort(msg) do
-    IO.puts("ERROR! " <> msg)
+    IO.puts(:stderr, "ERROR! " <> msg)
    :erlang.raise(:error, "aborting boot", [{Config.Provider, :boot, 2, []}])
  end
 end
@@ -4,27 +4,19 @@ defmodule Config.Reader do

  ## As a provider

-  `Config.Reader` can also be used as a `Config.Provider`. A config
-  provider is used during releases to customize how applications are
-  configured. When used as a provider, it expects a single argument:
-  the configuration path (as outlined in `t:Config.Provider.config_path/0`)
-  for the file to be read and loaded during the system boot.
+  `Config.Reader` can also be used as a `Config.Provider`. When used
+  as a provider, it expects a single argument: the configuration path
+  (as outlined in `t:Config.Provider.config_path/0`) for the file to
+  be read and loaded during the system boot.

  For example, if you expect the target system to have a config file
-  in an absolute path, you can add this inside the `def project` portion
-  of  your `mix.exs`:
+  in an absolute path, you can configure your `mix release` as:

-      releases: [
-        demo: [
-          config_providers: [
-            {Config.Reader, "/etc/config.exs"}
-          ]
-        ]
-      ]
+      config_providers: [{Config.Reader, "/etc/config.exs"}]

  Or if you want to read a custom path inside the release:

-      config_providers: [{Config.Reader, {:system, "RELEASE_ROOT", "/config.exs"}}]
+      config_provider: [{Config.Reader, {:system, "RELEASE_ROOT", "/config.exs"}}]

  You can also pass a keyword list of options to the reader,
  where the `:path` is a required key:
@@ -36,8 +28,10 @@ defmodule Config.Reader do
         imports: :disabled}
      ]

-  Remember Mix already loads `config/runtime.exs` by default.
-  For more examples and scenarios, see the `Config.Provider` module.
+  Note by default Mix releases supports runtime configuration via
+  a `config/runtime.exs`. If a `config/runtime.exs` exists in your
+  application, it is automatically copied inside the release and
+  automatically set as a config provider.
  """

  @behaviour Config.Provider
@@ -23,7 +23,7 @@ defmodule Dict do
    import Kernel, except: [size: 1]

    if __CALLER__.module != HashDict do
-      IO.warn("use Dict is deprecated. " <> unquote(message), __CALLER__)
+      IO.warn("use Dict is deprecated. " <> unquote(message), Macro.Env.stacktrace(__CALLER__))
    end

    quote do
@@ -1,21 +1,21 @@
 defmodule DynamicSupervisor do
  @moduledoc ~S"""
-  A supervisor optimized to only start children dynamically.
+  A supervisor that starts children dynamically.

  The `Supervisor` module was designed to handle mostly static children
  that are started in the given order when the supervisor starts. A
  `DynamicSupervisor` starts with no children. Instead, children are
-  started on demand via `start_child/2` and there is no ordering between
-  children. This allows the `DynamicSupervisor` to hold millions of
-  children by using efficient data structures and to execute certain
-  operations, such as shutting down, concurrently.
+  started on demand via `start_child/2`. When a dynamic supervisor
+  terminates, all children are shut down at the same time, with no guarantee
+  of ordering.

  ## Examples

-  A dynamic supervisor is started with no children and often a name:
+  A dynamic supervisor is started with no children, a supervision strategy
+  (the only strategy currently supported is `:one_for_one`), and a name:

      children = [
-        {DynamicSupervisor, name: MyApp.DynamicSupervisor}
+        {DynamicSupervisor, strategy: :one_for_one, name: MyApp.DynamicSupervisor}
      ]

      Supervisor.start_link(children, strategy: :one_for_one)
@@ -37,46 +37,6 @@ defmodule DynamicSupervisor do
      DynamicSupervisor.count_children(MyApp.DynamicSupervisor)
      #=> %{active: 2, specs: 2, supervisors: 0, workers: 2}

-  ## Scalability and partitioning
-
-  The `DynamicSupervisor` is a single process responsible for starting
-  other processes. In some applications, the `DynamicSupervisor` may
-  become a bottleneck. To address this, you can start multiple instances
-  of the `DynamicSupervisor` and then pick a "random" instance to start
-  the child on.
-
-  Instead of:
-
-      children = [
-        {DynamicSupervisor, name: MyApp.DynamicSupervisor}
-      ]
-
-  and:
-
-      DynamicSupervisor.start_child(MyApp.DynamicSupervisor, {Agent, fn -> %{} end})
-
-  You can do this:
-
-      children = [
-        {PartitionSupervisor,
-         child_spec: DynamicSupervisor,
-         name: MyApp.DynamicSupervisors}
-      ]
-
-  and then:
-
-      DynamicSupervisor.start_child(
-        {:via, PartitionSupervisor, {MyApp.DynamicSupervisors, self()}},
-        {Agent, fn -> %{} end}
-      )
-
-  In the code above, we start a partition supervisor that will by default
-  start a dynamic supervisor for each core in your machine. Then, instead
-  of calling the `DynamicSupervisor` by name, you call it through the
-  partition supervisor, using `self()` as the routing key. This means each
-  process will be assigned one of the existing dynamic supervisors.
-  Read the `PartitionSupervisor` docs for more information.
-
  ## Module-based supervisors

  Similar to `Supervisor`, dynamic supervisors also support module-based
@@ -187,10 +147,10 @@ defmodule DynamicSupervisor do
          extra_arguments: [term()]
        }

-  @typedoc "Options given to `start_link` functions"
+  @typedoc "Option values used by the `start*` functions"
  @type option :: GenServer.option()

-  @typedoc "Options given to `start_link` and `init/1` functions"
+  @typedoc "Options given to `start_link/1` and `init/1`"
  @type init_option ::
          {:strategy, strategy()}
          | {:max_restarts, non_neg_integer()}
@@ -272,74 +232,12 @@ defmodule DynamicSupervisor do
  @doc """
  Starts a supervisor with the given options.

-  This function is typically not invoked directly, instead it is invoked
-  when using a `DynamicSupervisor` as a child of another supervisor:
+  The `:strategy` is a required option and the currently supported
+  value is `:one_for_one`. The remaining options can be found in the
+  `init/1` docs.

-      children = [
-        {DynamicSupervisor, name: MySupervisor}
-      ]
-
-  If the supervisor is successfully spawned, this function returns
-  `{:ok, pid}`, where `pid` is the PID of the supervisor. If the supervisor
-  is given a name and a process with the specified name already exists,
-  the function returns `{:error, {:already_started, pid}}`, where `pid`
-  is the PID of that process.
-
-  Note that a supervisor started with this function is linked to the parent
-  process and exits not only on crashes but also if the parent process exits
-  with `:normal` reason.
-
-  ## Options
-
-    * `:name` - registers the supervisor under the given name.
-      The supported values are described under the "Name registration"
-      section in the `GenServer` module docs.
-
-    * `:strategy` - the restart strategy option. The only supported
-      value is `:one_for_one` which means that no other child is
-      terminated if a child process terminates. You can learn more
-      about strategies in the `Supervisor` module docs.
-
-    * `:max_restarts` - the maximum number of restarts allowed in
-      a time frame. Defaults to `3`.
-
-    * `:max_seconds` - the time frame in which `:max_restarts` applies.
-      Defaults to `5`.
-
-    * `:max_children` - the maximum amount of children to be running
-      under this supervisor at the same time. When `:max_children` is
-      exceeded, `start_child/2` returns `{:error, :max_children}`. Defaults
-      to `:infinity`.
-
-    * `:extra_arguments` - arguments that are prepended to the arguments
-      specified in the child spec given to `start_child/2`. Defaults to
-      an empty list.
-
-  """
-  @doc since: "1.6.0"
-  @spec start_link([option | init_option]) :: Supervisor.on_start()
-  def start_link(options) when is_list(options) do
-    keys = [:extra_arguments, :max_children, :max_seconds, :max_restarts, :strategy]
-    {sup_opts, start_opts} = Keyword.split(options, keys)
-    start_link(Supervisor.Default, init(sup_opts), start_opts)
-  end
-
-  @doc """
-  Starts a module-based supervisor process with the given `module` and `init_arg`.
-
-  To start the supervisor, the `c:init/1` callback will be invoked in the given
-  `module`, with `init_arg` as its argument. The `c:init/1` callback must return a
-  supervisor specification which can be created with the help of the `init/1`
-  function.
-
-  If the `c:init/1` callback returns `:ignore`, this function returns
-  `:ignore` as well and the supervisor terminates with reason `:normal`.
-  If it fails or returns an incorrect value, this function returns
-  `{:error, term}` where `term` is a term with information about the
-  error, and the supervisor terminates with reason `term`.
-
-  The `:name` option can also be given in order to register a supervisor
-  name, the supported values are described in the "Name registration"
+  The `:name` option can also be used to register a supervisor name.
+  The supported values are described under the "Name registration"
  section in the `GenServer` module docs.

  If the supervisor is successfully spawned, this function returns
@@ -353,9 +251,35 @@ defmodule DynamicSupervisor do
  with `:normal` reason.
  """
  @doc since: "1.6.0"
+  @spec start_link([option | init_option]) :: Supervisor.on_start()
+  def start_link(options) when is_list(options) do
+    keys = [:extra_arguments, :max_children, :max_seconds, :max_restarts, :strategy]
+    {sup_opts, start_opts} = Keyword.split(options, keys)
+    start_link(Supervisor.Default, init(sup_opts), start_opts)
+  end
+
+  @doc """
+  Starts a module-based supervisor process with the given `module` and `arg`.
+
+  To start the supervisor, the `c:init/1` callback will be invoked in the given
+  `module`, with `arg` as its argument. The `c:init/1` callback must return a
+  supervisor specification which can be created with the help of the `init/1`
+  function.
+
+  If the `c:init/1` callback returns `:ignore`, this function returns
+  `:ignore` as well and the supervisor terminates with reason `:normal`.
+  If it fails or returns an incorrect value, this function returns
+  `{:error, term}` where `term` is a term with information about the
+  error, and the supervisor terminates with reason `term`.
+
+  The `:name` option can also be given in order to register a supervisor
+  name, the supported values are described in the "Name registration"
+  section in the `GenServer` module docs.
+  """
+  @doc since: "1.6.0"
  @spec start_link(module, term, [option]) :: Supervisor.on_start()
-  def start_link(module, init_arg, opts \\ []) do
-    GenServer.start_link(__MODULE__, {module, init_arg, opts[:name]}, opts)
+  def start_link(mod, init_arg, opts \\ []) do
+    GenServer.start_link(__MODULE__, {mod, init_arg, opts[:name]}, opts)
  end

  @doc """
@@ -363,9 +287,7 @@ defmodule DynamicSupervisor do

  `child_spec` should be a valid child specification as detailed in the
  "Child specification" section of the documentation for `Supervisor`. The child
-  process will be started as defined in the child specification. Note that while
-  the `:id` field is still required in the spec, the value is ignored and
-  therefore does not need to be unique.
+  process will be started as defined in the child specification.

  If the child process start function returns `{:ok, child}` or `{:ok, child,
  info}`, then child specification and PID are added to the supervisor and
@@ -497,7 +419,7 @@ defmodule DynamicSupervisor do
  @doc since: "1.6.0"
  @spec which_children(Supervisor.supervisor()) :: [
          # module() | :dynamic here because :supervisor.modules() is not exported
-          {:undefined, pid | :restarting, :worker | :supervisor, [module()] | :dynamic}
+          {:undefined, pid | :restarting, :worker | :supervisor, module() | :dynamic}
        ]
  def which_children(supervisor) do
    call(supervisor, :which_children)
@@ -554,20 +476,46 @@ defmodule DynamicSupervisor do
  module-based supervisors. See the "Module-based supervisors" section
  in the module documentation for more information.

-  It accepts the same `options` as `start_link/1` (except for `:name`)
-  and it returns a tuple containing the supervisor options.
+  The `options` received by this function are also supported by `start_link/1`.
+
+  This function returns a tuple containing the supervisor options.

  ## Examples

      def init(_arg) do
-        DynamicSupervisor.init(max_children: 1000)
+        DynamicSupervisor.init(max_children: 1000, strategy: :one_for_one)
      end

+  ## Options
+
+    * `:strategy` - the restart strategy option. The only supported
+      value is `:one_for_one` which means that no other child is
+      terminated if a child process terminates. You can learn more
+      about strategies in the `Supervisor` module docs.
+
+    * `:max_restarts` - the maximum number of restarts allowed in
+      a time frame. Defaults to `3`.
+
+    * `:max_seconds` - the time frame in which `:max_restarts` applies.
+      Defaults to `5`.
+
+    * `:max_children` - the maximum amount of children to be running
+      under this supervisor at the same time. When `:max_children` is
+      exceeded, `start_child/2` returns `{:error, :max_children}`. Defaults
+      to `:infinity`.
+
+    * `:extra_arguments` - arguments that are prepended to the arguments
+      specified in the child spec given to `start_child/2`. Defaults to
+      an empty list.
+
  """
  @doc since: "1.6.0"
  @spec init([init_option]) :: {:ok, sup_flags()}
  def init(options) when is_list(options) do
-    strategy = Keyword.get(options, :strategy, :one_for_one)
+    unless strategy = options[:strategy] do
+      raise ArgumentError, "expected :strategy option to be given"
+    end
+
    intensity = Keyword.get(options, :max_restarts, 3)
    period = Keyword.get(options, :max_seconds, 5)
    max_children = Keyword.get(options, :max_children, :infinity)
@@ -43,16 +43,10 @@ defmodule Exception do
  @callback blame(t, stacktrace) :: {t, stacktrace}
  @optional_callbacks [blame: 2]

-  @doc false
-  # Callback for formatting Erlang exceptions
-  def format_error(%struct{} = exception, _stacktrace) do
-    %{general: message(exception), reason: "#" <> Atom.to_string(struct)}
-  end
-
  @doc """
  Returns `true` if the given `term` is an exception.
  """
-  # TODO: Deprecate this on Elixir v1.15
+  # TODO: Remove this on Elixir v1.15
  @doc deprecated: "Use Kernel.is_exception/1 instead"
  def exception?(term)
  def exception?(%_{__exception__: true}), do: true
@@ -68,7 +62,7 @@ defmodule Exception do
      caught_exception ->
        "got #{inspect(caught_exception.__struct__)} with message " <>
          "#{inspect(message(caught_exception))} while retrieving Exception.message/1 " <>
-          "for #{inspect(exception)}. Stacktrace:\n#{format_stacktrace(__STACKTRACE__)}"
+          "for #{inspect(exception)}"
    else
      result when is_binary(result) ->
        result
@@ -217,21 +211,16 @@ defmodule Exception do
      clauses =
        for {meta, ex_args, guards, _block} <- clauses do
          scope = :elixir_erl.scope(meta, true)
-          ann = :elixir_erl.get_ann(meta)

          {erl_args, scope} =
-            :elixir_erl_clauses.match(ann, &:elixir_erl_pass.translate_args/3, ex_args, scope)
+            :elixir_erl_clauses.match(&:elixir_erl_pass.translate_args/2, ex_args, scope)

          {args, binding} =
            [call_args, ex_args, erl_args]
            |> Enum.zip()
            |> Enum.map_reduce([], &blame_arg/2)

-          guards =
-            guards
-            |> Enum.map(&blame_guard(&1, ann, scope, binding))
-            |> Enum.map(&Macro.prewalk(&1, fn guard -> translate_guard(guard) end))
-
+          guards = Enum.map(guards, &blame_guard(&1, scope, binding))
          {args, guards}
        end

@@ -241,69 +230,6 @@ defmodule Exception do
    end
  end

-  defp is_map_node?({:is_map, _, [_]}), do: true
-  defp is_map_node?(_), do: false
-  defp is_map_key_node?({:is_map_key, _, [_, _]}), do: true
-  defp is_map_key_node?(_), do: false
-
-  defp struct_validation_node?(
-         {:is_atom, _, [{{:., [], [:erlang, :map_get]}, _, [:__struct__, _]}]}
-       ),
-       do: true
-
-  defp struct_validation_node?(
-         {:==, _, [{{:., [], [:erlang, :map_get]}, _, [:__struct__, _]}, _module]}
-       ),
-       do: true
-
-  defp struct_validation_node?(_), do: false
-
-  defp is_struct_macro?(
-         {:and, _,
-          [
-            {:and, _, [%{node: node_1 = {_, _, [arg]}}, %{node: node_2 = {_, _, [arg, _]}}]},
-            %{node: node_3 = {_, _, [{_, _, [_, arg]}]}}
-          ]}
-       ),
-       do: is_map_node?(node_1) and is_map_key_node?(node_2) and struct_validation_node?(node_3)
-
-  defp is_struct_macro?(
-         {:and, _,
-          [
-            {:and, _,
-             [
-               {:and, _,
-                [
-                  %{node: node_1 = {_, _, [arg]}},
-                  {:or, _, [%{node: {:is_atom, _, [_]}}, %{node: :fail}]}
-                ]},
-               %{node: node_2 = {_, _, [arg, _]}}
-             ]},
-            %{node: node_3 = {_, _, [{_, _, [_, arg]}, _]}}
-          ]}
-       ),
-       do: is_map_node?(node_1) and is_map_key_node?(node_2) and struct_validation_node?(node_3)
-
-  defp is_struct_macro?(_), do: false
-
-  defp translate_guard(guard) do
-    if is_struct_macro?(guard) do
-      undo_is_struct_guard(guard)
-    else
-      guard
-    end
-  end
-
-  defp undo_is_struct_guard({:and, meta, [_, %{node: {_, _, [{_, _, [_, arg]} | optional]}}]}) do
-    args =
-      case optional do
-        [] -> [arg]
-        [module] -> [arg, module]
-      end
-
-    %{match?: meta[:value], node: {:is_struct, meta, args}}
-  end
-
  defp blame_arg({call_arg, ex_arg, erl_arg}, binding) do
    {match?, binding} = blame_arg(erl_arg, call_arg, binding)
    {blame_wrap(match?, rewrite_arg(ex_arg)), binding}
@@ -326,19 +252,19 @@ defmodule Exception do

  defp rewrite_arg(arg) do
    Macro.prewalk(arg, fn
-      {:%{}, meta, [__struct__: Range, first: first, last: last, step: step]} ->
-        {:"..//", meta, [first, last, step]}
+      {:%{}, meta, [__struct__: Range, first: first, last: last]} ->
+        {:.., meta, [first, last]}

      other ->
        other
    end)
  end

-  defp blame_guard({{:., _, [:erlang, op]}, meta, [left, right]}, ann, scope, binding)
+  defp blame_guard({{:., _, [:erlang, op]}, meta, [left, right]}, scope, binding)
       when op == :andalso or op == :orelse do
    guards = [
-      blame_guard(left, ann, scope, binding),
-      blame_guard(right, ann, scope, binding)
+      blame_guard(left, scope, binding),
+      blame_guard(right, scope, binding)
    ]

    kernel_op =
@@ -347,38 +273,23 @@ defmodule Exception do
        :andalso -> :and
      end

-    evaluate_guard(kernel_op, meta, guards)
+    {kernel_op, meta, guards}
  end

-  defp blame_guard(ex_guard, ann, scope, binding) do
-    ex_guard
-    |> blame_guard?(binding, ann, scope)
-    |> blame_wrap(rewrite_guard(ex_guard))
-  end
+  defp blame_guard(ex_guard, scope, binding) do
+    {erl_guard, _} = :elixir_erl_pass.translate(ex_guard, scope)

-  defp blame_guard?(ex_guard, binding, ann, scope) do
-    {erl_guard, _} = :elixir_erl_pass.translate(ex_guard, ann, scope)
-    {:value, true, _} = :erl_eval.expr(erl_guard, binding, :none)
-    true
-  rescue
-    _ -> false
-  end
-
-  defp evaluate_guard(kernel_op, meta, guards = [_, _]) do
-    [x, y] = Enum.map(guards, &evaluate_guard/1)
-
-    logic_value =
-      case kernel_op do
-        :or -> x or y
-        :and -> x and y
+    match? =
+      try do
+        {:value, true, _} = :erl_eval.expr(erl_guard, binding, :none)
+        true
+      rescue
+        _ -> false
      end

-    {kernel_op, Keyword.put(meta, :value, logic_value), guards}
+    blame_wrap(match?, rewrite_guard(ex_guard))
  end

-  defp evaluate_guard(%{match?: value}), do: value
-  defp evaluate_guard({_, meta, _}) when is_list(meta), do: meta[:value]
-
  defp rewrite_guard(guard) do
    Macro.prewalk(guard, fn
      {{:., _, [mod, fun]}, meta, args} -> erl_to_ex(mod, fun, args, meta)
@@ -704,12 +615,12 @@ defmodule Exception do
    case Code.Identifier.extract_anonymous_fun_parent(fun) do
      {outer_name, outer_arity} ->
        "anonymous fn#{format_arity(arity)} in " <>
-          "#{Macro.inspect_atom(:literal, module)}." <>
-          "#{Macro.inspect_atom(:remote_call, outer_name)}/#{outer_arity}"
+          "#{Code.Identifier.inspect_as_atom(module)}." <>
+          "#{Code.Identifier.inspect_as_function(outer_name)}/#{outer_arity}"

      :error ->
-        "#{Macro.inspect_atom(:literal, module)}." <>
-          "#{Macro.inspect_atom(:remote_call, fun)}#{format_arity(arity)}"
+        "#{Code.Identifier.inspect_as_atom(module)}." <>
+          "#{Code.Identifier.inspect_as_function(fun)}#{format_arity(arity)}"
    end
  end

@@ -779,17 +690,6 @@ defmodule Exception do
    end
  end

-  @doc false
-  def format_snippet(snippet, error_line) do
-    line_digits = error_line |> Integer.to_string() |> byte_size()
-    placeholder = String.duplicate(" ", max(line_digits, 2))
-    padding = if line_digits < 2, do: " "
-
-    " #{placeholder} |\n" <>
-      " #{padding}#{error_line} | #{snippet.content}\n" <>
-      " #{placeholder} | #{String.duplicate(" ", snippet.offset)}^"
-  end
-
  defp format_location(opts) when is_list(opts) do
    format_file_line(Keyword.get(opts, :file), Keyword.get(opts, :line), " ")
  end
@@ -809,30 +709,29 @@ defmodule ArgumentError do

  @impl true
  def blame(
-        exception,
+        %{message: "argument error"} = exception,
        [{:erlang, :apply, [module, function, args], _} | _] = stacktrace
      ) do
    message =
      cond do
-        not proper_list?(args) ->
-          "you attempted to apply a function named #{inspect(function)} on module #{inspect(module)} " <>
-            "with arguments #{inspect(args)}. Arguments (the third argument of apply) must always be a proper list"
-
        # Note that args may be an empty list even if they were supplied
        not is_atom(module) and is_atom(function) and args == [] ->
-          "you attempted to apply a function named #{inspect(function)} on #{inspect(module)}. " <>
-            "If you are using Kernel.apply/3, make sure the module is an atom. " <>
-            "If you are using the dot syntax, such as module.function(), " <>
-            "make sure the left-hand side of the dot is a module atom"
+          "you attempted to apply #{inspect(function)} on #{inspect(module)}. " <>
+            "If you are using apply/3, make sure the module is an atom. " <>
+            "If you are using the dot syntax, such as map.field or module.function(), " <>
+            "make sure the left side of the dot is an atom or a map"

        not is_atom(module) ->
          "you attempted to apply a function on #{inspect(module)}. " <>
            "Modules (the first argument of apply) must always be an atom"

        not is_atom(function) ->
-          "you attempted to apply a function named #{inspect(function)} on module #{inspect(module)}. " <>
-            "However #{inspect(function)} is not a valid function name. Function names (the second argument " <>
-            "of apply) must always be an atom"
+          "you attempted to apply #{inspect(function)} on module #{inspect(module)}. " <>
+            "Functions (the second argument of apply) must always be an atom"
+
+        not is_list(args) ->
+          "you attempted to apply #{inspect(function)} on module #{inspect(module)} " <>
+            "with arguments #{inspect(args)}. Arguments (the third argument of apply) must always be a list"
      end

    {%{exception | message: message}, stacktrace}
@@ -841,9 +740,6 @@ defmodule ArgumentError do
  def blame(exception, stacktrace) do
    {exception, stacktrace}
  end
-
-  defp proper_list?(list) when length(list) >= 0, do: true
-  defp proper_list?(_), do: false
 end

 defmodule ArithmeticError do
@@ -887,60 +783,29 @@ defmodule ArithmeticError do
 end

 defmodule SystemLimitError do
-  defexception message: "a system limit has been reached"
+  defexception []
+
+  @impl true
+  def message(_) do
+    "a system limit has been reached"
+  end
 end

 defmodule SyntaxError do
-  defexception [:file, :line, :column, :snippet, description: "syntax error"]
+  defexception [:file, :line, :column, description: "syntax error"]

  @impl true
-  def message(%{
-        file: file,
-        line: line,
-        column: column,
-        description: description,
-        snippet: snippet
-      })
-      when not is_nil(snippet) and not is_nil(column) do
-    Exception.format_file_line_column(Path.relative_to_cwd(file), line, column) <>
-      " " <> description <> "\n" <> Exception.format_snippet(snippet, line)
-  end
-
-  @impl true
-  def message(%{
-        file: file,
-        line: line,
-        column: column,
-        description: description
-      }) do
+  def message(%{file: file, line: line, column: column, description: description}) do
    Exception.format_file_line_column(Path.relative_to_cwd(file), line, column) <>
      " " <> description
  end
 end

 defmodule TokenMissingError do
-  defexception [:file, :line, :snippet, :column, description: "expression is incomplete"]
+  defexception [:file, :line, :column, description: "expression is incomplete"]

  @impl true
-  def message(%{
-        file: file,
-        line: line,
-        column: column,
-        description: description,
-        snippet: snippet
-      })
-      when not is_nil(snippet) and not is_nil(column) do
-    Exception.format_file_line_column(Path.relative_to_cwd(file), line, column) <>
-      " " <> description <> "\n" <> Exception.format_snippet(snippet, line)
-  end
-
-  @impl true
-  def message(%{
-        file: file,
-        line: line,
-        column: column,
-        description: description
-      }) do
+  def message(%{file: file, line: line, column: column, description: description}) do
    Exception.format_file_line_column(file && Path.relative_to_cwd(file), line, column) <>
      " " <> description
  end
@@ -1112,8 +977,8 @@ defmodule UndefinedFunctionError do
  end

  defp hint(nil, _function, 0, _loaded?) do
-    ". If you are using the dot syntax, such as module.function(), " <>
-      "make sure the left-hand side of the dot is a module atom"
+    ". If you are using the dot syntax, such as map.field or module.function(), " <>
+      "make sure the left side of the dot is an atom or a map"
  end

  defp hint(module, function, arity, true) do
@@ -1127,23 +992,11 @@ defmodule UndefinedFunctionError do

  @doc false
  def hint_for_loaded_module(module, function, arity, exports) do
-    cond do
-      macro_exported?(module, function, arity) ->
-        ". However there is a macro with the same name and arity. " <>
-          "Be sure to require #{inspect(module)} if you intend to invoke this macro"
-
-      message = otp_obsolete(module, function, arity) ->
-        ", #{message}"
-
-      true ->
-        IO.iodata_to_binary(did_you_mean(module, function, exports))
-    end
-  end
-
-  defp otp_obsolete(module, function, arity) do
-    case :otp_internal.obsolete(module, function, arity) do
-      {:removed, [_ | _] = string} -> string
-      _ -> nil
+    if macro_exported?(module, function, arity) do
+      ". However there is a macro with the same name and arity. " <>
+        "Be sure to require #{inspect(module)} if you intend to invoke this macro"
+    else
+      IO.iodata_to_binary(did_you_mean(module, function, exports))
    end
  end

@@ -1173,12 +1026,12 @@ defmodule UndefinedFunctionError do

    case result do
      [] -> []
-      suggestions -> [". Did you mean:\n\n" | Enum.map(suggestions, &format_fa/1)]
+      suggestions -> [". Did you mean one of:\n\n" | Enum.map(suggestions, &format_fa/1)]
    end
  end

  defp format_fa({_dist, fun, arity}) do
-    ["      * ", Macro.inspect_atom(:remote_call, fun), ?/, Integer.to_string(arity), ?\n]
+    ["      * ", Code.Identifier.inspect_as_function(fun), ?/, Integer.to_string(arity), ?\n]
  end

  defp behaviour_hint(module, function, arity) do
@@ -1204,9 +1057,7 @@ defmodule UndefinedFunctionError do
  end

  defp expects_callback?(behaviour, function, arity) do
-    callbacks =
-      behaviour.behaviour_info(:callbacks) -- behaviour.behaviour_info(:optional_callbacks)
-
+    callbacks = behaviour.behaviour_info(:callbacks)
    Enum.member?(callbacks, {function, arity})
  end

@@ -1248,7 +1099,7 @@ defmodule FunctionClauseError do

      %{module: module, function: function, arity: arity} ->
        formatted = Exception.format_mfa(module, function, arity)
-        blamed = blame(exception, &inspect/1, &blame_match/1)
+        blamed = blame(exception, &inspect/1, &blame_match/2)
        "no function clause matching in #{formatted}" <> blamed
    end
  end
@@ -1270,24 +1121,24 @@ defmodule FunctionClauseError do
    end
  end

-  defp blame_match(%{match?: true, node: node}), do: Macro.to_string(node)
-  defp blame_match(%{match?: false, node: node}), do: "-" <> Macro.to_string(node) <> "-"
+  defp blame_match(%{match?: true, node: node}, _), do: Macro.to_string(node)
+  defp blame_match(%{match?: false, node: node}, _), do: "-" <> Macro.to_string(node) <> "-"
+  defp blame_match(_, string), do: string

  @doc false
  def blame(%{args: nil}, _, _) do
    ""
  end

-  def blame(exception, inspect_fun, fun) do
+  def blame(exception, inspect_fun, ast_fun) do
    %{module: module, function: function, arity: arity, kind: kind, args: args, clauses: clauses} =
      exception

    mfa = Exception.format_mfa(module, function, arity)

    format_clause_fun = fn {args, guards} ->
-      args = Enum.map_join(args, ", ", fun)
-      base = "    #{kind} #{function}(#{args})"
-      Enum.reduce(guards, base, &"#{&2} when #{clause_to_string(&1, fun)}") <> "\n"
+      code = Enum.reduce(guards, {function, [], args}, &{:when, [], [&2, &1]})
+      "    #{kind} " <> Macro.to_string(code, ast_fun) <> "\n"
    end

    "\n\nThe following arguments were given to #{mfa}:\n" <>
@@ -1295,11 +1146,6 @@ defmodule FunctionClauseError do
      "#{format_clauses(clauses, format_clause_fun, @clause_limit)}"
  end

-  defp clause_to_string({op, _, [left, right]}, fun),
-    do: clause_to_string(left, fun) <> " #{op} " <> clause_to_string(right, fun)
-
-  defp clause_to_string(node, fun), do: fun.(node)
-
  defp format_args(args, inspect_fun) do
    args
    |> Enum.with_index(1)
@@ -1336,13 +1182,11 @@ defmodule FunctionClauseError do
 end

 defmodule Code.LoadError do
-  defexception [:file, :message, :reason]
+  defexception [:file, :message]

  def exception(opts) do
    file = Keyword.fetch!(opts, :file)
-    reason = Keyword.fetch!(opts, :reason)
-    message = "could not load #{file}. Reason: #{reason}"
-    %Code.LoadError{message: message, file: file, reason: reason}
+    %Code.LoadError{message: "could not load #{file}", file: file}
  end
 end

@@ -1404,10 +1248,6 @@ defmodule KeyError do
  end

  @impl true
-  def blame(exception = %{message: message}, stacktrace) when is_binary(message) do
-    {exception, stacktrace}
-  end
-
  def blame(exception = %{term: nil}, stacktrace) do
    message = message(exception.key, exception.term)
    {%{exception | message: message}, stacktrace}
@@ -1446,7 +1286,7 @@ defmodule KeyError do

    case suggestions do
      [] -> []
-      suggestions -> [". Did you mean:\n\n" | format_suggestions(suggestions)]
+      suggestions -> [". Did you mean one of:\n\n" | format_suggestions(suggestions)]
    end
  end

@@ -1557,38 +1397,24 @@ defmodule File.LinkError do
 end

 defmodule ErlangError do
-  defexception [:original, :reason]
+  defexception [:original]

  @impl true
-  def message(exception)
-
-  def message(%__MODULE__{original: original, reason: nil}) do
-    "Erlang error: #{inspect(original)}"
-  end
-
-  def message(%__MODULE__{original: original, reason: reason}) do
-    IO.iodata_to_binary(["Erlang error: ", inspect(original), reason])
+  def message(exception) do
+    "Erlang error: #{inspect(exception.original)}"
  end

  @doc false
-  def normalize(:badarg, stacktrace) do
-    case error_info(:badarg, stacktrace, "errors were found at the given arguments") do
-      {:ok, reason, details} -> %ArgumentError{message: reason <> details}
-      :error -> %ArgumentError{}
-    end
+  def normalize(:badarg, _stacktrace) do
+    %ArgumentError{}
  end

  def normalize(:badarith, _stacktrace) do
    %ArithmeticError{}
  end

-  def normalize(:system_limit, stacktrace) do
-    default_reason = "a system limit has been reached due to errors at the given arguments"
-
-    case error_info(:system_limit, stacktrace, default_reason) do
-      {:ok, reason, details} -> %SystemLimitError{message: reason <> details}
-      :error -> %SystemLimitError{}
-    end
+  def normalize(:system_limit, _stacktrace) do
+    %SystemLimitError{}
  end

  def normalize(:cond_clause, _stacktrace) do
@@ -1633,19 +1459,10 @@ defmodule ErlangError do
    %KeyError{key: key, term: term}
  end

-  def normalize({:badkey, key, map}, _stacktrace) when is_map(map) do
+  def normalize({:badkey, key, map}, _stacktrace) do
    %KeyError{key: key, term: map}
  end

-  def normalize({:badkey, key, term}, _stacktrace) do
-    message =
-      "key #{inspect(key)} not found in: #{inspect(term)}. " <>
-        "If you are using the dot syntax, such as map.field, " <>
-        "make sure the left-hand side of the dot is a map"
-
-    %KeyError{key: key, term: term, message: message}
-  end
-
  def normalize({:case_clause, term}, _stacktrace) do
    %CaseClauseError{term: term}
  end
@@ -1672,11 +1489,8 @@ defmodule ErlangError do
    %ArgumentError{message: "argument error: #{inspect(payload)}"}
  end

-  def normalize(other, stacktrace) do
-    case error_info(other, stacktrace, "") do
-      {:ok, _reason, details} -> %ErlangError{original: other, reason: details}
-      :error -> %ErlangError{original: other}
-    end
+  def normalize(other, _stacktrace) do
+    %ErlangError{original: other}
  end

  defp from_stacktrace([{module, function, args, _} | _]) when is_list(args) do
@@ -1690,104 +1504,4 @@ defmodule ErlangError do
  defp from_stacktrace(_) do
    {nil, nil, nil}
  end
-
-  defp error_info(erl_exception, stacktrace, default_reason) do
-    with [{module, fun, args_or_arity, opts} | tail] <- stacktrace,
-         %{} = error_info <- opts[:error_info] do
-      error_module = Map.get(error_info, :module, module)
-      error_fun = Map.get(error_info, :function, :format_error)
-
-      error_info = Map.put(error_info, :pretty_printer, &inspect/1)
-      head = {module, fun, args_or_arity, Keyword.put(opts, :error_info, error_info)}
-
-      extra =
-        try do
-          apply(error_module, error_fun, [erl_exception, [head | tail]])
-        rescue
-          _ -> %{}
-        end
-
-      arity = if is_integer(args_or_arity), do: args_or_arity, else: length(args_or_arity)
-      args_errors = Map.take(extra, Enum.to_list(1..arity//1))
-      reason = Map.get(extra, :reason, default_reason)
-
-      cond do
-        map_size(args_errors) > 0 ->
-          {:ok, reason, IO.iodata_to_binary([":\n\n" | Enum.map(args_errors, &arg_error/1)])}
-
-        general = extra[:general] ->
-          {:ok, reason, ": " <> general}
-
-        true ->
-          :error
-      end
-    else
-      _ -> :error
-    end
-  end
-
-  defp arg_error({n, message}), do: "  * #{nth(n)} argument: #{message}\n"
-
-  defp nth(1), do: "1st"
-  defp nth(2), do: "2nd"
-  defp nth(3), do: "3rd"
-  defp nth(n), do: "#{n}th"
-end
-
-defmodule Inspect.Error do
-  @moduledoc """
-  Raised when a struct cannot be inspected.
-  """
-  @enforce_keys [:exception_module, :exception_message, :stacktrace, :inspected_struct]
-  defexception @enforce_keys
-
-  @impl true
-  def exception(arguments) when is_list(arguments) do
-    exception = Keyword.fetch!(arguments, :exception)
-    exception_module = exception.__struct__
-    exception_message = Exception.message(exception) |> String.trim_trailing("\n")
-    stacktrace = Keyword.fetch!(arguments, :stacktrace)
-    inspected_struct = Keyword.fetch!(arguments, :inspected_struct)
-
-    %Inspect.Error{
-      exception_module: exception_module,
-      exception_message: exception_message,
-      stacktrace: stacktrace,
-      inspected_struct: inspected_struct
-    }
-  end
-
-  @impl true
-  def message(%__MODULE__{
-        exception_module: exception_module,
-        exception_message: exception_message,
-        inspected_struct: inspected_struct
-      }) do
-    ~s'''
-    got #{inspect(exception_module)} with message:
-
-        """
-    #{pad(exception_message, 4)}
-        """
-
-    while inspecting:
-
-    #{pad(inspected_struct, 4)}
-    '''
-  end
-
-  @doc false
-  def pad(message, padding_length)
-      when is_binary(message) and is_integer(padding_length) and padding_length >= 0 do
-    padding = String.duplicate(" ", padding_length)
-
-    message
-    |> String.split("\n")
-    |> Enum.map(fn
-      "" -> "\n"
-      line -> [padding, line, ?\n]
-    end)
-    |> IO.iodata_to_binary()
-    |> String.trim_trailing("\n")
-  end
 end
@@ -112,7 +112,6 @@ defmodule File do
          encoding_mode()
          | :append
          | :compressed
-          | :delayed_write
          | :trim_bom
          | {:read_ahead, pos_integer | false}
          | {:delayed_write, non_neg_integer, non_neg_integer}
@@ -123,8 +122,6 @@ defmodule File do

  @type posix_time :: integer()

-  @type on_conflict_callback :: (Path.t(), Path.t() -> boolean)
-
  @doc """
  Returns `true` if the path is a regular file.

@@ -696,10 +693,7 @@ defmodule File do
  @spec copy(Path.t() | io_device, Path.t() | io_device, pos_integer | :infinity) ::
          {:ok, non_neg_integer} | {:error, posix}
  def copy(source, destination, bytes_count \\ :infinity) do
-    source = normalize_path_or_io_device(source)
-    destination = normalize_path_or_io_device(destination)
-
-    :file.copy(source, destination, bytes_count)
+    :file.copy(maybe_to_string(source), maybe_to_string(destination), bytes_count)
  end

  @doc """
@@ -717,8 +711,8 @@ defmodule File do
        raise File.CopyError,
          reason: reason,
          action: "copy",
-          source: normalize_path_or_io_device(source),
-          destination: normalize_path_or_io_device(destination)
+          source: maybe_to_string(source),
+          destination: maybe_to_string(destination)
    end
  end

@@ -746,8 +740,6 @@ defmodule File do
  @doc since: "1.1.0"
  @spec rename(Path.t(), Path.t()) :: :ok | {:error, posix}
  def rename(source, destination) do
-    source = IO.chardata_to_string(source)
-    destination = IO.chardata_to_string(destination)
    :file.rename(source, destination)
  end

@@ -772,11 +764,15 @@ defmodule File do
  end

  @doc """
-  Copies the contents of `source_file` to `destination_file` preserving its modes.
+  Copies the contents in `source_file` to `destination_file` preserving its modes.

-  `source_file` must be a file or a symbolic link to one. `destination_file` must
-  be a path to a non-existent file. If either is a directory, `{:error, :eisdir}`
-  will be returned.
+  `source_file` and `destination_file` must be a file or a symbolic link to one,
+  or in the case of destination, a path to a non-existent file. If either one of
+  them is a directory, `{:error, :eisdir}` will be returned.
+
+  If a file already exists in the destination, it invokes a
+  callback which should return `true` if the existing file
+  should be overwritten, `false` otherwise. The callback defaults to return `true`.

  The function returns `:ok` in case of success. Otherwise, it returns
  `{:error, reason}`.
@@ -789,30 +785,13 @@ defmodule File do
  whether the destination is an existing directory or not. We have chosen to
  explicitly disallow copying to a destination which is a directory,
  and an error will be returned if tried.
-
-  ## Options
-
-    * `:on_conflict` - (since v1.14.0) Invoked when a file already exists in the destination.
-      The function receives arguments for `source_file` and `destination_file`. It should
-      return `true` if the existing file should be overwritten, `false` if otherwise.
-      The default callback returns `true`. On earlier versions, this callback could be
-      given as third argument, but such behaviour is now deprecated.
-
  """
-  @spec cp(Path.t(), Path.t(), on_conflict: on_conflict_callback) :: :ok | {:error, posix}
-  def cp(source_file, destination_file, options \\ [])
-
-  # TODO: Deprecate me on Elixir v1.19
-  def cp(source_file, destination_file, callback) when is_function(callback, 2) do
-    cp(source_file, destination_file, on_conflict: callback)
-  end
-
-  def cp(source_file, destination_file, options) when is_list(options) do
-    on_conflict = Keyword.get(options, :on_conflict, fn _, _ -> true end)
+  @spec cp(Path.t(), Path.t(), (Path.t(), Path.t() -> boolean)) :: :ok | {:error, posix}
+  def cp(source_file, destination_file, callback \\ fn _, _ -> true end) do
    source_file = IO.chardata_to_string(source_file)
    destination_file = IO.chardata_to_string(destination_file)

-    case do_cp_file(source_file, destination_file, on_conflict, []) do
+    case do_cp_file(source_file, destination_file, callback, []) do
      {:error, reason, _} -> {:error, reason}
      _ -> :ok
    end
@@ -828,9 +807,9 @@ defmodule File do
  The same as `cp/3`, but raises a `File.CopyError` exception if it fails.
  Returns `:ok` otherwise.
  """
-  @spec cp!(Path.t(), Path.t(), on_conflict: on_conflict_callback) :: :ok
-  def cp!(source_file, destination_file, options \\ []) do
-    case cp(source_file, destination_file, options) do
+  @spec cp!(Path.t(), Path.t(), (Path.t(), Path.t() -> boolean)) :: :ok
+  def cp!(source_file, destination_file, callback \\ fn _, _ -> true end) do
+    case cp(source_file, destination_file, callback) do
      :ok ->
        :ok

@@ -853,15 +832,18 @@ defmodule File do
  If `source` is a directory, or a symbolic link to it, then `destination` must
  be an existent `directory` or a symbolic link to one, or a path to a non-existent directory.

-  If the source is a file, it copies `source` to `destination`. If the `source`
-  is a directory, it copies the contents inside source into the `destination` directory.
+  If the source is a file, it copies `source` to
+  `destination`. If the `source` is a directory, it copies
+  the contents inside source into the `destination` directory.

-  If a file already exists in the destination, it invokes the optional `on_conflict`
-  callback given as an option. See "Options" for more information.
+  If a file already exists in the destination, it invokes `callback`.
+  `callback` must be a function that takes two arguments: `source` and `destination`.
+  The callback should return `true` if the existing file should be overwritten and `false` otherwise.

-  This function may fail while copying files, in such cases, it will leave the
-  destination directory in a dirty state, where file which have already been
-  copied won't be removed.
+  This function may fail while copying files,
+  in such cases, it will leave the destination
+  directory in a dirty state, where file which have already been copied
+  won't be removed.

  The function returns `{:ok, files_and_directories}` in case of
  success, `files_and_directories` lists all files and directories copied in no
@@ -872,19 +854,6 @@ defmodule File do
  explicitly disallow this behaviour. If `source` is a `file` and `destination`
  is a directory, `{:error, :eisdir}` will be returned.

-  ## Options
-
-    * `:on_conflict` - (since v1.14.0) Invoked when a file already exists in the destination.
-      The function receives arguments for `source` and `destination`. It should return
-      `true` if the existing file should be overwritten, `false` if otherwise. The default
-      callback returns `true`. On earlier versions, this callback could be given as third
-      argument, but such behaviour is now deprecated.
-
-    * `:dereference_symlinks` - (since v1.14.0) By default, this function will copy symlinks
-      by creating symlinks that point to the same location. This option forces symlinks to be
-      dereferenced and have their contents copied instead when set to `true`. If the dereferenced
-      files do not exist, than the operation fails. The default is `false`.
-
  ## Examples

      # Copies file "a.txt" to "b.txt"
@@ -894,28 +863,14 @@ defmodule File do
      File.cp_r("samples", "tmp")

      # Same as before, but asks the user how to proceed in case of conflicts
-      File.cp_r("samples", "tmp", on_conflict: fn source, destination ->
+      File.cp_r("samples", "tmp", fn source, destination ->
        IO.gets("Overwriting #{destination} by #{source}. Type y to confirm. ") == "y\n"
      end)

  """
-  @spec cp_r(Path.t(), Path.t(),
-          on_conflict: on_conflict_callback,
-          dereference_symlinks: boolean()
-        ) ::
+  @spec cp_r(Path.t(), Path.t(), (Path.t(), Path.t() -> boolean)) ::
          {:ok, [binary]} | {:error, posix, binary}
-
-  def cp_r(source, destination, options \\ [])
-
-  # TODO: Deprecate me on Elixir v1.19
-  def cp_r(source, destination, callback) when is_function(callback, 2) do
-    cp_r(source, destination, on_conflict: callback)
-  end
-
-  def cp_r(source, destination, options) when is_list(options) do
-    on_conflict = Keyword.get(options, :on_conflict, fn _, _ -> true end)
-    dereference? = Keyword.get(options, :dereference_symlinks, false)
-
+  def cp_r(source, destination, callback \\ fn _, _ -> true end) when is_function(callback, 2) do
    source =
      source
      |> IO.chardata_to_string()
@@ -926,7 +881,7 @@ defmodule File do
      |> IO.chardata_to_string()
      |> assert_no_null_byte!("File.cp_r/3")

-    case do_cp_r(source, destination, on_conflict, dereference?, []) do
+    case do_cp_r(source, destination, callback, []) do
      {:error, _, _} = error -> error
      res -> {:ok, res}
    end
@@ -936,12 +891,9 @@ defmodule File do
  The same as `cp_r/3`, but raises a `File.CopyError` exception if it fails.
  Returns the list of copied files otherwise.
  """
-  @spec cp_r!(Path.t(), Path.t(),
-          on_conflict: on_conflict_callback,
-          dereference_symlinks: boolean()
-        ) :: [binary]
-  def cp_r!(source, destination, options \\ []) do
-    case cp_r(source, destination, options) do
+  @spec cp_r!(Path.t(), Path.t(), (Path.t(), Path.t() -> boolean)) :: [binary]
+  def cp_r!(source, destination, callback \\ fn _, _ -> true end) do
+    case cp_r(source, destination, callback) do
      {:ok, files} ->
        files

@@ -955,21 +907,15 @@ defmodule File do
    end
  end

-  defp do_cp_r(src, dest, on_conflict, dereference?, acc) when is_list(acc) do
+  defp do_cp_r(src, dest, callback, acc) when is_list(acc) do
    case :elixir_utils.read_link_type(src) do
      {:ok, :regular} ->
-        do_cp_file(src, dest, on_conflict, acc)
+        do_cp_file(src, dest, callback, acc)

      {:ok, :symlink} ->
        case :file.read_link(src) do
-          {:ok, link} when dereference? ->
-            do_cp_r(Path.expand(link, Path.dirname(src)), dest, on_conflict, dereference?, acc)
-
-          {:ok, link} ->
-            do_cp_link(link, src, dest, on_conflict, acc)
-
-          {:error, reason} ->
-            {:error, reason, src}
+          {:ok, link} -> do_cp_link(link, src, dest, callback, acc)
+          {:error, reason} -> {:error, reason, src}
        end

      {:ok, :directory} ->
@@ -978,7 +924,7 @@ defmodule File do
            case mkdir(dest) do
              success when success in [:ok, {:error, :eexist}] ->
                Enum.reduce(files, [dest | acc], fn x, acc ->
-                  do_cp_r(Path.join(src, x), Path.join(dest, x), on_conflict, dereference?, acc)
+                  do_cp_r(Path.join(src, x), Path.join(dest, x), callback, acc)
                end)

              {:error, reason} ->
@@ -997,8 +943,9 @@ defmodule File do
    end
  end

-  # If we reach this clause, there was an error while processing a file.
-  defp do_cp_r(_, _, _, _, acc) do
+  # If we reach this clause, there was an error while
+  # processing a file.
+  defp do_cp_r(_, _, _, acc) do
    acc
  end

@@ -1007,14 +954,14 @@ defmodule File do
  end

  # Both src and dest are files.
-  defp do_cp_file(src, dest, on_conflict, acc) do
+  defp do_cp_file(src, dest, callback, acc) do
    case :file.copy(src, {dest, [:exclusive]}) do
      {:ok, _} ->
        copy_file_mode!(src, dest)
        [dest | acc]

      {:error, :eexist} ->
-        if path_differs?(src, dest) and on_conflict.(src, dest) do
+        if path_differs?(src, dest) and callback.(src, dest) do
          case copy(src, dest) do
            {:ok, _} ->
              copy_file_mode!(src, dest)
@@ -1033,13 +980,13 @@ defmodule File do
  end

  # Both src and dest are files.
-  defp do_cp_link(link, src, dest, on_conflict, acc) do
+  defp do_cp_link(link, src, dest, callback, acc) do
    case :file.make_symlink(link, dest) do
      :ok ->
        [dest | acc]

      {:error, :eexist} ->
-        if path_differs?(src, dest) and on_conflict.(src, dest) do
+        if path_differs?(src, dest) and callback.(src, dest) do
          # If rm/1 fails, :file.make_symlink/2 will fail
          _ = rm(dest)

@@ -1096,7 +1043,9 @@ defmodule File do
  """
  @spec write!(Path.t(), iodata, [mode]) :: :ok
  def write!(path, content, modes \\ []) do
-    case write(path, content, modes) do
+    modes = normalize_modes(modes, false)
+
+    case :file.write_file(path, content, modes) do
      :ok ->
        :ok

@@ -1244,79 +1193,82 @@ defmodule File do
  """
  @spec rm_rf(Path.t()) :: {:ok, [binary]} | {:error, posix, binary}
  def rm_rf(path) do
-    {major, _} = :os.type()
-
    path
    |> IO.chardata_to_string()
    |> assert_no_null_byte!("File.rm_rf/1")
-    |> do_rm_rf([], major)
+    |> do_rm_rf({:ok, []})
  end

-  defp do_rm_rf(path, acc, major) do
-    case safe_list_dir(path, major) do
+  defp do_rm_rf(path, {:ok, _} = entry) do
+    case safe_list_dir(path) do
      {:ok, files} when is_list(files) ->
-        acc =
-          Enum.reduce(files, acc, fn file, acc ->
-            # In case we can't delete, continue anyway, we might succeed
-            # to delete it on Windows due to how they handle symlinks.
-            case do_rm_rf(Path.join(path, file), acc, major) do
-              {:ok, acc} -> acc
-              {:error, _, _} -> acc
-            end
+        res =
+          Enum.reduce(files, entry, fn file, tuple ->
+            do_rm_rf(Path.join(path, file), tuple)
          end)

-        case rmdir(path) do
-          :ok -> {:ok, [path | acc]}
-          {:error, :enoent} -> {:ok, acc}
-          {:error, reason} -> {:error, reason, path}
+        case res do
+          {:ok, acc} ->
+            case rmdir(path) do
+              :ok -> {:ok, [path | acc]}
+              {:error, :enoent} -> res
+              {:error, reason} -> {:error, reason, path}
+            end
+
+          reason ->
+            reason
        end

      {:ok, :directory} ->
-        do_rm_directory(path, acc)
+        do_rm_directory(path, entry)

      {:ok, :regular} ->
-        do_rm_regular(path, acc)
+        do_rm_regular(path, entry)

      {:error, reason} when reason in [:enoent, :enotdir] ->
-        {:ok, acc}
+        entry

      {:error, reason} ->
        {:error, reason, path}
    end
  end

-  defp do_rm_regular(path, acc) do
+  defp do_rm_rf(_, reason) do
+    reason
+  end
+
+  defp do_rm_regular(path, {:ok, acc} = entry) do
    case rm(path) do
      :ok -> {:ok, [path | acc]}
-      {:error, :enoent} -> {:ok, acc}
+      {:error, :enoent} -> entry
      {:error, reason} -> {:error, reason, path}
    end
  end

  # On Windows, symlinks are treated as directory and must be removed
-  # with rmdir/1. But on Unix-like systems, we remove them via rm/1.
-  # So we first try to remove it as a directory and, if we get :enotdir,
-  # we fall back to a file removal.
-  defp do_rm_directory(path, acc) do
+  # with rmdir/1. But on Unix-like systems, we remove them via rm/1. So we first try
+  # to remove it as a directory and, if we get :enotdir, we fall back to
+  # a file removal.
+  defp do_rm_directory(path, {:ok, acc} = entry) do
    case rmdir(path) do
      :ok -> {:ok, [path | acc]}
-      {:error, :enotdir} -> do_rm_regular(path, acc)
-      {:error, :enoent} -> {:ok, acc}
+      {:error, :enotdir} -> do_rm_regular(path, entry)
+      {:error, :enoent} -> entry
      {:error, reason} -> {:error, reason, path}
    end
  end

-  defp safe_list_dir(path, major) do
+  defp safe_list_dir(path) do
    case :elixir_utils.read_link_type(path) do
-      {:ok, :directory} ->
-        :file.list_dir_all(path)
-
-      {:ok, :symlink} when major == :win32 ->
+      {:ok, :symlink} ->
        case :elixir_utils.read_file_type(path) do
          {:ok, :directory} -> {:ok, :directory}
          _ -> {:ok, :regular}
        end

+      {:ok, :directory} ->
+        :file.list_dir(path)
+
      {:ok, _} ->
        {:ok, :regular}

@@ -1589,12 +1541,6 @@ defmodule File do
  executes the given function and then reverts back
  to the previous path regardless of whether there is an exception.

-  The current working directory is temporarily set for the BEAM globally. This
-  can lead to race conditions if multiple processes are changing the current
-  working directory concurrently. To run an external command in a given
-  directory without changing the global current working directory, use the
-  `:cd` option of `System.cmd/3` and `Port.open/2`.
-
  Raises an error if retrieving or changing the current
  directory fails.
  """
@@ -1654,16 +1600,14 @@ defmodule File do
    :file.close(io_device)
  end

-  @doc ~S"""
+  @doc """
  Returns a `File.Stream` for the given `path` with the given `modes`.

  The stream implements both `Enumerable` and `Collectable` protocols,
  which means it can be used both for read and write.

  The `line_or_bytes` argument configures how the file is read when
-  streaming, by `:line` (default) or by a given number of bytes. When
-  using the `:line` option, CRLF line breaks (`"\r\n"`) are normalized
-  to LF (`"\n"`).
+  streaming, by `:line` (default) or by a given number of bytes.

  Operating the stream can fail on open for the same reasons as
  `File.open!/2`. Note that the file is automatically opened each time streaming
@@ -1852,8 +1796,7 @@ defmodule File do
  defp normalize_modes([], true), do: [:binary]
  defp normalize_modes([], false), do: []

-  defp normalize_path_or_io_device(path) when is_list(path), do: IO.chardata_to_string(path)
-  defp normalize_path_or_io_device(path) when is_binary(path), do: path
-  defp normalize_path_or_io_device(io_device) when is_pid(io_device), do: io_device
-  defp normalize_path_or_io_device(io_device = {:file_descriptor, _, _}), do: io_device
+  defp maybe_to_string(path) when is_list(path), do: IO.chardata_to_string(path)
+  defp maybe_to_string(path) when is_binary(path), do: path
+  defp maybe_to_string(path), do: path
 end
@@ -15,7 +15,7 @@ defmodule Float do
  ## Known issues

  There are some very well known problems with floating-point numbers
-  and arithmetic due to the fact most decimal fractions cannot be
+  and arithmetics due to the fact most decimal fractions cannot be
  represented by a floating-point binary and most operations are not exact,
  but operate on approximations. Those issues are not specific
  to Elixir, they are a property of floating point representation itself.
@@ -46,71 +46,6 @@ defmodule Float do
  @precision_range 0..15
  @type precision_range :: 0..15

-  @min_finite then(<<0xFFEFFFFFFFFFFFFF::64>>, fn <<num::float>> -> num end)
-  @max_finite then(<<0x7FEFFFFFFFFFFFFF::64>>, fn <<num::float>> -> num end)
-
-  @doc """
-  Returns the maximum finite value for a float.
-
-  ## Examples
-
-      iex> Float.max_finite()
-      1.7976931348623157e308
-
-  """
-  def max_finite, do: @max_finite
-
-  @doc """
-  Returns the minimum finite value for a float.
-
-  ## Examples
-
-      iex> Float.min_finite()
-      -1.7976931348623157e308
-
-  """
-  def min_finite, do: @min_finite
-
-  @doc """
-  Computes `base` raised to power of `exponent`.
-
-  `base` must be a float and `exponent` can be any number.
-  However, if a negative base and a fractional exponent
-  are given, it raises `ArithmeticError`.
-
-  It always returns a float. See `Integer.pow/2` for
-  exponentiation that returns integers.
-
-  ## Examples
-
-      iex> Float.pow(2.0, 0)
-      1.0
-      iex> Float.pow(2.0, 1)
-      2.0
-      iex> Float.pow(2.0, 10)
-      1024.0
-      iex> Float.pow(2.0, -1)
-      0.5
-      iex> Float.pow(2.0, -3)
-      0.125
-
-      iex> Float.pow(3.0, 1.5)
-      5.196152422706632
-
-      iex> Float.pow(-2.0, 3)
-      -8.0
-      iex> Float.pow(-2.0, 4)
-      16.0
-
-      iex> Float.pow(-1.0, 0.5)
-      ** (ArithmeticError) bad argument in arithmetic expression
-
-  """
-  @doc since: "1.12.0"
-  @spec pow(float, number) :: float
-  def pow(base, exponent) when is_float(base) and is_number(exponent),
-    do: :math.pow(base, exponent)
-
  @doc """
  Parses a binary into a float.

@@ -119,8 +54,7 @@ defmodule Float do
  returned.

  If the size of float exceeds the maximum size of `1.7976931348623157e+308`,
-  `:error` is returned even though the textual representation itself might be
-  well formed.
+  the `ArgumentError` exception is raised.

  If you want to convert a string-formatted float directly to a float,
  `String.to_float/1` can be used instead.
@@ -136,8 +70,6 @@ defmodule Float do

      iex> Float.parse("pi")
      :error
-      iex> Float.parse("1.7976931348623159e+308")
-      :error

  """
  @spec parse(binary) :: {float, binary} | :error
@@ -175,18 +107,7 @@ defmodule Float do
       when exp_marker in 'eE' and sign in '-+' and digit in ?0..?9,
       do: parse_unsigned(rest, true, true, <<add_dot(acc, dot?)::binary, ?e, sign, digit>>)

-  # When floats are expressed in scientific notation, :erlang.binary_to_float/1 can raise an
-  # ArgumentError if the e exponent is too big. For example, "1.0e400". Because of this, we
-  # rescue the ArgumentError here and return an error.
-  defp parse_unsigned(rest, dot?, true = _e?, acc) do
-    :erlang.binary_to_float(add_dot(acc, dot?))
-  rescue
-    ArgumentError -> :error
-  else
-    float -> {float, rest}
-  end
-
-  defp parse_unsigned(rest, dot?, false = _e?, acc),
+  defp parse_unsigned(rest, dot?, _e?, acc),
    do: {:erlang.binary_to_float(add_dot(acc, dot?)), rest}

  defp add_dot(acc, true), do: acc
@@ -347,11 +268,11 @@ defmodule Float do
    raise ArgumentError, invalid_precision_message(precision)
  end

-  defp round(0.0 = num, _precision, _rounding), do: num
+  defp round(0.0, _precision, _rounding), do: 0.0

  defp round(float, precision, rounding) do
    <<sign::1, exp::11, significant::52-bitstring>> = <<float::float>>
-    {num, count} = decompose(significant, 1)
+    {num, count, _} = decompose(significant, 1)
    count = count - exp + 1023

    cond do
@@ -403,22 +324,6 @@ defmodule Float do
    end
  end

-  defp decompose(significant, initial) do
-    decompose(significant, 1, 0, initial)
-  end
-
-  defp decompose(<<1::1, bits::bitstring>>, count, last_count, acc) do
-    decompose(bits, count + 1, count, (acc <<< (count - last_count)) + 1)
-  end
-
-  defp decompose(<<0::1, bits::bitstring>>, count, last_count, acc) do
-    decompose(bits, count + 1, last_count, acc)
-  end
-
-  defp decompose(<<>>, _count, last_count, acc) do
-    {acc, last_count}
-  end
-
  defp scale_up(num, boundary, exp) when num >= boundary, do: {num, exp}
  defp scale_up(num, boundary, exp), do: scale_up(num <<< 1, boundary, exp - 1)

@@ -498,70 +403,63 @@ defmodule Float do
  def ratio(0.0), do: {0, 1}

  def ratio(float) when is_float(float) do
-    <<sign::1, exp::11, mantissa::52>> = <<float::float>>
+    case <<float::float>> do
+      <<sign::1, 0::11, significant::52-bitstring>> ->
+        {num, _, den} = decompose(significant, 0)
+        {sign(sign, num), shift_left(den, 1022)}

-    {num, den_exp} =
-      if exp != 0 do
-        # Floats are expressed like this:
-        # (2**52 + mantissa) * 2**(-52 + exp - 1023)
-        #
-        # We compute the root factors of the mantissa so we have this:
-        # (2**52 + mantissa * 2**count) * 2**(-52 + exp - 1023)
-        {mantissa, count} = root_factors(mantissa, 0)
+      <<sign::1, exp::11, significant::52-bitstring>> ->
+        {num, _, den} = decompose(significant, 1)
+        num = sign(sign, num)

-        # Now we can move the count around so we have this:
-        # (2**(52-count) + mantissa) * 2**(count + -52 + exp - 1023)
-        if mantissa == 0 do
-          {1, exp - 1023}
-        else
-          num = (1 <<< (52 - count)) + mantissa
-          den_exp = count - 52 + exp - 1023
-          {num, den_exp}
+        case exp - 1023 do
+          exp when exp > 0 ->
+            {den, exp} = shift_right(den, exp)
+            {shift_left(num, exp), den}
+
+          exp when exp < 0 ->
+            {num, shift_left(den, -exp)}
+
+          0 ->
+            {num, den}
        end
-      else
-        # Subnormals are expressed like this:
-        # (mantissa) * 2**(-52 + 1 - 1023)
-        #
-        # So we compute it to this:
-        # (mantissa * 2**(count)) * 2**(-52 + 1 - 1023)
-        #
-        # Which becomes:
-        # mantissa * 2**(count-1074)
-        root_factors(mantissa, -1074)
-      end
-
-    if den_exp > 0 do
-      {sign(sign, num <<< den_exp), 1}
-    else
-      {sign(sign, num), 1 <<< -den_exp}
    end
  end

-  defp root_factors(mantissa, count) when mantissa != 0 and (mantissa &&& 1) == 0,
-    do: root_factors(mantissa >>> 1, count + 1)
+  defp decompose(significant, initial) do
+    decompose(significant, 1, 0, 2, 1, initial)
+  end

-  defp root_factors(mantissa, count),
-    do: {mantissa, count}
+  defp decompose(<<1::1, bits::bitstring>>, count, last_count, power, _last_power, acc) do
+    decompose(bits, count + 1, count, power <<< 1, power, shift_left(acc, count - last_count) + 1)
+  end

-  @compile {:inline, sign: 2}
+  defp decompose(<<0::1, bits::bitstring>>, count, last_count, power, last_power, acc) do
+    decompose(bits, count + 1, last_count, power <<< 1, last_power, acc)
+  end
+
+  defp decompose(<<>>, _count, last_count, _power, last_power, acc) do
+    {acc, last_count, last_power}
+  end
+
+  @compile {:inline, sign: 2, shift_left: 2}
  defp sign(0, num), do: num
  defp sign(1, num), do: -num

+  defp shift_left(num, times), do: num <<< times
+
+  defp shift_right(num, 0), do: {num, 0}
+  defp shift_right(1, times), do: {1, times}
+  defp shift_right(num, times), do: shift_right(num >>> 1, times - 1)
+
  @doc """
-  Returns a charlist which corresponds to the shortest text representation
+  Returns a charlist which corresponds to the text representation
  of the given float.

-  The underlying algorithm changes depending on the Erlang/OTP version:
-
-    * For OTP >= 24, it uses the algorithm presented in "Ryū: fast
-      float-to-string conversion" in Proceedings of the SIGPLAN '2018
-      Conference on Programming Language Design and Implementation.
-
-    * For OTP < 24, it uses the algorithm presented in "Printing Floating-Point
-      Numbers Quickly and Accurately" in Proceedings of the SIGPLAN '1996
-      Conference on Programming Language Design and Implementation.
-
-  For a configurable representation, use `:erlang.float_to_list/2`.
+  It uses the shortest representation according to algorithm described
+  in "Printing Floating-Point Numbers Quickly and Accurately" in
+  Proceedings of the SIGPLAN '96 Conference on Programming Language
+  Design and Implementation.

  ## Examples

@@ -575,20 +473,13 @@ defmodule Float do
  end

  @doc """
-  Returns a binary which corresponds to the shortest text representation
+  Returns a binary which corresponds to the text representation
  of the given float.

-  The underlying algorithm changes depending on the Erlang/OTP version:
-
-    * For OTP >= 24, it uses the algorithm presented in "Ryū: fast
-      float-to-string conversion" in Proceedings of the SIGPLAN '2018
-      Conference on Programming Language Design and Implementation.
-
-    * For OTP < 24, it uses the algorithm presented in "Printing Floating-Point
-      Numbers Quickly and Accurately" in Proceedings of the SIGPLAN '1996
-      Conference on Programming Language Design and Implementation.
-
-  For a configurable representation, use `:erlang.float_to_binary/2`.
+  It uses the shortest representation according to algorithm described
+  in "Printing Floating-Point Numbers Quickly and Accurately" in
+  Proceedings of the SIGPLAN '96 Conference on Programming Language
+  Design and Implementation.

  ## Examples

@@ -22,7 +22,7 @@ defmodule Function do

  It is also possible to capture public module functions and pass them
  around as if they were anonymous functions by using the capture
-  operator `&/1`:
+  operator `Kernel.SpecialForms.&/1`:

      iex> add = &Kernel.+/2
      iex> add.(1, 2)
@@ -2,12 +2,12 @@ defmodule GenEvent do
  # Functions from this module are deprecated in elixir_dispatch.

  @moduledoc """
-  An event manager with event handlers behaviour.
+  A event manager with event handlers behaviour.

  If you are interested in implementing an event manager, please read the
  "Alternatives" section below. If you have to implement an event handler to
  integrate with an existing system, such as Elixir's Logger, please use
-  [`:gen_event`](`:gen_event`) instead.
+  [`:gen_event`](https://erlang.org/doc/man/gen_event.html) instead.

  ## Alternatives

@@ -38,7 +38,7 @@ defmodule GenEvent do

  If your use case requires exactly what GenEvent provided, or you have to
  integrate with an existing `:gen_event`-based system, you can still use the
-  [`:gen_event`](`:gen_event`) Erlang module.
+  [`:gen_event`](http://erlang.org/doc/man/gen_event.html) Erlang module.
  """

  @moduledoc deprecated: "Use Erlang/OTP's :gen_event module instead"
@@ -91,7 +91,7 @@ defmodule GenEvent do
    deprecation_message =
      "the GenEvent module is deprecated, see its documentation for alternatives"

-    IO.warn(deprecation_message, __CALLER__)
+    IO.warn(deprecation_message, Macro.Env.stacktrace(__CALLER__))

    quote location: :keep do
      @behaviour :gen_event
@@ -61,7 +61,7 @@ defmodule GenServer do

  Every time you do a `GenServer.call/3`, the client will send a message
  that must be handled by the `c:handle_call/3` callback in the GenServer.
-  A `cast/2` message must be handled by `c:handle_cast/2`. There are 8 possible
+  A `cast/2` message must be handled by `c:handle_cast/2`. There are 7 possible
  callbacks to be implemented when you use a `GenServer`. The only required
  callback is `c:init/1`.

@@ -153,27 +153,22 @@ defmodule GenServer do
  detailed information. The `@doc` annotation immediately preceding
  `use GenServer` will be attached to the generated `child_spec/1` function.

-  When stopping the GenServer, for example by returning a `{:stop, reason, new_state}`
-  tuple from a callback, the exit reason is used by the supervisor to determine
-  whether the GenServer needs to be restarted. See the "Exit reasons and restarts"
-  section in the `Supervisor` module.
-
  ## Name registration

  Both `start_link/3` and `start/3` support the `GenServer` to register
  a name on start via the `:name` option. Registered names are also
  automatically cleaned up on termination. The supported values are:

-    * an atom - the GenServer is registered locally (to the current node)
-      with the given name using `Process.register/2`.
+    * an atom - the GenServer is registered locally with the given name
+      using `Process.register/2`.

    * `{:global, term}` - the GenServer is registered globally with the given
-      term using the functions in the [`:global` module](`:global`).
+      term using the functions in the [`:global` module](http://www.erlang.org/doc/man/global.html).

    * `{:via, module, term}` - the GenServer is registered with the given
      mechanism and name. The `:via` option expects a module that exports
      `register_name/2`, `unregister_name/1`, `whereis_name/1` and `send/2`.
-      One such example is the [`:global` module](`:global`) which uses these functions
+      One such example is the [`:global` module](http://www.erlang.org/doc/man/global.html) which uses these functions
      for keeping the list of names of processes and their associated PIDs
      that are available globally for a network of Elixir nodes. Elixir also
      ships with a local, decentralized and scalable registry called `Registry`
@@ -212,7 +207,7 @@ defmodule GenServer do
  the GenServer callbacks as doing so will cause the GenServer to misbehave.

  Besides the synchronous and asynchronous communication provided by `call/3`
-  and `cast/2`, "regular" messages sent by functions such as `send/2`,
+  and `cast/2`, "regular" messages sent by functions such as `Kernel.send/2`,
  `Process.send_after/4` and similar, can be handled inside the `c:handle_info/2`
  callback.

@@ -247,8 +242,7 @@ defmodule GenServer do
        end

        defp schedule_work do
-          # We schedule the work to happen in 2 hours (written in milliseconds).
-          # Alternatively, one might write :timer.hours(2)
+          # In 2 hours
          Process.send_after(self(), :work, 2 * 60 * 60 * 1000)
        end
      end
@@ -259,20 +253,15 @@ defmodule GenServer do
  a timeout value in milliseconds; if not, `:infinity` is assumed.
  The timeout can be used to detect a lull in incoming messages.

-  The `timeout()` value is used as follows:
+  If the process has no messages waiting when the timeout is set and the
+  number of given milliseconds pass without any message arriving,
+  then `handle_info/2` will be called with `:timeout` as the first argument.
+  The timeout is cleared if any message is waiting or arrives before the
+  given timeout.

-    * If the process has any message already waiting when the `timeout()` value
-      is returned, the timeout is ignored and the waiting message is handled as
-      usual. This means that even a timeout of `0` milliseconds is not guaranteed
-      to execute (if you want to take another action immediately and unconditionally,
-      use a `:continue` instruction instead).
-
-    * If any message arrives before the specified number of milliseconds
-      elapse, the timeout is cleared and that message is handled as usual.
-
-    * Otherwise, when the specified number of milliseconds have elapsed with no
-      message arriving, `handle_info/2` is called with `:timeout` as the first
-      argument.
+  Because a message may arrive before the timeout is set, even a timeout of `0`
+  milliseconds is not guaranteed to execute. To take another action immediately
+  and unconditionally, use a `:continue` instruction.

  ## When (not) to use a GenServer

@@ -322,14 +311,14 @@ defmodule GenServer do

  ## Debugging with the :sys module

-  GenServers, as [special processes](https://www.erlang.org/doc/design_principles/spec_proc.html),
-  can be debugged using the [`:sys` module](`:sys`).
+  GenServers, as [special processes](http://erlang.org/doc/design_principles/spec_proc.html),
+  can be debugged using the [`:sys` module](http://www.erlang.org/doc/man/sys.html).
  Through various hooks, this module allows developers to introspect the state of
  the process and trace system events that happen during its execution, such as
  received messages, sent replies and state changes.

  Let's explore the basic functions from the
-  [`:sys` module](`:sys`) used for debugging:
+  [`:sys` module](http://www.erlang.org/doc/man/sys.html) used for debugging:

    * `:sys.get_state/2` - allows retrieval of the state of the process.
      In the case of a GenServer process, it will be the callback module state,
@@ -411,8 +400,8 @@ defmodule GenServer do
  in Erlang can also provide extra insight.

    * [GenServer - Elixir's Getting Started Guide](https://elixir-lang.org/getting-started/mix-otp/genserver.html)
-    * [`:gen_server` module documentation](`:gen_server`)
-    * [gen_server Behaviour - OTP Design Principles](https://www.erlang.org/doc/design_principles/gen_server_concepts.html)
+    * [`:gen_server` module documentation](http://www.erlang.org/doc/man/gen_server.html)
+    * [gen_server Behaviour - OTP Design Principles](http://www.erlang.org/doc/design_principles/gen_server_concepts.html)
    * [Clients and Servers - Learn You Some Erlang for Great Good!](http://learnyousomeerlang.com/clients-and-servers)

  """
@@ -434,10 +423,10 @@ defmodule GenServer do
  except the process is hibernated before entering the loop. See
  `c:handle_call/3` for more information on hibernation.

-  Returning `{:ok, state, {:continue, continue_arg}}` is similar to
-  `{:ok, state}` except that immediately after entering the loop,
-  the `c:handle_continue/2` callback will be invoked with `continue_arg`
-  as the first argument and `state` as the second one.
+  Returning `{:ok, state, {:continue, continue}}` is similar to
+  `{:ok, state}` except that immediately after entering the loop
+  the `c:handle_continue/2` callback will be invoked with the value
+  `continue` as first argument.

  Returning `:ignore` will cause `start_link/3` to return `:ignore` and
  the process will exit normally without entering the loop or calling
@@ -460,7 +449,7 @@ defmodule GenServer do
  """
  @callback init(init_arg :: term) ::
              {:ok, state}
-              | {:ok, state, timeout | :hibernate | {:continue, continue_arg :: term}}
+              | {:ok, state, timeout | :hibernate | {:continue, term}}
              | :ignore
              | {:stop, reason :: any}
            when state: any
@@ -482,15 +471,14 @@ defmodule GenServer do

  Returning `{:reply, reply, new_state, :hibernate}` is similar to
  `{:reply, reply, new_state}` except the process is hibernated and will
-  continue the loop once a message is in its message queue. However, if a message is
-  already in the message queue, the process will continue the loop immediately. Hibernating a
+  continue the loop once a message is in its message queue. If a message is
+  already in the message queue this will be immediately. Hibernating a
  `GenServer` causes garbage collection and leaves a continuous heap that
  minimises the memory used by the process.

-  Returning `{:reply, reply, new_state, {:continue, continue_arg}}` is similar to
-  `{:reply, reply, new_state}` except that `c:handle_continue/2` will be invoked
-  immediately after with `continue_arg` as the first argument and
-  `state` as the second one.
+  Returning `{:reply, reply, new_state, {:continue, continue}}` is similar to
+  `{:reply, reply, new_state}` except `c:handle_continue/2` will be invoked
+  immediately after with the value `continue` as first argument.

  Hibernating should not be used aggressively as too much time could be spent
  garbage collecting. Normally it should only be used when a message is not
@@ -513,12 +501,12 @@ defmodule GenServer do
  process exits without replying as the caller will be blocking awaiting a
  reply.

-  Returning `{:noreply, new_state, timeout | :hibernate | {:continue, continue_arg}}`
+  Returning `{:noreply, new_state, timeout | :hibernate | {:continue, continue}}`
  is similar to `{:noreply, new_state}` except a timeout, hibernation or continue
  occurs as with a `:reply` tuple.

  Returning `{:stop, reason, reply, new_state}` stops the loop and `c:terminate/2`
-  is called with reason `reason` and state `new_state`. Then, the `reply` is sent
+  is called with reason `reason` and state `new_state`. Then the `reply` is sent
  as the response to call and the process exits with reason `reason`.

  Returning `{:stop, reason, new_state}` is similar to
@@ -529,10 +517,9 @@ defmodule GenServer do
  """
  @callback handle_call(request :: term, from, state :: term) ::
              {:reply, reply, new_state}
-              | {:reply, reply, new_state,
-                 timeout | :hibernate | {:continue, continue_arg :: term}}
+              | {:reply, reply, new_state, timeout | :hibernate | {:continue, term}}
              | {:noreply, new_state}
-              | {:noreply, new_state, timeout | :hibernate | {:continue, continue_arg :: term}}
+              | {:noreply, new_state, timeout | :hibernate | {:continue, term}}
              | {:stop, reason, reply, new_state}
              | {:stop, reason, new_state}
            when reply: term, new_state: term, reason: term
@@ -553,10 +540,9 @@ defmodule GenServer do
  `{:noreply, new_state}` except the process is hibernated before continuing the
  loop. See `c:handle_call/3` for more information.

-  Returning `{:noreply, new_state, {:continue, continue_arg}}` is similar to
+  Returning `{:noreply, new_state, {:continue, continue}}` is similar to
  `{:noreply, new_state}` except `c:handle_continue/2` will be invoked
-  immediately after with `continue_arg` as the first argument and
-  `state` as the second one.
+  immediately after with the value `continue` as first argument.

  Returning `{:stop, reason, new_state}` stops the loop and `c:terminate/2` is
  called with the reason `reason` and state `new_state`. The process exits with
@@ -567,7 +553,7 @@ defmodule GenServer do
  """
  @callback handle_cast(request :: term, state :: term) ::
              {:noreply, new_state}
-              | {:noreply, new_state, timeout | :hibernate | {:continue, continue_arg :: term}}
+              | {:noreply, new_state, timeout | :hibernate | {:continue, term}}
              | {:stop, reason :: term, new_state}
            when new_state: term

@@ -584,12 +570,12 @@ defmodule GenServer do
  """
  @callback handle_info(msg :: :timeout | term, state :: term) ::
              {:noreply, new_state}
-              | {:noreply, new_state, timeout | :hibernate | {:continue, continue_arg :: term}}
+              | {:noreply, new_state, timeout | :hibernate | {:continue, term}}
              | {:stop, reason :: term, new_state}
            when new_state: term

  @doc """
-  Invoked to handle continue instructions.
+  Invoked to handle `continue` instructions.

  It is useful for performing work after initialization or for splitting the work
  in a callback in multiple steps, updating the process state along the way.
@@ -598,12 +584,14 @@ defmodule GenServer do

  This callback is optional. If one is not implemented, the server will fail
  if a continue instruction is used.
+
+  This callback is only supported on Erlang/OTP 21+.
  """
-  @callback handle_continue(continue_arg, state :: term) ::
+  @callback handle_continue(continue :: term, state :: term) ::
              {:noreply, new_state}
-              | {:noreply, new_state, timeout | :hibernate | {:continue, continue_arg}}
+              | {:noreply, new_state, timeout | :hibernate | {:continue, term}}
              | {:stop, reason :: term, new_state}
-            when new_state: term, continue_arg: term
+            when new_state: term

  @doc """
  Invoked when the server is about to exit. It should do any cleanup required.
@@ -611,13 +599,15 @@ defmodule GenServer do
  `reason` is exit reason and `state` is the current state of the `GenServer`.
  The return value is ignored.

-  `c:terminate/2` is called if the `GenServer` traps exits (using `Process.flag/2`)
-  *and* the parent process sends an exit signal, or a callback (except `c:init/1`)
-  does one of the following:
+  `c:terminate/2` is called if a callback (except `c:init/1`) does one of the
+  following:

    * returns a `:stop` tuple
-    * raises (via `raise/2`) or exits (via `exit/1`)
+    * raises
+    * calls `Kernel.exit/1`
    * returns an invalid value
+    * the `GenServer` traps exits (using `Process.flag/2`) *and* the parent
+      process sends an exit signal

  If part of a supervision tree, a `GenServer` will receive an exit
  signal when the tree is shutting down. The exit signal is based on
@@ -683,7 +673,11 @@ defmodule GenServer do
            when old_vsn: term | {:down, term}

  @doc """
-  Invoked in some cases to retrieve a formatted version of the `GenServer` status:
+  Invoked in some cases to retrieve a formatted version of the `GenServer` status.
+
+  This callback can be useful to control the *appearance* of the status of the
+  `GenServer`. For example, it can be used to return a compact representation of
+  the `GenServer`'s state to avoid having large state terms printed.

    * one of `:sys.get_status/1` or `:sys.get_status/2` is invoked to get the
      status of the `GenServer`; in such cases, `reason` is `:normal`
@@ -691,10 +685,6 @@ defmodule GenServer do
    * the `GenServer` terminates abnormally and logs an error; in such cases,
      `reason` is `:terminate`

-  This callback can be useful to control the *appearance* of the status of the
-  `GenServer`. For example, it can be used to return a compact representation of
-  the `GenServer`'s state to avoid having large state terms printed.
-
  `pdict_and_state` is a two-elements list `[pdict, state]` where `pdict` is a
  list of `{key, value}` tuples representing the current process dictionary of
  the `GenServer` and `state` is the current state of the `GenServer`.
@@ -724,7 +714,7 @@ defmodule GenServer do
          {:debug, debug}
          | {:name, name}
          | {:timeout, timeout}
-          | {:spawn_opt, [Process.spawn_opt()]}
+          | {:spawn_opt, Process.spawn_opt()}
          | {:hibernate_after, timeout}

  @typedoc "Debug options supported by the `start*` functions"
@@ -866,7 +856,7 @@ defmodule GenServer do
      the arguments given to GenServer.start_link/3 to the server state.
      """

-      IO.warn(message, env)
+      IO.warn(message, Macro.Env.stacktrace(env))

      quote do
        @doc false
@@ -903,7 +893,7 @@ defmodule GenServer do
      milliseconds initializing or it will be terminated and the start function
      will return `{:error, :timeout}`

-    * `:debug` - if present, the corresponding function in the [`:sys` module](`:sys`) is invoked
+    * `:debug` - if present, the corresponding function in the [`:sys` module](http://www.erlang.org/doc/man/sys.html) is invoked

    * `:spawn_opt` - if present, its value is passed as options to the
      underlying process as in `Process.spawn/4`
@@ -1026,7 +1016,6 @@ defmodule GenServer do
      nil ->
        exit({:noproc, {__MODULE__, :call, [server, request, timeout]}})

-      # TODO: remove this clause when we require Erlang/OTP 25+
      pid when pid == self() ->
        exit({:calling_self, {__MODULE__, :call, [server, request, timeout]}})

@@ -1050,8 +1039,18 @@ defmodule GenServer do
  is unknown whether the destination `server` successfully
  handled the message.

+  `c:handle_cast/2` will be called on the server to handle
+  the request. In case the `server` is on a node which is
+  not yet connected to the caller one, the semantics differ
+  depending on the used Erlang/OTP version.
+
  `server` can be any of the values described in the "Name registration"
  section of the documentation for this module.
+
+  Before Erlang/OTP 21, the call is going to block until a
+  connection happens. This was done to guarantee ordering.
+  Starting with Erlang/OTP 21, both Erlang and Elixir do
+  not block the call.
  """
  @spec cast(server, term) :: :ok
  def cast(server, request)
@@ -1174,8 +1173,11 @@ defmodule GenServer do

  """
  @spec reply(from, term) :: :ok
-  def reply(client, reply) do
-    :gen.reply(client, reply)
+  def reply(client, reply)
+
+  def reply({to, tag}, reply) when is_pid(to) do
+    send(to, {tag, reply})
+    :ok
  end

  @doc """
@@ -8,85 +8,16 @@ defprotocol Inspect do
  The `Inspect` protocol converts an Elixir data structure into an
  algebra document.

-  This is typically done when you want to customize how your own
-  structs are inspected in logs and the terminal.
-
  This documentation refers to implementing the `Inspect` protocol
  for your own data structures. To learn more about using inspect,
  see `Kernel.inspect/2` and `IO.inspect/2`.

-  ## Inspect representation
+  The `inspect/2` function receives the entity to be inspected
+  followed by the inspecting options, represented by the struct
+  `Inspect.Opts`. Building of the algebra document is done with
+  `Inspect.Algebra`.

-  There are typically three choices of inspect representation. In order
-  to understand them, let's imagine we have the following `User` struct:
-
-      defmodule User do
-        defstruct [:id, :name, :address]
-      end
-
-  Our choices are:
-
-    1. Print the struct using Elixir's struct syntax, for example:
-       `%User{address: "Earth", id: 13, name: "Jane"}`. This is the
-       default representation and best choice if all struct fields
-       are public.
-
-    2. Print using the `#User<...>` notation, for example: `#User<id: 13, name: "Jane", ...>`.
-       This notation does not emit valid Elixir code and is typically
-       used when the struct has private fields (for example, you may want
-       to hide the field `:address` to redact person identifiable information).
-
-    3. Print the struct using the expression syntax, for example:
-       `User.new(13, "Jane", "Earth")`. This assumes there is a `User.new/3`
-       function. This option is mostly used as an alternative to option 2
-       for representing custom data structures, such as `MapSet`, `Date.Range`,
-       and others.
-
-  You can implement the Inspect protocol for your own structs while
-  adhering to the conventions above. Option 1 is the default representation
-  and you can quickly achieve option 2 by deriving the `Inspect` protocol.
-  For option 3, you need your custom implementation.
-
-  ## Deriving
-
-  The `Inspect` protocol can be derived to customize the order of fields
-  (the default is alphabetical) and hide certain fields from structs,
-  so they don't show up in logs, inspects and similar. The latter is
-  especially useful for fields containing private information.
-
-  The supported options are:
-
-    * `:only` - only include the given fields when inspecting.
-
-    * `:except` - remove the given fields when inspecting.
-
-    * `:optional` - (since v1.14.0) do not include a field if it
-      matches its default value. This can be used to simplify the
-      struct representation at the cost of hiding information.
-
-  Whenever `:only` or `:except` are used to restrict fields,
-  the struct will be printed using the `#User<...>` notation,
-  as the struct can no longer be copy and pasted as valid Elixir
-  code. Let's see an example:
-
-      defmodule User do
-        @derive {Inspect, only: [:id, :name]}
-        defstruct [:id, :name, :address]
-      end
-
-      inspect(%User{id: 1, name: "Jane", address: "Earth"})
-      #=> #User<id: 1, name: "Jane", ...>
-
-  If you use only the `:optional` option, the struct will still be
-  printed as `%User{...}`.
-
-  ## Custom implementation
-
-  You can also define your custom protocol implementation by
-  defining the `inspect/2` function. The function receives the
-  entity to be inspected followed by the inspecting options,
-  represented by the struct `Inspect.Opts`. Building of the
-  algebra document is done with `Inspect.Algebra`.
+  ## Examples

  Many times, inspecting a structure can be implemented in function
  of existing entities. For example, here is `MapSet`'s `inspect/2`
@@ -95,25 +26,24 @@ defprotocol Inspect do
      defimpl Inspect, for: MapSet do
        import Inspect.Algebra

-        def inspect(map_set, opts) do
-          concat(["MapSet.new(", Inspect.List.inspect(MapSet.to_list(map_set), opts), ")"])
+        def inspect(dict, opts) do
+          concat(["#MapSet<", to_doc(MapSet.to_list(dict), opts), ">"])
        end
      end

  The [`concat/1`](`Inspect.Algebra.concat/1`) function comes from
  `Inspect.Algebra` and it concatenates algebra documents together.
-  In the example above it is concatenating the string `"MapSet.new("`,
+  In the example above it is concatenating the string `"#MapSet<"`,
  the document returned by `Inspect.Algebra.to_doc/2`, and the final
-  string `")"`. Therefore, the MapSet with the numbers 1, 2, and 3
-  will be printed as:
+  string `">"`. We prefix the module name `#` to denote the inspect
+  presentation is not actually valid Elixir syntax.

-      iex> MapSet.new([1, 2, 3], fn x -> x * 2 end)
-      MapSet.new([2, 4, 6])
+  Finally, note strings themselves are valid algebra documents that
+  keep their formatting when pretty printed. This means your `Inspect`
+  implementation may simply return a string, although that will devoid
+  it of any pretty-printing.

-  In other words, `MapSet`'s inspect representation returns an expression
-  that, when evaluated, builds the `MapSet` itself.
-
-  ### Error handling
+  ## Error handling

  In case there is an error while your structure is being inspected,
  Elixir will raise an `ArgumentError` error and will automatically fall back
@@ -125,6 +55,24 @@ defprotocol Inspect do

      Inspect.MapSet.inspect(MapSet.new(), %Inspect.Opts{})

+  ## Deriving
+
+  The `Inspect` protocol can be derived to hide certain fields from
+  structs, so they don't show up in logs, inspects and similar. This
+  is especially useful for fields containing private information.
+
+  The options `:only` and `:except` can be used with `@derive` to
+  specify which fields should and should not appear in the
+  algebra document:
+
+      defmodule User do
+        @derive {Inspect, only: [:id, :name]}
+        defstruct [:id, :name, :address]
+      end
+
+      inspect(%User{id: 1, name: "Homer", address: "742 Evergreen Terrace"})
+      #=> #User<id: 1, name: "Homer", ...>
+
  """

  # Handle structs in Any
@@ -146,7 +94,7 @@ defimpl Inspect, for: Atom do
  require Macro

  def inspect(atom, opts) do
-    color(Macro.inspect_atom(:literal, atom), color_key(atom), opts)
+    color(Identifier.inspect_as_atom(atom), color_key(atom), opts)
  end

  defp color_key(atom) when is_boolean(atom), do: :boolean
@@ -209,7 +157,7 @@ defimpl Inspect, for: BitString do
  defp each_bit(bitstring, _counter, opts) do
    size = bit_size(bitstring)
    <<h::size(size)>> = bitstring
-    concat(Inspect.Integer.inspect(h, opts), "::size(" <> Integer.to_string(size) <> ")")
+    Inspect.Integer.inspect(h, opts) <> "::size(" <> Integer.to_string(size) <> ")"
  end

  @compile {:inline, decrement: 1}
@@ -262,7 +210,7 @@ defimpl Inspect, for: List do
            {escaped, _} -> [?', escaped, ?', " ++ ..."]
          end

-        color(IO.iodata_to_binary(inspected), :charlist, opts)
+        IO.iodata_to_binary(inspected)

      keyword?(term) ->
        container_doc(open, term, close, opts, &keyword/2, separator: sep, break: :strict)
@@ -274,7 +222,7 @@ defimpl Inspect, for: List do

  @doc false
  def keyword({key, value}, opts) do
-    key = color(Macro.inspect_atom(:key, key), :atom, opts)
+    key = color(Identifier.inspect_as_key(key), :atom, opts)
    concat(key, concat(" ", to_doc(value, opts)))
  end

@@ -302,38 +250,28 @@ end

 defimpl Inspect, for: Map do
  def inspect(map, opts) do
-    list =
-      if Keyword.get(opts.custom_options, :sort_maps) do
-        map |> Map.to_list() |> :lists.sort()
-      else
-        Map.to_list(map)
-      end
-
-    fun =
-      if Inspect.List.keyword?(list) do
-        &Inspect.List.keyword/2
-      else
-        sep = color(" => ", :map, opts)
-        &to_assoc(&1, &2, sep)
-      end
-
-    map_container_doc(list, "", opts, fun)
+    inspect(map, "", opts)
  end

-  def inspect(map, name, infos, opts) do
-    fun = fn %{field: field}, opts -> Inspect.List.keyword({field, Map.get(map, field)}, opts) end
-    map_container_doc(infos, name, opts, fun)
-  end
-
-  defp to_assoc({key, value}, opts, sep) do
-    concat(concat(to_doc(key, opts), sep), to_doc(value, opts))
-  end
-
-  defp map_container_doc(list, name, opts, fun) do
+  def inspect(map, name, opts) do
+    map = Map.to_list(map)
    open = color("%" <> name <> "{", :map, opts)
    sep = color(",", :map, opts)
    close = color("}", :map, opts)
-    container_doc(open, list, close, opts, fun, separator: sep, break: :strict)
+    container_doc(open, map, close, opts, traverse_fun(map, opts), separator: sep, break: :strict)
+  end
+
+  defp traverse_fun(list, opts) do
+    if Inspect.List.keyword?(list) do
+      &Inspect.List.keyword/2
+    else
+      sep = color(" => ", :map, opts)
+      &to_map(&1, &2, sep)
+    end
+  end
+
+  defp to_map({key, value}, opts, sep) do
+    concat(concat(to_doc(key, opts), sep), to_doc(value, opts))
  end
 end

@@ -371,31 +309,13 @@ defimpl Inspect, for: Integer do
 end

 defimpl Inspect, for: Float do
-  def inspect(float, opts) do
-    abs = abs(float)
-
-    formatted =
-      if abs >= 1.0 and abs < 1.0e16 and trunc(float) == float do
-        [Integer.to_string(trunc(float)), ?., ?0]
-      else
-        :io_lib_format.fwrite_g(float)
-      end
-
-    color(IO.iodata_to_binary(formatted), :number, opts)
+  def inspect(term, opts) do
+    inspected = IO.iodata_to_binary(:io_lib_format.fwrite_g(term))
+    color(inspected, :number, opts)
  end
 end

 defimpl Inspect, for: Regex do
-  def inspect(regex = %{opts: regex_opts}, opts) when is_list(regex_opts) do
-    concat([
-      "Regex.compile!(",
-      Inspect.BitString.inspect(regex.source, opts),
-      ", ",
-      Inspect.List.inspect(regex_opts, opts),
-      ")"
-    ])
-  end
-
  def inspect(regex, opts) do
    {escaped, _} =
      regex.source
@@ -427,12 +347,9 @@ defimpl Inspect, for: Function do
    name = fun_info[:name]

    cond do
-      not is_atom(mod) ->
-        "#Function<#{uniq(fun_info)}/#{fun_info[:arity]}>"
-
      fun_info[:type] == :external and fun_info[:env] == [] ->
-        inspected_as_atom = Macro.inspect_atom(:literal, mod)
-        inspected_as_function = Macro.inspect_atom(:remote_call, name)
+        inspected_as_atom = Identifier.inspect_as_atom(mod)
+        inspected_as_function = Identifier.inspect_as_function(name)
        "&#{inspected_as_atom}.#{inspected_as_function}/#{fun_info[:arity]}"

      match?('elixir_compiler_' ++ _, Atom.to_charlist(mod)) ->
@@ -448,7 +365,7 @@ defimpl Inspect, for: Function do
  end

  defp default_inspect(mod, fun_info) do
-    inspected_as_atom = Macro.inspect_atom(:literal, mod)
+    inspected_as_atom = Identifier.inspect_as_atom(mod)
    extracted_name = extract_name(fun_info[:name])
    "#Function<#{uniq(fun_info)}/#{fun_info[:arity]} in #{inspected_as_atom}#{extracted_name}>"
  end
@@ -460,10 +377,10 @@ defimpl Inspect, for: Function do
  defp extract_name(name) do
    case Identifier.extract_anonymous_fun_parent(name) do
      {name, arity} ->
-        "." <> Macro.inspect_atom(:remote_call, name) <> "/" <> arity
+        "." <> Identifier.inspect_as_function(name) <> "/" <> arity

      :error ->
-        "." <> Macro.inspect_atom(:remote_call, name)
+        "." <> Identifier.inspect_as_function(name)
    end
  end

@@ -472,36 +389,6 @@ defimpl Inspect, for: Function do
  end
 end

-defimpl Inspect, for: Inspect.Error do
-  @impl true
-  def inspect(%{stacktrace: stacktrace} = inspect_error, _opts) do
-    message = Exception.message(inspect_error)
-    format_output(message, stacktrace)
-  end
-
-  defp format_output(message, [_ | _] = stacktrace) do
-    stacktrace = Exception.format_stacktrace(stacktrace)
-
-    """
-    #Inspect.Error<
-    #{Inspect.Error.pad(message, 2)}
-
-      Stacktrace:
-
-    #{stacktrace}
-    >\
-    """
-  end
-
-  defp format_output(message, []) do
-    """
-    #Inspect.Error<
-      #{Inspect.Error.pad(message, 2)}
-    >\
-    """
-  end
-end
-
 defimpl Inspect, for: PID do
  def inspect(pid, _opts) do
    "#PID" <> IO.iodata_to_binary(:erlang.pid_to_list(pid))
@@ -526,11 +413,11 @@ defimpl Inspect, for: Any do
    fields = Map.keys(struct) -- [:__exception__, :__struct__]
    only = Keyword.get(options, :only, fields)
    except = Keyword.get(options, :except, [])
-    optional = Keyword.get(options, :optional, [])

-    :ok = validate_option(:only, only, fields, module)
-    :ok = validate_option(:except, except, fields, module)
-    :ok = validate_option(:optional, optional, fields, module)
+    filtered_fields =
+      fields
+      |> Enum.reject(&(&1 in except))
+      |> Enum.filter(&(&1 in only))

    inspect_module =
      if fields == only and except == [] do
@@ -539,86 +426,44 @@ defimpl Inspect, for: Any do
        Inspect.Any
      end

-    filtered_fields =
-      fields
-      |> Enum.reject(&(&1 in except))
-      |> Enum.filter(&(&1 in only))
-
-    optional? =
-      if optional == [] do
-        false
-      else
-        optional_map = for field <- optional, into: %{}, do: {field, Map.fetch!(struct, field)}
-
-        quote do
-          case unquote(Macro.escape(optional_map)) do
-            %{^var!(field) => var!(default)} ->
-              var!(default) == Map.get(var!(struct), var!(field))
-
-            %{} ->
-              false
-          end
-        end
-      end
-
    quote do
      defimpl Inspect, for: unquote(module) do
        def inspect(var!(struct), var!(opts)) do
-          var!(infos) =
-            for %{field: var!(field)} = var!(info) <- unquote(module).__info__(:struct),
-                var!(field) in unquote(filtered_fields) and not unquote(optional?),
-                do: var!(info)
-
-          var!(name) = Macro.inspect_atom(:literal, unquote(module))
-          unquote(inspect_module).inspect(var!(struct), var!(name), var!(infos), var!(opts))
+          var!(map) = Map.take(var!(struct), unquote(filtered_fields))
+          var!(name) = Identifier.inspect_as_atom(unquote(module))
+          unquote(inspect_module).inspect(var!(map), var!(name), var!(opts))
        end
      end
    end
  end

-  defp validate_option(option, option_list, fields, module) do
-    case option_list -- fields do
-      [] ->
-        :ok
-
-      unknown_fields ->
-        raise ArgumentError,
-              "unknown fields #{Kernel.inspect(unknown_fields)} in #{Kernel.inspect(option)} " <>
-                "when deriving the Inspect protocol for #{Kernel.inspect(module)}"
-    end
-  end
-
  def inspect(%module{} = struct, opts) do
    try do
-      {module.__struct__(), module.__info__(:struct)}
+      module.__struct__()
    rescue
      _ -> Inspect.Map.inspect(struct, opts)
    else
-      {dunder, fields} ->
+      dunder ->
        if Map.keys(dunder) == Map.keys(struct) do
-          infos =
-            for %{field: field} = info <- fields,
-                field not in [:__struct__, :__exception__],
-                do: info
-
-          Inspect.Map.inspect(struct, Macro.inspect_atom(:literal, module), infos, opts)
+          pruned = Map.drop(struct, [:__struct__, :__exception__])
+          Inspect.Map.inspect(pruned, Identifier.inspect_as_atom(module), opts)
        else
          Inspect.Map.inspect(struct, opts)
        end
    end
  end

-  def inspect(map, name, infos, opts) do
+  def inspect(map, name, opts) do
+    # Use the :limit option and an extra element to force
+    # `container_doc/6` to append "...".
+    opts = %{opts | limit: min(opts.limit, map_size(map))}
+    map = Map.to_list(map) ++ ["..."]
+
    open = color("#" <> name <> "<", :map, opts)
    sep = color(",", :map, opts)
    close = color(">", :map, opts)

-    fun = fn
-      %{field: field}, opts -> Inspect.List.keyword({field, Map.get(map, field)}, opts)
-      :..., _opts -> "..."
-    end
-
-    container_doc(open, infos ++ [:...], close, opts, fun, separator: sep, break: :strict)
+    container_doc(open, map, close, opts, &Inspect.List.keyword/2, separator: sep, break: :strict)
  end
 end

@@ -31,13 +31,8 @@ defmodule Inspect.Opts do
      options. Useful when implementing the `Inspect` protocol for nested structs
      to pass the custom options through.

-      It supports some pre-defined keys:
-      - `:sort_maps` (since v1.15.0) - if set to `true`, sorts key-value pairs in maps.
-        This can be helpful to make map inspection deterministic for testing,
-        especially since key order is random since OTP 26.
-
    * `:inspect_fun` (since v1.9.0) - a function to build algebra documents.
-      Defaults to `Inspect.Opts.default_inspect_fun/0`.
+      Defaults to `Inspect.inspect/2`.

    * `:limit` - limits the number of items that are inspected for tuples,
      bitstrings, maps, lists and any other collection of items, with the exception of
@@ -58,7 +53,7 @@ defmodule Inspect.Opts do
    * `:safe` - when `false`, failures while inspecting structs will be raised
      as errors instead of being wrapped in the `Inspect.Error` exception. This
      is useful when debugging failures and crashes for custom inspect
-      implementations. Defaults to `true`.
+      implementations.

    * `:structs` - when `false`, structs are not formatted by the inspect
      protocol, they are instead printed as maps. Defaults to `true`.
@@ -69,7 +64,6 @@ defmodule Inspect.Opts do
      `:atom`, `:binary`, `:boolean`, `:list`, `:map`, `:number`, `:regex`,
      `:string`, and `:tuple`. Custom data types may provide their own options.
      Colors can be any `t:IO.ANSI.ansidata/0` as accepted by `IO.ANSI.format/1`.
-      A default list of colors can be retrieved from `IO.ANSI.syntax_colors/0`.

    * `:width` - number of characters per line used when pretty is `true` or when
      printing to IO devices. Set to `0` to force each item to be printed on its
@@ -95,9 +89,11 @@ defmodule Inspect.Opts do

  @type color_key :: atom

+  # TODO: Remove :char_lists key and :as_char_lists value on v2.0
  @type t :: %__MODULE__{
          base: :decimal | :binary | :hex | :octal,
          binaries: :infer | :as_binaries | :as_strings,
+          char_lists: :infer | :as_lists | :as_char_lists,
          charlists: :infer | :as_lists | :as_charlists,
          custom_options: keyword,
          inspect_fun: (any, t -> Inspect.Algebra.t()),
@@ -109,62 +105,13 @@ defmodule Inspect.Opts do
          syntax_colors: [{color_key, IO.ANSI.ansidata()}],
          width: non_neg_integer | :infinity
        }
+end

-  @doc """
-  Builds an `Inspect.Opts` struct.
+defmodule Inspect.Error do
+  @moduledoc """
+  Raised when a struct cannot be inspected.
  """
-  @doc since: "1.13.0"
-  @spec new(keyword()) :: t
-  def new(opts) do
-    struct(%Inspect.Opts{inspect_fun: default_inspect_fun()}, opts)
-  end
-
-  @doc """
-  Returns the default inspect function.
-  """
-  @doc since: "1.13.0"
-  @spec default_inspect_fun() :: (term, t -> Inspect.Algebra.t())
-  def default_inspect_fun do
-    :persistent_term.get({__MODULE__, :inspect_fun}, &Inspect.inspect/2)
-  end
-
-  @doc """
-  Sets the default inspect function.
-
-  Set this option with care as it will change how all values
-  in the system are inspected. The main use of this functionality
-  is to provide an entry point to filter inspected values,
-  in order for entities to comply with rules and legislations
-  on data security and data privacy.
-
-  It is **extremely discouraged** for libraries to set their own
-  function as this must be controlled by applications. Libraries
-  should instead define their own structs with custom inspect
-  implementations. If a library must change the default inspect
-  function, then it is best to define to ask users of your library
-  to explicitly call `default_inspect_fun/1` with your function of
-  choice.
-
-  The default is `Inspect.inspect/2`.
-
-  ## Examples
-
-      previous_fun = Inspect.Opts.default_inspect_fun()
-
-      Inspect.Opts.default_inspect_fun(fn
-        %{address: _} = map, opts ->
-          previous_fun.(%{map | address: "[REDACTED]"}, opts)
-
-        value, opts ->
-          previous_fun.(value, opts)
-      end)
-
-  """
-  @doc since: "1.13.0"
-  @spec default_inspect_fun((term, t -> Inspect.Algebra.t())) :: :ok
-  def default_inspect_fun(fun) when is_function(fun, 2) do
-    :persistent_term.put({__MODULE__, :inspect_fun}, fun)
-  end
+  defexception [:message]
 end

 defmodule Inspect.Algebra do
@@ -259,18 +206,12 @@ defmodule Inspect.Algebra do
          | doc_group
          | doc_nest
          | doc_string
-          | doc_limit

  @typep doc_string :: {:doc_string, t, non_neg_integer}
  defmacrop doc_string(string, length) do
    quote do: {:doc_string, unquote(string), unquote(length)}
  end

-  @typep doc_limit :: {:doc_limit, t, pos_integer | :infinity}
-  defmacrop doc_limit(doc, limit) do
-    quote do: {:doc_limit, unquote(doc), unquote(limit)}
-  end
-
  @typep doc_cons :: {:doc_cons, t, t}
  defmacrop doc_cons(left, right) do
    quote do: {:doc_cons, unquote(left), unquote(right)}
@@ -320,8 +261,7 @@ defmodule Inspect.Algebra do
    :doc_force,
    :doc_group,
    :doc_nest,
-    :doc_string,
-    :doc_limit
+    :doc_string
  ]

  defguard is_doc(doc)
@@ -358,28 +298,19 @@ defmodule Inspect.Algebra do
            try do
              Process.put(:inspect_trap, true)

-              inspected_struct =
-                struct
-                |> Inspect.Map.inspect(%{
-                  opts
-                  | syntax_colors: [],
-                    inspect_fun: Inspect.Opts.default_inspect_fun()
-                })
-                |> format(opts.width)
-                |> IO.iodata_to_binary()
+              res = Inspect.Map.inspect(struct, %{opts | syntax_colors: []})
+              res = IO.iodata_to_binary(format(res, :infinity))

-              inspect_error =
-                Inspect.Error.exception(
-                  exception: caught_exception,
-                  stacktrace: __STACKTRACE__,
-                  inspected_struct: inspected_struct
-                )
+              message =
+                "got #{inspect(caught_exception.__struct__)} with message " <>
+                  "#{inspect(Exception.message(caught_exception))} while inspecting #{res}"
+
+              exception = Inspect.Error.exception(message: message)

              if opts.safe do
-                opts = %{opts | inspect_fun: Inspect.Opts.default_inspect_fun()}
-                Inspect.inspect(inspect_error, opts)
+                Inspect.inspect(exception, opts)
              else
-                reraise(inspect_error, __STACKTRACE__)
+                reraise(exception, __STACKTRACE__)
              end
            after
              Process.delete(:inspect_trap)
@@ -473,9 +404,8 @@ defmodule Inspect.Algebra do

  defp container_each([term | terms], limit, opts, fun, acc, simple?)
       when is_list(terms) and is_limit(limit) do
-    new_limit = decrement(limit)
-    doc = fun.(term, %{opts | limit: new_limit})
-    limit = if doc == :doc_nil, do: limit, else: new_limit
+    limit = decrement(limit)
+    doc = fun.(term, %{opts | limit: limit})
    container_each(terms, limit, opts, fun, [doc | acc], simple? and simple?(doc))
  end

@@ -587,10 +517,6 @@ defmodule Inspect.Algebra do
    doc_cons(doc1, doc2)
  end

-  def no_limit(doc) do
-    doc_limit(doc, :infinity)
-  end
-
  @doc ~S"""
  Concatenates a list of documents returning a new document.

@@ -610,7 +536,7 @@ defmodule Inspect.Algebra do
  Colors a document if the `color_key` has a color in the options.
  """
  @doc since: "1.4.0"
-  @spec color(t, Inspect.Opts.color_key(), Inspect.Opts.t()) :: t
+  @spec color(t, Inspect.Opts.color_key(), Inspect.Opts.t()) :: doc_color
  def color(doc, color_key, %Inspect.Opts{syntax_colors: syntax_colors}) when is_doc(doc) do
    if precolor = Keyword.get(syntax_colors, color_key) do
      postcolor = Keyword.get(syntax_colors, :reset, :reset)
@@ -640,7 +566,7 @@ defmodule Inspect.Algebra do
      ["hello", "\n     ", "world"]

  """
-  @spec nest(t, non_neg_integer | :cursor | :reset, :always | :break) :: doc_nest | t
+  @spec nest(t, non_neg_integer | :cursor | :reset, :always | :break) :: doc_nest
  def nest(doc, level, mode \\ :always)

  def nest(doc, :cursor, mode) when is_doc(doc) and mode in [:always, :break] do
@@ -968,12 +894,12 @@ defmodule Inspect.Algebra do
    format(width, 0, [{0, :flat, doc}])
  end

-  # Type representing the document mode to be rendered:
+  # Type representing the document mode to be rendered
  #
  #   * flat - represents a document with breaks as flats (a break may fit, as it may break)
  #   * break - represents a document with breaks as breaks (a break always fits, since it breaks)
  #
-  # The following modes are exclusive to fitting:
+  # The following modes are exclusive to fitting
  #
  #   * flat_no_break - represents a document with breaks as flat not allowed to enter in break mode
  #   * break_no_flat - represents a document with breaks as breaks not allowed to enter in flat mode
@@ -981,7 +907,7 @@ defmodule Inspect.Algebra do
  @typep mode :: :flat | :flat_no_break | :break | :break_no_flat

  @spec fits?(
-          width :: non_neg_integer() | :infinity,
+          width :: non_neg_integer(),
          column :: non_neg_integer(),
          break? :: boolean(),
          entries
@@ -1046,17 +972,9 @@ defmodule Inspect.Algebra do
  defp fits?(w, k, b?, [{i, m, doc_group(x, _)} | t]),
    do: fits?(w, k, b?, [{i, m, x} | {:tail, b?, t}])

-  defp fits?(w, k, b?, [{i, m, doc_limit(x, :infinity)} | t]) when w != :infinity,
-    do: fits?(:infinity, k, b?, [{i, :flat, x}, {i, m, doc_limit(empty(), w)} | t])
-
-  defp fits?(_w, k, b?, [{i, m, doc_limit(x, w)} | t]),
-    do: fits?(w, k, b?, [{i, m, x} | t])
-
-  @spec format(
-          width :: non_neg_integer() | :infinity,
-          column :: non_neg_integer(),
-          [{integer, mode, t}]
-        ) :: [binary]
+  @spec format(width :: non_neg_integer() | :infinity, column :: non_neg_integer(), [
+          {integer, mode, t}
+        ]) :: [binary]
  defp format(_, _, []), do: []
  defp format(w, k, [{_, _, :doc_nil} | t]), do: format(w, k, t)
  defp format(w, _, [{i, _, :doc_line} | t]), do: [indent(i) | format(w, i, t)]
@@ -1110,15 +1028,6 @@ defmodule Inspect.Algebra do
    end
  end

-  # Limit is set to infinity and then reverts
-  defp format(w, k, [{i, m, doc_limit(x, :infinity)} | t]) when w != :infinity do
-    format(:infinity, k, [{i, :flat, x}, {i, m, doc_limit(empty(), w)} | t])
-  end
-
-  defp format(_w, k, [{i, m, doc_limit(x, w)} | t]) do
-    format(w, k, [{i, m, x} | t])
-  end
-
  defp collapse(["\n" <> _ | t], max, count, i) do
    collapse(t, max, count + 1, i)
  end
@@ -4,11 +4,11 @@ defmodule Integer do

  Some functions that work on integers are found in `Kernel`:

-    * `Kernel.abs/1`
-    * `Kernel.div/2`
-    * `Kernel.max/2`
-    * `Kernel.min/2`
-    * `Kernel.rem/2`
+    * `abs/1`
+    * `div/2`
+    * `max/2`
+    * `min/2`
+    * `rem/2`

  """

@@ -64,53 +64,10 @@ defmodule Integer do
  """
  defguard is_even(integer) when is_integer(integer) and (integer &&& 1) == 0

-  @doc """
-  Computes `base` raised to power of `exponent`.
-
-  Both `base` and `exponent` must be integers.
-  The exponent must be zero or positive.
-
-  See `Float.pow/2` for exponentiation of negative
-  exponents as well as floats.
-
-  ## Examples
-
-      iex> Integer.pow(2, 0)
-      1
-      iex> Integer.pow(2, 1)
-      2
-      iex> Integer.pow(2, 10)
-      1024
-      iex> Integer.pow(2, 11)
-      2048
-      iex> Integer.pow(2, 64)
-      0x10000000000000000
-
-      iex> Integer.pow(3, 4)
-      81
-      iex> Integer.pow(4, 3)
-      64
-
-      iex> Integer.pow(-2, 3)
-      -8
-      iex> Integer.pow(-2, 4)
-      16
-
-      iex> Integer.pow(2, -2)
-      ** (ArithmeticError) bad argument in arithmetic expression
-
-  """
-  @doc since: "1.12.0"
-  @spec pow(integer, non_neg_integer) :: integer
-  def pow(base, exponent) when is_integer(base) and is_integer(exponent) do
-    if exponent < 0, do: :erlang.error(:badarith, [base, exponent])
-    base ** exponent
-  end
-
  @doc """
  Computes the modulo remainder of an integer division.

-  This function performs a [floored division](`floor_div/2`), which means that
+  `Integer.mod/2` uses floored division, which means that
  the result will always have the sign of the `divisor`.

  Raises an `ArithmeticError` exception if one of the arguments is not an
@@ -142,8 +99,8 @@ defmodule Integer do
  Raises an `ArithmeticError` exception if one of the arguments is not an
  integer, or when the `divisor` is `0`.

-  This function performs a *floored* integer division, which means that
-  the result will always be rounded towards negative infinity.
+  `Integer.floor_div/2` performs *floored* integer division. This means that
+  the result is always rounded towards negative infinity.

  If you want to perform truncated integer division (rounding towards zero),
  use `Kernel.div/2` instead.
@@ -269,7 +226,7 @@ defmodule Integer do
      ** (ArgumentError) invalid base 38

  """
-  @spec parse(binary, 2..36) :: {integer, remainder_of_binary :: binary} | :error
+  @spec parse(binary, 2..36) :: {integer, binary} | :error
  def parse(binary, base \\ 10)

  def parse(_binary, base) when base not in 2..36 do
@@ -312,12 +269,12 @@ defmodule Integer do

  defp count_digits_nosign(<<_::bits>>, _, count), do: count

+  # TODO: Remove Integer.to_string/1 once the minimum supported version is
+  #       Erlang/OTP 22, since it is covered by the now BIF Integer.to_string/2.
+  #       Please reapply commit 2622fd6b0aa419a983a899a1fbdb5deefba3d85d.
  @doc """
  Returns a binary which corresponds to the text representation
-  of `integer` in the given `base`.
-
-  `base` can be an integer between 2 and 36. If no `base` is given,
-  it defaults to `10`.
+  of `integer`.

  Inlined by the compiler.

@@ -335,6 +292,22 @@ defmodule Integer do
      iex> Integer.to_string(0123)
      "123"

+  """
+  @spec to_string(integer) :: String.t()
+  def to_string(integer) do
+    :erlang.integer_to_binary(integer)
+  end
+
+  @doc """
+  Returns a binary which corresponds to the text representation
+  of `integer` in the given `base`.
+
+  `base` can be an integer between 2 and 36.
+
+  Inlined by the compiler.
+
+  ## Examples
+
      iex> Integer.to_string(100, 16)
      "64"

@@ -346,16 +319,15 @@ defmodule Integer do

  """
  @spec to_string(integer, 2..36) :: String.t()
-  def to_string(integer, base \\ 10) do
+  def to_string(integer, base) do
    :erlang.integer_to_binary(integer, base)
  end

+  # TODO: Remove Integer.to_charlist/1 once the minimum supported version is
+  #       Erlang/OTP 22, since it is covered by the now BIF Integer.to_charlist/2.
+  #       Please reapply commit 2622fd6b0aa419a983a899a1fbdb5deefba3d85d.
  @doc """
-  Returns a charlist which corresponds to the text representation
-  of `integer` in the given `base`.
-
-  `base` can be an integer between 2 and 36. If no `base` is given,
-  it defaults to `10`.
+  Returns a charlist which corresponds to the text representation of the given `integer`.

  Inlined by the compiler.

@@ -373,6 +345,21 @@ defmodule Integer do
      iex> Integer.to_charlist(0123)
      '123'

+  """
+  @spec to_charlist(integer) :: charlist
+  def to_charlist(integer) do
+    :erlang.integer_to_list(integer)
+  end
+
+  @doc """
+  Returns a charlist which corresponds to the text representation of `integer` in the given `base`.
+
+  `base` can be an integer between 2 and 36.
+
+  Inlined by the compiler.
+
+  ## Examples
+
      iex> Integer.to_charlist(100, 16)
      '64'

@@ -384,7 +371,7 @@ defmodule Integer do

  """
  @spec to_charlist(integer, 2..36) :: charlist
-  def to_charlist(integer, base \\ 10) do
+  def to_charlist(integer, base) do
    :erlang.integer_to_list(integer, base)
  end

@@ -427,58 +414,6 @@ defmodule Integer do
  defp gcd_positive(integer1, 0), do: integer1
  defp gcd_positive(integer1, integer2), do: gcd_positive(integer2, rem(integer1, integer2))

-  @doc """
-  Returns the extended greatest common divisor of the two given integers.
-
-  This function uses the extended Euclidean algorithm to return a three-element tuple with the `gcd`
-  and the coefficients `m` and `n` of Bézout's identity such that:
-
-      gcd(a, b) = m*a + n*b
-
-  By convention, `extended_gcd(0, 0)` returns `{0, 0, 0}`.
-
-  ## Examples
-
-      iex> Integer.extended_gcd(240, 46)
-      {2, -9, 47}
-      iex> Integer.extended_gcd(46, 240)
-      {2, 47, -9}
-      iex> Integer.extended_gcd(-46, 240)
-      {2, -47, -9}
-      iex> Integer.extended_gcd(-46, -240)
-      {2, -47, 9}
-
-      iex> Integer.extended_gcd(14, 21)
-      {7, -1, 1}
-
-      iex> Integer.extended_gcd(10, 0)
-      {10, 1, 0}
-      iex> Integer.extended_gcd(0, 10)
-      {10, 0, 1}
-      iex> Integer.extended_gcd(0, 0)
-      {0, 0, 0}
-
-  """
-  @doc since: "1.12.0"
-  @spec extended_gcd(integer, integer) :: {non_neg_integer, integer, integer}
-  def extended_gcd(0, 0), do: {0, 0, 0}
-  def extended_gcd(0, b), do: {b, 0, 1}
-  def extended_gcd(a, 0), do: {a, 1, 0}
-
-  def extended_gcd(integer1, integer2) when is_integer(integer1) and is_integer(integer2) do
-    extended_gcd(integer2, integer1, 0, 1, 1, 0)
-  end
-
-  defp extended_gcd(r1, r0, s1, s0, t1, t0) do
-    div = div(r0, r1)
-
-    case r0 - div * r1 do
-      0 when r1 > 0 -> {r1, s1, t1}
-      0 when r1 < 0 -> {-r1, -s1, -t1}
-      r2 -> extended_gcd(r2, r1, s0 - div * s1, s1, t0 - div * t1, t1)
-    end
-  end
-
  @doc false
  @deprecated "Use Integer.to_charlist/1 instead"
  def to_char_list(integer), do: Integer.to_charlist(integer)
@@ -34,7 +34,7 @@ defmodule IO do
  IO data is a data type that can be used as a more efficient alternative to binaries
  in certain situations.

-  A term of type **IO data** is a binary or a list containing bytes (integers within the `0..255` range)
+  A term of type **IO data** is a binary or a list containing bytes (integers in `0..255`)
  or nested IO data. The type is recursive. Let's see an example of one of
  the possible IO data representing the binary `"hello"`:

@@ -99,8 +99,8 @@ defmodule IO do
  Erlang and Elixir also have the idea of `t:chardata/0`. Chardata is very
  similar to IO data: the only difference is that integers in IO data represent
  bytes while integers in chardata represent Unicode code points. Bytes
-  (`t:byte/0`) are integers within the `0..255` range, while Unicode code points
-  (`t:char/0`) are integers within the `0..0x10FFFF` range. The `IO` module provides
+  (`t:byte/0`) are integers in the `0..255` range, while Unicode code points
+  (`t:char/0`) are integers in the range `0..0x10FFFF`. The `IO` module provides
  the `chardata_to_string/1` function for chardata as the "counter-part" of the
  `iodata_to_binary/1` function for IO data.

@@ -108,8 +108,8 @@ defmodule IO do
  argument error. For example, let's try to put a code point that is not
  representable with one byte, like `?π`, inside IO data:

-      IO.iodata_to_binary(["The symbol for pi is: ", ?π])
-      #=> ** (ArgumentError) argument error
+      iex> IO.iodata_to_binary(["The symbol for pi is: ", ?π])
+      ** (ArgumentError) argument error

  If we use chardata instead, it will work as expected:

@@ -122,14 +122,14 @@ defmodule IO do
  @type nodata :: {:error, term} | :eof
  @type chardata :: String.t() | maybe_improper_list(char | chardata, String.t() | [])

-  defguardp is_device(term) when is_atom(term) or is_pid(term)
  defguardp is_iodata(data) when is_list(data) or is_binary(data)

  @doc """
  Reads from the IO `device`.

-  The `device` is iterated by the given number of characters, line by line if
-  `:line` is given, or until `:eof`.
+  The `device` is iterated by the given number of characters or line by line if
+  `:line` is given.
+  Alternatively, if `:all` is given, then whole `device` is returned.

  It returns:

@@ -141,24 +141,14 @@ defmodule IO do
      for instance, `{:error, :estale}` if reading from an
      NFS volume

+  If `:all` is given, `:eof` is never returned, but an
+  empty string in case the device has reached EOF.
  """
-  @spec read(device, :eof | :line | non_neg_integer) :: chardata | nodata
+  @spec read(device, :all | :line | non_neg_integer) :: chardata | nodata
  def read(device \\ :stdio, line_or_chars)

-  # TODO: Deprecate me on v1.17
  def read(device, :all) do
-    with :eof <- read(device, :eof) do
-      with [_ | _] = opts <- :io.getopts(device),
-           false <- Keyword.get(opts, :binary, true) do
-        ''
-      else
-        _ -> ""
-      end
-    end
-  end
-
-  def read(device, :eof) do
-    getn(device, '', :eof)
+    do_read_all(map_dev(device), :empty)
  end

  def read(device, :line) do
@@ -169,20 +159,35 @@ defmodule IO do
    :io.get_chars(map_dev(device), '', count)
  end

+  defp do_read_all(mapped_dev, acc) do
+    case :io.get_line(mapped_dev, "") do
+      line when is_binary(line) or is_list(line) -> do_read_all(mapped_dev, concat(acc, line))
+      :eof -> read_eof(mapped_dev, acc)
+      other -> other
+    end
+  end
+
+  defp concat(:empty, line), do: line
+  defp concat(acc, line) when is_binary(acc), do: acc <> line
+  defp concat(acc, line) when is_list(acc), do: acc ++ line
+
+  defp read_eof(device, :empty) do
+    with [_ | _] = opts <- :io.getopts(device),
+         false <- Keyword.get(opts, :binary, true) do
+      ''
+    else
+      _ -> ""
+    end
+  end
+
+  defp read_eof(_device, acc), do: acc
+
  @doc """
  Reads from the IO `device`. The operation is Unicode unsafe.

-  The `device` is iterated as specified by the `line_or_chars` argument:
-
-    * if `line_or_chars` is an integer, it represents a number of bytes. The device is
-      iterated by that number of bytes.
-
-    * if `line_or_chars` is `:line`, the device is iterated line by line.
-
-    * if `line_or_chars` is `:eof`, the device is iterated until `:eof`. `line_or_chars`
-      can only be `:eof` since Elixir 1.13.0. `:eof` replaces the deprecated `:all`,
-      with the difference that `:all` returns `""` on end of file, while `:eof` returns
-      `:eof` itself.
+  The `device` is iterated by the given number of bytes or line by line if
+  `:line` is given.
+  Alternatively, if `:all` is given, then whole `device` is returned.

  It returns:

@@ -194,19 +199,17 @@ defmodule IO do
      for instance, `{:error, :estale}` if reading from an
      NFS volume

+  If `:all` is given, `:eof` is never returned, but an
+  empty string in case the device has reached EOF.
+
  Note: do not use this function on IO devices in Unicode mode
  as it will return the wrong result.
  """
-  @spec binread(device, :eof | :line | non_neg_integer) :: iodata | nodata
+  @spec binread(device, :all | :line | non_neg_integer) :: iodata | nodata
  def binread(device \\ :stdio, line_or_chars)

-  # TODO: Deprecate me on v1.17
  def binread(device, :all) do
-    with :eof <- binread(device, :eof), do: ""
-  end
-
-  def binread(device, :eof) do
-    binread_eof(map_dev(device), "")
+    do_binread_all(map_dev(device), "")
  end

  def binread(device, :line) do
@@ -224,10 +227,10 @@ defmodule IO do
  end

  @read_all_size 4096
-  defp binread_eof(mapped_dev, acc) do
+  defp do_binread_all(mapped_dev, acc) do
    case :file.read(mapped_dev, @read_all_size) do
-      {:ok, data} -> binread_eof(mapped_dev, acc <> data)
-      :eof -> if acc == "", do: :eof, else: acc
+      {:ok, data} -> do_binread_all(mapped_dev, acc <> data)
+      :eof -> acc
      other -> other
    end
  end
@@ -290,29 +293,19 @@ defmodule IO do

  """
  @spec puts(device, chardata | String.Chars.t()) :: :ok
-  def puts(device \\ :stdio, item) when is_device(device) do
+  def puts(device \\ :stdio, item) do
    :io.put_chars(map_dev(device), [to_chardata(item), ?\n])
  end

  @doc """
-  Writes a `message` to stderr, along with the given `stacktrace_info`.
-
-  The `stacktrace_info` must be one of:
-
-    * a `__STACKTRACE__`, where all entries in the stacktrace will be
-      included in the error message
-
-    * a `Macro.Env` structure (since v1.14.0), where a single stacktrace
-      entry from the compilation environment will be used
-
-    * a keyword list with at least the `:file` option representing
-      a single stacktrace entry (since v1.14.0). The `:line`, `:module`,
-      `:function` options are also supported
+  Writes a `message` to stderr, along with the given `stacktrace`.

  This function also notifies the compiler a warning was printed
  (in case --warnings-as-errors was enabled). It returns `:ok`
  if it succeeds.

+  An empty list can be passed to avoid stacktrace printing.
+
  ## Examples

      stacktrace = [{MyApp, :main, 1, [file: 'my_app.ex', line: 4]}]
@@ -321,34 +314,10 @@ defmodule IO do
      #=>   my_app.ex:4: MyApp.main/1

  """
-  @spec warn(chardata | String.Chars.t(), Exception.stacktrace() | keyword() | Macro.Env.t()) ::
-          :ok
-  def warn(message, stacktrace_info)
-
+  @spec warn(chardata | String.Chars.t(), Exception.stacktrace()) :: :ok
  def warn(message, []) do
    message = [to_chardata(message), ?\n]
-    :elixir_errors.log_and_print_warning(0, nil, message, message)
-  end
-
-  def warn(message, %Macro.Env{} = env) do
-    warn(message, Macro.Env.stacktrace(env))
-  end
-
-  def warn(message, [{_, _} | _] = keyword) do
-    if file = keyword[:file] do
-      warn(
-        message,
-        %{
-          __ENV__
-          | module: keyword[:module],
-            function: keyword[:function],
-            line: keyword[:line],
-            file: file
-        }
-      )
-    else
-      warn(message, [])
-    end
+    :elixir_errors.io_warn(0, nil, message, message)
  end

  def warn(message, [{_, _, _, opts} | _] = stacktrace) do
@@ -357,7 +326,7 @@ defmodule IO do
    line = opts[:line]
    file = opts[:file]

-    :elixir_errors.log_and_print_warning(
+    :elixir_errors.io_warn(
      line || 0,
      file && List.to_string(file),
      message,
@@ -459,9 +428,9 @@ defmodule IO do
  See `inspect/2` for a full list of options.
  """
  @spec inspect(device, item, keyword) :: item when item: var
-  def inspect(device, item, opts) when is_device(device) and is_list(opts) do
+  def inspect(device, item, opts) when is_list(opts) do
    label = if label = opts[:label], do: [to_chardata(label), ": "], else: []
-    opts = Inspect.Opts.new(opts)
+    opts = struct(Inspect.Opts, opts)
    doc = Inspect.Algebra.group(Inspect.Algebra.to_doc(item, opts))
    chardata = Inspect.Algebra.format(doc, opts.width)
    puts(device, [label, chardata])
@@ -476,18 +445,12 @@ defmodule IO do
  Otherwise, `count` is the number of raw bytes to be retrieved.

  See `IO.getn/3` for a description of return values.
+
  """
-  @spec getn(
-          device | chardata | String.Chars.t(),
-          pos_integer | :eof | chardata | String.Chars.t()
-        ) ::
+  @spec getn(device | chardata | String.Chars.t(), pos_integer | chardata | String.Chars.t()) ::
          chardata | nodata
  def getn(prompt, count \\ 1)

-  def getn(prompt, :eof) do
-    getn(:stdio, prompt, :eof)
-  end
-
  def getn(prompt, count) when is_integer(count) and count > 0 do
    getn(:stdio, prompt, count)
  end
@@ -514,27 +477,11 @@ defmodule IO do
      NFS volume

  """
-  @spec getn(device, chardata | String.Chars.t(), pos_integer | :eof) :: chardata | nodata
-  def getn(device, prompt, :eof) do
-    getn_eof(map_dev(device), to_chardata(prompt), [])
-  end
-
+  @spec getn(device, chardata | String.Chars.t(), pos_integer) :: chardata | nodata
  def getn(device, prompt, count) when is_integer(count) and count > 0 do
    :io.get_chars(map_dev(device), to_chardata(prompt), count)
  end

-  defp getn_eof(device, prompt, acc) do
-    case :io.get_line(device, prompt) do
-      line when is_binary(line) or is_list(line) -> getn_eof(device, '', [line | acc])
-      :eof -> wrap_eof(:lists.reverse(acc))
-      other -> other
-    end
-  end
-
-  defp wrap_eof([h | _] = acc) when is_binary(h), do: IO.iodata_to_binary(acc)
-  defp wrap_eof([h | _] = acc) when is_list(h), do: :lists.flatten(acc)
-  defp wrap_eof([]), do: :eof
-
  @doc ~S"""
  Reads a line from the IO `device`.

@@ -561,17 +508,6 @@ defmodule IO do
    :io.get_line(map_dev(device), to_chardata(prompt))
  end

-  @doc """
-  Returns a line-based `IO.Stream` on `:stdio`.
-
-  This is equivalent to:
-
-      IO.stream(:stdio, :line)
-
-  """
-  @doc since: "1.12.0"
-  def stream, do: stream(:stdio, :line)
-
  @doc """
  Converts the IO `device` into an `IO.Stream`.

@@ -588,9 +524,6 @@ defmodule IO do
  Note that an IO stream has side effects and every time
  you go over the stream you may get different results.

-  `stream/0` has been introduced in Elixir v1.12.0,
-  while `stream/2` has been available since v1.0.0.
-
  ## Examples

  Here is an example on how we mimic an echo server
@@ -600,23 +533,12 @@ defmodule IO do

  """
  @spec stream(device, :line | pos_integer) :: Enumerable.t()
-  def stream(device \\ :stdio, line_or_codepoints)
+  def stream(device, line_or_codepoints)
      when line_or_codepoints == :line
      when is_integer(line_or_codepoints) and line_or_codepoints > 0 do
    IO.Stream.__build__(map_dev(device), false, line_or_codepoints)
  end

-  @doc """
-  Returns a raw, line-based `IO.Stream` on `:stdio`. The operation is Unicode unsafe.
-
-  This is equivalent to:
-
-      IO.binstream(:stdio, :line)
-
-  """
-  @doc since: "1.12.0"
-  def binstream, do: binstream(:stdio, :line)
-
  @doc """
  Converts the IO `device` into an `IO.Stream`. The operation is Unicode unsafe.

@@ -625,7 +547,8 @@ defmodule IO do
  and write.

  The `device` is iterated by the given number of bytes or line by line if
-  `:line` is given. This reads from the IO device as a raw binary.
+  `:line` is given.
+  This reads from the IO device as a raw binary.

  Note that an IO stream has side effects and every time
  you go over the stream you may get different results.
@@ -633,11 +556,9 @@ defmodule IO do
  Finally, do not use this function on IO devices in Unicode
  mode as it will return the wrong result.

-  `binstream/0` has been introduced in Elixir v1.12.0,
-  while `binstream/2` has been available since v1.0.0.
  """
  @spec binstream(device, :line | pos_integer) :: Enumerable.t()
-  def binstream(device \\ :stdio, line_or_bytes)
+  def binstream(device, line_or_bytes)
      when line_or_bytes == :line
      when is_integer(line_or_bytes) and line_or_bytes > 0 do
    IO.Stream.__build__(map_dev(device), true, line_or_bytes)
@@ -665,8 +586,6 @@ defmodule IO do

  """
  @spec chardata_to_string(chardata) :: String.t()
-  def chardata_to_string(chardata)
-
  def chardata_to_string(string) when is_binary(string) do
    string
  end
@@ -3,7 +3,6 @@ defmodule IO.ANSI.Sequence do

  defmacro defsequence(name, code, terminator \\ "m") do
    quote bind_quoted: [name: name, code: code, terminator: terminator] do
-      @spec unquote(name)() :: String.t()
      def unquote(name)() do
        "\e[#{unquote(code)}#{unquote(terminator)}"
      end
@@ -69,34 +68,6 @@ defmodule IO.ANSI do
    Application.get_env(:elixir, :ansi_enabled, false)
  end

-  @doc """
-  Syntax colors to be used by `Inspect`.
-
-  Those colors are used throughout Elixir's standard library,
-  such as `dbg/2` and `IEx`.
-
-  The colors can be changed by setting the `:ansi_syntax_colors`
-  in the `:elixir` application configuration. Configuration for
-  most built-in data types are supported: `:atom`, `:binary`,
-  `:boolean`, `:charlist`, `:list`, `:map`, `:nil`, `:number`,
-  `:string`, and `:tuple`. The default is:
-
-      [
-        atom: :cyan
-        boolean: :magenta,
-        charlist: :yellow,
-        nil: :magenta,
-        number: :yellow,
-        string: :green
-      ]
-
-  """
-  @doc since: "1.14.0"
-  @spec syntax_colors :: Keyword.t(ansidata)
-  def syntax_colors do
-    Application.fetch_env!(:elixir, :ansi_syntax_colors)
-  end
-
  @doc "Sets foreground color."
  @spec color(0..255) :: String.t()
  def color(code) when code in 0..255, do: "\e[38;5;#{code}m"
@@ -271,7 +242,7 @@ defmodule IO.ANSI do
  performed. If you don't want this behaviour, use `format_fragment/2`.

  An optional boolean parameter can be passed to enable or disable
-  emitting actual ANSI codes. When `false`, no ANSI codes will be emitted.
+  emitting actual ANSI codes. When `false`, no ANSI codes will emitted.
  By default checks if ANSI is enabled using the `enabled?/0` function.

  ## Examples
@@ -280,9 +251,8 @@ defmodule IO.ANSI do
      [[[[[[], "Hello, "] | "\e[31m"] | "\e[1m"], "world!"] | "\e[0m"]

  """
-  @spec format(ansidata, boolean) :: IO.chardata()
-  def format(ansidata, emit? \\ enabled?()) when is_boolean(emit?) do
-    do_format(ansidata, [], [], emit?, :maybe)
+  def format(chardata, emit? \\ enabled?()) when is_boolean(emit?) do
+    do_format(chardata, [], [], emit?, :maybe)
  end

  @doc ~S"""
@@ -301,9 +271,8 @@ defmodule IO.ANSI do
      [[[[[[] | "\e[1m"], 87], 111], 114], 100]

  """
-  @spec format_fragment(ansidata, boolean) :: IO.chardata()
-  def format_fragment(ansidata, emit? \\ enabled?()) when is_boolean(emit?) do
-    do_format(ansidata, [], [], emit?, false)
+  def format_fragment(chardata, emit? \\ enabled?()) when is_boolean(emit?) do
+    do_format(chardata, [], [], emit?, false)
  end

  defp do_format([term | rest], rem, acc, emit?, append_reset) do
@@ -78,9 +78,7 @@ defmodule IO.ANSI.Docs do
  @metadata_filter [:deprecated, :guard, :since]

  defp print_each_metadata(metadata, options) do
-    metadata
-    |> Enum.sort()
-    |> Enum.reduce(false, fn
+    Enum.reduce(metadata, false, fn
      {key, value}, _printed when is_binary(value) and key in @metadata_filter ->
        label = metadata_label(key, options)
        indent = String.duplicate(" ", length_without_escape(label, 0) + 1)
@@ -196,10 +194,6 @@ defmodule IO.ANSI.Docs do
    inline_text("*", traverse_erlang_html(entries, indent, options), options)
  end

-  defp traverse_erlang_html({tag, _, entries}, indent, options) when tag in [:strong, :b] do
-    inline_text("**", traverse_erlang_html(entries, indent, options), options)
-  end
-
  defp traverse_erlang_html({:code, _, entries}, indent, options) do
    inline_text("`", traverse_erlang_html(entries, indent, options), options)
  end
@@ -301,7 +295,7 @@ defmodule IO.ANSI.Docs do
  end

  defp inline_html?(binary) when is_binary(binary), do: true
-  defp inline_html?({tag, _, _}) when tag in [:a, :code, :em, :i, :strong, :b, :br], do: true
+  defp inline_html?({tag, _, _}) when tag in [:a, :code, :em, :i, :br], do: true
  defp inline_html?(_), do: false

  ## Markdown
@@ -804,14 +798,14 @@ defmodule IO.ANSI.Docs do
    Regex.replace(~r{\[([^\]]*?)\]\((.*?)\)}, text, "\\1 (\\2)")
  end

-  # We have four entries: **, __, *, _ and `.
+  # We have four entries: **, *, _ and `.
  #
-  # The first four behave the same while the last one is simpler
+  # The first three behave the same while the last one is simpler
  # when it comes to delimiters as it ignores spaces and escape
-  # characters. But, since the first two has two characters,
-  # we need to handle 3 cases:
+  # characters. But, since the first has two characters, we need to
+  # handle 3 cases:
  #
-  # 1. __ and **
+  # 1. **
  # 2. _ and *
  # 3. `
  #
@@ -825,8 +819,8 @@ defmodule IO.ANSI.Docs do

  ### Inline start

-  defp handle_inline(<<mark, mark, rest::binary>>, options) when mark in @single do
-    handle_inline(rest, [mark | mark], [<<mark, mark>>], [], options)
+  defp handle_inline(<<?*, ?*, rest::binary>>, options) do
+    handle_inline(rest, ?d, ["**"], [], options)
  end

  defp handle_inline(<<mark, rest::binary>>, options) when mark in @single do
@@ -839,10 +833,9 @@ defmodule IO.ANSI.Docs do

  ### Inline delimiters

-  defp handle_inline(<<delimiter, mark, mark, rest::binary>>, nil, buffer, acc, options)
-       when rest != "" and delimiter in @delimiters and mark in @single do
-    acc = [delimiter, Enum.reverse(buffer) | acc]
-    handle_inline(rest, [mark | mark], [<<mark, mark>>], acc, options)
+  defp handle_inline(<<delimiter, ?*, ?*, rest::binary>>, nil, buffer, acc, options)
+       when rest != "" and delimiter in @delimiters do
+    handle_inline(rest, ?d, ["**"], [delimiter, Enum.reverse(buffer) | acc], options)
  end

  defp handle_inline(<<delimiter, mark, rest::binary>>, nil, buffer, acc, options)
@@ -857,10 +850,9 @@ defmodule IO.ANSI.Docs do

  ### Clauses for handling escape

-  defp handle_inline(<<?\\, ?\\, mark, mark, rest::binary>>, nil, buffer, acc, options)
-       when rest != "" and mark in @single do
-    acc = [?\\, Enum.reverse(buffer) | acc]
-    handle_inline(rest, [mark | mark], [<<mark, mark>>], acc, options)
+  defp handle_inline(<<?\\, ?\\, ?*, ?*, rest::binary>>, nil, buffer, acc, options)
+       when rest != "" do
+    handle_inline(rest, ?d, ["**"], [?\\, Enum.reverse(buffer) | acc], options)
  end

  defp handle_inline(<<?\\, ?\\, mark, rest::binary>>, nil, buffer, acc, options)
@@ -879,8 +871,8 @@ defmodule IO.ANSI.Docs do

  ### Inline end

-  defp handle_inline(<<mark, mark, delimiter, rest::binary>>, [mark | mark], buffer, acc, options)
-       when delimiter in @delimiters and mark in @single do
+  defp handle_inline(<<?*, ?*, delimiter, rest::binary>>, ?d, buffer, acc, options)
+       when delimiter in @delimiters do
    inline_buffer = inline_buffer(buffer, options)
    handle_inline(<<delimiter, rest::binary>>, nil, [], [inline_buffer | acc], options)
  end
@@ -891,8 +883,8 @@ defmodule IO.ANSI.Docs do
    handle_inline(<<delimiter, rest::binary>>, nil, [], [inline_buffer | acc], options)
  end

-  defp handle_inline(<<mark, mark, rest::binary>>, [mark | mark], buffer, acc, options)
-       when rest == "" and mark in @single do
+  defp handle_inline(<<?*, ?*, rest::binary>>, ?d, buffer, acc, options)
+       when rest == "" do
    handle_inline(<<>>, nil, [], [inline_buffer(buffer, options) | acc], options)
  end

@@ -938,11 +930,10 @@ defmodule IO.ANSI.Docs do

  defp color_for(mark, colors) do
    case mark do
-      "__" -> color(:doc_bold, colors)
-      "**" -> color(:doc_bold, colors)
-      "_" -> color(:doc_underline, colors)
-      "*" -> color(:doc_underline, colors)
      "`" -> color(:doc_inline_code, colors)
+      "_" -> color(:doc_underline, colors)
+      "*" -> color(:doc_bold, colors)
+      "**" -> color(:doc_bold, colors)
    end
  end

@@ -26,11 +26,7 @@ defmodule IO.Stream do

  defstruct device: nil, raw: true, line_or_bytes: :line

-  @type t :: %__MODULE__{
-          device: IO.device(),
-          raw: boolean(),
-          line_or_bytes: :line | non_neg_integer()
-        }
+  @type t :: %__MODULE__{}

  @doc false
  def __build__(device, raw, line_or_bytes) do
@@ -13,12 +13,9 @@ defmodule Kernel.CLI do
    pa: [],
    pz: [],
    verbose_compile: false,
-    profile: nil,
-    pry: false
+    profile: nil
  }

-  @standalone_opts ["-h", "--help", "--short-version"]
-
  @doc """
  This is the API invoked by Elixir boot process.
  """
@@ -29,10 +26,6 @@ defmodule Kernel.CLI do
    System.argv(argv)
    System.no_halt(config.no_halt)

-    if config.pry do
-      Application.put_env(:elixir, :dbg_callback, {IEx.Pry, :dbg, []})
-    end
-
    fun = fn _ ->
      errors = process_commands(config)

@@ -95,7 +88,7 @@ defmodule Kernel.CLI do
      case blamed do
        %FunctionClauseError{} ->
          formatted = Exception.format_banner(kind, reason, stacktrace)
-          padded_blame = pad(FunctionClauseError.blame(blamed, &inspect/1, &blame_match/1))
+          padded_blame = pad(FunctionClauseError.blame(blamed, &inspect/1, &blame_match/2))
          [formatted, padded_blame]

        _ ->
@@ -183,8 +176,9 @@ defmodule Kernel.CLI do
    IO.write(:stderr, format_error(kind, reason, stacktrace))
  end

-  defp blame_match(%{match?: true, node: node}), do: blame_ansi(:normal, "+", node)
-  defp blame_match(%{match?: false, node: node}), do: blame_ansi(:red, "-", node)
+  defp blame_match(%{match?: true, node: node}, _), do: blame_ansi(:normal, "+", node)
+  defp blame_match(%{match?: false, node: node}, _), do: blame_ansi(:red, "-", node)
+  defp blame_match(_, string), do: string

  defp blame_ansi(color, no_ansi, node) do
    if IO.ANSI.enabled?() do
@@ -201,9 +195,8 @@ defmodule Kernel.CLI do
  end

  @elixir_internals [:elixir, :elixir_aliases, :elixir_expand, :elixir_compiler, :elixir_module] ++
-                      [:elixir_clauses, :elixir_lexical, :elixir_def, :elixir_map, :elixir_locals] ++
-                      [:elixir_erl, :elixir_erl_clauses, :elixir_erl_compiler, :elixir_erl_pass] ++
-                      [Kernel.ErrorHandler, Module.ParallelChecker]
+                      [:elixir_clauses, :elixir_lexical, :elixir_def, :elixir_map] ++
+                      [:elixir_erl, :elixir_erl_clauses, :elixir_erl_pass, Kernel.ErrorHandler]

  defp prune_stacktrace([{mod, _, _, _} | t]) when mod in @elixir_internals do
    prune_stacktrace(t)
@@ -223,16 +216,7 @@ defmodule Kernel.CLI do

  # Parse shared options

-  defp halt_standalone(opt) do
-    IO.puts(:stderr, "#{opt} : Standalone options can't be combined with other options")
-    System.halt(1)
-  end
-
-  defp parse_shared([opt | _], _config) when opt in @standalone_opts do
-    halt_standalone(opt)
-  end
-
-  defp parse_shared([opt | t], _config) when opt in ["-v", "--version"] do
+  defp parse_shared([opt | _t], _config) when opt in ["-v", "--version"] do
    if function_exported?(IEx, :started?, 0) and IEx.started?() do
      IO.puts("IEx " <> System.build_info()[:build])
    else
@@ -240,11 +224,7 @@ defmodule Kernel.CLI do
      IO.puts("Elixir " <> System.build_info()[:build])
    end

-    if t != [] do
-      halt_standalone(opt)
-    else
-      System.halt(0)
-    end
+    System.halt(0)
  end

  defp parse_shared(["-pa", h | t], config) do
@@ -280,11 +260,6 @@ defmodule Kernel.CLI do
    parse_shared(t, %{config | commands: [{:rpc_eval, node, h} | config.commands]})
  end

-  defp parse_shared(["--rpc-eval" | _], config) do
-    new_config = %{config | errors: ["--rpc-eval : wrong number of arguments" | config.errors]}
-    {[], new_config}
-  end
-
  defp parse_shared(["-r", h | t], config) do
    parse_shared(t, %{config | commands: [{:require, h} | config.commands]})
  end
@@ -324,7 +299,7 @@ defmodule Kernel.CLI do
  end

  defp parse_argv(["+iex" | t], config) do
-    parse_iex(t, %{config | pry: true})
+    parse_iex(t, config)
  end

  defp parse_argv(["-S", h | t], config) do
@@ -409,16 +384,20 @@ defmodule Kernel.CLI do
    {config, t}
  end

+  # This clause is here so that Kernel.CLI does not
+  # error out with "unknown option"
+  defp parse_iex(["--dot-iex", _ | t], config) do
+    parse_iex(t, config)
+  end
+
+  defp parse_iex([opt, _ | t], config) when opt in ["--remsh"] do
+    parse_iex(t, config)
+  end
+
  defp parse_iex(["-S", h | t], config) do
    {%{config | commands: [{:script, h} | config.commands]}, t}
  end

-  # These clauses are here so that Kernel.CLI does not error out with "unknown option"
-  defp parse_iex(["--dot-iex", _ | t], config), do: parse_iex(t, config)
-  defp parse_iex(["--remsh", _ | t], config), do: parse_iex(t, config)
-
-  defp parse_iex(["--no-pry" | t], config), do: parse_iex(t, %{config | pry: false})
-
  defp parse_iex([h | t] = list, config) do
    case h do
      "-" <> _ -> shared_option?(list, config, &parse_iex(&1, &2))
@@ -30,10 +30,10 @@ defmodule Kernel.ErrorHandler do
  end

  def ensure_compiled(module, kind, deadlock) do
-    {compiler_pid, file_pid} = :erlang.get(:elixir_compiler_info)
+    parent = :erlang.get(:elixir_compiler_pid)
    ref = :erlang.make_ref()
    modules = :elixir_module.compiler_modules()
-    send(compiler_pid, {:waiting, kind, self(), ref, file_pid, module, modules, deadlock})
+    send(parent, {:waiting, kind, self(), ref, module, modules, deadlock})
    :erlang.garbage_collect(self())

    receive do
@@ -30,8 +30,8 @@ defmodule Kernel.LexicalTracker do
  end

  @doc false
-  def add_export(pid, module) when is_atom(module) do
-    :gen_server.cast(pid, {:add_export, module})
+  def add_require(pid, module) when is_atom(module) do
+    :gen_server.cast(pid, {:add_require, module})
  end

  @doc false
@@ -59,11 +59,6 @@ defmodule Kernel.LexicalTracker do
    :gen_server.cast(pid, {:alias_dispatch, module})
  end

-  @doc false
-  def import_quoted(pid, module, function, arities) when is_atom(module) do
-    :gen_server.cast(pid, {:import_quoted, module, function, arities})
-  end
-
  @doc false
  def add_compile_env(pid, app, path, return) do
    :gen_server.cast(pid, {:compile_env, app, path, return})
@@ -93,24 +88,23 @@ defmodule Kernel.LexicalTracker do

  @doc false
  def collect_unused_imports(pid) do
-    unused(pid, :unused_imports)
+    unused(pid, :import)
  end

  @doc false
  def collect_unused_aliases(pid) do
-    unused(pid, :unused_aliases)
+    unused(pid, :alias)
  end

  defp unused(pid, tag) do
-    :gen_server.call(pid, tag, @timeout)
+    :gen_server.call(pid, {:unused, tag}, @timeout)
  end

  # Callbacks

  def init(:ok) do
    state = %{
-      aliases: %{},
-      imports: %{},
+      directives: %{},
      references: %{},
      exports: %{},
      cache: %{},
@@ -122,12 +116,13 @@ defmodule Kernel.LexicalTracker do
  end

  @doc false
-  def handle_call(:unused_aliases, _from, state) do
-    {:reply, Enum.sort(state.aliases), state}
-  end
+  def handle_call({:unused, tag}, _from, state) do
+    directives =
+      for {{^tag, module_or_mfa}, marker} <- state.directives, is_integer(marker) do
+        {module_or_mfa, marker}
+      end

-  def handle_call(:unused_imports, _from, state) do
-    {:reply, Enum.sort(state.imports), state}
+    {:reply, Enum.sort(directives), state}
  end

  def handle_call(:references, _from, state) do
@@ -153,44 +148,12 @@ defmodule Kernel.LexicalTracker do
  end

  def handle_cast({:import_dispatch, module, {function, arity}, mode}, state) do
-    %{imports: imports, references: references} = state
-
-    imports =
-      case imports do
-        %{^module => modules_and_fas} ->
-          modules_and_fas
-          |> Map.delete(module)
-          |> Map.delete({function, arity})
-          |> then(&Map.put(imports, module, &1))
-
-        %{} ->
-          imports
-      end
-
-    references = add_reference(references, module, mode)
-    {:noreply, %{state | imports: imports, references: references}}
+    state = add_import_dispatch(state, module, function, arity, mode)
+    {:noreply, state}
  end

-  def handle_cast({:alias_dispatch, module}, %{aliases: aliases} = state) do
-    {:noreply, %{state | aliases: Map.delete(aliases, module)}}
-  end
-
-  def handle_cast({:import_quoted, module, function, arities}, state) do
-    %{imports: imports} = state
-
-    imports =
-      case imports do
-        %{^module => modules_and_fas} ->
-          arities
-          |> Enum.reduce(modules_and_fas, &Map.delete(&2, {function, &1}))
-          |> Map.delete(module)
-          |> then(&Map.put(imports, module, &1))
-
-        %{} ->
-          imports
-      end
-
-    {:noreply, %{state | imports: imports}}
+  def handle_cast({:alias_dispatch, module}, state) do
+    {:noreply, %{state | directives: add_dispatch(state.directives, module, :alias)}}
  end

  def handle_cast({:set_file, file}, state) do
@@ -205,25 +168,27 @@ defmodule Kernel.LexicalTracker do
    {:noreply, update_in(state.compile_env, &:ordsets.add_element({app, path, return}, &1))}
  end

-  def handle_cast({:add_export, module}, state) do
+  def handle_cast({:add_require, module}, state) do
    {:noreply, put_in(state.exports[module], true)}
  end

  def handle_cast({:add_import, module, fas, line, warn}, state) do
-    if warn do
-      imports = for module_or_fa <- [module | fas], do: {module_or_fa, line}, into: %{}
-      {:noreply, put_in(state.imports[module], imports)}
-    else
-      {:noreply, state}
-    end
+    directives =
+      state.directives
+      |> Enum.reject(&match?({{:import, {^module, _, _}}, _}, &1))
+      |> Map.new()
+      |> add_directive(module, line, warn, :import)
+
+    directives =
+      Enum.reduce(fas, directives, fn {function, arity}, directives ->
+        add_directive(directives, {module, function, arity}, line, warn, :import)
+      end)
+
+    {:noreply, %{state | directives: directives}}
  end

  def handle_cast({:add_alias, module, line, warn}, state) do
-    if warn do
-      {:noreply, put_in(state.aliases[module], line)}
-    else
-      {:noreply, state}
-    end
+    {:noreply, %{state | directives: add_directive(state.directives, module, line, warn, :alias)}}
  end

  @doc false
@@ -255,9 +220,31 @@ defmodule Kernel.LexicalTracker do
    do: Map.put(references, module, :compile)

  defp add_reference(references, module, :runtime) when is_atom(module) do
-    case references do
-      %{^module => _} -> references
-      %{} -> Map.put(references, module, :runtime)
+    case Map.fetch(references, module) do
+      {:ok, _} -> references
+      :error -> Map.put(references, module, :runtime)
    end
  end
+
+  defp add_import_dispatch(state, module, function, arity, mode) do
+    directives =
+      state.directives
+      |> add_dispatch(module, :import)
+      |> add_dispatch({module, function, arity}, :import)
+
+    references = add_reference(state.references, module, mode)
+    %{state | directives: directives, references: references}
+  end
+
+  # In the map we keep imports and aliases.
+  # If the value is a line, it was imported/aliased and has a pending warning
+  # If the value is true, it was imported/aliased and used
+  defp add_directive(directives, module_or_mfa, line, warn, tag) do
+    marker = if warn, do: line, else: true
+    Map.put(directives, {tag, module_or_mfa}, marker)
+  end
+
+  defp add_dispatch(directives, module_or_mfa, tag) do
+    Map.put(directives, {tag, module_or_mfa}, true)
+  end
 end
@@ -3,12 +3,6 @@ defmodule Kernel.ParallelCompiler do
  A module responsible for compiling and requiring files in parallel.
  """

-  @typedoc "The line. 0 indicates no line."
-  @type line() :: non_neg_integer()
-  @type location() :: line() | {pos_integer(), column :: non_neg_integer}
-  @type warning() :: {file :: Path.t(), location(), message :: String.t()}
-  @type error() :: {file :: Path.t(), location(), message :: String.t()}
-
  @doc """
  Starts a task for parallel compilation.

@@ -22,28 +16,23 @@ defmodule Kernel.ParallelCompiler do
  """
  @doc since: "1.6.0"
  def async(fun) when is_function(fun, 0) do
-    case :erlang.get(:elixir_compiler_info) do
-      {compiler, _} ->
-        file = :erlang.get(:elixir_compiler_file)
-        dest = :erlang.get(:elixir_compiler_dest)
+    if parent = :erlang.get(:elixir_compiler_pid) do
+      file = :erlang.get(:elixir_compiler_file)
+      dest = :erlang.get(:elixir_compiler_dest)
+      {:error_handler, error_handler} = :erlang.process_info(self(), :error_handler)

-        {:error_handler, error_handler} = :erlang.process_info(self(), :error_handler)
-        {_parent, checker} = Module.ParallelChecker.get()
-
-        Task.async(fn ->
-          send(compiler, {:async, self()})
-          Module.ParallelChecker.put(compiler, checker)
-          :erlang.put(:elixir_compiler_info, {compiler, self()})
-          :erlang.put(:elixir_compiler_file, file)
-          dest != :undefined and :erlang.put(:elixir_compiler_dest, dest)
-          :erlang.process_flag(:error_handler, error_handler)
-          fun.()
-        end)
-
-      :undefined ->
-        raise ArgumentError,
-              "cannot spawn parallel compiler task because " <>
-                "the current file is not being compiled/required"
+      Task.async(fn ->
+        send(parent, {:async, self()})
+        :erlang.put(:elixir_compiler_pid, parent)
+        :erlang.put(:elixir_compiler_file, file)
+        dest != :undefined and :erlang.put(:elixir_compiler_dest, dest)
+        :erlang.process_flag(:error_handler, error_handler)
+        fun.()
+      end)
+    else
+      raise ArgumentError,
+            "cannot spawn parallel compiler task because " <>
+              "the current file is not being compiled/required"
    end
  end

@@ -97,19 +86,11 @@ defmodule Kernel.ParallelCompiler do

  """
  @doc since: "1.6.0"
-  @spec compile([Path.t()], keyword()) :: {:ok, [atom], [warning]} | {:error, [error], [warning]}
  def compile(files, options \\ []) when is_list(options) do
    spawn_workers(files, :compile, options)
  end

-  @doc """
-  Compiles the given files and writes resulting BEAM files into path.
-
-  See `compile/2` for more information.
-  """
  @doc since: "1.6.0"
-  @spec compile_to_path([Path.t()], Path.t(), keyword()) ::
-          {:ok, [atom], [warning]} | {:error, [error], [warning]}
  def compile_to_path(files, path, options \\ []) when is_binary(path) and is_list(options) do
    spawn_workers(files, {:compile, path}, options)
  end
@@ -135,21 +116,10 @@ defmodule Kernel.ParallelCompiler do

  """
  @doc since: "1.6.0"
-  @spec require([Path.t()], keyword()) ::
-          {:ok, [atom], [warning]} | {:error, [error], [warning]}
  def require(files, options \\ []) when is_list(options) do
    spawn_workers(files, :require, options)
  end

-  @doc """
-  Prints a warning returned by the compiler.
-  """
-  @doc since: "1.13.0"
-  @spec print_warning(warning) :: :ok
-  def print_warning({file, location, warning}) do
-    :elixir_errors.print_warning(location, file, warning)
-  end
-
  @doc false
  @deprecated "Use Kernel.ParallelCompiler.compile/2 instead"
  def files(files, options \\ []) when is_list(options) do
@@ -171,32 +141,7 @@ defmodule Kernel.ParallelCompiler do
  defp spawn_workers(files, output, options) do
    {:module, _} = :code.ensure_loaded(Kernel.ErrorHandler)
    schedulers = max(:erlang.system_info(:schedulers_online), 2)
-    {:ok, checker} = Module.ParallelChecker.start_link(schedulers)
-
-    try do
-      outcome = spawn_workers(schedulers, checker, files, output, options)
-      {outcome, Code.get_compiler_option(:warnings_as_errors)}
-    else
-      {{:ok, _, [_ | _] = warnings}, true} ->
-        message = "Compilation failed due to warnings while using the --warnings-as-errors option"
-        IO.puts(:stderr, message)
-        {:error, warnings, []}
-
-      {{:ok, outcome, warnings}, _} ->
-        beam_timestamp = Keyword.get(options, :beam_timestamp)
-        {:ok, write_module_binaries(outcome, output, beam_timestamp), warnings}
-
-      {{:error, errors, warnings}, true} ->
-        {:error, errors ++ warnings, []}
-
-      {{:error, errors, warnings}, _} ->
-        {:error, errors, warnings}
-    after
-      Module.ParallelChecker.stop(checker)
-    end
-  end
-
-  defp spawn_workers(schedulers, checker, files, output, options) do
+    beam_timestamp = Keyword.get(options, :beam_timestamp)
    threshold = Keyword.get(options, :long_compilation_threshold, 10) * 1000
    timer_ref = Process.send_after(self(), :threshold_check, threshold)

@@ -211,8 +156,7 @@ defmodule Kernel.ParallelCompiler do
        output: output,
        timer_ref: timer_ref,
        long_compilation_threshold: threshold,
-        schedulers: schedulers,
-        checker: checker
+        schedulers: schedulers
      })

    Process.cancel_timer(state.timer_ref)
@@ -223,7 +167,21 @@ defmodule Kernel.ParallelCompiler do
      0 -> :ok
    end

-    outcome
+    case {outcome, Code.get_compiler_option(:warnings_as_errors)} do
+      {{:ok, _, [_ | _] = warnings}, true} ->
+        message = "Compilation failed due to warnings while using the --warnings-as-errors option"
+        IO.puts(:stderr, message)
+        {:error, warnings, []}
+
+      {{:ok, outcome, warnings}, _} ->
+        {:ok, write_module_binaries(outcome, output, beam_timestamp), warnings}
+
+      {{:error, errors, warnings}, true} ->
+        {:error, errors ++ warnings, []}
+
+      {{:error, errors, warnings}, _} ->
+        {:error, errors, warnings}
+    end
  end

  defp each_file(fun) when is_function(fun, 1), do: fn file, _ -> fun.(file) end
@@ -241,7 +199,7 @@ defmodule Kernel.ParallelCompiler do

  defp write_module_binaries(result, {:compile, path}, timestamp) do
    Enum.flat_map(result, fn
-      {{:module, module}, binary} ->
+      {{:module, module}, {binary, _map}} ->
        full_path = Path.join(path, Atom.to_string(module) <> ".beam")
        File.write!(full_path, binary)
        if timestamp, do: File.touch!(full_path, timestamp)
@@ -265,15 +223,32 @@ defmodule Kernel.ParallelCompiler do
  end

  defp maybe_check_modules(result, runtime_modules, state) do
-    %{profile: profile, checker: checker} = state
+    %{schedulers: schedulers, profile: profile} = state

-    compiled_modules =
-      for {{:module, module}, _} <- result,
-          do: module
+    if :elixir_config.get(:bootstrap) do
+      []
+    else
+      compiled_modules = checker_compiled_modules(result)
+      runtime_modules = checker_runtime_modules(runtime_modules)

-    profile_checker(profile, compiled_modules, runtime_modules, fn ->
-      Module.ParallelChecker.verify(checker, runtime_modules)
-    end)
+      profile_checker(profile, compiled_modules, runtime_modules, fn ->
+        Module.ParallelChecker.verify(compiled_modules, runtime_modules, schedulers)
+      end)
+    end
+  end
+
+  defp checker_compiled_modules(result) do
+    for {{:module, _module}, {binary, module_map}} <- result do
+      {module_map, binary}
+    end
+  end
+
+  defp checker_runtime_modules(modules) do
+    for module <- modules,
+        path = :code.which(module),
+        is_list(path) and path != [] do
+      {module, File.read!(path)}
+    end
  end

  defp profile_init(:time), do: {:time, System.monotonic_time(), 0}
@@ -311,9 +286,9 @@ defmodule Kernel.ParallelCompiler do
  defp spawn_workers([{ref, found} | t], spawned, waiting, files, result, warnings, state) do
    {files, waiting} =
      case List.keytake(waiting, ref, 2) do
-        {{_kind, pid, ^ref, file_pid, _on, _defining, _deadlock}, waiting} ->
+        {{_kind, pid, ^ref, _on, _defining, _deadlock}, waiting} ->
          send(pid, {ref, found})
-          {update_timing(files, file_pid, :waiting), waiting}
+          {update_timing(files, pid, :waiting), waiting}

        nil ->
          # In case the waiting process died (for example, it was an async process),
@@ -325,14 +300,13 @@ defmodule Kernel.ParallelCompiler do
  end

  defp spawn_workers([file | queue], spawned, waiting, files, result, warnings, state) do
-    %{output: output, dest: dest, checker: checker} = state
+    %{output: output, dest: dest} = state
    parent = self()
    file = Path.expand(file)

    {pid, ref} =
      :erlang.spawn_monitor(fn ->
-        Module.ParallelChecker.put(parent, checker)
-        :erlang.put(:elixir_compiler_info, {parent, self()})
+        :erlang.put(:elixir_compiler_pid, parent)
        :erlang.put(:elixir_compiler_file, file)

        try do
@@ -386,7 +360,7 @@ defmodule Kernel.ParallelCompiler do
  defp spawn_workers(
         [],
         1,
-         [{_, pid, ref, _, _, _, _}] = waiting,
+         [{_, pid, ref, _, _, _}] = waiting,
         [%{pid: pid}] = files,
         result,
         warnings,
@@ -401,31 +375,24 @@ defmodule Kernel.ParallelCompiler do
    # There is potentially a deadlock. We will release modules with
    # the following order:
    #
-    #   1. Code.ensure_compiled/1 checks without a known definition (deadlock = soft)
-    #   2. Code.ensure_compiled/1 checks with a known definition (deadlock = soft)
-    #   3. Struct/import/require/ensure_compiled! checks without a known definition (deadlock = hard)
-    #   4. Modules without a known definition
-    #   5. Code invocation (deadlock = raise)
+    #   1. Code.ensure_compiled/1 checks (deadlock = soft)
+    #   2. Struct checks (deadlock = hard)
+    #   3. Modules without a known definition
+    #   4. Code invocation (deadlock = raise)
    #
-    # The reason for step 3 and 4 is to not treat typos as deadlocks and
-    # help developers handle those sooner. However, this can have false
-    # positives in case multiple modules are defined in the same file
-    # and the module we are waiting for is defined later on.
-    #
-    # Finally, note there is no difference between hard and raise, the
+    # In theory there is no difference between hard and raise, the
    # difference is where the raise is happening, inside the compiler
    # or in the caller.
+    cond do
+      deadlocked = deadlocked(waiting, :soft) || deadlocked(waiting, :hard) ->
+        spawn_workers(deadlocked, spawned, waiting, files, result, warnings, state)

-    deadlocked =
-      deadlocked(waiting, :soft, false) ||
-        deadlocked(waiting, :soft, true) || deadlocked(waiting, :hard, false) ||
-        without_definition(waiting, files)
+      without_definition = without_definition(waiting, files) ->
+        spawn_workers(without_definition, spawned, waiting, files, result, warnings, state)

-    if deadlocked do
-      spawn_workers(deadlocked, spawned, waiting, files, result, warnings, state)
-    else
-      errors = handle_deadlock(waiting, files)
-      {{:error, errors, warnings}, state}
+      true ->
+        errors = handle_deadlock(waiting, files)
+        {{:error, errors, warnings}, state}
    end
  end

@@ -473,45 +440,29 @@ defmodule Kernel.ParallelCompiler do
    Enum.count(result, &match?({{:module, _}, _}, &1))
  end

+  # TODO: Deprecate other returns on v1.14
  defp each_cycle_return({kind, modules, warnings}), do: {kind, modules, warnings}
-
-  defp each_cycle_return(other) do
-    IO.warn(
-      "the :each_cycle callback must return a tuple of format {:compile | :runtime, modules, warnings}"
-    )
-
-    case other do
-      {kind, modules} -> {kind, modules, []}
-      modules when is_list(modules) -> {:compile, modules, []}
-    end
-  end
+  defp each_cycle_return({kind, modules}), do: {kind, modules, []}
+  defp each_cycle_return(modules) when is_list(modules), do: {:compile, modules, []}

  # The goal of this function is to find leaves in the dependency graph,
  # i.e. to find code that depends on code that we know is not being defined.
-  # Note that not all files have been compiled yet, so they may not be in waiting.
+  # Note that not all files have been compile yet, so they may not be in waiting.
  defp without_definition(waiting, files) do
-    nilify_empty(
+    nillify_empty(
      for %{pid: pid} <- files,
-          {_, _, ref, ^pid, on, _, _} <- waiting,
-          not defining?(on, waiting),
+          {_, ^pid, ref, on, _, _} <- List.wrap(List.keyfind(waiting, pid, 1)),
+          not Enum.any?(waiting, fn {_, _, _, _, defining, _} -> on in defining end),
          do: {ref, :not_found}
    )
  end

-  defp deadlocked(waiting, type, defining?) do
-    nilify_empty(
-      for {_, _, ref, _, on, _, ^type} <- waiting,
-          defining?(on, waiting) == defining?,
-          do: {ref, :deadlock}
-    )
+  defp deadlocked(waiting, type) do
+    nillify_empty(for {_, _, ref, _, _, ^type} <- waiting, do: {ref, :deadlock})
  end

-  defp defining?(on, waiting) do
-    Enum.any?(waiting, fn {_, _, _, _, _, defining, _} -> on in defining end)
-  end
-
-  defp nilify_empty([]), do: nil
-  defp nilify_empty([_ | _] = list), do: list
+  defp nillify_empty([]), do: nil
+  defp nillify_empty([_ | _] = list), do: list

  # Wait for messages from child processes
  defp wait_for_messages(queue, spawned, waiting, files, result, warnings, state) do
@@ -524,41 +475,41 @@ defmodule Kernel.ParallelCompiler do

      {:available, kind, module} ->
        available =
-          for {^kind, _, ref, _, ^module, _defining, _deadlock} <- waiting,
+          for {^kind, _, ref, ^module, _defining, _deadlock} <- waiting,
              do: {ref, :found}

        result = Map.put(result, {kind, module}, true)
        spawn_workers(available ++ queue, spawned, waiting, files, result, warnings, state)

-      {:module_available, child, ref, file, module, binary} ->
+      {:module_available, child, ref, file, module, binary, module_map} ->
        state.each_module.(file, module, binary)

        # Release the module loader which is waiting for an ack
        send(child, {ref, :ack})

        available =
-          for {:module, _, ref, _, ^module, _defining, _deadlock} <- waiting,
+          for {:module, _, ref, ^module, _defining, _deadlock} <- waiting,
              do: {ref, :found}

-        result = Map.put(result, {:module, module}, binary)
+        result = Map.put(result, {:module, module}, {binary, module_map})
        spawn_workers(available ++ queue, spawned, waiting, files, result, warnings, state)

      # If we are simply requiring files, we do not add to waiting.
-      {:waiting, _kind, child, ref, _file_pid, _on, _defining, _deadlock} when output == :require ->
+      {:waiting, _kind, child, ref, _on, _defining, _deadlock} when output == :require ->
        send(child, {ref, :not_found})
        spawn_workers(queue, spawned, waiting, files, result, warnings, state)

-      {:waiting, kind, child_pid, ref, file_pid, on, defining, deadlock?} ->
+      {:waiting, kind, child, ref, on, defining, deadlock?} ->
        # If we already got what we were waiting for, do not put it on waiting.
        # If we're waiting on ourselves, send :found so that we can crash with
        # a better error.
        {files, waiting} =
          if Map.has_key?(result, {kind, on}) or on in defining do
-            send(child_pid, {ref, :found})
+            send(child, {ref, :found})
            {files, waiting}
          else
-            files = update_timing(files, file_pid, :compiling)
-            {files, [{kind, child_pid, ref, file_pid, on, defining, deadlock?} | waiting]}
+            files = update_timing(files, child, :compiling)
+            {files, [{kind, child, ref, on, defining, deadlock?} | waiting]}
          end

        spawn_workers(queue, spawned, waiting, files, result, warnings, state)
@@ -579,10 +530,10 @@ defmodule Kernel.ParallelCompiler do
        state = %{state | timer_ref: timer_ref}
        spawn_workers(queue, spawned, waiting, files, result, warnings, state)

-      {:warning, file, location, message} ->
+      {:warning, file, line, message} ->
        file = file && Path.absname(file)
        message = :unicode.characters_to_binary(message)
-        warning = {file, location, message}
+        warning = {file, line, message}
        wait_for_messages(queue, spawned, waiting, files, result, [warning | warnings], state)

      {:file_ok, child_pid, ref, file, lexical} ->
@@ -652,13 +603,13 @@ defmodule Kernel.ParallelCompiler do
        data = maybe_warn_long_compilation(data, state)

        if state.profile != :none do
-          compiling = to_padded_ms(data.compiling)
-          waiting = to_padded_ms(data.waiting)
-          relative = Path.relative_to_cwd(data.file)
+          compiling = System.convert_time_unit(data.compiling, :native, :millisecond)
+          waiting = System.convert_time_unit(data.waiting, :native, :millisecond)
+          extra = if waiting > 0, do: " (plus #{waiting}ms waiting)", else: ""

          IO.puts(
            :stderr,
-            "[profile] #{compiling}ms compiling + #{waiting}ms waiting for #{relative}"
+            "[profile] #{Path.relative_to_cwd(data.file)} compiled in #{compiling}ms" <> extra
          )
        end

@@ -669,13 +620,6 @@ defmodule Kernel.ParallelCompiler do
    end)
  end

-  defp to_padded_ms(time) do
-    time
-    |> System.convert_time_unit(:native, :millisecond)
-    |> Integer.to_string()
-    |> String.pad_leading(6, " ")
-  end
-
  defp discard_down(pid) do
    receive do
      {:DOWN, _, :process, ^pid, _} -> :ok
@@ -704,7 +648,7 @@ defmodule Kernel.ParallelCompiler do
        {:current_stacktrace, stacktrace} = Process.info(pid, :current_stacktrace)
        Process.exit(pid, :kill)

-        {kind, ^pid, _, _, on, _, _} = List.keyfind(waiting, pid, 1)
+        {kind, ^pid, _, on, _, _} = List.keyfind(waiting, pid, 1)
        description = "deadlocked waiting on #{kind} #{inspect(on)}"
        error = CompileError.exception(description: description, file: nil, line: nil)
        print_error(file, :error, error, stacktrace)
@@ -751,12 +695,7 @@ defmodule Kernel.ParallelCompiler do
    line = get_line(file, reason, stack)
    file = Path.absname(file)
    message = :unicode.characters_to_binary(Kernel.CLI.format_error(kind, reason, stack))
-    {file, line || 0, message}
-  end
-
-  defp get_line(_file, %{line: line, column: column}, _stack)
-       when is_integer(line) and line > 0 and is_integer(column) and column >= 0 do
-    {line, column}
+    {file, line, message}
  end

  defp get_line(_file, %{line: line}, _stack) when is_integer(line) and line > 0 do
@@ -769,8 +708,7 @@ defmodule Kernel.ParallelCompiler do
    end
  end

-  defp get_line(file, _reason, [{_, _, _, [file: expanding]}, {_, _, _, info} | _])
-       when expanding in ['expanding macro', 'expanding struct'] do
+  defp get_line(file, _reason, [{_, _, _, [file: 'expanding macro']}, {_, _, _, info} | _]) do
    if Keyword.get(info, :file) == to_charlist(Path.relative_to_cwd(file)) do
      Keyword.get(info, :line)
    end
@@ -182,7 +182,7 @@ defmodule Kernel.SpecialForms do
      <<1, 2, 3>>

  Elixir also accepts by default the segment to be a literal
-  string which expands to integers:
+  string or a literal charlist, which are by default expanded to integers:

      iex> <<0, "foo">>
      <<0, 102, 111, 111>>
@@ -201,7 +201,7 @@ defmodule Kernel.SpecialForms do
      iex> <<"foo"::utf32>>
      <<0, 0, 0, 102, 0, 0, 0, 111, 0, 0, 0, 111>>

-  Otherwise we get an `ArgumentError` when constructing the binary:
+  Otherwise we get an `ArgumentError` when construcing the binary:

      rest = "oo"
      <<102, rest>>
@@ -246,20 +246,20 @@ defmodule Kernel.SpecialForms do
      iex> {name, species}
      {"Frank", "Walrus"}

-  The size can be a variable or any valid guard expression:
+  The size can be a variable:

      iex> name_size = 5
      iex> <<name::binary-size(name_size), " the ", species::binary>> = <<"Frank the Walrus">>
      iex> {name, species}
      {"Frank", "Walrus"}

-  The size can access prior variables defined in the binary itself:
+  And the variable can be defined in the match itself (prior to its use):

      iex> <<name_size::size(8), name::binary-size(name_size), " the ", species::binary>> = <<5, "Frank the Walrus">>
      iex> {name, species}
      {"Frank", "Walrus"}

-  However, it cannot access variables defined in the match outside of the binary/bitstring:
+  However, the size cannot be defined in the match outside the binary/bitstring match:

      {name_size, <<name::binary-size(name_size), _rest::binary>>} = {5, <<"Frank the Walrus">>}
      ** (CompileError): undefined variable "name_size" in bitstring segment
@@ -365,8 +365,8 @@ defmodule Kernel.SpecialForms do
      ERL_COMPILER_OPTIONS=bin_opt_info mix compile

  To learn more about specific optimizations and performance considerations,
-  check out the
-  ["Constructing and matching binaries" chapter of the Erlang's Efficiency Guide](https://www.erlang.org/doc/efficiency_guide/binaryhandling.html).
+  check out
+  [Erlang's Efficiency Guide on handling binaries](http://www.erlang.org/doc/efficiency_guide/binaryhandling.html).
  """
  defmacro unquote(:<<>>)(args), do: error!([args])

@@ -604,12 +604,11 @@ defmodule Kernel.SpecialForms do

      import List

-  A developer can filter to import only functions, macros, or sigils
-  (which can be functions or macros) via the `:only` option:
+  A developer can filter to import only macros or functions via
+  the only option:

      import List, only: :functions
      import List, only: :macros
-      import Kernel, only: :sigils

  Alternatively, Elixir allows a developer to pass pairs of
  name/arities to `:only` or `:except` as a fine grained control
@@ -618,11 +617,9 @@ defmodule Kernel.SpecialForms do
      import List, only: [flatten: 1]
      import String, except: [split: 2]

-  Importing the same module again will erase the previous imports,
-  except when the `except` option is used, which is always exclusive
-  on a previously declared `import/2`. If there is no previous import,
-  then it applies to all functions and macros in the module. For
-  example:
+  Note that calling `except` is always exclusive on a previously
+  declared `import/2`. If there is no previous import, then it applies
+  to all functions and macros in the module. For example:

      import List, only: [flatten: 1, keyfind: 4]
      import List, except: [flatten: 1]
@@ -779,7 +776,7 @@ defmodule Kernel.SpecialForms do

      <<int::integer-little, rest::bits>> = bits

-  Read the documentation on the [Typespecs page](typespecs.md) and
+  Read the documentation on the `Typespec` page and
  `<<>>/1` for more information on typespecs and
  bitstrings respectively.
  """
@@ -1212,12 +1209,6 @@ defmodule Kernel.SpecialForms do
  reported to where `defadd` was invoked. `location: :keep` affects
  only definitions inside the quote.

-  > **Important:** do not use location: :keep if the function definition
-  > also `unquote`s some of the macro arguments. If you do so, Elixir
-  > will store the file definition of the current location but the
-  > unquoted arguments may contain line information of the macro caller,
-  > leading to erroneous stacktraces.
-
  ## Binding and unquote fragments

  Elixir quote/unquote mechanisms provide a functionality called
@@ -1316,13 +1307,11 @@ defmodule Kernel.SpecialForms do
        sum(1, value, 3)
      end

-
-  Which the argument for the `:sum` function call is not the
-  expected result:
+  Which would then return:

      {:sum, [], [1, {:value, [], Elixir}, 3]}

-  For this, we use `unquote`:
+  Which is not the expected result. For this, we use `unquote`:

      iex> value =
      ...>   quote do
@@ -1389,10 +1378,6 @@ defmodule Kernel.SpecialForms do
      iex> for n <- [1, 2, 3, 4, 5, 6], rem(n, 2) == 0, do: n
      [2, 4, 6]

-  Filters must evaluate to truthy values (everything but `nil`
-  and `false`). If a filter is falsy, then the current value is
-  discarded.
-
  Generators can also be used to filter as it removes any value
  that doesn't match the pattern on the left side of `<-`:

@@ -1413,35 +1398,6 @@ defmodule Kernel.SpecialForms do
  filters or inside the block, are not reflected outside of the
  comprehension.

-  Variable assignments inside filters must still return a truthy value,
-  otherwise values are discarded. Let's see an example. Imagine you have
-  a keyword list where the key is a programming language and the value
-  is its direct parent. Then let's try to compute the grandparent of each
-  language. You could try this:
-
-      iex> languages = [elixir: :erlang, erlang: :prolog, prolog: nil]
-      iex> for {language, parent} <- languages, grandparent = languages[parent], do: {language, grandparent}
-      [elixir: :prolog]
-
-  Given the grandparents of Erlang and Prolog were nil, those values were
-  filtered out. If you don't want this behaviour, a simple option is to
-  move the filter inside the do-block:
-
-      iex> languages = [elixir: :erlang, erlang: :prolog, prolog: nil]
-      iex> for {language, parent} <- languages do
-      ...>   grandparent = languages[parent]
-      ...>   {language, grandparent}
-      ...> end
-      [elixir: :prolog, erlang: nil, prolog: nil]
-
-  However, such option is not always available, as you may have further
-  filters. An alternative is to convert the filter into a generator by
-  wrapping the right side of `=` in a list:
-
-      iex> languages = [elixir: :erlang, erlang: :prolog, prolog: nil]
-      iex> for {language, parent} <- languages, grandparent <- [languages[parent]], do: {language, grandparent}
-      [elixir: :prolog, erlang: nil, prolog: nil]
-
  ## The `:into` and `:uniq` options

  In the examples above, the result returned by the comprehension was
@@ -1458,7 +1414,7 @@ defmodule Kernel.SpecialForms do
  The `IO` module provides streams, that are both `Enumerable` and
  `Collectable`, here is an upcase echo server using comprehensions:

-      for line <- IO.stream(), into: IO.stream() do
+      for line <- IO.stream(:stdio, :line), into: IO.stream(:stdio, :line) do
        String.upcase(line)
      end

@@ -1561,15 +1517,15 @@ defmodule Kernel.SpecialForms do
      iex> width
      nil

-  The behaviour of any expression in a clause is the same as if it was
-  written outside of `with`. For example, `=` will raise a `MatchError`
-  instead of returning the non-matched value:
+  The behaviour of any expression in a clause is the same as outside.
+  For example, `=` will raise a `MatchError` instead of returning the
+  non-matched value:

      with :foo = :bar, do: :ok
      ** (MatchError) no match of right hand side value: :bar

  As with any other function or macro call in Elixir, explicit parens can
-  also be used around the arguments before the `do`-`end` block:
+  also be used around the arguments before the `do`/`end` block:

      iex> opts = %{width: 10, height: 15}
      iex> with(
@@ -1582,8 +1538,6 @@ defmodule Kernel.SpecialForms do

  The choice between parens and no parens is a matter of preference.

-  ## Else clauses
-
  An `else` option can be given to modify what is being returned from
  `with` in the case of a failed match:

@@ -1594,60 +1548,11 @@ defmodule Kernel.SpecialForms do
      ...> else
      ...>   :error ->
      ...>     {:error, :wrong_data}
-      ...>
-      ...>   _other_error ->
-      ...>     :unexpected_error
      ...> end
      {:error, :wrong_data}

-  The `else` block works like a `case` clause: it can have multiple clauses,
-  and the first match will be used. Variables bound inside `with` (such as
-  `width` in this example) are not available in the `else` block.
-
  If an `else` block is used and there are no matching clauses, a `WithClauseError`
  exception is raised.
-
-  ### Beware!
-
-  Keep in mind that, one of potential drawback of `with` is that all
-  failure clauses are flattened into a single `else` block. For example,
-  take this code that checks if a given path points to an Elixir file
-  and that it exists before creating a backup copy:
-
-      with ".ex" <- Path.extname(path),
-           true <- File.exists?(path) do
-        backup_path = path <> ".backup"
-        File.cp!(path, backup_path)
-        {:ok, backup_path}
-      else
-        binary when is_binary(binary) ->
-          {:error, :invalid_extension}
-
-        false ->
-          {:error, :missing_file}
-      end
-
-  Note how we are having to reconstruct the result types of `Path.extname/1`
-  and `File.exists?/1` to build error messages. In this case, it is better
-  to change the with clauses to already return the desired format, like this:
-
-      with :ok <- validate_extension(path),
-           :ok <- validate_exists(path) do
-        backup_path = path <> ".backup"
-        File.cp!(path, backup_path)
-        {:ok, backup_path}
-      end
-
-      defp validate_extension(path) do
-        if Path.extname(path) == ".ex", do: :ok, else: {:error, :invalid_extension}
-      end
-
-      defp validate_exists(path) do
-        if File.exists?(path), do: :ok, else: {:error, :missing_file}
-      end
-
-  Note how the code above is better organized and clearer once we
-  make sure each clause in `with` returns a normalized format.
  """
  defmacro with(args), do: error!([args])

@@ -1693,7 +1598,7 @@ defmodule Kernel.SpecialForms do
  defmacro unquote(:__block__)(args), do: error!([args])

  @doc """
-  Capture operator. Captures or creates an anonymous function.
+  Caputure operator. Captures or creates an anonymous function.

  ## Capture

@@ -1816,21 +1721,19 @@ defmodule Kernel.SpecialForms do

  ## Examples

-      case File.read(file) do
-        {:ok, contents} when is_binary(contents) ->
-          String.split(contents, "\n")
-
-        {:error, _reason} ->
-          Logger.warning "could not find #{file}, assuming empty..."
-          []
+      case thing do
+        {:selector, i, value} when is_integer(i) ->
+          value
+        value ->
+          value
      end

-  In the example above, we match the result of `File.read/1`
-  against each clause "head" and execute the clause "body"
-  corresponding to the first clause that matches.
+  In the example above, we match `thing` against each clause "head"
+  and execute the clause "body" corresponding to the first clause
+  that matches.

-  If no clause matches, an error is raised. For this reason,
-  it may be necessary to add a final catch-all clause (like `_`)
+  If no clause matches, an error is raised.
+  For this reason, it may be necessary to add a final catch-all clause (like `_`)
  which will always match.

      x = 10
@@ -1838,7 +1741,6 @@ defmodule Kernel.SpecialForms do
      case x do
        0 ->
          "This clause won't match"
-
        _ ->
          "This clause would match any value (x = #{x})"
      end
@@ -1856,7 +1758,8 @@ defmodule Kernel.SpecialForms do
      value
      #=> unbound variable value

-  Variables in the outer context cannot be overridden either:
+  When binding variables with the same names as variables in the outer context,
+  the variables in the outer context are not affected.

      value = 7

@@ -1883,19 +1786,6 @@ defmodule Kernel.SpecialForms do
      end
      #=> "Will match"

-  ## Using guards to match against multiple values
-
-  While it is not possible to match against multiple patterns in a single
-  clause, it's possible to match against multiple values by using guards:
-
-      case data do
-        value when value in [:one, :two] ->
-          "#{value} has been matched"
-
-        :three ->
-          "three has been matched"
-      end
-
  """
  defmacro case(condition, clauses), do: error!([condition, clauses])

@@ -2093,25 +1983,6 @@ defmodule Kernel.SpecialForms do
        File.rm("tmp/story.txt")
      end

-  Although `after` clauses are invoked whether or not there was an error, they do not
-  modify the return value. All of the following examples return `:return_me`:
-
-      try do
-        :return_me
-      after
-        IO.puts("I will be printed")
-        :not_returned
-      end
-
-      try do
-        raise "boom"
-      rescue
-        _ -> :return_me
-      after
-        IO.puts("I will be printed")
-        :not_returned
-      end
-
  ## `else` clauses

  `else` clauses allow the result of the body passed to `try/1` to be pattern
@@ -104,7 +104,7 @@ defmodule Kernel.Typespec do
  @doc """
  Defines a typespec.

-  Invoked by `@/1` expansion.
+  Invoked by `Kernel.@/1` expansion.
  """
  def deftypespec(:spec, expr, _line, _file, module, pos) do
    {_set, bag} = :elixir_module.data_tables(module)
@@ -194,14 +194,14 @@ defmodule Kernel.Typespec do

  defp get_doc_info(set, attr, line) do
    case :ets.take(set, attr) do
-      [{^attr, {line, doc}, _, _}] -> {line, doc}
+      [{^attr, {line, doc}, _}] -> {line, doc}
      [] -> {line, nil}
    end
  end

  defp get_doc_meta(spec_meta, doc_kind, set) do
    case :ets.take(set, {doc_kind, :meta}) do
-      [{{^doc_kind, :meta}, metadata}] -> Map.merge(metadata, spec_meta)
+      [{{^doc_kind, :meta}, metadata, _}] -> Map.merge(metadata, spec_meta)
      [] -> spec_meta
    end
  end
@@ -553,7 +553,9 @@ defmodule Kernel.Typespec do
  end

  defp typespec({:%, _, [name, {:%{}, meta, fields}]}, vars, caller, state) do
-    module = Macro.expand(name, %{caller | function: {:__info__, 1}})
+    # We cannot set a function name to avoid tracking
+    # as a compile time dependency, because for structs it actually is one.
+    module = Macro.expand(name, caller)

    struct =
      module
@@ -567,10 +569,7 @@ defmodule Kernel.Typespec do

    types =
      :lists.map(
-        fn
-          {:__exception__ = field, true} -> {field, Keyword.get(fields, field, true)}
-          {field, _} -> {field, Keyword.get(fields, field, quote(do: term()))}
-        end,
+        fn {field, _} -> {field, Keyword.get(fields, field, quote(do: term()))} end,
        :lists.sort(struct)
      )

@@ -578,7 +577,7 @@ defmodule Kernel.Typespec do
      unless Keyword.has_key?(struct, field) do
        compile_error(
          caller,
-          "undefined field #{inspect(field)} on struct #{inspect(module)}"
+          "undefined field #{inspect(field)} on struct #{Macro.to_string(name)}"
        )
      end
    end
@@ -644,7 +643,10 @@ defmodule Kernel.Typespec do
  end

  defp typespec({:__aliases__, _, _} = alias, vars, caller, state) do
-    typespec(expand_remote(alias, caller), vars, caller, state)
+    # We set a function name to avoid tracking
+    # aliases in typespecs as compile time dependencies.
+    atom = Macro.expand(alias, %{caller | function: {:typespec, 0}})
+    typespec(atom, vars, caller, state)
  end

  # Handle funs
@@ -681,20 +683,10 @@ defmodule Kernel.Typespec do
    end
  end

-  defp typespec({:"::", meta, [left, right]}, vars, caller, state) do
+  defp typespec({:"::", meta, [left, right]} = expr, vars, caller, state) do
    message =
-      "invalid type annotation. The left side of :: must be a variable, got: #{Macro.to_string(left)}"
-
-    message =
-      case left do
-        {:|, _, _} ->
-          message <>
-            ". Note \"left | right :: ann\" is the same as \"(left | right) :: ann\". " <>
-            "To solve this, use parentheses around the union operands: \"left | (right :: ann)\""
-
-        _ ->
-          message
-      end
+      "invalid type annotation. When using the | operator to represent the union of types, " <>
+        "make sure to wrap type annotations in parentheses: #{Macro.to_string(expr)}"

    # TODO: Make this an error on v2.0, and remove the code below and
    # the :undefined_type_error_enabled? key from the state
@@ -742,7 +734,9 @@ defmodule Kernel.Typespec do

  # Handle remote calls
  defp typespec({{:., meta, [remote, name]}, _, args} = orig, vars, caller, state) do
-    remote = expand_remote(remote, caller)
+    # We set a function name to avoid tracking
+    # aliases in typespecs as compile time dependencies.
+    remote = Macro.expand(remote, %{caller | function: {:typespec, 0}})

    cond do
      not is_atom(remote) ->
@@ -913,25 +907,6 @@ defmodule Kernel.Typespec do

  ## Helpers

-  # This is a backport of Macro.expand/2 because we want to expand
-  # aliases but we don't them to become compile-time references.
-  defp expand_remote({:__aliases__, _, _} = alias, env) do
-    case :elixir_aliases.expand(alias, env) do
-      receiver when is_atom(receiver) ->
-        receiver
-
-      aliases ->
-        aliases = :lists.map(&Macro.expand_once(&1, env), aliases)
-
-        case :lists.all(&is_atom/1, aliases) do
-          true -> :elixir_aliases.concat(aliases)
-          false -> alias
-        end
-    end
-  end
-
-  defp expand_remote(other, env), do: Macro.expand(other, env)
-
  defp compile_error(caller, desc) do
    raise CompileError, file: caller.file, line: caller.line, description: desc
  end
@@ -1033,11 +1008,7 @@ defmodule Kernel.Typespec do
          :elixir_errors.erl_warn(caller.line, caller.file, warning)

        {_, :used_once} ->
-          compile_error(
-            caller,
-            "type variable #{name} is used only once. Type variables in typespecs " <>
-              "must be referenced at least twice, otherwise it is equivalent to term()"
-          )
+          compile_error(caller, "type variable #{name} is unused")

        _ ->
          :ok
@@ -22,52 +22,16 @@ defmodule Kernel.Utils do
  defp destructure_nil(count), do: [nil | destructure_nil(count - 1)]

  @doc """
-  Callback for defdelegate entry point.
+  Callback for defdelegate.
  """
-  def defdelegate_all(funs, opts, env) do
-    to = Keyword.get(opts, :to) || raise ArgumentError, "expected to: to be given as argument"
-    as = Keyword.get(opts, :as)
-
-    if to == env.module and is_nil(as) do
-      raise ArgumentError,
-            "defdelegate function is calling itself, which will lead to an infinite loop. You should either change the value of the :to option or specify the :as option"
-    end
-
-    if is_list(funs) do
-      IO.warn(
-        "passing a list to Kernel.defdelegate/2 is deprecated, please define each delegate separately",
-        Macro.Env.stacktrace(env)
-      )
-    end
-
-    if Keyword.has_key?(opts, :append_first) do
-      IO.warn(
-        "Kernel.defdelegate/2 :append_first option is deprecated",
-        Macro.Env.stacktrace(env)
-      )
-    end
-
-    to
-  end
-
-  @doc """
-  Callback for each function in defdelegate.
-  """
-  def defdelegate_each(fun, opts) when is_list(opts) do
+  def defdelegate(fun, opts) when is_list(opts) do
    # TODO: Remove on v2.0
    append_first? = Keyword.get(opts, :append_first, false)

    {name, args} =
-      case fun do
-        {:when, _, [_left, right]} ->
-          raise ArgumentError,
-                "guards are not allowed in defdelegate/2, got: when #{Macro.to_string(right)}"
-
-        _ ->
-          case Macro.decompose_call(fun) do
-            {_, _} = pair -> pair
-            _ -> raise ArgumentError, "invalid syntax in defdelegate #{Macro.to_string(fun)}"
-          end
+      case Macro.decompose_call(fun) do
+        {_, _} = pair -> pair
+        _ -> raise ArgumentError, "invalid syntax in defdelegate #{Macro.to_string(fun)}"
      end

    as = Keyword.get(opts, :as, name)
@@ -100,15 +64,7 @@ defmodule Kernel.Utils do
  @doc """
  Callback for defstruct.
  """
-  def defstruct(module, fields, bootstrapped?) do
-    {set, bag} = :elixir_module.data_tables(module)
-
-    if :ets.member(set, :__struct__) do
-      raise ArgumentError,
-            "defstruct has already been called for " <>
-              "#{Kernel.inspect(module)}, defstruct can only be called once per module"
-    end
-
+  def defstruct(module, fields) do
    case fields do
      fs when is_list(fs) ->
        :ok
@@ -120,7 +76,7 @@ defmodule Kernel.Utils do
    mapper = fn
      {key, val} when is_atom(key) ->
        try do
-          :elixir_quote.escape(val, false, :none)
+          Macro.escape(val)
        rescue
          e in [ArgumentError] ->
            raise ArgumentError, "invalid value for struct field #{key}, " <> Exception.message(e)
@@ -136,20 +92,7 @@ defmodule Kernel.Utils do
    end

    fields = :lists.map(mapper, fields)
-
-    enforce_keys =
-      case :ets.lookup(set, :enforce_keys) do
-        [{_, enforce_keys, _, _}] when is_list(enforce_keys) ->
-          :ets.update_element(set, :enforce_keys, {3, :used})
-          enforce_keys
-
-        [{_, enforce_key, _, _}] ->
-          :ets.update_element(set, :enforce_keys, {3, :used})
-          [enforce_key]
-
-        [] ->
-          []
-      end
+    enforce_keys = List.wrap(Module.get_attribute(module, :enforce_keys))

    # TODO: Make it raise on v2.0
    warn_on_duplicate_struct_key(:lists.keysort(1, fields))
@@ -163,68 +106,9 @@ defmodule Kernel.Utils do
    end

    :lists.foreach(foreach, enforce_keys)
+
    struct = :maps.put(:__struct__, module, :maps.from_list(fields))
-
-    body =
-      case bootstrapped? do
-        true ->
-          case enforce_keys do
-            [] ->
-              quote do
-                Enum.reduce(kv, @__struct__, fn {key, val}, map ->
-                  %{map | key => val}
-                end)
-              end
-
-            _ ->
-              quote do
-                {map, keys} =
-                  Enum.reduce(kv, {@__struct__, unquote(enforce_keys)}, fn
-                    {key, val}, {map, keys} ->
-                      {%{map | key => val}, List.delete(keys, key)}
-                  end)
-
-                case keys do
-                  [] ->
-                    map
-
-                  _ ->
-                    raise ArgumentError,
-                          "the following keys must also be given when building " <>
-                            "struct #{inspect(__MODULE__)}: #{inspect(keys)}"
-                end
-              end
-          end
-
-        false ->
-          quote do
-            :lists.foldl(
-              fn {key, val}, acc -> %{acc | key => val} end,
-              @__struct__,
-              kv
-            )
-          end
-      end
-
-    case enforce_keys -- :maps.keys(struct) do
-      [] ->
-        # The __struct__ field is used for expansion and for loading remote structs
-        :ets.insert(set, {:__struct__, struct, nil, []})
-
-        # Store all field metadata to go into __info__(:struct)
-        mapper = fn {key, val} ->
-          %{field: key, default: val, required: :lists.member(key, enforce_keys)}
-        end
-
-        :ets.insert(set, {{:elixir, :struct}, :lists.map(mapper, fields)})
-        derive = :lists.map(fn {_, value} -> value end, :ets.take(bag, {:accumulate, :derive}))
-        {struct, :lists.reverse(derive), quote(do: kv), body}
-
-      error_keys ->
-        raise ArgumentError,
-              "@enforce_keys required keys (#{inspect(error_keys)}) that are not defined in defstruct: " <>
-                "#{inspect(fields)}"
-    end
+    {struct, enforce_keys, Module.get_attribute(module, :derive)}
  end

  defp warn_on_duplicate_struct_key([]) do
@@ -244,9 +128,9 @@ defmodule Kernel.Utils do
  Announcing callback for defstruct.
  """
  def announce_struct(module) do
-    case :erlang.get(:elixir_compiler_info) do
+    case :erlang.get(:elixir_compiler_pid) do
      :undefined -> :ok
-      {pid, _} -> send(pid, {:available, :struct, module})
+      pid -> send(pid, {:available, :struct, module})
    end
  end

@@ -326,12 +210,12 @@ defmodule Kernel.Utils do
  def defguard(args, expr, env) do
    {^args, vars} = extract_refs_from_args(args)
    env = :elixir_env.with_vars(%{env | context: :guard}, vars)
-    {expr, _, _} = :elixir_expand.expand(expr, :elixir_env.env_to_ex(env), env)
+    {expr, _scope} = :elixir_expand.expand(expr, env)

    quote do
      case Macro.Env.in_guard?(__CALLER__) do
        true -> unquote(literal_quote(unquote_every_ref(expr, vars)))
-        false -> unquote(literal_quote(unquote_refs_once(expr, vars, env.module)))
+        false -> unquote(literal_quote(unquote_refs_once(expr, vars)))
      end
    end
  end
@@ -361,7 +245,7 @@ defmodule Kernel.Utils do
  end

  # Prefaces `guard` with unquoted versions of `refs`.
-  defp unquote_refs_once(guard, refs, module) do
+  defp unquote_refs_once(guard, refs) do
    {guard, used_refs} =
      Macro.postwalk(guard, %{}, fn
        {ref, meta, context} = var, acc when is_atom(ref) and is_atom(context) ->
@@ -374,8 +258,8 @@ defmodule Kernel.Utils do
                  {new_var, acc}

                %{} ->
-                  generated = String.to_atom("arg" <> Integer.to_string(map_size(acc) + 1))
-                  new_var = Macro.unique_var(generated, module)
+                  generated = String.to_atom("arg" <> Integer.to_string(map_size(acc)))
+                  new_var = Macro.var(generated, Elixir)
                  {new_var, Map.put(acc, pair, {new_var, var})}
              end

@@ -13,43 +13,45 @@ defmodule Keyword do

      [{:exit_on_close, true}, {:active, :once}, {:packet_size, 1024}]

-  Elixir provides a special and more concise syntax for keyword lists:
+  Elixir provides a special and more concise syntax for keyword lists
+  that looks like this:

      [exit_on_close: true, active: :once, packet_size: 1024]

-  The two syntaxes return the exact same value.
-
-  A *key* can be any atom, consisting of Unicode letters, numbers,
-  an underscore or the `@` sign. If the *key* should have any other
-  characters, such as spaces, you can wrap it in quotes:
+  The two syntaxes are completely equivalent. Like atoms, keyword
+  lists keys must be composed of Unicode characters such as letters,
+  numbers, underscore, and `@`. If the keyword has a character that
+  does not belong to the category above, such as spaces, you can wrap
+  it in quotes:

      iex> ["exit on close": true]
      ["exit on close": true]

-  Wrapping an atom in quotes does not make it a string. Keyword list
-  *keys* are always atoms. Quotes should only be used when necessary
-  or Elixir will issue a warning.
+  Wrapping a keyword in quotes does not make it a string. Keyword lists
+  keys are always atoms. If you use quotes around the key when quoting
+  is not necessary, Elixir will warn.

  ## Duplicate keys and ordering

-  A keyword may have duplicate keys so it is not strictly a key-value
-  data type. However most of the functions in this module work on a
-  key-value structure and behave similar to the functions you would
-  find in the `Map` module. For example, `Keyword.get/3` will get the first
-  entry matching the given key, regardless if duplicate entries exist.
-  Similarly, `Keyword.put/3` and `Keyword.delete/2` ensure all duplicate
+  A keyword may have duplicated keys so it is not strictly a key-value
+  data type. However most of the functions in this module behave exactly
+  as a key-value so they work similarly to the functions you would find
+  in the `Map` module. For example, `Keyword.get/3` will get the first
+  entry matching the given key, regardless if duplicated entries exist.
+  Similarly, `Keyword.put/3` and `Keyword.delete/2` ensure all duplicated
  entries for a given key are removed when invoked. Note, however, that
  keyword list operations need to traverse the whole list in order to find
  keys, so these operations are slower than their map counterparts.

-  A handful of functions exist to handle duplicate keys, for example,
+  A handful of functions exist to handle duplicated keys, for example,
  `get_values/2` returns all values for a given key and `delete_first/2`
-  deletes just the first entry of the existing ones.
+  deletes just one of the existing entries.

-  Even though lists preserve the existing order, the functions in
+  Even though lists preserve the user ordering, the functions in
  `Keyword` do not guarantee any ordering. For example, if you invoke
-  `Keyword.put(opts, new_key, new_value)`, there is no guarantee for
-  where `new_key` will be added to (the front, the end or anywhere else).
+  `Keyword.put(opts, new_key, new_value)`, there is no guarantee to
+  where `new_key` will be added (to the front, to the end, or
+  anywhere else).

  Given ordering is not guaranteed, it is not recommended to pattern
  match on keyword lists either. For example, a function such as:
@@ -65,7 +67,7 @@ defmodule Keyword do
      my_function([another_key: :bar, some_key: :foo])

  Most of the functions in this module work in linear time. This means
-  that the time it takes to perform an operation grows at the same
+  that, the time it takes to perform an operation grows at the same
  rate as the length of the list.

  ## Call syntax
@@ -81,8 +83,8 @@ defmodule Keyword do

      String.split("1-0", "-", trim: true, parts: 2)

-  Since tuples, lists and maps are treated similarly to function
-  arguments in Elixir syntax, this property is also available to them:
+  Since tuples, lists, maps, and others are treated the same as function
+  calls in Elixir syntax, this property is also available to them:

      iex> {1, 2, foo: :bar}
      {1, 2, [{:foo, :bar}]}
@@ -92,7 +94,6 @@ defmodule Keyword do

      iex> %{1 => 2, foo: :bar}
      %{1 => 2, :foo => :bar}
-
  """

  @compile :inline_list_funcs
@@ -104,24 +105,7 @@ defmodule Keyword do
  @type t(value) :: [{key, value}]

  @doc """
-  Builds a keyword from the given `keys` and the fixed `value`.
-
-  ## Examples
-
-      iex> Keyword.from_keys([:foo, :bar, :baz], :atom)
-      [foo: :atom, bar: :atom, baz: :atom]
-
-  """
-  @doc since: "1.14.0"
-  @spec from_keys([key], value) :: t(value)
-  def from_keys(keys, value) when is_list(keys) do
-    :lists.map(&{&1, value}, keys)
-  end
-
-  @doc """
-  Returns `true` if `term` is a keyword list, otherwise `false`.
-
-  When `term` is a list it is traversed to the end.
+  Returns `true` if `term` is a keyword list; otherwise returns `false`.

  ## Examples

@@ -161,7 +145,7 @@ defmodule Keyword do
  @doc """
  Creates a keyword list from an enumerable.

-  Removes duplicate entries and the last one prevails.
+  Duplicated entries are removed, the latest one prevails.
  Unlike `Enum.into(enumerable, [])`, `Keyword.new(enumerable)`
  guarantees the keys are unique.

@@ -174,7 +158,7 @@ defmodule Keyword do
      [a: 3]

  """
-  @spec new(Enumerable.t()) :: t
+  @spec new(Enum.t()) :: t
  def new(pairs) do
    new(pairs, fn pair -> pair end)
  end
@@ -182,7 +166,7 @@ defmodule Keyword do
  @doc """
  Creates a keyword list from an enumerable via the transformation function.

-  Removes duplicate entries and the last one prevails.
+  Duplicated entries are removed, the latest one prevails.
  Unlike `Enum.into(enumerable, [], fun)`,
  `Keyword.new(enumerable, fun)` guarantees the keys are unique.

@@ -192,7 +176,7 @@ defmodule Keyword do
      [a: :a, b: :b]

  """
-  @spec new(Enumerable.t(), (term -> {key, value})) :: t
+  @spec new(Enum.t(), (term -> {key, value})) :: t
  def new(pairs, transform) when is_function(transform, 1) do
    fun = fn el, acc ->
      {k, v} = transform.(el)
@@ -203,166 +187,12 @@ defmodule Keyword do
  end

  @doc """
-  Ensures the given `keyword` has only the keys given in `values`.
+  Gets the value for a specific `key`.

-  The second argument must be a list of atoms, specifying
-  a given key, or tuples specifying a key and a default value.
+  If `key` does not exist, return the default value
+  (`nil` if no default value).

-  If the keyword list has only the given keys, it returns
-  `{:ok, keyword}` with default values applied. Otherwise it
-  returns `{:error, invalid_keys}` with invalid keys.
-
-  See also: `validate!/2`.
-
-  ## Examples
-
-      iex> {:ok, result} = Keyword.validate([], [one: 1, two: 2])
-      iex> Enum.sort(result)
-      [one: 1, two: 2]
-
-      iex> {:ok, result} = Keyword.validate([two: 3], [one: 1, two: 2])
-      iex> Enum.sort(result)
-      [one: 1, two: 3]
-
-  If atoms are given, they are supported as keys but do not
-  provide a default value:
-
-      iex> {:ok, result} = Keyword.validate([], [:one, two: 2])
-      iex> Enum.sort(result)
-      [two: 2]
-
-      iex> {:ok, result} = Keyword.validate([one: 1], [:one, two: 2])
-      iex> Enum.sort(result)
-      [one: 1, two: 2]
-
-  Passing unknown keys returns an error:
-
-      iex> Keyword.validate([three: 3, four: 4], [one: 1, two: 2])
-      {:error, [:four, :three]}
-
-  Passing the same key multiple times also errors:
-
-      iex> Keyword.validate([one: 1, two: 2, one: 1], [:one, :two])
-      {:error, [:one]}
-
-  """
-  @doc since: "1.13.0"
-  @spec validate(keyword(), values :: [atom() | {atom(), term()}]) ::
-          {:ok, keyword()} | {:error, [atom]}
-  def validate(keyword, values) when is_list(keyword) and is_list(values) do
-    validate(keyword, values, [], [], [])
-  end
-
-  defp validate([{key, _} = pair | keyword], values1, values2, acc, bad_keys) when is_atom(key) do
-    case find_key!(key, values1, values2) do
-      {values1, values2} ->
-        validate(keyword, values1, values2, [pair | acc], bad_keys)
-
-      :error ->
-        case find_key!(key, values2, values1) do
-          {values1, values2} ->
-            validate(keyword, values1, values2, [pair | acc], bad_keys)
-
-          :error ->
-            validate(keyword, values1, values2, acc, [key | bad_keys])
-        end
-    end
-  end
-
-  defp validate([], values1, values2, acc, []) do
-    {:ok, move_pairs!(values1, move_pairs!(values2, acc))}
-  end
-
-  defp validate([], _values1, _values2, _acc, bad_keys) do
-    {:error, bad_keys}
-  end
-
-  defp validate([pair | _], _values1, _values2, _acc, []) do
-    raise ArgumentError,
-          "expected a keyword list as first argument, got invalid entry: #{inspect(pair)}"
-  end
-
-  defp find_key!(key, [key | rest], acc), do: {rest, acc}
-  defp find_key!(key, [{key, _} | rest], acc), do: {rest, acc}
-  defp find_key!(key, [head | tail], acc), do: find_key!(key, tail, [head | acc])
-  defp find_key!(_key, [], _acc), do: :error
-
-  defp move_pairs!([key | rest], acc) when is_atom(key),
-    do: move_pairs!(rest, acc)
-
-  defp move_pairs!([{key, _} = pair | rest], acc) when is_atom(key),
-    do: move_pairs!(rest, [pair | acc])
-
-  defp move_pairs!([], acc),
-    do: acc
-
-  defp move_pairs!([other | _], _) do
-    raise ArgumentError,
-          "expected the second argument to be a list of atoms or tuples, got: #{inspect(other)}"
-  end
-
-  @doc """
-  Similar to `validate/2` but returns the keyword or raises an error.
-
-  ## Examples
-
-      iex> Keyword.validate!([], [one: 1, two: 2]) |> Enum.sort()
-      [one: 1, two: 2]
-      iex> Keyword.validate!([two: 3], [one: 1, two: 2]) |> Enum.sort()
-      [one: 1, two: 3]
-
-  If atoms are given, they are supported as keys but do not
-  provide a default value:
-
-      iex> Keyword.validate!([], [:one, two: 2]) |> Enum.sort()
-      [two: 2]
-      iex> Keyword.validate!([one: 1], [:one, two: 2]) |> Enum.sort()
-      [one: 1, two: 2]
-
-  Passing unknown keys raises an error:
-
-      iex> Keyword.validate!([three: 3], [one: 1, two: 2])
-      ** (ArgumentError) unknown keys [:three] in [three: 3], the allowed keys are: [:one, :two]
-
-  Passing the same key multiple times also errors:
-
-      iex> Keyword.validate!([one: 1, two: 2, one: 1], [:one, :two])
-      ** (ArgumentError) duplicate keys [:one] in [one: 1, two: 2, one: 1]
-
-  """
-  @doc since: "1.13.0"
-  @spec validate!(keyword(), values :: [atom() | {atom(), term()}]) :: keyword()
-  def validate!(keyword, values) do
-    case validate(keyword, values) do
-      {:ok, kw} ->
-        kw
-
-      {:error, invalid_keys} ->
-        keys =
-          for value <- values,
-              do: if(is_atom(value), do: value, else: elem(value, 0))
-
-        message =
-          case Enum.split_with(invalid_keys, &(&1 in keys)) do
-            {_, [_ | _] = unknown} ->
-              "unknown keys #{inspect(unknown)} in #{inspect(keyword)}, " <>
-                "the allowed keys are: #{inspect(keys)}"
-
-            {[_ | _] = known, _} ->
-              "duplicate keys #{inspect(known)} in #{inspect(keyword)}"
-          end
-
-        raise ArgumentError, message
-    end
-  end
-
-  @doc """
-  Gets the value under the given `key`.
-
-  Returns the default value if `key` does not exist
-  (`nil` if no default value is provided).
-
-  If duplicate entries exist, it returns the first one.
+  If duplicated entries exist, the first one is returned.
  Use `get_values/2` to retrieve all entries.

  ## Examples
@@ -376,7 +206,7 @@ defmodule Keyword do
      iex> Keyword.get([a: 1], :b, 3)
      3

-  With duplicate keys:
+  With duplicated keys:

      iex> Keyword.get([a: 1, a: 2], :a, 3)
      1
@@ -393,14 +223,14 @@ defmodule Keyword do
  end

  @doc """
-  Gets the value under the given `key`.
+  Gets the value for a specific `key`.

  If `key` does not exist, lazily evaluates `fun` and returns its result.

  This is useful if the default value is very expensive to calculate or
-  generally difficult to set up and tear down again.
+  generally difficult to setup and teardown again.

-  If duplicate entries exist, it returns the first one.
+  If duplicated entries exist, the first one is returned.
  Use `get_values/2` to retrieve all entries.

  ## Examples
@@ -428,14 +258,14 @@ defmodule Keyword do
  @doc """
  Gets the value from `key` and updates it, all in one pass.

-  The `fun` argument receives the value of `key` (or `nil` if `key`
+  This `fun` argument receives the value of `key` (or `nil` if `key`
  is not present) and must return a two-element tuple: the current value
  (the retrieved value, which can be operated on before being returned)
  and the new value to be stored under `key`. The `fun` may also
  return `:pop`, implying the current value shall be removed from the
  keyword list and returned.

-  Returns a tuple that contains the current value returned by
+  The returned value is a tuple with the current value returned by
  `fun` and a new keyword list with the updated value under `key`.

  ## Examples
@@ -450,11 +280,6 @@ defmodule Keyword do
      ...> end)
      {nil, [b: "new value!", a: 1]}

-      iex> Keyword.get_and_update([a: 2], :a, fn number ->
-      ...>   {2 * number, 3 * number}
-      ...> end)
-      {4, [a: 6]}
-
      iex> Keyword.get_and_update([a: 1], :a, fn _ -> :pop end)
      {1, []}

@@ -462,8 +287,8 @@ defmodule Keyword do
      {nil, [a: 1]}

  """
-  @spec get_and_update(t, key, (value | nil -> {current_value, new_value :: value} | :pop)) ::
-          {current_value, new_keywords :: t}
+  @spec get_and_update(t, key, (value -> {current_value, new_value :: value} | :pop)) ::
+          {current_value, value}
        when current_value: value
  def get_and_update(keywords, key, fun)
      when is_list(keywords) and is_atom(key),
@@ -498,15 +323,15 @@ defmodule Keyword do
  end

  @doc """
-  Gets the value under `key` and updates it. Raises if there is no `key`.
+  Gets the value from `key` and updates it. Raises if there is no `key`.

-  The `fun` argument receives the value under `key` and must return a
+  This `fun` argument receives the value of `key` and must return a
  two-element tuple: the current value (the retrieved value, which can be
  operated on before being returned) and the new value to be stored under
  `key`.

-  Returns a tuple that contains the current value returned by
-  `fun` and a new keyword list with the updated value under `key`.
+  The returned value is a tuple with the current value returned by `fun` and a new
+  keyword list with the updated value under `key`.

  ## Examples

@@ -526,8 +351,8 @@ defmodule Keyword do
      {1, []}

  """
-  @spec get_and_update!(t, key, (value | nil -> {current_value, new_value :: value} | :pop)) ::
-          {current_value, new_keywords :: t}
+  @spec get_and_update!(t, key, (value -> {current_value, new_value :: value} | :pop)) ::
+          {current_value, t}
        when current_value: value
  def get_and_update!(keywords, key, fun) do
    get_and_update!(keywords, key, fun, [])
@@ -551,13 +376,13 @@ defmodule Keyword do
  end

  defp get_and_update!([], key, _fun, acc) when is_atom(key) do
-    raise KeyError, key: key, term: acc
+    raise(KeyError, key: key, term: acc)
  end

  @doc """
  Fetches the value for a specific `key` and returns it in a tuple.

-  If the `key` does not exist, it returns `:error`.
+  If the `key` does not exist, returns `:error`.

  ## Examples

@@ -578,7 +403,7 @@ defmodule Keyword do
  @doc """
  Fetches the value for specific `key`.

-  If the `key` does not exist, it raises a `KeyError`.
+  If `key` does not exist, a `KeyError` is raised.

  ## Examples

@@ -592,12 +417,12 @@ defmodule Keyword do
  def fetch!(keywords, key) when is_list(keywords) and is_atom(key) do
    case :lists.keyfind(key, 1, keywords) do
      {^key, value} -> value
-      false -> raise KeyError, key: key, term: keywords
+      false -> raise(KeyError, key: key, term: keywords)
    end
  end

  @doc """
-  Gets all values under a specific `key`.
+  Gets all values for a specific `key`.

  ## Examples

@@ -621,7 +446,7 @@ defmodule Keyword do
  @doc """
  Returns all keys from the keyword list.

-  Keeps duplicate keys in the resulting list of keys.
+  Duplicated keys appear duplicated in the final list of keys.

  ## Examples

@@ -637,24 +462,26 @@ defmodule Keyword do
  """
  @spec keys(t) :: [key]
  def keys(keywords) when is_list(keywords) do
-    :lists.map(
-      fn
-        {key, _} when is_atom(key) -> key
-        element -> throw(element)
-      end,
-      keywords
-    )
-  catch
-    element ->
-      raise ArgumentError,
-            "expected a keyword list, but an entry in the list is not a two-element tuple " <>
-              "with an atom as its first element, got: #{inspect(element)}"
+    try do
+      :lists.map(
+        fn
+          {key, _} when is_atom(key) -> key
+          element -> throw(element)
+        end,
+        keywords
+      )
+    catch
+      element ->
+        raise ArgumentError,
+              "expected a keyword list, but an entry in the list is not a two-element tuple with an atom as its first element, " <>
+                "got: #{inspect(element)}"
+    end
  end

  @doc """
  Returns all values from the keyword list.

-  Keeps values from duplicate keys in the resulting list of values.
+  Values from duplicated keys will be kept in the final list of values.

  ## Examples

@@ -691,11 +518,11 @@ defmodule Keyword do
  end

  @doc """
-  Deletes the entries in the keyword list under a specific `key`.
+  Deletes the entries in the keyword list for a specific `key`.

-  If the `key` does not exist, it returns the keyword list unchanged.
+  If the `key` does not exist, returns the keyword list unchanged.
  Use `delete_first/2` to delete just the first entry in case of
-  duplicate keys.
+  duplicated keys.

  ## Examples

@@ -721,9 +548,9 @@ defmodule Keyword do
  defp delete_key([], _key), do: []

  @doc """
-  Deletes the first entry in the keyword list under a specific `key`.
+  Deletes the first entry in the keyword list for a specific `key`.

-  If the `key` does not exist, it returns the keyword list unchanged.
+  If the `key` does not exist, returns the keyword list unchanged.

  ## Examples

@@ -754,10 +581,10 @@ defmodule Keyword do
  end

  @doc """
-  Puts the given `value` under the specified `key`.
+  Puts the given `value` under `key`.

-  If a value under `key` already exists, it overrides the value
-  and removes all duplicate entries.
+  If a previous value is already stored, all entries are
+  removed and the value is overridden.

  ## Examples

@@ -779,19 +606,19 @@ defmodule Keyword do
  in keyword list unless `key` is already present.

  This is useful if the value is very expensive to calculate or
-  generally difficult to set up and tear down again.
+  generally difficult to setup and teardown again.

  ## Examples

      iex> keyword = [a: 1]
      iex> fun = fn ->
      ...>   # some expensive operation here
-      ...>   13
+      ...>   3
      ...> end
      iex> Keyword.put_new_lazy(keyword, :a, fun)
      [a: 1]
      iex> Keyword.put_new_lazy(keyword, :b, fun)
-      [b: 13, a: 1]
+      [b: 3, a: 1]

  """
  @spec put_new_lazy(t, key, (() -> value)) :: t
@@ -804,7 +631,8 @@ defmodule Keyword do
  end

  @doc """
-  Puts the given `value` under `key`, unless the entry `key` already exists.
+  Puts the given `value` under `key` unless the entry `key`
+  already exists.

  ## Examples

@@ -825,8 +653,8 @@ defmodule Keyword do
  @doc """
  Puts a value under `key` only if the `key` already exists in `keywords`.

-  In case a key exists multiple times in the keyword list,
-  it removes later occurrences.
+  In the case a value is stored multiple times in the keyword list,
+  later occurrences are removed.

  ## Examples

@@ -858,7 +686,7 @@ defmodule Keyword do
  @doc """
  Puts a value under `key` only if the `key` already exists in `keywords`.

-  If `key` is not present in `keywords`, it raises a `KeyError`.
+  If `key` is not present in `keywords`, a `KeyError` exception is raised.

  ## Examples

@@ -886,50 +714,13 @@ defmodule Keyword do
  end

  defp replace!([], key, _value, original) do
-    raise KeyError, key: key, term: original
+    raise(KeyError, key: key, term: original)
  end

-  @doc """
-  Replaces the value under `key` using the given function only if
-  `key` already exists in `keywords`.
-
-  In comparison to `replace/3`, this can be useful when it's expensive to calculate the value.
-
-  If `key` does not exist, the original keyword list is returned unchanged.
-
-  ## Examples
-
-      iex> Keyword.replace_lazy([a: 1, b: 2], :a, fn v -> v * 4 end)
-      [a: 4, b: 2]
-
-      iex> Keyword.replace_lazy([a: 2, b: 2, a: 1], :a, fn v -> v * 4 end)
-      [a: 8, b: 2]
-
-      iex> Keyword.replace_lazy([a: 1, b: 2], :c, fn v -> v * 4 end)
-      [a: 1, b: 2]
-
-  """
-  @doc since: "1.14.0"
-  @spec replace_lazy(t, key, (existing_value :: value -> new_value :: value)) :: t
-  def replace_lazy(keywords, key, fun)
-      when is_list(keywords) and is_atom(key) and is_function(fun, 1) do
-    do_replace_lazy(keywords, key, fun)
-  end
-
-  defp do_replace_lazy([{key, value} | keywords], key, fun) do
-    [{key, fun.(value)} | delete(keywords, key)]
-  end
-
-  defp do_replace_lazy([{_, _} = e | keywords], key, fun) do
-    [e | do_replace_lazy(keywords, key, fun)]
-  end
-
-  defp do_replace_lazy([], _key, _value), do: []
-
  @doc """
  Checks if two keywords are equal.

-  Considers two keywords to be equal if they contain
+  Two keywords are considered to be equal if they contain
  the same keys and those keys contain the same values.

  ## Examples
@@ -941,25 +732,19 @@ defmodule Keyword do
      iex> Keyword.equal?([a: 1, b: 2, a: 3], [b: 2, a: 3, a: 1])
      true

-  Comparison between values is done with `===/3`,
-  which means integers are not equivalent to floats:
-
-      iex> Keyword.equal?([a: 1.0], [a: 1])
-      false
-
  """
  @spec equal?(t, t) :: boolean
  def equal?(left, right) when is_list(left) and is_list(right) do
-    :lists.sort(left) === :lists.sort(right)
+    :lists.sort(left) == :lists.sort(right)
  end

  @doc """
  Merges two keyword lists into one.

-  Adds all keys, including duplicate keys, given in `keywords2`
-  to `keywords1`, overriding any existing ones.
+  All keys, including duplicated keys, given in `keywords2` will be added
+  to `keywords1`, overriding any existing one.

-  There are no guarantees about the order of the keys in the returned keyword.
+  There are no guarantees about the order of keys in the returned keyword.

  ## Examples

@@ -1000,13 +785,13 @@ defmodule Keyword do
  @doc """
  Merges two keyword lists into one.

-  Adds all keys, including duplicate keys, given in `keywords2`
-  to `keywords1`. Invokes the given function to solve conflicts.
+  All keys, including duplicated keys, given in `keywords2` will be added
+  to `keywords1`. The given function will be invoked to solve conflicts.

-  If `keywords2` has duplicate keys, it invokes the given function
+  If `keywords2` has duplicate keys, the given function will be invoked
  for each matching pair in `keywords1`.

-  There are no guarantees about the order of the keys in the returned keyword.
+  There are no guarantees about the order of keys in the returned keyword.

  ## Examples

@@ -1080,11 +865,12 @@ defmodule Keyword do
  end

  @doc """
-  Updates the value under `key` using the given function.
+  Updates the `key` with the given function.

-  Raises `KeyError` if the `key` does not exist.
+  If the `key` does not exist, raises `KeyError`.

-  Removes all duplicate keys and only updates the first one.
+  If there are duplicated keys, they are all removed and only the first one
+  is updated.

  ## Examples

@@ -1107,21 +893,23 @@ defmodule Keyword do
    [{key, fun.(value)} | delete(keywords, key)]
  end

-  defp update!([{_, _} = pair | keywords], key, fun, original) do
-    [pair | update!(keywords, key, fun, original)]
+  defp update!([{_, _} = e | keywords], key, fun, original) do
+    [e | update!(keywords, key, fun, original)]
  end

-  defp update!([], key, _fun, original) do
-    raise KeyError, key: key, term: original
+  defp update!([], key, _fun, original) when is_atom(key) do
+    raise(KeyError, key: key, term: original)
  end

  @doc """
-  Updates the value under `key` in `keywords` using the given function.
+  Updates the `key` in `keywords` with the given function.

  If the `key` does not exist, it inserts the given `default` value.
-  Does not pass the `default` value through the update function.

-  Removes all duplicate keys and only updates the first one.
+  If there are duplicated keys, they are all removed and only the first one
+  is updated.
+
+  The default value will not be passed through the update function.

  ## Examples

@@ -1135,33 +923,30 @@ defmodule Keyword do
      [a: 1, b: 11]

  """
-  @spec update(t, key, default :: value, (existing_value :: value -> new_value :: value)) :: t
+  @spec update(t, key, default :: value, (existing_value :: value -> updated_value :: value)) :: t
  def update(keywords, key, default, fun)
-      when is_list(keywords) and is_atom(key) and is_function(fun, 1) do
-    update_guarded(keywords, key, default, fun)
-  end

-  defp update_guarded([{key, value} | keywords], key, _default, fun) do
+  def update([{key, value} | keywords], key, _default, fun) do
    [{key, fun.(value)} | delete(keywords, key)]
  end

-  defp update_guarded([{_, _} = pair | keywords], key, default, fun) do
-    [pair | update_guarded(keywords, key, default, fun)]
+  def update([{_, _} = e | keywords], key, default, fun) do
+    [e | update(keywords, key, default, fun)]
  end

-  defp update_guarded([], key, default, _fun) do
+  def update([], key, default, _fun) when is_atom(key) do
    [{key, default}]
  end

  @doc """
-  Takes all entries corresponding to the given `keys` and extracts them into a
+  Takes all entries corresponding to the given keys and extracts them into a
  separate keyword list.

  Returns a tuple with the new list and the old list with removed keys.

-  Ignores keys for which there are no entries in the keyword list.
+  Keys for which there are no entries in the keyword list are ignored.

-  Entries with duplicate keys end up in the same keyword list.
+  Entries with duplicated keys end up in the same keyword list.

  ## Examples

@@ -1186,10 +971,10 @@ defmodule Keyword do
  end

  @doc """
-  Takes all entries corresponding to the given `keys` and returns them as a new
+  Takes all entries corresponding to the given keys and returns them in a new
  keyword list.

-  Preserves duplicate keys in the new keyword list.
+  Duplicated keys are preserved in the new keyword list.

  ## Examples

@@ -1201,18 +986,16 @@ defmodule Keyword do
  """
  @spec take(t, [key]) :: t
  def take(keywords, keys) when is_list(keywords) and is_list(keys) do
-    :lists.filter(fn {k, _} -> :lists.member(k, keys) end, keywords)
+    :lists.filter(fn {k, _} -> k in keys end, keywords)
  end

  @doc """
-  Drops the given `keys` from the keyword list.
+  Drops the given keys from the keyword list.

-  Removes duplicate keys from the new keyword list.
+  Duplicated keys are preserved in the new keyword list.

  ## Examples

-      iex> Keyword.drop([a: 1, a: 2], [:a])
-      []
      iex> Keyword.drop([a: 1, b: 2, c: 3], [:b, :d])
      [a: 1, c: 3]
      iex> Keyword.drop([a: 1, b: 2, b: 3, c: 3, a: 5], [:b, :d])
@@ -1221,7 +1004,7 @@ defmodule Keyword do
  """
  @spec drop(t, [key]) :: t
  def drop(keywords, keys) when is_list(keywords) and is_list(keys) do
-    :lists.filter(fn {k, _} -> k not in keys end, keywords)
+    :lists.filter(fn {key, _} -> key not in keys end, keywords)
  end

  @doc """
@@ -1229,10 +1012,11 @@ defmodule Keyword do

  It returns a tuple where the first element is the first value for `key` and the
  second element is a keyword list with all entries associated with `key` removed.
-  If the `key` is not present in the keyword list, it returns `{default, keyword_list}`.
+  If the `key` is not present in the keyword list, `{default, keyword_list}` is
+  returned.

  If you don't want to remove all the entries associated with `key` use `pop_first/3`
-  instead, which will remove only the first entry.
+  instead, that function will remove only the first entry.

  ## Examples

@@ -1258,7 +1042,7 @@ defmodule Keyword do
  Returns the first value for `key` and removes all associated entries in the keyword list,
  raising if `key` is not present.

-  This function behaves like `pop/3`, but raises in case the `key` is not present in the
+  This function behaves like `pop/3`, but raises in cases the `key` is not present in the
  given `keywords`.

  ## Examples
@@ -1285,10 +1069,11 @@ defmodule Keyword do

  It returns a tuple where the first element is a list of values for `key` and the
  second element is a keyword list with all entries associated with `key` removed.
-  If the `key` is not present in the keyword list, it returns `{[], keyword_list}`.
+  If the `key` is not present in the keyword list, `{[], keyword_list}` is
+  returned.

  If you don't want to remove all the entries associated with `key` use `pop_first/3`
-  instead, which will remove only the first entry.
+  instead, that function will remove only the first entry.

  ## Examples

@@ -1319,9 +1104,10 @@ defmodule Keyword do
  Lazily returns and removes all values associated with `key` in the keyword list.

  This is useful if the default value is very expensive to calculate or
-  generally difficult to set up and tear down again.
+  generally difficult to setup and teardown again.

-  Removes all duplicate keys. See `pop_first/3` for removing only the first entry.
+  All duplicated keys are removed. See `pop_first/3` for
+  removing only the first entry.

  ## Examples

@@ -1340,15 +1126,18 @@ defmodule Keyword do
  def pop_lazy(keywords, key, fun)
      when is_list(keywords) and is_atom(key) and is_function(fun, 0) do
    case fetch(keywords, key) do
-      {:ok, value} -> {value, delete(keywords, key)}
-      :error -> {fun.(), keywords}
+      {:ok, value} ->
+        {value, delete(keywords, key)}
+
+      :error ->
+        {fun.(), keywords}
    end
  end

  @doc """
  Returns and removes the first value associated with `key` in the keyword list.

-  Keeps duplicate keys in the resulting keyword list.
+  Duplicated keys are not removed.

  ## Examples

@@ -1380,76 +1169,13 @@ defmodule Keyword do

  """
  @spec to_list(t) :: t
-  def to_list(keywords) when is_list(keywords) do
-    keywords
+  def to_list(keyword) when is_list(keyword) do
+    keyword
  end

  @doc false
  @deprecated "Use Kernel.length/1 instead"
-  def size(keywords) do
-    length(keywords)
-  end
-
-  @doc """
-  Returns a keyword list containing only the entries from `keywords`
-  for which the function `fun` returns a truthy value.
-
-  See also `reject/2` which discards all entries where the function
-  returns a truthy value.
-
-  ## Examples
-
-      iex> Keyword.filter([one: 1, two: 2, three: 3], fn {_key, val} -> rem(val, 2) == 1 end)
-      [one: 1, three: 3]
-
-  """
-  @doc since: "1.13.0"
-  @spec filter(t, ({key, value} -> as_boolean(term))) :: t
-  def filter(keywords, fun) when is_list(keywords) and is_function(fun, 1) do
-    do_filter(keywords, fun)
-  end
-
-  defp do_filter([], _fun), do: []
-
-  defp do_filter([{_, _} = entry | entries], fun) do
-    if fun.(entry) do
-      [entry | do_filter(entries, fun)]
-    else
-      do_filter(entries, fun)
-    end
-  end
-
-  @doc """
-  Returns a keyword list excluding the entries from `keywords`
-  for which the function `fun` returns a truthy value.
-
-  See also `filter/2`.
-
-  ## Examples
-
-      iex> Keyword.reject([one: 1, two: 2, three: 3], fn {_key, val} -> rem(val, 2) == 1 end)
-      [two: 2]
-
-  """
-  @doc since: "1.13.0"
-  @spec reject(t, ({key, value} -> as_boolean(term))) :: t
-  def reject(keywords, fun) when is_list(keywords) and is_function(fun, 1) do
-    do_reject(keywords, fun)
-  end
-
-  defp do_reject([], _fun), do: []
-
-  defp do_reject([{_, _} = entry | entries], fun) do
-    if fun.(entry) do
-      do_reject(entries, fun)
-    else
-      [entry | do_reject(entries, fun)]
-    end
-  end
-
-  @doc false
-  @deprecated "Use Keyword.new/2 instead"
-  def map(keywords, fun) when is_list(keywords) do
-    Enum.map(keywords, fn {k, v} -> {k, fun.({k, v})} end)
+  def size(keyword) do
+    length(keyword)
  end
 end
@@ -8,20 +8,13 @@ defmodule List do
      [1, "two", 3, :four]

  Two lists can be concatenated and subtracted using the
-  `++/2` and `--/2` operators:
+  `Kernel.++/2` and `Kernel.--/2` operators:

      iex> [1, 2, 3] ++ [4, 5, 6]
      [1, 2, 3, 4, 5, 6]
      iex> [1, true, 2, false, 3, true] -- [true, false]
      [1, 2, 3, true]

-  An element can be prepended to a list using `|`:
-
-      iex> new = 0
-      iex> list = [1, 2, 3]
-      iex> [new | list]
-      [0, 1, 2, 3]
-
  Lists in Elixir are effectively linked lists, which means
  they are internally represented in pairs containing the
  head and the tail of a list:
@@ -230,7 +223,7 @@ defmodule List do

  @doc """
  Folds (reduces) the given list from the left with
-  a function. Requires an accumulator, which can be any value.
+  a function. Requires an accumulator.

  ## Examples

@@ -240,9 +233,6 @@ defmodule List do
      iex> List.foldl([1, 2, 3, 4], 0, fn x, acc -> x - acc end)
      2

-      iex> List.foldl([1, 2, 3], {0, 0}, fn x, {a1, a2} -> {a1 + x, a2 - x} end)
-      {6, -6}
-
  """
  @spec foldl([elem], acc, (elem, acc -> acc)) :: acc when elem: var, acc: var
  def foldl(list, acc, fun) when is_list(list) and is_function(fun) do
@@ -251,16 +241,13 @@ defmodule List do

  @doc """
  Folds (reduces) the given list from the right with
-  a function. Requires an accumulator, which can be any value.
+  a function. Requires an accumulator.

  ## Examples

      iex> List.foldr([1, 2, 3, 4], 0, fn x, acc -> x - acc end)
      -2

-      iex> List.foldr([1, 2, 3, 4], %{sum: 0, product: 1}, fn x, %{sum: a1, product: a2} -> %{sum: a1 + x, product: a2 * x} end)
-      %{product: 24, sum: 10}
-
  """
  @spec foldr([elem], acc, (elem, acc -> acc)) :: acc when elem: var, acc: var
  def foldr(list, acc, fun) when is_list(list) and is_function(fun) do
@@ -268,18 +255,13 @@ defmodule List do
  end

  @doc """
-  Returns the first element in `list` or `default` if `list` is empty.
-
-  `first/2` has been introduced in Elixir v1.12.0, while `first/1` has been available since v1.0.0.
+  Returns the first element in `list` or `nil` if `list` is empty.

  ## Examples

      iex> List.first([])
      nil

-      iex> List.first([], 1)
-      1
-
      iex> List.first([1])
      1

@@ -287,25 +269,19 @@ defmodule List do
      1

  """
-  @spec first([], any) :: any
-  @spec first([elem, ...], any) :: elem when elem: var
-  def first(list, default \\ nil)
-  def first([], default), do: default
-  def first([head | _], _default), do: head
+  @spec first([]) :: nil
+  @spec first([elem, ...]) :: elem when elem: var
+  def first([]), do: nil
+  def first([head | _]), do: head

  @doc """
-  Returns the last element in `list` or `default` if `list` is empty.
-
-  `last/2` has been introduced in Elixir v1.12.0, while `last/1` has been available since v1.0.0.
+  Returns the last element in `list` or `nil` if `list` is empty.

  ## Examples

      iex> List.last([])
      nil

-      iex> List.last([], 1)
-      1
-
      iex> List.last([1])
      1

@@ -313,13 +289,11 @@ defmodule List do
      3

  """
-  @spec last([], any) :: any
-  @spec last([elem, ...], any) :: elem when elem: var
-  @compile {:inline, last: 2}
-  def last(list, default \\ nil)
-  def last([], default), do: default
-  def last([head], _default), do: head
-  def last([_ | tail], default), do: last(tail, default)
+  @spec last([]) :: nil
+  @spec last([elem, ...]) :: elem when elem: var
+  def last([]), do: nil
+  def last([head]), do: head
+  def last([_ | tail]), do: last(tail)

  @doc """
  Receives a list of tuples and returns the first tuple
@@ -339,52 +313,12 @@ defmodule List do
      iex> List.keyfind([a: 1, b: 2], :c, 0)
      nil

-  This function works for any list of tuples:
-
-      iex> List.keyfind([{22, "SSH"}, {80, "HTTP"}], 22, 0)
-      {22, "SSH"}
-
  """
  @spec keyfind([tuple], any, non_neg_integer, any) :: any
-  def keyfind(list, key, position, default \\ nil) when is_integer(position) do
+  def keyfind(list, key, position, default \\ nil) do
    :lists.keyfind(key, position + 1, list) || default
  end

-  @doc """
-  Receives a list of tuples and returns the first tuple
-  where the element at `position` in the tuple matches the
-  given `key`.
-
-  If no matching tuple is found, an error is raised.
-
-  ## Examples
-
-      iex> List.keyfind!([a: 1, b: 2], :a, 0)
-      {:a, 1}
-
-      iex> List.keyfind!([a: 1, b: 2], 2, 1)
-      {:b, 2}
-
-      iex> List.keyfind!([a: 1, b: 2], :c, 0)
-      ** (KeyError) key :c at position 0 not found in: [a: 1, b: 2]
-
-  This function works for any list of tuples:
-
-      iex> List.keyfind!([{22, "SSH"}, {80, "HTTP"}], 22, 0)
-      {22, "SSH"}
-
-  """
-  @doc since: "1.13.0"
-  @spec keyfind!([tuple], any, non_neg_integer) :: any
-  def keyfind!(list, key, position) when is_integer(position) do
-    :lists.keyfind(key, position + 1, list) ||
-      raise KeyError,
-        key: key,
-        term: list,
-        message:
-          "key #{inspect(key)} at position #{inspect(position)} not found in: #{inspect(list)}"
-  end
-
  @doc """
  Receives a list of tuples and returns `true` if there is
  a tuple where the element at `position` in the tuple matches
@@ -401,14 +335,9 @@ defmodule List do
      iex> List.keymember?([a: 1, b: 2], :c, 0)
      false

-  This function works for any list of tuples:
-
-      iex> List.keymember?([{22, "SSH"}, {80, "HTTP"}], 22, 0)
-      true
-
  """
  @spec keymember?([tuple], any, non_neg_integer) :: boolean
-  def keymember?(list, key, position) when is_integer(position) do
+  def keymember?(list, key, position) do
    :lists.keymember(key, position + 1, list)
  end

@@ -424,26 +353,15 @@ defmodule List do
      iex> List.keyreplace([a: 1, b: 2], :a, 1, {:a, 3})
      [a: 1, b: 2]

-  This function works for any list of tuples:
-
-      iex> List.keyreplace([{22, "SSH"}, {80, "HTTP"}], 22, 0, {22, "Secure Shell"})
-      [{22, "Secure Shell"}, {80, "HTTP"}]
-
  """
  @spec keyreplace([tuple], any, non_neg_integer, tuple) :: [tuple]
-  def keyreplace(list, key, position, new_tuple) when is_integer(position) do
+  def keyreplace(list, key, position, new_tuple) do
    :lists.keyreplace(key, position + 1, list, new_tuple)
  end

  @doc """
  Receives a list of tuples and sorts the elements
-  at `position` of the tuples.
-
-  The sort is stable.
-
-  A `sorter` argument is available since Elixir v1.14.0. Similar to
-  `Enum.sort/2`, the sorter can be an anonymous function, the atoms
-  `:asc` or `:desc`, or module that implements a compare function.
+  at `position` of the tuples. The sort is stable.

  ## Examples

@@ -453,69 +371,12 @@ defmodule List do
      iex> List.keysort([a: 5, c: 1, b: 3], 0)
      [a: 5, b: 3, c: 1]

-  To sort in descending order:
-
-      iex> List.keysort([a: 5, c: 1, b: 3], 0, :desc)
-      [c: 1, b: 3, a: 5]
-
-  As in `Enum.sort/2`, avoid using the default sorting function to sort
-  structs, as by default it performs structural comparison instead of a
-  semantic one. In such cases, you shall pass a sorting function as third
-  element or any module that implements a `compare/2` function. For example,
-  if you have tuples with user names and their birthday, and you want to
-  sort on their birthday, in both ascending and descending order, you should
-  do:
-
-      iex> users = [
-      ...>   {"Ellis", ~D[1943-05-11]},
-      ...>   {"Lovelace", ~D[1815-12-10]},
-      ...>   {"Turing", ~D[1912-06-23]}
-      ...> ]
-      iex> List.keysort(users, 1, Date)
-      [
-        {"Lovelace", ~D[1815-12-10]},
-        {"Turing", ~D[1912-06-23]},
-        {"Ellis", ~D[1943-05-11]}
-      ]
-      iex> List.keysort(users, 1, {:desc, Date})
-      [
-        {"Ellis", ~D[1943-05-11]},
-        {"Turing", ~D[1912-06-23]},
-        {"Lovelace", ~D[1815-12-10]}
-      ]
-
  """
-  @doc since: "1.14.0"
-  @spec keysort(
-          [tuple],
-          non_neg_integer,
-          (any, any -> boolean) | :asc | :desc | module() | {:asc | :desc, module()}
-        ) :: [tuple]
-  def keysort(list, position, sorter \\ :asc)
-
-  def keysort(list, position, :asc) when is_list(list) and is_integer(position) do
+  @spec keysort([tuple], non_neg_integer) :: [tuple]
+  def keysort(list, position) do
    :lists.keysort(position + 1, list)
  end

-  def keysort(list, position, sorter) when is_list(list) and is_integer(position) do
-    :lists.sort(keysort_fun(sorter, position + 1), list)
-  end
-
-  defp keysort_fun(sorter, position) when is_function(sorter, 2),
-    do: &sorter.(:erlang.element(position, &1), :erlang.element(position, &2))
-
-  defp keysort_fun(:desc, position),
-    do: &(:erlang.element(position, &1) >= :erlang.element(position, &2))
-
-  defp keysort_fun(module, position) when is_atom(module),
-    do: &(module.compare(:erlang.element(position, &1), :erlang.element(position, &2)) != :gt)
-
-  defp keysort_fun({:asc, module}, position) when is_atom(module),
-    do: &(module.compare(:erlang.element(position, &1), :erlang.element(position, &2)) != :gt)
-
-  defp keysort_fun({:desc, module}, position) when is_atom(module),
-    do: &(module.compare(:erlang.element(position, &1), :erlang.element(position, &2)) != :lt)
-
  @doc """
  Receives a `list` of tuples and replaces the element
  identified by `key` at `position` with `new_tuple`.
@@ -530,14 +391,9 @@ defmodule List do
      iex> List.keystore([a: 1, b: 2], :c, 0, {:c, 3})
      [a: 1, b: 2, c: 3]

-  This function works for any list of tuples:
-
-      iex> List.keystore([{22, "SSH"}], 80, 0, {80, "HTTP"})
-      [{22, "SSH"}, {80, "HTTP"}]
-
  """
  @spec keystore([tuple], any, non_neg_integer, tuple) :: [tuple, ...]
-  def keystore(list, key, position, new_tuple) when is_integer(position) do
+  def keystore(list, key, position, new_tuple) do
    :lists.keystore(key, position + 1, list, new_tuple)
  end

@@ -557,14 +413,9 @@ defmodule List do
      iex> List.keydelete([a: 1, b: 2], :c, 0)
      [a: 1, b: 2]

-  This function works for any list of tuples:
-
-      iex> List.keydelete([{22, "SSH"}, {80, "HTTP"}], 80, 0)
-      [{22, "SSH"}]
-
  """
  @spec keydelete([tuple], any, non_neg_integer) :: [tuple]
-  def keydelete(list, key, position) when is_integer(position) do
+  def keydelete(list, key, position) do
    :lists.keydelete(key, position + 1, list)
  end

@@ -586,14 +437,9 @@ defmodule List do
      iex> List.keytake([a: 1, b: 2], :c, 0)
      nil

-  This function works for any list of tuples:
-
-      iex> List.keytake([{22, "SSH"}, {80, "HTTP"}], 80, 0)
-      {{80, "HTTP"}, [{22, "SSH"}]}
-
  """
  @spec keytake([tuple], any, non_neg_integer) :: {tuple, [tuple]} | nil
-  def keytake(list, key, position) when is_integer(position) do
+  def keytake(list, key, position) do
    case :lists.keytake(key, position + 1, list) do
      {:value, element, list} -> {element, list}
      false -> nil
@@ -947,22 +793,14 @@ defmodule List do
  end

  @doc """
-  Converts a charlist to an existing atom.
+  Converts a charlist to an existing atom. Raises an `ArgumentError`
+  if the atom does not exist.

  Elixir supports conversions from charlists which contains any Unicode
-  code point. Raises an `ArgumentError` if the atom does not exist.
+  code point.

  Inlined by the compiler.

-  > #### Atoms and modules {: .info}
-  >
-  > Since Elixir is a compiled language, the atoms defined in a module
-  > will only exist after said module is loaded, which typically happens
-  > whenever a function in the module is executed. Therefore, it is
-  > generally recommended to call `List.to_existing_atom/1` only to
-  > convert atoms defined within the module making the function call
-  > to `to_existing_atom/1`.
-
  ## Examples

      iex> _ = :my_atom
@@ -973,6 +811,9 @@ defmodule List do
      iex> List.to_existing_atom('🌢 Elixir')
      :"🌢 Elixir"

+      iex> List.to_existing_atom('this_atom_will_never_exist')
+      ** (ArgumentError) argument error
+
  """
  @spec to_existing_atom(charlist) :: atom
  def to_existing_atom(charlist) do
@@ -1058,7 +899,7 @@ defmodule List do

  Note that this function expects a list of integers representing
  Unicode code points. If you have a list of bytes, you must instead use
-  the [`:binary` module](`:binary`).
+  the [`:binary` module](http://www.erlang.org/doc/man/binary.html).

  ## Examples

@@ -1113,7 +954,7 @@ defmodule List do

  Note that this function expects a list of integers representing
  Unicode code points. If you have a list of bytes, you must instead use
-  the [`:binary` module](`:binary`).
+  the [`:binary` module](http://www.erlang.org/doc/man/binary.html).

  ## Examples

@@ -21,51 +21,75 @@ defmodule Macro.Env do

  It contains the following fields:

+    * `aliases` -  a list of two-element tuples, where the first
+      element is the aliased name and the second one the actual name
    * `context` - the context of the environment; it can be `nil`
      (default context), `:guard` (inside a guard) or `:match` (inside a match)
    * `context_modules` - a list of modules defined in the current context
-    * `file` - the current absolute file name as a binary
+    * `file` - the current file name as a binary
    * `function` - a tuple as `{atom, integer}`, where the first
      element is the function name and the second its arity; returns
      `nil` if not inside a function
+    * `functions` - a list of functions imported from each module
    * `line` - the current line as an integer
+    * `macro_aliases` - a list of aliases defined inside the current macro
+    * `macros` - a list of macros imported from each module
    * `module` - the current module name
+    * `requires` - the list of required modules

  The following fields are private to Elixir's macro expansion mechanism and
  must not be accessed directly:

-    * `aliases`
-    * `functions`
-    * `macro_aliases`
-    * `macros`
+    * `contextual_vars`
+    * `current_vars`
    * `lexical_tracker`
-    * `requires`
+    * `prematch_vars`
    * `tracers`
-    * `versioned_vars`
+    * `unused_vars`
+
+  The following fields are deprecated and must not be accessed or relied on:
+
+    * `vars` - a list keeping all defined variables as `{var, context}`

  """

+  @type aliases :: [{module, module}]
  @type context :: :match | :guard | nil
  @type context_modules :: [module]
  @type file :: binary
+  @type functions :: [{module, [name_arity]}]
+  @type lexical_tracker :: pid | nil
  @type line :: non_neg_integer
+  @type macro_aliases :: [{module, {term, module}}]
+  @type macros :: [{module, [name_arity]}]
  @type name_arity :: {atom, arity}
+  @type requires :: [module]
  @type variable :: {atom, atom | term}

-  @typep aliases :: [{module, module}]
-  @typep functions :: [{module, [name_arity]}]
-  @typep lexical_tracker :: pid | nil
-  @typep macro_aliases :: [{module, {term, module}}]
-  @typep macros :: [{module, [name_arity]}]
-  @typep requires :: [module]
+  @typep contextual_vars :: [atom]
+  @typep current_vars ::
+           {%{optional(variable) => {var_version, var_type}},
+            %{optional(variable) => {var_version, var_type}} | false}
+  @typep unused_vars ::
+           {%{optional({atom, var_version}) => non_neg_integer | false}, non_neg_integer}
+  @typep prematch_vars ::
+           {%{optional(variable) => {var_version, var_type}}, non_neg_integer}
+           | :warn
+           | :raise
+           | :pin
+           | :apply
  @typep tracers :: [module]
-  @typep versioned_vars :: %{optional(variable) => var_version :: non_neg_integer}
+  @typep var_type :: :term
+  @typep var_version :: non_neg_integer
+  @typep vars :: [variable]

  @type t :: %{
          __struct__: __MODULE__,
          aliases: aliases,
          context: context,
          context_modules: context_modules,
+          contextual_vars: contextual_vars,
+          current_vars: current_vars,
          file: file,
          function: name_arity | nil,
          functions: functions,
@@ -73,45 +97,41 @@ defmodule Macro.Env do
          line: line,
          macro_aliases: macro_aliases,
          macros: macros,
-          module: module,
+          module: atom,
+          prematch_vars: prematch_vars,
+          unused_vars: unused_vars,
          requires: requires,
          tracers: tracers,
-          versioned_vars: versioned_vars
+          vars: vars
        }

-  fields = [
-    aliases: [],
-    context: nil,
-    context_modules: [],
-    file: "nofile",
-    function: nil,
-    functions: [],
-    lexical_tracker: nil,
-    line: 0,
-    macro_aliases: [],
-    macros: [],
-    module: nil,
-    requires: [],
-    tracers: [],
-    versioned_vars: %{}
-  ]
+  # TODO: Remove :vars field on v2.0
+  def __struct__ do
+    %{
+      __struct__: __MODULE__,
+      aliases: [],
+      context: nil,
+      context_modules: [],
+      contextual_vars: [],
+      current_vars: {%{}, %{}},
+      file: "nofile",
+      function: nil,
+      functions: [],
+      lexical_tracker: nil,
+      line: 0,
+      macro_aliases: [],
+      macros: [],
+      module: nil,
+      prematch_vars: :warn,
+      requires: [],
+      tracers: [],
+      unused_vars: {%{}, 0},
+      vars: []
+    }
+  end

-  # Define the __struct__ callbacks by hand for bootstrap reasons.
-  {struct, [], kv, body} = Kernel.Utils.defstruct(__MODULE__, fields, false)
-  def __struct__(), do: unquote(:elixir_quote.escape(struct, false, :none))
-  def __struct__(unquote(kv)), do: unquote(body)
-
-  @doc """
-  Prunes compile information from the environment.
-
-  This happens when the environment is captured at compilation
-  time, for example, in the module body, and then used to
-  evaluate code after the module has been defined.
-  """
-  @doc since: "1.14.0"
-  @spec prune_compile_info(t) :: t
-  def prune_compile_info(env) do
-    %{env | lexical_tracker: nil, tracers: []}
+  def __struct__(kv) do
+    Enum.reduce(kv, __struct__(), fn {k, v}, acc -> :maps.update(k, v, acc) end)
  end

  @doc """
@@ -126,30 +146,19 @@ defmodule Macro.Env do
  @spec vars(t) :: [variable]
  def vars(env)

-  def vars(%{__struct__: Macro.Env, versioned_vars: vars}) do
-    Map.keys(vars)
+  def vars(%{__struct__: Macro.Env, current_vars: {read, _}}) do
+    Map.keys(read)
  end

  @doc """
  Checks if a variable belongs to the environment.
-
-  ## Examples
-
-      iex> x = 13
-      iex> x
-      13
-      iex> Macro.Env.has_var?(__ENV__, {:x, nil})
-      true
-      iex> Macro.Env.has_var?(__ENV__, {:unknown, nil})
-      false
-
  """
  @doc since: "1.7.0"
  @spec has_var?(t, variable) :: boolean()
  def has_var?(env, var)

-  def has_var?(%{__struct__: Macro.Env, versioned_vars: vars}, var) do
-    Map.has_key?(vars, var)
+  def has_var?(%{__struct__: Macro.Env, current_vars: {read, _}}, var) do
+    Map.has_key?(read, var)
  end

  @doc """
@@ -163,117 +172,16 @@ defmodule Macro.Env do
    [file: file, line: line]
  end

-  @doc """
-  Fetches the alias for the given atom.
-
-  Returns `{:ok, alias}` if the alias exists, `:error`
-  otherwise.
-
-  ## Examples
-
-      iex> alias Foo.Bar, as: Baz
-      iex> Baz
-      Foo.Bar
-      iex> Macro.Env.fetch_alias(__ENV__, :Baz)
-      {:ok, Foo.Bar}
-      iex> Macro.Env.fetch_alias(__ENV__, :Unknown)
-      :error
-
-  """
-  @doc since: "1.13.0"
-  @spec fetch_alias(t, atom) :: {:ok, atom} | :error
-  def fetch_alias(%{__struct__: Macro.Env, aliases: aliases}, atom) when is_atom(atom),
-    do: Keyword.fetch(aliases, :"Elixir.#{atom}")
-
-  @doc """
-  Fetches the macro alias for the given atom.
-
-  Returns `{:ok, macro_alias}` if the alias exists, `:error`
-  otherwise.
-
-  A macro alias is only used inside quoted expansion. See
-  `fetch_alias/2` for a more general example.
-  """
-  @doc since: "1.13.0"
-  @spec fetch_macro_alias(t, atom) :: {:ok, atom} | :error
-  def fetch_macro_alias(%{__struct__: Macro.Env, macro_aliases: aliases}, atom)
-      when is_atom(atom),
-      do: Keyword.fetch(aliases, :"Elixir.#{atom}")
-
-  @doc """
-  Returns the modules from which the given `{name, arity}` was
-  imported.
-
-  It returns a list of two element tuples in the shape of
-  `{:function | :macro, module}`. The elements in the list
-  are in no particular order and the order is not guaranteed.
-
-  ## Examples
-
-      iex> Macro.Env.lookup_import(__ENV__, {:duplicate, 2})
-      []
-      iex> import Tuple, only: [duplicate: 2], warn: false
-      iex> Macro.Env.lookup_import(__ENV__, {:duplicate, 2})
-      [{:function, Tuple}]
-      iex> import List, only: [duplicate: 2], warn: false
-      iex> Macro.Env.lookup_import(__ENV__, {:duplicate, 2})
-      [{:function, List}, {:function, Tuple}]
-
-      iex> Macro.Env.lookup_import(__ENV__, {:def, 1})
-      [{:macro, Kernel}]
-
-  """
-  @doc since: "1.13.0"
-  @spec lookup_import(t, name_arity) :: [{:function | :macro, module}]
-  def lookup_import(
-        %{__struct__: Macro.Env, functions: functions, macros: macros},
-        {name, arity} = pair
-      )
-      when is_atom(name) and is_integer(arity) do
-    f = for {mod, pairs} <- functions, :ordsets.is_element(pair, pairs), do: {:function, mod}
-    m = for {mod, pairs} <- macros, :ordsets.is_element(pair, pairs), do: {:macro, mod}
-    f ++ m
-  end
-
-  @doc """
-  Returns true if the given module has been required.
-
-  ## Examples
-
-      iex> Macro.Env.required?(__ENV__, Integer)
-      false
-      iex> require Integer
-      iex> Macro.Env.required?(__ENV__, Integer)
-      true
-
-      iex> Macro.Env.required?(__ENV__, Kernel)
-      true
-  """
-  @doc since: "1.13.0"
-  @spec required?(t, module) :: boolean
-  def required?(%{__struct__: Macro.Env, requires: requires}, mod) when is_atom(mod),
-    do: mod in requires
-
-  @doc """
-  Prepend a tracer to the list of tracers in the environment.
-
-  ## Examples
-
-      Macro.Env.prepend_tracer(__ENV__, MyCustomTracer)
-
-  """
-  @doc since: "1.13.0"
-  @spec prepend_tracer(t, module) :: t
-  def prepend_tracer(%{__struct__: Macro.Env, tracers: tracers} = env, tracer) do
-    %{env | tracers: [tracer | tracers]}
-  end
-
  @doc """
  Returns a `Macro.Env` in the match context.
  """
  @spec to_match(t) :: t
-  def to_match(%{__struct__: Macro.Env} = env) do
-    %{env | context: :match}
+  def to_match(%{__struct__: Macro.Env, context: :match} = env) do
+    env
+  end
+
+  def to_match(%{__struct__: Macro.Env, current_vars: {read, _}, unused_vars: {_, counter}} = env) do
+    %{env | context: :match, prematch_vars: {read, counter}}
  end

  @doc """
@@ -19,13 +19,8 @@ defmodule Map do
  in a map literal, the last one prevails.

  When the key in a key-value pair is an atom, the `key: value` shorthand syntax
-  can be used (as in many other special forms):
-
-      iex> %{a: 1, b: 2}
-      %{a: 1, b: 2}
-
-  If you want to mix the shorthand syntax with `=>`, the shorthand syntax must come
-  at the end:
+  can be used (as in many other special forms), provided key-value pairs are put at
+  the end:

      iex> %{"hello" => "world", a: 1, b: 2}
      %{:a => 1, :b => 2, "hello" => "world"}
@@ -50,11 +45,11 @@ defmodule Map do
      map.foo
      #=> "bar"
      map.non_existing_key
-      ** (KeyError) key :non_existing_key not found in: %{baz: "bong", foo: "bar"}
+      #=> ** (KeyError) key :non_existing_key not found in: %{baz: "bong", foo: "bar"}

  > Note: do not add parens when accessing fields, such as in `data.key()`.
-  > If parenthesis are used, Elixir will expect `data` to be an atom representing
-  > a module and attempt to call the *function* `key/0` in it.
+  > If parenthesis are used, Elixir will consider it to be a function call
+  > on `data`, which would be expected to be an atom.

  The two syntaxes for accessing keys reveal the dual nature of maps. The `map[key]`
  syntax is used for dynamically created maps that may have any key, of any type.
@@ -88,18 +83,12 @@ defmodule Map do
      %{1 => :one, 2 => :two, 3 => :three}

  Maps also support a specific update syntax to update the value stored under
-  *existing* keys. You can update using the atom keys syntax:
+  *existing* atom keys:

      iex> map = %{one: 1, two: 2}
      iex> %{map | one: "one"}
      %{one: "one", two: 2}

-  Or any other key:
-
-      iex> other_map = %{"three" => 3, "four" => 4}
-      iex> %{other_map | "three" => "three"}
-      %{"four" => 4, "three" => "three"}
-
  When a key that does not exist in the map is updated a `KeyError` exception will be raised:

      %{map | three: 3}
@@ -123,27 +112,6 @@ defmodule Map do
  @type value :: any
  @compile {:inline, fetch: 2, fetch!: 2, get: 2, put: 3, delete: 2, has_key?: 2, replace!: 3}

-  # TODO: Remove conditional on Erlang/OTP 24+
-  @compile {:no_warn_undefined, {:maps, :from_keys, 2}}
-  @doc """
-  Builds a map from the given `keys` and the fixed `value`.
-
-  ## Examples
-
-      iex> Map.from_keys([1, 2, 3], :number)
-      %{1 => :number, 2 => :number, 3 => :number}
-
-  """
-  @doc since: "1.14.0"
-  @spec from_keys([key], value) :: map
-  def from_keys(keys, value) do
-    if function_exported?(:maps, :from_keys, 2) do
-      :maps.from_keys(keys, value)
-    else
-      :maps.from_list(:lists.map(&{&1, value}, keys))
-    end
-  end
-
  @doc """
  Returns all keys from `map`.

@@ -241,29 +209,22 @@ defmodule Map do

  """
  @spec new(Enumerable.t(), (term -> {key, value})) :: map
-  def new(enumerable, transform)
-  def new(%_{} = enumerable, transform), do: new_from_enum(enumerable, transform)
-  def new(%{} = map, transform), do: new_from_map(map, transform)
-  def new(enumerable, transform), do: new_from_enum(enumerable, transform)
-
-  defp new_from_map(map, transform) when is_function(transform, 1) do
-    iter = :maps.iterator(map)
-    next = :maps.next(iter)
-    :maps.from_list(do_map(next, transform))
-  end
-
-  defp do_map(:none, _fun), do: []
-
-  defp do_map({key, value, iter}, transform) do
-    [transform.({key, value}) | do_map(:maps.next(iter), transform)]
-  end
-
-  defp new_from_enum(enumerable, transform) when is_function(transform, 1) do
+  def new(enumerable, transform) when is_function(transform, 1) do
    enumerable
-    |> Enum.map(transform)
+    |> Enum.to_list()
+    |> new_transform(transform, [])
+  end
+
+  defp new_transform([], _fun, acc) do
+    acc
+    |> :lists.reverse()
    |> :maps.from_list()
  end

+  defp new_transform([element | rest], fun, acc) do
+    new_transform(rest, fun, [fun.(element) | acc])
+  end
+
  @doc """
  Returns whether the given `key` exists in the given `map`.

@@ -362,7 +323,7 @@ defmodule Map do
  def replace(map, key, value) do
    case map do
      %{^key => _value} ->
-        %{map | key => value}
+        put(map, key, value)

      %{} ->
        map
@@ -394,32 +355,6 @@ defmodule Map do
    :maps.update(key, value, map)
  end

-  @doc """
-  Replaces the value under `key` using the given function only if
-  `key` already exists in `map`.
-
-  In comparison to `replace/3`, this can be useful when it's expensive to calculate the value.
-
-  If `key` does not exist, the original map is returned unchanged.
-
-  ## Examples
-
-      iex> Map.replace_lazy(%{a: 1, b: 2}, :a, fn v -> v * 4 end)
-      %{a: 4, b: 2}
-
-      iex> Map.replace_lazy(%{a: 1, b: 2}, :c, fn v -> v * 4 end)
-      %{a: 1, b: 2}
-
-  """
-  @doc since: "1.14.0"
-  @spec replace_lazy(map, key, (existing_value :: value -> new_value :: value)) :: map
-  def replace_lazy(map, key, fun) when is_map(map) and is_function(fun, 1) do
-    case map do
-      %{^key => val} -> %{map | key => fun.(val)}
-      %{} -> map
-    end
-  end
-
  @doc """
  Evaluates `fun` and puts the result under `key`
  in `map` unless `key` is already present.
@@ -616,7 +551,7 @@ defmodule Map do
  If you have a struct and you would like to merge a set of keys into the
  struct, do not use this function, as it would merge all keys on the right
  side into the struct, even if the key is not part of the struct. Instead,
-  use `struct/2`.
+  use `Kernel.struct/2`.

  Inlined by the compiler.

@@ -679,12 +614,12 @@ defmodule Map do
      %{a: 1, b: 11}

  """
-  @spec update(map, key, default :: value, (existing_value :: value -> new_value :: value)) ::
+  @spec update(map, key, default :: value, (existing_value :: value -> updated_value :: value)) ::
          map
  def update(map, key, default, fun) when is_function(fun, 1) do
    case map do
      %{^key => value} ->
-        %{map | key => fun.(value)}
+        put(map, key, fun.(value))

      %{} ->
        put(map, key, default)
@@ -697,8 +632,8 @@ defmodule Map do
  @doc """
  Removes the value associated with `key` in `map` and returns the value and the updated map.

-  If `key` is present in `map`, it returns `{value, updated_map}` where `value` is the value of
-  the key and `updated_map` is the result of removing `key` from `map`. If `key`
+  If `key` is present in `map`, it returns `{value, new_map}` where `value` is the value of
+  the key and `new_map` is the result of removing `key` from `map`. If `key`
  is not present in `map`, `{default, map}` is returned.

  ## Examples
@@ -711,7 +646,7 @@ defmodule Map do
      {3, %{a: 1}}

  """
-  @spec pop(map, key, default) :: {value, updated_map :: map} | {default, map} when default: value
+  @spec pop(map, key, value) :: {value, new_map :: map}
  def pop(map, key, default \\ nil) do
    case :maps.take(key, map) do
      {_, _} = tuple -> tuple
@@ -720,8 +655,8 @@ defmodule Map do
  end

  @doc """
-  Removes the value associated with `key` in `map` and returns the value
-  and the updated map, or it raises if `key` is not present.
+  Returns and removes the value associated with `key` in `map` or raises
+  if `key` is not present.

  Behaves the same as `pop/3` but raises if `key` is not present in `map`.

@@ -736,7 +671,7 @@ defmodule Map do

  """
  @doc since: "1.10.0"
-  @spec pop!(map, key) :: {value, updated_map :: map}
+  @spec pop!(map, key) :: {value, map}
  def pop!(map, key) do
    case :maps.take(key, map) do
      {_, _} = tuple -> tuple
@@ -877,10 +812,10 @@ defmodule Map do
      ** (KeyError) key :b not found in: %{a: 1}

  """
-  @spec update!(map, key, (existing_value :: value -> new_value :: value)) :: map
+  @spec update!(map, key, (existing_value :: value -> updated_value :: value)) :: map
  def update!(map, key, fun) when is_function(fun, 1) do
    value = fetch!(map, key)
-    %{map | key => fun.(value)}
+    put(map, key, fun.(value))
  end

  @doc """
@@ -906,7 +841,7 @@ defmodule Map do
      iex> Map.get_and_update(%{a: 1}, :b, fn current_value ->
      ...>   {current_value, "new value!"}
      ...> end)
-      {nil, %{a: 1, b: "new value!"}}
+      {nil, %{b: "new value!", a: 1}}

      iex> Map.get_and_update(%{a: 1}, :a, fn _ -> :pop end)
      {1, %{}}
@@ -915,8 +850,8 @@ defmodule Map do
      {nil, %{a: 1}}

  """
-  @spec get_and_update(map, key, (value | nil -> {current_value, new_value :: value} | :pop)) ::
-          {current_value, new_map :: map}
+  @spec get_and_update(map, key, (value -> {current_value, new_value :: value} | :pop)) ::
+          {current_value, map}
        when current_value: value
  def get_and_update(map, key, fun) when is_function(fun, 1) do
    current = get(map, key)
@@ -957,7 +892,7 @@ defmodule Map do
      {1, %{}}

  """
-  @spec get_and_update!(map, key, (value | nil -> {current_value, new_value :: value} | :pop)) ::
+  @spec get_and_update!(map, key, (value -> {current_value, new_value :: value} | :pop)) ::
          {current_value, map}
        when current_value: value
  def get_and_update!(map, key, fun) when is_function(fun, 1) do
@@ -965,7 +900,7 @@ defmodule Map do

    case fun.(value) do
      {get, update} ->
-        {get, %{map | key => update}}
+        {get, put(map, key, update)}

      :pop ->
        {value, delete(map, key)}
@@ -1010,11 +945,6 @@ defmodule Map do
  Two maps are considered to be equal if they contain
  the same keys and those keys contain the same values.

-  Note this function exists for completeness so the `Map`
-  and `Keyword` modules provide similar APIs. In practice,
-  developers often compare maps using `==/2` or `===/2`
-  directly.
-
  ## Examples

      iex> Map.equal?(%{a: 1, b: 2}, %{b: 2, a: 1})
@@ -1022,12 +952,6 @@ defmodule Map do
      iex> Map.equal?(%{a: 1, b: 2}, %{b: 1, a: 2})
      false

-  Comparison between keys and values is done with `===/3`,
-  which means integers are not equivalent to floats:
-
-      iex> Map.equal?(%{a: 1.0}, %{a: 1})
-      false
-
  """
  @spec equal?(map, map) :: boolean
  def equal?(map1, map2)
@@ -1041,79 +965,4 @@ defmodule Map do
  def size(map) do
    map_size(map)
  end
-
-  @doc """
-  Returns a map containing only those pairs from `map`
-  for which `fun` returns a truthy value.
-
-  `fun` receives the key and value of each of the
-  elements in the map as a key-value pair.
-
-  See also `reject/2` which discards all elements where the
-  function returns a truthy value.
-
-  > Note: if you find yourself doing multiple calls to `Map.filter/2`
-  > and `Map.reject/2` in a pipeline, it is likely more efficient
-  > to use `Enum.map/2` and `Enum.filter/2` instead and convert to
-  > a map at the end using `Map.new/1`.
-
-  ## Examples
-
-      iex> Map.filter(%{one: 1, two: 2, three: 3}, fn {_key, val} -> rem(val, 2) == 1 end)
-      %{one: 1, three: 3}
-
-  """
-  @doc since: "1.13.0"
-  @spec filter(map, ({key, value} -> as_boolean(term))) :: map
-  def filter(map, fun) when is_map(map) and is_function(fun, 1) do
-    iter = :maps.iterator(map)
-    next = :maps.next(iter)
-    :maps.from_list(do_filter(next, fun))
-  end
-
-  defp do_filter(:none, _fun), do: []
-
-  defp do_filter({key, value, iter}, fun) do
-    if fun.({key, value}) do
-      [{key, value} | do_filter(:maps.next(iter), fun)]
-    else
-      do_filter(:maps.next(iter), fun)
-    end
-  end
-
-  @doc """
-  Returns map excluding the pairs from `map` for which `fun` returns
-  a truthy value.
-
-  See also `filter/2`.
-
-  ## Examples
-
-      iex> Map.reject(%{one: 1, two: 2, three: 3}, fn {_key, val} -> rem(val, 2) == 1 end)
-      %{two: 2}
-
-  """
-  @doc since: "1.13.0"
-  @spec reject(map, ({key, value} -> as_boolean(term))) :: map
-  def reject(map, fun) when is_map(map) and is_function(fun, 1) do
-    iter = :maps.iterator(map)
-    next = :maps.next(iter)
-    :maps.from_list(do_reject(next, fun))
-  end
-
-  defp do_reject(:none, _fun), do: []
-
-  defp do_reject({key, value, iter}, fun) do
-    if fun.({key, value}) do
-      do_reject(:maps.next(iter), fun)
-    else
-      [{key, value} | do_reject(:maps.next(iter), fun)]
-    end
-  end
-
-  @doc false
-  @deprecated "Use Map.new/2 instead (invoke Map.from_struct/1 before if you have a struct)"
-  def map(map, fun) when is_map(map) do
-    :maps.map(fn k, v -> fun.({k, v}) end, map)
-  end
 end
@@ -8,18 +8,18 @@ defmodule MapSet do
  A set can be constructed using `MapSet.new/0`:

      iex> MapSet.new()
-      MapSet.new([])
+      #MapSet<[]>

  Elements in a set don't have to be of the same type and they can be
  populated from an [enumerable](`t:Enumerable.t/0`) using `MapSet.new/1`:

      iex> MapSet.new([1, :two, {"three"}])
-      MapSet.new([1, :two, {"three"}])
+      #MapSet<[1, :two, {"three"}]>

  Elements can be inserted using `MapSet.put/2`:

      iex> MapSet.new([2]) |> MapSet.put(4) |> MapSet.put(0)
-      MapSet.new([0, 2, 4])
+      #MapSet<[0, 2, 4]>

  By definition, sets can't contain duplicate elements: when
  inserting an element in a set where it's already present, the insertion is
@@ -27,9 +27,9 @@ defmodule MapSet do

      iex> map_set = MapSet.new()
      iex> MapSet.put(map_set, "foo")
-      MapSet.new(["foo"])
+      #MapSet<["foo"]>
      iex> map_set |> MapSet.put("foo") |> MapSet.put("foo")
-      MapSet.new(["foo"])
+      #MapSet<["foo"]>

  A `MapSet` is represented internally using the `%MapSet{}` struct. This struct
  can be used whenever there's a need to pattern match on something being a `MapSet`:
@@ -54,12 +54,10 @@ defmodule MapSet do

  @type value :: term

-  @opaque internal(value) :: %{optional(value) => []}
-  @type t(value) :: %__MODULE__{map: internal(value)}
+  @opaque t(value) :: %__MODULE__{map: %{optional(value) => []}}
  @type t :: t(term)

-  # TODO: Remove version key when we require Erlang/OTP 24
-  # TODO: Implement the functions in this module using Erlang/OTP 24 new sets
+  # TODO: Remove version key on v2.0
  defstruct map: %{}, version: 2

  @doc """
@@ -68,7 +66,7 @@ defmodule MapSet do
  ## Examples

      iex> MapSet.new()
-      MapSet.new([])
+      #MapSet<[]>

  """
  @spec new :: t
@@ -80,19 +78,23 @@ defmodule MapSet do
  ## Examples

      iex> MapSet.new([:b, :a, 3])
-      MapSet.new([3, :a, :b])
+      #MapSet<[3, :a, :b]>
      iex> MapSet.new([3, 3, 3, 2, 2, 1])
-      MapSet.new([1, 2, 3])
+      #MapSet<[1, 2, 3]>

  """
-  @spec new(Enumerable.t()) :: t
+  @spec new(Enum.t()) :: t
  def new(enumerable)

  def new(%__MODULE__{} = map_set), do: map_set

  def new(enumerable) do
-    keys = Enum.to_list(enumerable)
-    %MapSet{map: Map.from_keys(keys, @dummy_value)}
+    map =
+      enumerable
+      |> Enum.to_list()
+      |> new_from_list([])
+
+    %MapSet{map: map}
  end

  @doc """
@@ -101,13 +103,33 @@ defmodule MapSet do
  ## Examples

      iex> MapSet.new([1, 2, 1], fn x -> 2 * x end)
-      MapSet.new([2, 4])
+      #MapSet<[2, 4]>

  """
-  @spec new(Enumerable.t(), (term -> val)) :: t(val) when val: value
+  @spec new(Enum.t(), (term -> val)) :: t(val) when val: value
  def new(enumerable, transform) when is_function(transform, 1) do
-    keys = Enum.map(enumerable, transform)
-    %MapSet{map: Map.from_keys(keys, @dummy_value)}
+    map =
+      enumerable
+      |> Enum.to_list()
+      |> new_from_list_transform(transform, [])
+
+    %MapSet{map: map}
+  end
+
+  defp new_from_list([], acc) do
+    Map.new(acc)
+  end
+
+  defp new_from_list([element | rest], acc) do
+    new_from_list(rest, [{element, @dummy_value} | acc])
+  end
+
+  defp new_from_list_transform([], _fun, acc) do
+    Map.new(acc)
+  end
+
+  defp new_from_list_transform([element | rest], fun, acc) do
+    new_from_list_transform(rest, fun, [{fun.(element), @dummy_value} | acc])
  end

  @doc """
@@ -119,9 +141,9 @@ defmodule MapSet do

      iex> map_set = MapSet.new([1, 2, 3])
      iex> MapSet.delete(map_set, 4)
-      MapSet.new([1, 2, 3])
+      #MapSet<[1, 2, 3]>
      iex> MapSet.delete(map_set, 2)
-      MapSet.new([1, 3])
+      #MapSet<[1, 3]>

  """
  @spec delete(t(val1), val2) :: t(val1) when val1: value, val2: value
@@ -135,7 +157,7 @@ defmodule MapSet do
  ## Examples

      iex> MapSet.difference(MapSet.new([1, 2]), MapSet.new([2, 3, 4]))
-      MapSet.new([1])
+      #MapSet<[1]>

  """
  @spec difference(t(val1), t(val2)) :: t(val1) when val1: value, val2: value
@@ -161,51 +183,13 @@ defmodule MapSet do
    %{map_set | map: Map.drop(map1, Map.keys(map2))}
  end

-  defp filter_not_in(:none, _map2, acc), do: Map.from_keys(acc, @dummy_value)
+  defp filter_not_in(:none, _map2, acc), do: Map.new(acc)

  defp filter_not_in({key, _val, iter}, map2, acc) do
-    if is_map_key(map2, key) do
+    if :erlang.is_map_key(key, map2) do
      filter_not_in(:maps.next(iter), map2, acc)
    else
-      filter_not_in(:maps.next(iter), map2, [key | acc])
-    end
-  end
-
-  @doc """
-  Returns a set with elements that are present in only one but not both sets.
-
-  ## Examples
-
-      iex> MapSet.symmetric_difference(MapSet.new([1, 2, 3]), MapSet.new([2, 3, 4]))
-      MapSet.new([1, 4])
-  """
-  @doc since: "1.14.0"
-  @spec symmetric_difference(t(val1), t(val2)) :: t(val1 | val2) when val1: value, val2: value
-  def symmetric_difference(%MapSet{map: map1}, %MapSet{map: map2}) do
-    {small, large} = order_by_size(map1, map2)
-
-    map =
-      large
-      |> :maps.iterator()
-      |> :maps.next()
-      |> disjointer(small, [])
-
-    %MapSet{map: map}
-  end
-
-  defp disjointer(:none, small, list) do
-    list |> Map.from_keys(@dummy_value) |> Map.merge(small)
-  end
-
-  defp disjointer({key, _val, iter}, small, list) do
-    if is_map_key(small, key) do
-      iter
-      |> :maps.next()
-      |> disjointer(Map.delete(small, key), list)
-    else
-      iter
-      |> :maps.next()
-      |> disjointer(small, [key | list])
+      filter_not_in(:maps.next(iter), map2, [{key, @dummy_value} | acc])
    end
  end

@@ -233,15 +217,13 @@ defmodule MapSet do
  defp none_in?(:none, _), do: true

  defp none_in?({key, _val, iter}, map2) do
-    not is_map_key(map2, key) and none_in?(:maps.next(iter), map2)
+    not :erlang.is_map_key(key, map2) and none_in?(:maps.next(iter), map2)
  end

  @doc """
  Checks if two sets are equal.

-  The comparison between elements is done using `===/2`,
-  which a set with `1` is not equivalent to a set with
-  `1.0`.
+  The comparison between elements must be done using `===/2`.

  ## Examples

@@ -249,13 +231,11 @@ defmodule MapSet do
      true
      iex> MapSet.equal?(MapSet.new([1, 2]), MapSet.new([3, 4]))
      false
-      iex> MapSet.equal?(MapSet.new([1]), MapSet.new([1.0]))
-      false

  """
  @spec equal?(t, t) :: boolean
  def equal?(%MapSet{map: map1, version: version}, %MapSet{map: map2, version: version}) do
-    map1 === map2
+    Map.equal?(map1, map2)
  end

  # Elixir v1.5 changed the map representation, so on
@@ -270,10 +250,10 @@ defmodule MapSet do
  ## Examples

      iex> MapSet.intersection(MapSet.new([1, 2]), MapSet.new([2, 3, 4]))
-      MapSet.new([2])
+      #MapSet<[2]>

      iex> MapSet.intersection(MapSet.new([1, 2]), MapSet.new([3, 4]))
-      MapSet.new([])
+      #MapSet<[]>

  """
  @spec intersection(t(val), t(val)) :: t(val) when val: value
@@ -295,7 +275,7 @@ defmodule MapSet do
  """
  @spec member?(t, value) :: boolean
  def member?(%MapSet{map: map}, value) do
-    is_map_key(map, value)
+    :erlang.is_map_key(value, map)
  end

  @doc """
@@ -304,9 +284,9 @@ defmodule MapSet do
  ## Examples

      iex> MapSet.put(MapSet.new([1, 2, 3]), 3)
-      MapSet.new([1, 2, 3])
+      #MapSet<[1, 2, 3]>
      iex> MapSet.put(MapSet.new([1, 2, 3]), 4)
-      MapSet.new([1, 2, 3, 4])
+      #MapSet<[1, 2, 3, 4]>

  """
  @spec put(t(val), new_val) :: t(val | new_val) when val: value, new_val: value
@@ -379,7 +359,7 @@ defmodule MapSet do
  ## Examples

      iex> MapSet.union(MapSet.new([1, 2]), MapSet.new([2, 3, 4]))
-      MapSet.new([1, 2, 3, 4])
+      #MapSet<[1, 2, 3, 4]>

  """
  @spec union(t(val1), t(val2)) :: t(val1 | val2) when val1: value, val2: value
@@ -390,88 +370,14 @@ defmodule MapSet do
  end

  def union(%MapSet{map: map1}, %MapSet{map: map2}) do
-    keys = Map.keys(map1) ++ Map.keys(map2)
-    %MapSet{map: Map.from_keys(keys, @dummy_value)}
+    map = new_from_list(Map.keys(map1) ++ Map.keys(map2), [])
+    %MapSet{map: map}
  end

  @compile {:inline, [order_by_size: 2]}
  defp order_by_size(map1, map2) when map_size(map1) > map_size(map2), do: {map2, map1}
  defp order_by_size(map1, map2), do: {map1, map2}

-  @doc """
-  Filters the set by returning only the elements from `set` for which invoking
-  `fun` returns a truthy value.
-
-  Also see `reject/2` which discards all elements where the function returns
-  a truthy value.
-
-  > Note: if you find yourself doing multiple calls to `MapSet.filter/2`
-  > and `MapSet.reject/2` in a pipeline, it is likely more efficient
-  > to use `Enum.map/2` and `Enum.filter/2` instead and convert to
-  > a map at the end using `Map.new/1`.
-
-  ## Examples
-
-      iex> MapSet.filter(MapSet.new(1..5), fn x -> x > 3 end)
-      MapSet.new([4, 5])
-
-      iex> MapSet.filter(MapSet.new(["a", :b, "c"]), &is_atom/1)
-      MapSet.new([:b])
-
-  """
-  @doc since: "1.14.0"
-  @spec filter(t(a), (a -> as_boolean(term))) :: t(a) when a: value
-  def filter(%MapSet{map: map}, fun) when is_map(map) and is_function(fun) do
-    iter = :maps.iterator(map)
-    next = :maps.next(iter)
-    keys = filter_keys(next, fun)
-    %MapSet{map: Map.from_keys(keys, @dummy_value)}
-  end
-
-  defp filter_keys(:none, _fun), do: []
-
-  defp filter_keys({key, _value, iter}, fun) do
-    if fun.(key) do
-      [key | filter_keys(:maps.next(iter), fun)]
-    else
-      filter_keys(:maps.next(iter), fun)
-    end
-  end
-
-  @doc """
-  Returns a set by excluding the elements from `set` for which invoking `fun`
-  returns a truthy value.
-
-  See also `filter/2`.
-
-  ## Examples
-
-      iex> MapSet.reject(MapSet.new(1..5), fn x -> rem(x, 2) != 0 end)
-      MapSet.new([2, 4])
-
-      iex> MapSet.reject(MapSet.new(["a", :b, "c"]), &is_atom/1)
-      MapSet.new(["a", "c"])
-
-  """
-  @doc since: "1.14.0"
-  @spec reject(t(a), (a -> as_boolean(term))) :: t(a) when a: value
-  def reject(%MapSet{map: map}, fun) when is_map(map) and is_function(fun) do
-    iter = :maps.iterator(map)
-    next = :maps.next(iter)
-    keys = reject_keys(next, fun)
-    %MapSet{map: Map.from_keys(keys, @dummy_value)}
-  end
-
-  defp reject_keys(:none, _fun), do: []
-
-  defp reject_keys({key, _value, iter}, fun) do
-    if fun.(key) do
-      reject_keys(:maps.next(iter), fun)
-    else
-      [key | reject_keys(:maps.next(iter), fun)]
-    end
-  end
-
  defimpl Enumerable do
    def count(map_set) do
      {:ok, MapSet.size(map_set)}
@@ -483,7 +389,7 @@ defmodule MapSet do

    def slice(map_set) do
      size = MapSet.size(map_set)
-      {:ok, size, &MapSet.to_list/1}
+      {:ok, size, &Enumerable.List.slice(MapSet.to_list(map_set), &1, &2, size)}
    end

    def reduce(map_set, acc, fun) do
@@ -494,8 +400,8 @@ defmodule MapSet do
  defimpl Collectable do
    def into(map_set) do
      fun = fn
-        list, {:cont, x} -> [x | list]
-        list, :done -> %{map_set | map: Map.merge(map_set.map, Map.from_keys(list, []))}
+        list, {:cont, x} -> [{x, []} | list]
+        list, :done -> %{map_set | map: Map.merge(map_set.map, Map.new(list))}
        _, :halt -> :ok
      end

@@ -508,7 +414,7 @@ defmodule MapSet do

    def inspect(map_set, opts) do
      opts = %Inspect.Opts{opts | charlists: :as_lists}
-      concat(["MapSet.new(", Inspect.List.inspect(MapSet.to_list(map_set), opts), ")"])
+      concat(["#MapSet<", Inspect.List.inspect(MapSet.to_list(map_set), opts), ">"])
    end
  end
 end
@@ -71,9 +71,8 @@ defmodule Module.LocalsTracker do
    :ok
  end

-  @doc """
-  Collect all conflicting imports with the given functions
-  """
+  # Collecting all conflicting imports with the given functions
+  @doc false
  def collect_imports_conflicts({set, _bag}, all_defined) do
    for {pair, _, meta, _} <- all_defined, n = out_neighbour(set, {:import, pair}) do
      {meta, {n, pair}}
@@ -1,168 +1,43 @@
 defmodule Module.ParallelChecker do
  @moduledoc false

-  import Kernel, except: [spawn: 3]
-
  @type cache() :: {pid(), :ets.tid()}
  @type warning() :: term()
  @type kind() :: :def | :defmacro
-  @type mode() :: :elixir | :erlang
-
-  @doc """
-  Initializes the parallel checker process.
-  """
-  def start_link(schedulers \\ nil) do
-    :gen_server.start_link(__MODULE__, schedulers, [])
-  end
-
-  @doc """
-  Stops the parallel checker process.
-  """
-  def stop(checker) do
-    send(checker, {__MODULE__, :stop})
-    :ok
-  end
-
-  @doc """
-  Gets the parallel checker data from pdict.
-  """
-  def get do
-    case :erlang.get(:elixir_checker_info) do
-      {parent, nil} ->
-        {:ok, checker} = start_link()
-        put(parent, checker)
-        {parent, checker}
-
-      {parent, checker} ->
-        {parent, checker}
-    end
-  end
-
-  @doc """
-  Stores the parallel checker information.
-  """
-  def put(pid, checker) when is_pid(pid) and is_pid(checker) do
-    :erlang.put(:elixir_checker_info, {pid, checker})
-  end
-
-  @doc """
-  Spawns a process that runs the parallel checker.
-  """
-  def spawn({pid, checker}, module, info) do
-    ref = make_ref()
-
-    spawned =
-      spawn(fn ->
-        Process.link(pid)
-        mon_ref = Process.monitor(pid)
-
-        receive do
-          {^ref, :cache, ets} ->
-            module_map =
-              if is_map(info) do
-                info
-              else
-                case File.read(info) do
-                  {:ok, binary} -> maybe_module_map(binary, module)
-                  {:error, _} -> nil
-                end
-              end
-
-            module_map && cache_from_module_map(ets, module_map)
-            send(checker, {ref, :cached})
-
-            receive do
-              {^ref, :check} ->
-                # Set the compiler info so we can collect warnings
-                :erlang.put(:elixir_compiler_info, {pid, self()})
-
-                warnings =
-                  if module_map do
-                    check_module(module_map, {checker, ets})
-                  else
-                    []
-                  end
-
-                send(pid, {__MODULE__, module, warnings})
-                send(checker, {__MODULE__, :done})
-            end
-
-          {:DOWN, ^mon_ref, _, _, _} ->
-            :ok
-        end
-      end)
-
-    register(checker, spawned, ref)
-    :ok
-  end
-
-  @doc """
-  Verifies the given compilation function
-  by starting a checker if one does not exist.
-  See `verify/3`.
-  """
-  def verify(fun) do
-    case :erlang.get(:elixir_compiler_info) do
-      :undefined ->
-        previous = :erlang.put(:elixir_checker_info, {self(), nil})
-
-        try do
-          result = fun.()
-
-          case :erlang.get(:elixir_checker_info) do
-            {_, nil} -> :ok
-            {_, checker} -> verify(checker, [])
-          end
-
-          result
-        after
-          {_, checker} = :erlang.get(:elixir_checker_info)
-
-          if previous != :undefined do
-            :erlang.put(:elixir_checker_info, previous)
-          else
-            :erlang.erase(:elixir_checker_info)
-          end
-
-          checker && stop(checker)
-        end
-
-      _ ->
-        # If we are during compilation, then they will be
-        # reported to the compiler, which will validate them.
-        fun.()
-    end
-  end

  @doc """
  Receives pairs of module maps and BEAM binaries. In parallel it verifies
  the modules and adds the ExCk chunk to the binaries. Returns the updated
-  list of warnings from the verification.
+  binaries and a list of warnings from the verification.
  """
-  @spec verify(pid(), [{module(), Path.t()}]) :: [warning()]
-  def verify(checker, runtime_files) do
-    for {module, file} <- runtime_files do
-      spawn({self(), checker}, module, file)
-    end
+  @spec verify([{map(), binary()}], [{module(), binary()}], pos_integer() | nil) :: [warning()]
+  def verify(compiled_modules, runtime_binaries, schedulers \\ nil) do
+    compiled_maps = Enum.map(compiled_modules, fn {map, _binary} -> {map.module, map} end)

-    modules = :gen_server.call(checker, :start, :infinity)
-    collect_results(modules, [])
+    case compiled_maps ++ runtime_binaries do
+      [] ->
+        []
+
+      check_modules ->
+        schedulers = schedulers || max(:erlang.system_info(:schedulers_online), 2)
+
+        {:ok, server} =
+          :gen_server.start_link(__MODULE__, [check_modules, self(), schedulers], [])
+
+        preload_cache(get_ets(server), check_modules)
+        start(server)
+        collect_results(length(check_modules), [])
+    end
  end

-  defp collect_results([], warnings) do
+  defp collect_results(0, warnings) do
    warnings
  end

-  defp collect_results(modules, warnings) do
+  defp collect_results(count, warnings) do
    receive do
-      {:warning, file, location, message} ->
-        file = file && Path.absname(file)
-        message = :unicode.characters_to_binary(message)
-        warning = {file, location, message}
-        collect_results(modules, [warning | warnings])
-
      {__MODULE__, _module, new_warnings} ->
-        collect_results(tl(modules), new_warnings ++ warnings)
+        collect_results(count - 1, new_warnings ++ warnings)
    end
  end

@@ -170,8 +45,8 @@ defmodule Module.ParallelChecker do
  Test cache.
  """
  def test_cache do
-    {:ok, checker} = start_link()
-    {checker, :gen_server.call(checker, :ets, :infinity)}
+    {:ok, pid} = :gen_server.start_link(__MODULE__, [[], self(), 1], [])
+    {pid, get_ets(pid)}
  end

  @doc """
@@ -192,17 +67,17 @@ defmodule Module.ParallelChecker do
  or if the function does not exist return `{:error, :function}`.
  """
  @spec fetch_export(cache(), module(), atom(), arity()) ::
-          {:ok, mode(), kind(), binary() | nil} | {:error, :function | :module}
+          {:ok, kind(), binary() | nil} | {:error, :function | :module}
  def fetch_export({_server, ets}, module, fun, arity) do
    case :ets.lookup(ets, {:cached, module}) do
-      [{_key, false}] ->
-        {:error, :module}
-
-      [{_key, mode}] ->
-        case :ets.lookup(ets, {:export, module, {fun, arity}}) do
-          [{_key, kind, reason}] -> {:ok, mode, kind, reason}
+      [{_key, true}] ->
+        case :ets.lookup(ets, {:export, {module, fun, arity}}) do
+          [{_key, kind, reason}] -> {:ok, kind, reason}
          [] -> {:error, :function}
        end
+
+      [{_key, false}] ->
+        {:error, :module}
    end
  end

@@ -214,34 +89,44 @@ defmodule Module.ParallelChecker do
  def all_exports({_server, ets}, module) do
    # This is only called after we get a deprecation notice
    # so we can assume it's a cached module
-    ets
-    |> :ets.match({{:export, module, :"$1"}, :_, :_})
-    |> Enum.flat_map(& &1)
+    [{_key, exports}] = :ets.lookup(ets, {:all_exports, module})
+
+    exports
+    |> Enum.map(fn {function, _kind} -> function end)
    |> Enum.sort()
  end

  ## Module checking

-  defp check_module(module_map, cache) do
-    %{module: module, file: file, compile_opts: compile_opts, definitions: definitions} =
-      module_map
+  defp check_module(module, cache) do
+    case extract_definitions(module) do
+      {:ok, module, file, definitions, no_warn_undefined} ->
+        Module.Types.warnings(module, file, definitions, no_warn_undefined, cache)
+        |> group_warnings()
+        |> emit_warnings()

+      :error ->
+        []
+    end
+  end
+
+  defp extract_definitions({module, module_map}) when is_map(module_map) do
    no_warn_undefined =
-      compile_opts
+      module_map.compile_opts
      |> extract_no_warn_undefined()
      |> merge_compiler_no_warn_undefined()

-    warnings =
-      module
-      |> Module.Types.warnings(file, definitions, no_warn_undefined, cache)
-      |> group_warnings()
-      |> emit_warnings()
+    {:ok, module, module_map.file, module_map.definitions, no_warn_undefined}
+  end

-    module_map
-    |> Map.get(:after_verify, [])
-    |> Enum.each(fn {verify_mod, verify_fun} -> apply(verify_mod, verify_fun, [module]) end)
-
-    warnings
+  defp extract_definitions({module, binary}) when is_binary(binary) do
+    with {:ok, {_, [debug_info: chunk]}} <- :beam_lib.chunks(binary, [:debug_info]),
+         {:debug_info_v1, backend, data} <- chunk,
+         {:ok, module_map} <- backend.debug_info(:elixir_v1, module, data, []) do
+      extract_definitions({module, module_map})
+    else
+      _ -> :error
+    end
  end

  defp extract_no_warn_undefined(compile_opts) do
@@ -254,8 +139,11 @@ defmodule Module.ParallelChecker do

  defp merge_compiler_no_warn_undefined(no_warn_undefined) do
    case Code.get_compiler_option(:no_warn_undefined) do
-      :all -> :all
-      list when is_list(list) -> no_warn_undefined ++ list
+      :all ->
+        :all
+
+      list when is_list(list) ->
+        no_warn_undefined ++ list
    end
  end

@@ -288,7 +176,7 @@ defmodule Module.ParallelChecker do

  defp format_locations(locations) do
    [
-      "Invalid call found at #{length(locations)} locations:\n",
+      "Found at #{length(locations)} locations:\n",
      Enum.map(locations, &format_location/1)
    ]
  end
@@ -316,166 +204,23 @@ defmodule Module.ParallelChecker do
    IO.puts(:stderr, [:elixir_errors.warning_prefix(), message])
  end

-  ## Cache
-
-  defp cache_module({server, ets}, module) do
-    if lock(server, module) do
-      cache_from_chunk(ets, module) || cache_from_info(ets, module)
-      unlock(server, module)
-    end
-  end
-
-  defp cache_from_chunk(ets, module) do
-    with {^module, binary, _filename} <- :code.get_object_code(module),
-         {:ok, {^module, [{~c"ExCk", chunk}]}} <- :beam_lib.chunks(binary, [~c"ExCk"]),
-         {:elixir_checker_v1, contents} <- :erlang.binary_to_term(chunk) do
-      cache_chunk(ets, module, contents.exports)
-      true
-    else
-      _ -> false
-    end
-  end
-
-  defp cache_from_info(ets, module) do
-    if Code.ensure_loaded?(module) do
-      {mode, exports} = info_exports(module)
-      deprecated = info_deprecated(module)
-      cache_info(ets, module, exports, deprecated, mode)
-    else
-      :ets.insert(ets, {{:cached, module}, false})
-    end
-  end
-
-  defp info_exports(module) do
-    map =
-      Map.new(
-        [{{:__info__, 1}, :def}] ++
-          behaviour_exports(module) ++
-          Enum.map(module.__info__(:macros), &{&1, :defmacro}) ++
-          Enum.map(module.__info__(:functions), &{&1, :def})
-      )
-
-    {:elixir, map}
-  rescue
-    _ -> {:erlang, Map.new(Enum.map(module.module_info(:exports), &{&1, :def}))}
-  end
-
-  defp info_deprecated(module) do
-    Map.new(module.__info__(:deprecated))
-  rescue
-    _ -> %{}
-  end
-
-  defp maybe_module_map(binary, module) when is_binary(binary) do
-    # If a module was compiled without debug_info,
-    # then there is no module_map for further verification.
-    with {:ok, {_, [debug_info: chunk]}} <- :beam_lib.chunks(binary, [:debug_info]),
-         {:debug_info_v1, backend, data} = chunk,
-         {:ok, module_map} <- backend.debug_info(:elixir_v1, module, data, []) do
-      module_map
-    else
-      _ -> nil
-    end
-  end
-
-  defp cache_from_module_map(ets, map) do
-    exports =
-      [{{:__info__, 1}, :def}] ++
-        behaviour_exports(map) ++
-        definitions_to_exports(map.definitions)
-
-    deprecated = Map.new(map.deprecated)
-    cache_info(ets, map.module, exports, deprecated, :elixir)
-  end
-
-  defp cache_info(ets, module, exports, deprecated, mode) do
-    Enum.each(exports, fn {{fun, arity}, kind} ->
-      reason = Map.get(deprecated, {fun, arity})
-      :ets.insert(ets, {{:export, module, {fun, arity}}, kind, reason})
-      {{fun, arity}, kind}
-    end)
-
-    :ets.insert(ets, {{:cached, module}, mode})
-  end
-
-  defp cache_chunk(ets, module, exports) do
-    Enum.each(exports, fn {{fun, arity}, %{kind: kind, deprecated_reason: reason}} ->
-      :ets.insert(ets, {{:export, module, {fun, arity}}, kind, reason})
-
-      {{fun, arity}, kind}
-    end)
-
-    :ets.insert(ets, {{:export, module, {:__info__, 1}}, :def, nil})
-    :ets.insert(ets, {{:cached, module}, :elixir})
-  end
-
-  defp behaviour_exports(%{is_behaviour: true}), do: [{{:behaviour_info, 1}, :def}]
-  defp behaviour_exports(%{is_behaviour: false}), do: []
-
-  defp behaviour_exports(module) when is_atom(module) do
-    if function_exported?(module, :behaviour_info, 1) do
-      [{{:behaviour_info, 1}, :def}]
-    else
-      []
-    end
-  end
-
-  defp definitions_to_exports(definitions) do
-    Enum.flat_map(definitions, fn {function, kind, _meta, _clauses} ->
-      if kind in [:def, :defmacro] do
-        [{function, kind}]
-      else
-        []
-      end
-    end)
-  end
-
-  defp lock(server, module) do
-    :gen_server.call(server, {:lock, module}, :infinity)
-  end
-
-  defp unlock(server, module) do
-    :gen_server.call(server, {:unlock, module}, :infinity)
-  end
-
-  defp register(server, pid, ref) do
-    :gen_server.cast(server, {:register, pid, ref})
-  end
-
  ## Server callbacks

-  def init(schedulers) do
-    ets = :ets.new(__MODULE__, [:set, :public, {:read_concurrency, true}])
+  def init([modules, send_results, schedulers]) do
+    ets = :ets.new(:checker_cache, [:set, :public, {:read_concurrency, true}])

    state = %{
      ets: ets,
      waiting: %{},
-      modules: [],
+      send_results: send_results,
+      modules: modules,
      spawned: 0,
-      schedulers: schedulers || max(:erlang.system_info(:schedulers_online), 2)
+      schedulers: schedulers
    }

    {:ok, state}
  end

-  def handle_call(:start, _from, %{ets: ets, modules: modules} = state) do
-    for {pid, ref} <- modules do
-      send(pid, {ref, :cache, ets})
-    end
-
-    for {_pid, ref} <- modules do
-      receive do
-        {^ref, :cached} -> :ok
-      end
-    end
-
-    {:reply, modules, run_checkers(state)}
-  end
-
-  def handle_call(:ets, _from, state) do
-    {:reply, state.ets, state}
-  end
-
  def handle_call({:lock, module}, from, %{waiting: waiting} = state) do
    case waiting do
      %{^module => froms} ->
@@ -495,30 +240,178 @@ defmodule Module.ParallelChecker do
    {:reply, :ok, %{state | waiting: waiting}}
  end

+  def handle_call(:get_ets, _from, %{ets: ets} = state) do
+    {:reply, ets, state}
+  end
+
+  def handle_cast(:start, state) do
+    {:noreply, spawn_checkers(state)}
+  end
+
  def handle_info({__MODULE__, :done}, state) do
    state = %{state | spawned: state.spawned - 1}
-    {:noreply, run_checkers(state)}
+
+    if state.spawned == 0 and state.modules == [] do
+      {:stop, :normal, state}
+    else
+      state = spawn_checkers(state)
+      {:noreply, state}
+    end
  end

-  def handle_info({__MODULE__, :stop}, state) do
-    {:stop, :normal, state}
+  defp lock(server, module) do
+    :gen_server.call(server, {:lock, module}, :infinity)
  end

-  def handle_cast({:register, pid, ref}, %{modules: modules} = state) do
-    {:noreply, %{state | modules: [{pid, ref} | modules]}}
+  defp unlock(server, module) do
+    :gen_server.call(server, {:unlock, module})
  end

-  defp run_checkers(%{modules: []} = state) do
+  defp get_ets(server) do
+    :gen_server.call(server, :get_ets)
+  end
+
+  defp start(server) do
+    :gen_server.cast(server, :start)
+  end
+
+  defp preload_cache(ets, modules) do
+    Enum.each(modules, fn
+      {_module, map} when is_map(map) -> cache_from_module_map(ets, map)
+      {module, binary} when is_binary(binary) -> cache_from_chunk(ets, module, binary)
+    end)
+  end
+
+  defp spawn_checkers(%{modules: []} = state) do
    state
  end

-  defp run_checkers(%{spawned: spawned, schedulers: schedulers} = state)
+  defp spawn_checkers(%{spawned: spawned, schedulers: schedulers} = state)
       when spawned >= schedulers do
    state
  end

-  defp run_checkers(%{modules: [{pid, ref} | modules]} = state) do
-    send(pid, {ref, :check})
-    run_checkers(%{state | modules: modules, spawned: state.spawned + 1})
+  defp spawn_checkers(%{modules: [{module, _} = verify | modules]} = state) do
+    parent = self()
+    ets = state.ets
+    send_results_pid = state.send_results
+
+    spawn_link(fn ->
+      warnings = check_module(verify, {parent, ets})
+      send(send_results_pid, {__MODULE__, module, warnings})
+      send(parent, {__MODULE__, :done})
+    end)
+
+    spawn_checkers(%{state | modules: modules, spawned: state.spawned + 1})
+  end
+
+  defp cache_module({server, ets}, module) do
+    if lock(server, module) do
+      cache_from_chunk(ets, module) || cache_from_info(ets, module)
+      unlock(server, module)
+    end
+  end
+
+  defp cache_from_chunk(ets, module) do
+    case :code.get_object_code(module) do
+      {^module, binary, _filename} -> cache_from_chunk(ets, module, binary)
+      _other -> false
+    end
+  end
+
+  defp cache_from_chunk(ets, module, binary) do
+    with {:ok, {_, [{'ExCk', chunk}]}} <- :beam_lib.chunks(binary, ['ExCk']),
+         {:elixir_checker_v1, contents} <- :erlang.binary_to_term(chunk) do
+      cache_chunk(ets, module, contents.exports)
+      true
+    else
+      _ -> false
+    end
+  end
+
+  defp cache_from_module_map(ets, map) do
+    exports =
+      [{{:__info__, 1}, :def}] ++
+        behaviour_exports(map) ++
+        definitions_to_exports(map.definitions)
+
+    deprecated = Map.new(map.deprecated)
+    cache_info(ets, map.module, exports, deprecated)
+  end
+
+  defp cache_from_info(ets, module) do
+    if Code.ensure_loaded?(module) do
+      exports = info_exports(module)
+      deprecated = info_deprecated(module)
+      cache_info(ets, module, exports, deprecated)
+    else
+      :ets.insert(ets, {{:cached, module}, false})
+    end
+  end
+
+  defp info_exports(module) do
+    Map.new(
+      [{{:__info__, 1}, :def}] ++
+        behaviour_exports(module) ++
+        Enum.map(module.__info__(:macros), &{&1, :defmacro}) ++
+        Enum.map(module.__info__(:functions), &{&1, :def})
+    )
+  rescue
+    _ -> Map.new(Enum.map(module.module_info(:exports), &{&1, :def}))
+  end
+
+  defp info_deprecated(module) do
+    Map.new(module.__info__(:deprecated))
+  rescue
+    _ -> %{}
+  end
+
+  defp cache_info(ets, module, exports, deprecated) do
+    exports =
+      Enum.map(exports, fn {{fun, arity}, kind} ->
+        reason = Map.get(deprecated, {fun, arity})
+        :ets.insert(ets, {{:export, {module, fun, arity}}, kind, reason})
+
+        {{fun, arity}, kind}
+      end)
+
+    :ets.insert(ets, {{:all_exports, module}, exports})
+    :ets.insert(ets, {{:cached, module}, true})
+  end
+
+  defp cache_chunk(ets, module, exports) do
+    exports =
+      Enum.map(exports, fn {{fun, arity}, %{kind: kind, deprecated_reason: reason}} ->
+        :ets.insert(ets, {{:export, {module, fun, arity}}, kind, reason})
+
+        {{fun, arity}, kind}
+      end)
+
+    :ets.insert(ets, {{:export, {module, :__info__, 1}}, :def, nil})
+    exports = [{{:__info__, 1}, :def} | exports]
+
+    :ets.insert(ets, {{:all_exports, module}, exports})
+    :ets.insert(ets, {{:cached, module}, true})
+  end
+
+  defp behaviour_exports(%{is_behaviour: true}), do: [{{:behaviour_info, 1}, :def}]
+  defp behaviour_exports(%{is_behaviour: false}), do: []
+
+  defp behaviour_exports(module) when is_atom(module) do
+    if {:behaviour_info, 1} in module.module_info(:functions) do
+      [{{:behaviour_info, 1}, :def}]
+    else
+      []
+    end
+  end
+
+  defp definitions_to_exports(definitions) do
+    Enum.flat_map(definitions, fn {function, kind, _meta, _clauses} ->
+      if kind in [:def, :defmacro] do
+        [{function, kind}]
+      else
+        []
+      end
+    end)
  end
 end
@@ -60,7 +60,7 @@ defmodule Module.Types do
    head_stack = Unify.push_expr_stack(def_expr, stack)

    with {:ok, _types, context} <- Pattern.of_head(args, guards, head_stack, context),
-         {:ok, _type, context} <- Expr.of_expr(body, :dynamic, stack, context) do
+         {:ok, _type, context} <- Expr.of_expr(body, stack, context) do
      context.warnings
    else
      {:error, {type, error, context}} ->
@@ -92,7 +92,7 @@ defmodule Module.Types do
      traces: %{},
      # Counter to give type variables unique names
      counter: 0,
-      # Track if a variable was inferred from a type guard function such is_tuple/1
+      # Track if a variable was infered from a type guard function such is_tuple/1
      # or a guard function that fails such as elem/2, possible values are:
      # `:guarded` when `is_tuple(x)`
      # `:guarded` when `is_tuple and elem(x, 0)`
@@ -115,59 +115,133 @@ defmodule Module.Types do
      # When false do not add a trace when a type variable is refined,
      # useful when merging contexts where the variables already have traces
      trace: true,
-      # There are two factors that control how we track guards.
-      #
-      # * consider_type_guards?: if type guards should be considered.
-      #   This applies only at the root and root-based "and" and "or" nodes.
-      #
-      # * keep_guarded? - if a guarded clause should remain as guarded
-      #   even on failure. Used on the right side of and.
-      #
-      type_guards: {_consider_type_guards? = true, _keep_guarded? = false},
+      # Track if we are in a context where type guard functions should
+      # affect inference
+      type_guards_enabled?: true,
      # Context used to determine if unification is bi-directional, :expr
      # is directional, :pattern is bi-directional
      context: nil
    }
  end

+  ## VARIABLE LIFTING
+
+  @doc """
+  Lifts type variables to their infered types from the context.
+  """
+  def lift_types(types, context) do
+    context = %{
+      types: context.types,
+      lifted_types: %{},
+      lifted_counter: 0
+    }
+
+    {types, _context} = Enum.map_reduce(types, context, &do_lift_type/2)
+    types
+  end
+
+  @doc """
+  Lifts a single type to its infered type from the context.
+  """
+  def lift_type(type, context) do
+    context = %{
+      types: context.types,
+      lifted_types: %{},
+      lifted_counter: 0
+    }
+
+    {type, _context} = do_lift_type(type, context)
+    type
+  end
+
+  # Lift type variable to its infered (hopefully concrete) types from the context
+  defp do_lift_type({:var, var}, context) do
+    case Map.fetch(context.lifted_types, var) do
+      {:ok, lifted_var} ->
+        {{:var, lifted_var}, context}
+
+      :error ->
+        case Map.fetch(context.types, var) do
+          {:ok, :unbound} ->
+            new_lifted_var(var, context)
+
+          {:ok, type} ->
+            # Remove visited types to avoid infinite loops
+            # then restore after we are done recursing on vars
+            types = context.types
+            context = %{context | types: Map.delete(context.types, var)}
+            {type, context} = do_lift_type(type, context)
+            {type, %{context | types: types}}
+
+          :error ->
+            new_lifted_var(var, context)
+        end
+    end
+  end
+
+  defp do_lift_type({:tuple, n, types}, context) do
+    {types, context} = Enum.map_reduce(types, context, &do_lift_type/2)
+    {{:tuple, n, types}, context}
+  end
+
+  defp do_lift_type({:map, pairs}, context) do
+    {pairs, context} =
+      Enum.map_reduce(pairs, context, fn {kind, key, value}, context ->
+        {key, context} = do_lift_type(key, context)
+        {value, context} = do_lift_type(value, context)
+        {{kind, key, value}, context}
+      end)
+
+    {{:map, pairs}, context}
+  end
+
+  defp do_lift_type({:list, type}, context) do
+    {type, context} = do_lift_type(type, context)
+    {{:list, type}, context}
+  end
+
+  defp do_lift_type(other, context) do
+    {other, context}
+  end
+
+  defp new_lifted_var(original_var, context) do
+    types = Map.put(context.lifted_types, original_var, context.lifted_counter)
+    counter = context.lifted_counter + 1
+
+    type = {:var, context.lifted_counter}
+    context = %{context | lifted_types: types, lifted_counter: counter}
+    {type, context}
+  end
+
  ## ERROR TO WARNING

  # Collect relevant information from context and traces to report error
-  def error_to_warning(:unable_apply, {mfa, args, expected, signature, stack}, context) do
-    {fun, arity} = context.function
-    location = {context.file, get_line(stack), {context.module, fun, arity}}
-
-    traces = type_traces(stack, context)
-    {[signature | args], traces} = lift_all_types([signature | args], traces, context)
-    error = {:unable_apply, mfa, args, expected, signature, {location, stack.last_expr, traces}}
-    {Module.Types, error, location}
-  end
-
  def error_to_warning(:unable_unify, {left, right, stack}, context) do
    {fun, arity} = context.function
-    location = {context.file, get_line(stack), {context.module, fun, arity}}
+    line = get_meta(stack.last_expr)[:line]
+    location = {context.file, line, {context.module, fun, arity}}

    traces = type_traces(stack, context)
-    {[left, right], traces} = lift_all_types([left, right], traces, context)
+    traces = tag_traces(traces, context)
+
    error = {:unable_unify, left, right, {location, stack.last_expr, traces}}
    {Module.Types, error, location}
  end

-  defp get_line(stack), do: stack.last_expr |> get_meta() |> Keyword.get(:line, 0)
-
  # Collect relevant traces from context.traces using stack.unify_stack
  defp type_traces(stack, context) do
    # TODO: Do we need the unify_stack or is enough to only get the last variable
    #       in the stack since we get related variables anyway?
    stack =
      stack.unify_stack
+      |> Enum.uniq()
      |> Enum.flat_map(&[&1 | related_variables(&1, context.types)])
      |> Enum.uniq()

    Enum.flat_map(stack, fn var_index ->
      with %{^var_index => traces} <- context.traces,
           %{^var_index => expr_var} <- context.types_to_vars do
-        Enum.map(traces, &tag_trace(expr_var, &1, context))
+        Enum.map(traces, &{expr_var, &1})
      else
        _other -> []
      end
@@ -185,96 +259,56 @@ defmodule Module.Types do
  end

  # Tag if trace is for a concrete type or type variable
-  defp tag_trace(var, {type, expr, location}, context) do
-    with {:var, var_index} <- type,
-         %{^var_index => expr_var} <- context.types_to_vars do
-      {:var, var, expr_var, expr, location}
-    else
-      _ -> {:type, var, type, expr, location}
-    end
-  end
-
-  defp lift_all_types(types, traces, context) do
-    trace_types = for({:type, _, type, _, _} <- traces, do: type)
-    {types, lift_context} = Unify.lift_types(types, context)
-    {trace_types, _lift_context} = Unify.lift_types(trace_types, lift_context)
-
-    {traces, []} =
-      Enum.map_reduce(traces, trace_types, fn
-        {:type, var, _, expr, location}, [type | acc] -> {{:type, var, type, expr, location}, acc}
-        other, acc -> {other, acc}
-      end)
-
-    {types, traces}
+  defp tag_traces(traces, context) do
+    Enum.flat_map(traces, fn {var, {type, expr, location}} ->
+      with {:var, var_index} <- type,
+           %{^var_index => expr_var} <- context.types_to_vars do
+        [{var, {:var, expr_var, expr, location}}]
+      else
+        _ -> [{var, {:type, type, expr, location}}]
+      end
+    end)
  end

  ## FORMAT WARNINGS

-  def format_warning({:unable_apply, mfa, args, expected, signature, {location, expr, traces}}) do
-    {original_module, original_function, arity} = mfa
-    {_, _, args} = mfa_or_fa = erl_to_ex(original_module, original_function, args, [])
-    {module, function, ^arity} = call_to_mfa(mfa_or_fa)
-    format_mfa = Exception.format_mfa(module, function, arity)
-    {traces, [] = _hints} = format_traces(traces, [], false)
-
-    clauses =
-      Enum.map(signature, fn {ins, out} ->
-        {_, _, ins} = erl_to_ex(original_module, original_function, ins, [])
-
-        {:fun, [{ins, out}]}
-        |> Unify.format_type(false)
-        |> IO.iodata_to_binary()
-        |> binary_slice(1..-2//1)
-      end)
-
-    [
-      "expected #{format_mfa} to have signature:\n\n    ",
-      Enum.map_join(args, ", ", &Unify.format_type(&1, false)),
-      " -> #{Unify.format_type(expected, false)}",
-      "\n\nbut it has signature:\n\n    ",
-      indent(Enum.join(clauses, "\n")),
-      "\n\n",
-      format_expr(expr, location),
-      traces,
-      "Conflict found at"
-    ]
-  end
-
  def format_warning({:unable_unify, left, right, {location, expr, traces}}) do
-    if map_type?(left) and map_type?(right) and match?({:ok, _, _}, missing_field(left, right)) do
-      {:ok, atom, known_atoms} = missing_field(left, right)
+    cond do
+      map_type?(left) and map_type?(right) and match?({:ok, _, _}, missing_field(left, right)) ->
+        {:ok, atom, known_atoms} = missing_field(left, right)

-      # Drop the last trace which is the expression map.foo
-      traces = Enum.drop(traces, 1)
-      {traces, hints} = format_traces(traces, [left, right], true)
+        # Drop the last trace which is the expression map.foo
+        traces = Enum.drop(traces, 1)
+        {traces, hints} = format_traces(traces, true)

-      [
-        "undefined field \"#{atom}\" ",
-        format_expr(expr, location),
-        "expected one of the following fields: ",
-        Enum.join(Enum.sort(known_atoms), ", "),
-        "\n\n",
-        traces,
-        format_message_hints(hints),
-        "Conflict found at"
-      ]
-    else
-      simplify_left? = simplify_type?(left, right)
-      simplify_right? = simplify_type?(right, left)
+        [
+          "undefined field \"#{atom}\" ",
+          format_expr(expr, location),
+          "expected one of the following fields: ",
+          Enum.map_join(Enum.sort(known_atoms), ", ", & &1),
+          "\n\n",
+          traces,
+          format_message_hints(hints),
+          "Conflict found at"
+        ]

-      {traces, hints} = format_traces(traces, [left, right], simplify_left? or simplify_right?)
+      true ->
+        simplify_left? = simplify_type?(left, right)
+        simplify_right? = simplify_type?(right, left)

-      [
-        "incompatible types:\n\n    ",
-        Unify.format_type(left, simplify_left?),
-        " !~ ",
-        Unify.format_type(right, simplify_right?),
-        "\n\n",
-        format_expr(expr, location),
-        traces,
-        format_message_hints(hints),
-        "Conflict found at"
-      ]
+        {traces, hints} = format_traces(traces, simplify_left? or simplify_right?)
+
+        [
+          "incompatible types:\n\n    ",
+          Unify.format_type(left, simplify_left?),
+          " !~ ",
+          Unify.format_type(right, simplify_right?),
+          "\n\n",
+          format_expr(expr, location),
+          traces,
+          format_message_hints(hints),
+          "Conflict found at"
+        ]
    end
  end

@@ -303,17 +337,16 @@ defmodule Module.Types do
    end
  end

-  defp format_traces([], _types, _simplify?) do
+  defp format_traces([], _simplify?) do
    {[], []}
  end

-  defp format_traces(traces, types, simplify?) do
+  defp format_traces(traces, simplify?) do
    traces
-    |> Enum.uniq()
    |> Enum.reverse()
    |> Enum.map_reduce([], fn
-      {:type, var, type, expr, location}, hints ->
-        {hint, hints} = format_type_hint(type, types, expr, hints)
+      {var, {:type, type, expr, location}}, hints ->
+        {hint, hints} = format_type_hint(type, expr, hints)

        trace = [
          "where \"",
@@ -330,7 +363,7 @@ defmodule Module.Types do

        {trace, hints}

-      {:var, var1, var2, expr, location}, hints ->
+      {var1, {:var, var2, expr, location}}, hints ->
        trace = [
          "where \"",
          Macro.to_string(var1),
@@ -358,7 +391,7 @@ defmodule Module.Types do
  end

  defp simplify_type?(type, other) do
-    map_like_type?(type) and not map_like_type?(other)
+    map_type?(type) and not map_type?(other)
  end

  ## EXPRESSION FORMATTING
@@ -401,16 +434,14 @@ defmodule Module.Types do
  ## Hints

  defp format_message_hints(hints) do
-    hints
-    |> Enum.uniq()
-    |> Enum.reverse()
-    |> Enum.map(&[format_message_hint(&1), "\n"])
+    hints |> Enum.uniq() |> Enum.reverse() |> Enum.map(&format_message_hint/1)
  end

  defp format_message_hint(:inferred_dot) do
    """
    HINT: "var.field" (without parentheses) implies "var" is a map() while \
    "var.fun()" (with parentheses) implies "var" is an atom()
+
    """
  end

@@ -420,24 +451,18 @@ defmodule Module.Types do
    integer() unless said otherwise. For example, <<expr>> assumes "expr" \
    is an integer. Pass a modifier, such as <<expr::float>> or <<expr::binary>>, \
    to change the default behaviour.
+
    """
  end

-  defp format_message_hint({:sized_and_unsize_tuples, {size, var}}) do
-    """
-    HINT: use pattern matching or "is_tuple(#{Macro.to_string(var)}) and \
-    tuple_size(#{Macro.to_string(var)}) == #{size}" to guard a sized tuple.
-    """
-  end
-
-  defp format_type_hint(type, types, expr, hints) do
-    case format_type_hint(type, types, expr) do
+  defp format_type_hint(type, expr, hints) do
+    case format_type_hint(type, expr) do
      {message, hint} -> {message, [hint | hints]}
      :error -> {[], hints}
    end
  end

-  defp format_type_hint(type, types, expr) do
+  defp format_type_hint(type, expr) do
    cond do
      dynamic_map_dot?(type, expr) ->
        {" (due to calling var.field)", :inferred_dot}
@@ -448,9 +473,6 @@ defmodule Module.Types do
      inferred_bitstring_spec?(type, expr) ->
        {[], :inferred_bitstring_spec}

-      message = sized_and_unsize_tuples(expr, types) ->
-        {[], {:sized_and_unsize_tuples, message}}
-
      true ->
        :error
    end
@@ -486,33 +508,15 @@ defmodule Module.Types do
    end
  end

-  defp sized_and_unsize_tuples({{:., _, [:erlang, :is_tuple]}, _, [var]}, types) do
-    case Enum.find(types, &match?({:tuple, _, _}, &1)) do
-      {:tuple, size, _} ->
-        {size, var}
-
-      nil ->
-        nil
-    end
-  end
-
-  defp sized_and_unsize_tuples(_expr, _types) do
-    nil
-  end
-
  ## Formatting helpers

  defp indent(string) do
-    String.replace(string, "\n", "\n    ")
+    String.replace(string, "\n", "    \n")
  end

  defp map_type?({:map, _}), do: true
  defp map_type?(_other), do: false

-  defp map_like_type?({:map, _}), do: true
-  defp map_like_type?({:union, union}), do: Enum.any?(union, &map_like_type?/1)
-  defp map_like_type?(_other), do: false
-
  defp atom_type?(:atom), do: true
  defp atom_type?({:atom, _}), do: false
  defp atom_type?({:union, union}), do: Enum.all?(union, &atom_type?/1)
@@ -520,7 +524,4 @@ defmodule Module.Types do

  defp integer_type?(:integer), do: true
  defp integer_type?(_other), do: false
-
-  defp call_to_mfa({{:., _, [mod, fun]}, _, args}), do: {mod, fun, length(args)}
-  defp call_to_mfa({fun, _, args}) when is_atom(fun), do: {Kernel, fun, length(args)}
 end
@@ -4,57 +4,58 @@ defmodule Module.Types.Expr do
  alias Module.Types.{Of, Pattern}
  import Module.Types.{Helpers, Unify}

-  def of_expr(expr, expected, %{context: stack_context} = stack, context)
-      when stack_context != :expr do
-    of_expr(expr, expected, %{stack | context: :expr}, context)
+  def of_expr(expr, %{context: stack_context} = stack, context) when stack_context != :expr do
+    of_expr(expr, %{stack | context: :expr}, context)
  end

  # :atom
-  def of_expr(atom, _expected, _stack, context) when is_atom(atom) do
+  def of_expr(atom, _stack, context) when is_atom(atom) do
    {:ok, {:atom, atom}, context}
  end

  # 12
-  def of_expr(literal, _expected, _stack, context) when is_integer(literal) do
+  def of_expr(literal, _stack, context) when is_integer(literal) do
    {:ok, :integer, context}
  end

  # 1.2
-  def of_expr(literal, _expected, _stack, context) when is_float(literal) do
+  def of_expr(literal, _stack, context) when is_float(literal) do
    {:ok, :float, context}
  end

  # "..."
-  def of_expr(literal, _expected, _stack, context) when is_binary(literal) do
+  def of_expr(literal, _stack, context) when is_binary(literal) do
    {:ok, :binary, context}
  end

  # #PID<...>
-  def of_expr(literal, _expected, _stack, context) when is_pid(literal) do
+  def of_expr(literal, _stack, context) when is_pid(literal) do
    {:ok, :dynamic, context}
  end

  # <<...>>>
-  def of_expr({:<<>>, _meta, args}, _expected, stack, context) do
-    case Of.binary(args, stack, context, &of_expr/4) do
+  def of_expr({:<<>>, _meta, args}, stack, context) do
+    result = Of.binary(args, stack, context, &of_expr/3)
+
+    case result do
      {:ok, context} -> {:ok, :binary, context}
      {:error, reason} -> {:error, reason}
    end
  end

  # left | []
-  def of_expr({:|, _meta, [left_expr, []]} = expr, _expected, stack, context) do
+  def of_expr({:|, _meta, [left_expr, []]} = expr, stack, context) do
    stack = push_expr_stack(expr, stack)
-    of_expr(left_expr, :dynamic, stack, context)
+    of_expr(left_expr, stack, context)
  end

  # left | right
-  def of_expr({:|, _meta, [left_expr, right_expr]} = expr, _expected, stack, context) do
+  def of_expr({:|, _meta, [left_expr, right_expr]} = expr, stack, context) do
    stack = push_expr_stack(expr, stack)

-    case of_expr(left_expr, :dynamic, stack, context) do
+    case of_expr(left_expr, stack, context) do
      {:ok, left, context} ->
-        case of_expr(right_expr, :dynamic, stack, context) do
+        case of_expr(right_expr, stack, context) do
          {:ok, {:list, right}, context} ->
            {:ok, to_union([left, right], context), context}

@@ -71,23 +72,22 @@ defmodule Module.Types.Expr do
  end

  # []
-  def of_expr([], _expected, _stack, context) do
+  def of_expr([], _stack, context) do
    {:ok, {:list, :dynamic}, context}
  end

  # [expr, ...]
-  def of_expr(exprs, _expected, stack, context) when is_list(exprs) do
+  def of_expr(exprs, stack, context) when is_list(exprs) do
    stack = push_expr_stack(exprs, stack)

-    case map_reduce_ok(exprs, context, &of_expr(&1, :dynamic, stack, &2)) do
+    case map_reduce_ok(exprs, context, &of_expr(&1, stack, &2)) do
      {:ok, types, context} -> {:ok, {:list, to_union(types, context)}, context}
      {:error, reason} -> {:error, reason}
    end
  end

  # __CALLER__
-  def of_expr({:__CALLER__, _meta, var_context}, _expected, _stack, context)
-      when is_atom(var_context) do
+  def of_expr({:__CALLER__, _meta, var_context}, _stack, context) when is_atom(var_context) do
    struct_pair = {:required, {:atom, :__struct__}, {:atom, Macro.Env}}

    pairs =
@@ -99,8 +99,7 @@ defmodule Module.Types.Expr do
  end

  # __STACKTRACE__
-  def of_expr({:__STACKTRACE__, _meta, var_context}, _expected, _stack, context)
-      when is_atom(var_context) do
+  def of_expr({:__STACKTRACE__, _meta, var_context}, _stack, context) when is_atom(var_context) do
    file = {:tuple, 2, [{:atom, :file}, {:list, :integer}]}
    line = {:tuple, 2, [{:atom, :line}, :integer]}
    file_line = {:list, {:union, [file, line]}}
@@ -109,152 +108,107 @@ defmodule Module.Types.Expr do
  end

  # var
-  def of_expr(var, _expected, _stack, context) when is_var(var) do
+  def of_expr(var, _stack, context) when is_var(var) do
    {:ok, get_var!(var, context), context}
  end

  # {left, right}
-  def of_expr({left, right}, expected, stack, context) do
-    of_expr({:{}, [], [left, right]}, expected, stack, context)
+  def of_expr({left, right}, stack, context) do
+    of_expr({:{}, [], [left, right]}, stack, context)
  end

  # {...}
-  def of_expr({:{}, _meta, exprs} = expr, _expected, stack, context) do
+  def of_expr({:{}, _meta, exprs} = expr, stack, context) do
    stack = push_expr_stack(expr, stack)

-    case map_reduce_ok(exprs, context, &of_expr(&1, :dynamic, stack, &2)) do
+    case map_reduce_ok(exprs, context, &of_expr(&1, stack, &2)) do
      {:ok, types, context} -> {:ok, {:tuple, length(types), types}, context}
      {:error, reason} -> {:error, reason}
    end
  end

  # left = right
-  def of_expr({:=, _meta, [left_expr, right_expr]} = expr, _expected, stack, context) do
-    # TODO: We might want to bring the expected type forward in case the type of this
-    #       pattern is not useful. For example: 1 = _ = expr
-
+  def of_expr({:=, _meta, [left_expr, right_expr]} = expr, stack, context) do
    stack = push_expr_stack(expr, stack)

    with {:ok, left_type, context} <-
           Pattern.of_pattern(left_expr, stack, context),
-         {:ok, right_type, context} <- of_expr(right_expr, left_type, stack, context),
-         do: unify(right_type, left_type, stack, context)
+         {:ok, right_type, context} <- of_expr(right_expr, stack, context),
+         do: unify(right_type, left_type, %{stack | context: :pattern}, context)
  end

  # %{map | ...}
-  def of_expr({:%{}, _, [{:|, _, [map, args]}]} = expr, _expected, stack, context) do
+  def of_expr({:%{}, _, [{:|, _, [map, args]}]} = expr, stack, context) do
    stack = push_expr_stack(expr, stack)
-    map_type = {:map, [{:optional, :dynamic, :dynamic}]}

-    with {:ok, map_type, context} <- of_expr(map, map_type, stack, context),
-         {:ok, {:map, arg_pairs}, context} <- Of.closed_map(args, stack, context, &of_expr/4),
+    with {:ok, map_type, context} <- of_expr(map, stack, context),
+         {:ok, {:map, arg_pairs}, context} <- Of.closed_map(args, stack, context, &of_expr/3),
         dynamic_value_pairs =
           Enum.map(arg_pairs, fn {:required, key, _value} -> {:required, key, :dynamic} end),
         args_type = {:map, dynamic_value_pairs ++ [{:optional, :dynamic, :dynamic}]},
-         {:ok, type, context} <- unify(map_type, args_type, stack, context) do
+         {:ok, type, context} <- unify(args_type, map_type, stack, context) do
      # Retrieve map type and overwrite with the new value types from the map update
-      case resolve_var(type, context) do
-        {:map, pairs} ->
-          updated_pairs =
-            Enum.reduce(arg_pairs, pairs, fn {:required, key, value}, pairs ->
-              List.keyreplace(pairs, key, 1, {:required, key, value})
-            end)
+      {:map, pairs} = resolve_var(type, context)

-          {:ok, {:map, updated_pairs}, context}
+      updated_pairs =
+        Enum.reduce(arg_pairs, pairs, fn {:required, key, value}, pairs ->
+          List.keyreplace(pairs, key, 1, {:required, key, value})
+        end)

-        _ ->
-          {:ok, :dynamic, context}
-      end
+      {:ok, {:map, updated_pairs}, context}
    end
  end

  # %Struct{map | ...}
-  def of_expr(
-        {:%, meta, [module, {:%{}, _, [{:|, _, [_, _]}]} = update]} = expr,
-        _expected,
-        stack,
-        context
-      ) do
+  def of_expr({:%, meta, [module, {:%{}, _, [{:|, _, [_, _]}]} = update]} = expr, stack, context) do
    stack = push_expr_stack(expr, stack)
-    map_type = {:map, [{:optional, :dynamic, :dynamic}]}

    with {:ok, struct, context} <- Of.struct(module, meta, context),
-         {:ok, update, context} <- of_expr(update, map_type, stack, context) do
+         {:ok, update, context} <- of_expr(update, stack, context) do
      unify(update, struct, stack, context)
    end
  end

  # %{...}
-  def of_expr({:%{}, _meta, args} = expr, _expected, stack, context) do
+  def of_expr({:%{}, _meta, args} = expr, stack, context) do
    stack = push_expr_stack(expr, stack)
-    Of.closed_map(args, stack, context, &of_expr/4)
+    Of.closed_map(args, stack, context, &of_expr/3)
  end

  # %Struct{...}
-  def of_expr({:%, meta1, [module, {:%{}, _meta2, args}]} = expr, _expected, stack, context) do
+  def of_expr({:%, meta1, [module, {:%{}, _meta2, args}]} = expr, stack, context) do
    stack = push_expr_stack(expr, stack)

    with {:ok, struct, context} <- Of.struct(module, meta1, context),
-         {:ok, map, context} <- Of.open_map(args, stack, context, &of_expr/4) do
+         {:ok, map, context} <- Of.open_map(args, stack, context, &of_expr/3) do
      unify(map, struct, stack, context)
    end
  end

  # ()
-  def of_expr({:__block__, _meta, []}, _expected, _stack, context) do
+  def of_expr({:__block__, _meta, []}, _stack, context) do
    {:ok, {:atom, nil}, context}
  end

  # (expr; expr)
-  def of_expr({:__block__, _meta, exprs}, expected, stack, context) do
-    expected_types = List.duplicate(:dynamic, length(exprs) - 1) ++ [expected]
-
-    result =
-      map_reduce_ok(Enum.zip(exprs, expected_types), context, fn {expr, expected}, context ->
-        of_expr(expr, expected, stack, context)
-      end)
-
-    case result do
+  def of_expr({:__block__, _meta, exprs}, stack, context) do
+    case map_reduce_ok(exprs, context, &of_expr(&1, stack, &2)) do
      {:ok, expr_types, context} -> {:ok, Enum.at(expr_types, -1), context}
      {:error, reason} -> {:error, reason}
    end
  end

-  # cond do pat -> expr end
-  def of_expr({:cond, _meta, [[{:do, clauses}]]} = expr, _expected, stack, context) do
-    stack = push_expr_stack(expr, stack)
-
-    {result, context} =
-      reduce_ok(clauses, context, fn {:->, meta, [head, body]}, context = acc ->
-        case of_expr(head, :dynamic, stack, context) do
-          {:ok, _, context} ->
-            with {:ok, _expr_type, context} <- of_expr(body, :dynamic, stack, context) do
-              {:ok, keep_warnings(acc, context)}
-            end
-
-          error ->
-            # Skip the clause if it the head has an error
-            if meta[:generated], do: {:ok, acc}, else: error
-        end
-      end)
-
-    case result do
-      :ok -> {:ok, :dynamic, context}
-      :error -> {:error, context}
-    end
-  end
-
  # case expr do pat -> expr end
-  def of_expr({:case, _meta, [case_expr, [{:do, clauses}]]} = expr, _expected, stack, context) do
+  def of_expr({:case, _meta, [case_expr, [{:do, clauses}]]} = expr, stack, context) do
    stack = push_expr_stack(expr, stack)

-    with {:ok, _expr_type, context} <- of_expr(case_expr, :dynamic, stack, context),
+    with {:ok, _expr_type, context} <- of_expr(case_expr, stack, context),
         {:ok, context} <- of_clauses(clauses, stack, context),
         do: {:ok, :dynamic, context}
  end

  # fn pat -> expr end
-  def of_expr({:fn, _meta, clauses} = expr, _expected, stack, context) do
+  def of_expr({:fn, _meta, clauses} = expr, stack, context) do
    stack = push_expr_stack(expr, stack)

    case of_clauses(clauses, stack, context) do
@@ -267,7 +221,7 @@ defmodule Module.Types.Expr do
  @try_clause_blocks [:catch, :else, :after]

  # try do expr end
-  def of_expr({:try, _meta, [blocks]} = expr, _expected, stack, context) do
+  def of_expr({:try, _meta, [blocks]} = expr, stack, context) do
    stack = push_expr_stack(expr, stack)

    {result, context} =
@@ -277,20 +231,20 @@ defmodule Module.Types.Expr do
            {:->, _, [[{:in, _, [var, _exceptions]}], body]}, context = acc ->
              {_type, context} = new_pattern_var(var, context)

-              with {:ok, context} <- of_expr_context(body, :dynamic, stack, context) do
+              with {:ok, context} <- of_expr_context(body, stack, context) do
                {:ok, keep_warnings(acc, context)}
              end

            {:->, _, [[var], body]}, context = acc ->
              {_type, context} = new_pattern_var(var, context)

-              with {:ok, context} <- of_expr_context(body, :dynamic, stack, context) do
+              with {:ok, context} <- of_expr_context(body, stack, context) do
                {:ok, keep_warnings(acc, context)}
              end
          end)

        {block, body}, context = acc when block in @try_blocks ->
-          with {:ok, context} <- of_expr_context(body, :dynamic, stack, context) do
+          with {:ok, context} <- of_expr_context(body, stack, context) do
            {:ok, keep_warnings(acc, context)}
          end

@@ -305,7 +259,7 @@ defmodule Module.Types.Expr do
  end

  # receive do pat -> expr end
-  def of_expr({:receive, _meta, [blocks]} = expr, _expected, stack, context) do
+  def of_expr({:receive, _meta, [blocks]} = expr, stack, context) do
    stack = push_expr_stack(expr, stack)

    {result, context} =
@@ -317,8 +271,8 @@ defmodule Module.Types.Expr do
          of_clauses(clauses, stack, context)

        {:after, [{:->, _meta, [head, body]}]}, context = acc ->
-          with {:ok, _type, context} <- of_expr(head, :dynamic, stack, context),
-               {:ok, _type, context} <- of_expr(body, :dynamic, stack, context),
+          with {:ok, _type, context} <- of_expr(head, stack, context),
+               {:ok, _type, context} <- of_expr(body, stack, context),
               do: {:ok, keep_warnings(acc, context)}
      end)

@@ -329,7 +283,7 @@ defmodule Module.Types.Expr do
  end

  # for pat <- expr do expr end
-  def of_expr({:for, _meta, [_ | _] = args} = expr, _expected, stack, context) do
+  def of_expr({:for, _meta, args} = expr, stack, context) do
    stack = push_expr_stack(expr, stack)
    {clauses, [[{:do, block} | opts]]} = Enum.split(args, -1)

@@ -340,7 +294,7 @@ defmodule Module.Types.Expr do
          {:ok, :dynamic, context}
        end
      else
-        with {:ok, _type, context} <- of_expr(block, :dynamic, stack, context) do
+        with {:ok, _type, context} <- of_expr(block, stack, context) do
          {:ok, :dynamic, context}
        end
      end
@@ -348,7 +302,7 @@ defmodule Module.Types.Expr do
  end

  # with pat <- expr do expr end
-  def of_expr({:with, _meta, [_ | _] = clauses} = expr, _expected, stack, context) do
+  def of_expr({:with, _meta, clauses} = expr, stack, context) do
    stack = push_expr_stack(expr, stack)

    case reduce_ok(clauses, context, &with_clause(&1, stack, &2)) do
@@ -357,25 +311,29 @@ defmodule Module.Types.Expr do
    end
  end

-  # fun.(args)
-  def of_expr({{:., _meta1, [fun]}, _meta2, args} = expr, _expected, stack, context) do
-    # TODO: Use expected type to infer intersection return type
+  # fun.(arg)
+  def of_expr({{:., _meta1, [fun]}, _meta2, args} = expr, stack, context) do
    stack = push_expr_stack(expr, stack)

-    with {:ok, _fun_type, context} <- of_expr(fun, :dynamic, stack, context),
-         {:ok, _arg_types, context} <-
-           map_reduce_ok(args, context, &of_expr(&1, :dynamic, stack, &2)) do
-      {:ok, :dynamic, context}
+    case of_expr(fun, stack, context) do
+      {:ok, _fun_type, context} ->
+        case map_reduce_ok(args, context, &of_expr(&1, stack, &2)) do
+          {:ok, _arg_types, context} -> {:ok, :dynamic, context}
+          {:error, reason} -> {:error, reason}
+        end
+
+      {:error, reason} ->
+        {:error, reason}
    end
  end

  # expr.key_or_fun
-  def of_expr({{:., _meta1, [expr1, key_or_fun]}, meta2, []} = expr2, _expected, stack, context)
+  def of_expr({{:., _meta1, [expr1, key_or_fun]}, meta2, []} = expr2, stack, context)
      when not is_atom(expr1) do
    stack = push_expr_stack(expr2, stack)

    if Keyword.get(meta2, :no_parens, false) do
-      with {:ok, expr_type, context} <- of_expr(expr1, :dynamic, stack, context),
+      with {:ok, expr_type, context} <- of_expr(expr1, stack, context),
           {value_var, context} = add_var(context),
           pair_type = {:required, {:atom, key_or_fun}, value_var},
           optional_type = {:optional, :dynamic, :dynamic},
@@ -383,35 +341,28 @@ defmodule Module.Types.Expr do
           {:ok, _map_type, context} <- unify(map_field_type, expr_type, stack, context),
           do: {:ok, value_var, context}
    else
-      # TODO: Use expected type to infer intersection return type
-      with {:ok, expr_type, context} <- of_expr(expr1, :dynamic, stack, context),
+      with {:ok, expr_type, context} <- of_expr(expr1, stack, context),
           {:ok, _map_type, context} <- unify(expr_type, :atom, stack, context),
           do: {:ok, :dynamic, context}
    end
  end

  # expr.fun(arg)
-  def of_expr({{:., meta1, [expr1, fun]}, _meta2, args} = expr2, _expected, stack, context) do
-    # TODO: Use expected type to infer intersection return type
-
+  def of_expr({{:., meta1, [expr1, fun]}, _meta2, args} = expr2, stack, context) do
    context = Of.remote(expr1, fun, length(args), meta1, context)
    stack = push_expr_stack(expr2, stack)

-    with {:ok, _expr_type, context} <- of_expr(expr1, :dynamic, stack, context),
-         {:ok, _fun_type, context} <- of_expr(fun, :dynamic, stack, context),
-         {:ok, _arg_types, context} <-
-           map_reduce_ok(args, context, &of_expr(&1, :dynamic, stack, &2)) do
-      {:ok, :dynamic, context}
+    with {:ok, _expr_type, context} <- of_expr(expr1, stack, context),
+         {:ok, _fun_type, context} <- of_expr(fun, stack, context) do
+      case map_reduce_ok(args, context, &of_expr(&1, stack, &2)) do
+        {:ok, _arg_types, context} -> {:ok, :dynamic, context}
+        {:error, reason} -> {:error, reason}
+      end
    end
  end

  # &Foo.bar/1
-  def of_expr(
-        {:&, meta, [{:/, _, [{{:., _, [module, fun]}, _, []}, arity]}]},
-        _expected,
-        _stack,
-        context
-      )
+  def of_expr({:&, meta, [{:/, _, [{{:., _, [module, fun]}, _, []}, arity]}]}, _stack, context)
      when is_atom(module) and is_atom(fun) do
    context = Of.remote(module, fun, arity, meta, context)
    {:ok, :dynamic, context}
@@ -419,19 +370,16 @@ defmodule Module.Types.Expr do

  # &foo/1
  # & &1
-  def of_expr({:&, _meta, _arg}, _expected, _stack, context) do
+  def of_expr({:&, _meta, _arg}, _stack, context) do
    # TODO: Function type
    {:ok, :dynamic, context}
  end

  # fun(arg)
-  def of_expr({fun, _meta, args} = expr, _expected, stack, context)
-      when is_atom(fun) and is_list(args) do
-    # TODO: Use expected type to infer intersection return type
-
+  def of_expr({fun, _meta, args} = expr, stack, context) when is_atom(fun) and is_list(args) do
    stack = push_expr_stack(expr, stack)

-    case map_reduce_ok(args, context, &of_expr(&1, :dynamic, stack, &2)) do
+    case map_reduce_ok(args, context, &of_expr(&1, stack, &2)) do
      {:ok, _arg_types, context} -> {:ok, :dynamic, context}
      {:error, reason} -> {:error, reason}
    end
@@ -440,15 +388,17 @@ defmodule Module.Types.Expr do
  defp for_clause({:<-, _, [left, expr]}, stack, context) do
    {pattern, guards} = extract_head([left])

-    with {:ok, _pattern_type, context} <- Pattern.of_head([pattern], guards, stack, context),
-         {:ok, _expr_type, context} <- of_expr(expr, :dynamic, stack, context),
+    with {:ok, _pattern_type, context} <- Pattern.of_pattern(pattern, stack, context),
+         # TODO: Check that of_guard/3 returns a boolean
+         {:ok, _guard_type, context} <- Pattern.of_guard(guards_to_or(guards), stack, context),
+         {:ok, _expr_type, context} <- of_expr(expr, stack, context),
         do: {:ok, context}
  end

  defp for_clause({:<<>>, _, [{:<-, _, [pattern, expr]}]}, stack, context) do
    # TODO: the compiler guarantees pattern is a binary but we need to check expr is a binary
    with {:ok, _pattern_type, context} <- Pattern.of_pattern(pattern, stack, context),
-         {:ok, _expr_type, context} <- of_expr(expr, :dynamic, stack, context),
+         {:ok, _expr_type, context} <- of_expr(expr, stack, context),
         do: {:ok, context}
  end

@@ -457,15 +407,15 @@ defmodule Module.Types.Expr do
  end

  defp for_clause(expr, stack, context) do
-    of_expr_context(expr, :dynamic, stack, context)
+    of_expr_context(expr, stack, context)
  end

  defp for_option({:into, expr}, stack, context) do
-    of_expr_context(expr, :dynamic, stack, context)
+    of_expr_context(expr, stack, context)
  end

  defp for_option({:reduce, expr}, stack, context) do
-    of_expr_context(expr, :dynamic, stack, context)
+    of_expr_context(expr, stack, context)
  end

  defp for_option({:uniq, _}, _stack, context) do
@@ -475,8 +425,10 @@ defmodule Module.Types.Expr do
  defp with_clause({:<-, _, [left, expr]}, stack, context) do
    {pattern, guards} = extract_head([left])

-    with {:ok, _pattern_type, context} <- Pattern.of_head([pattern], guards, stack, context),
-         {:ok, _expr_type, context} <- of_expr(expr, :dynamic, stack, context),
+    with {:ok, _pattern_type, context} <- Pattern.of_pattern(pattern, stack, context),
+         # TODO: Check that of_guard/3 returns a boolean
+         {:ok, _guard_type, context} <- Pattern.of_guard(guards_to_or(guards), stack, context),
+         {:ok, _expr_type, context} <- of_expr(expr, stack, context),
         do: {:ok, context}
  end

@@ -485,11 +437,11 @@ defmodule Module.Types.Expr do
  end

  defp with_clause(expr, stack, context) do
-    of_expr_context(expr, :dynamic, stack, context)
+    of_expr_context(expr, stack, context)
  end

  defp with_option({:do, body}, stack, context) do
-    of_expr_context(body, :dynamic, stack, context)
+    of_expr_context(body, stack, context)
  end

  defp with_option({:else, clauses}, stack, context) do
@@ -497,19 +449,12 @@ defmodule Module.Types.Expr do
  end

  defp of_clauses(clauses, stack, context) do
-    reduce_ok(clauses, context, fn {:->, meta, [head, body]}, context = acc ->
+    reduce_ok(clauses, context, fn {:->, _meta, [head, body]}, context = acc ->
      {patterns, guards} = extract_head(head)

-      case Pattern.of_head(patterns, guards, stack, context) do
-        {:ok, _, context} ->
-          with {:ok, _expr_type, context} <- of_expr(body, :dynamic, stack, context) do
-            {:ok, keep_warnings(acc, context)}
-          end
-
-        error ->
-          # Skip the clause if it the head has an error
-          if meta[:generated], do: {:ok, acc}, else: error
-      end
+      with {:ok, _, context} <- Pattern.of_head(patterns, guards, stack, context),
+           {:ok, _expr_type, context} <- of_expr(body, stack, context),
+           do: {:ok, keep_warnings(acc, context)}
    end)
  end

@@ -536,8 +481,8 @@ defmodule Module.Types.Expr do
    [other]
  end

-  defp of_expr_context(expr, expected, stack, context) do
-    case of_expr(expr, expected, stack, context) do
+  defp of_expr_context(expr, stack, context) do
+    case of_expr(expr, stack, context) do
      {:ok, _type, context} -> {:ok, context}
      {:error, reason} -> {:error, reason}
    end
@@ -101,30 +101,6 @@ defmodule Module.Types.Helpers do

  defp do_map_reduce_ok([], {list, acc}, _fun), do: {:ok, Enum.reverse(list), acc}

-  @doc """
-  Like `Enum.flat_map/2` but only continues while `fun` returns `{:ok, list}`
-  and stops on `{:error, reason}`.
-  """
-  def flat_map_ok(list, fun) do
-    do_flat_map_ok(list, [], fun)
-  end
-
-  defp do_flat_map_ok([head | tail], acc, fun) do
-    case fun.(head) do
-      {:ok, elem} ->
-        do_flat_map_ok(tail, [elem | acc], fun)
-
-      {:error, reason} ->
-        {:error, reason}
-    end
-  end
-
-  defp do_flat_map_ok([], acc, _fun), do: {:ok, Enum.reverse(Enum.concat(acc))}
-
-  @doc """
-  Like `Enum.flat_map_reduce/3` but only continues while `fun` returns `{:ok, list, acc}`
-  and stops on `{:error, reason}`.
-  """
  def flat_map_reduce_ok(list, acc, fun) do
    do_flat_map_reduce_ok(list, {[], acc}, fun)
  end
@@ -154,10 +130,6 @@ defmodule Module.Types.Helpers do
    end
  end

-  @doc """
-  Combines a list of guard expressions `when x when y when z` to an expression
-  combined with `or`, `x or y or z`.
-  """
  # TODO: Remove this and let multiple when be treated as multiple clauses,
  #       meaning they will be intersection types
  def guards_to_or([]) do
@@ -167,30 +139,4 @@ defmodule Module.Types.Helpers do
  def guards_to_or(guards) do
    Enum.reduce(guards, fn guard, acc -> {{:., [], [:erlang, :orelse]}, [], [guard, acc]} end)
  end
-
-  @doc """
-  Like `Enum.zip/1` but will zip multiple lists together instead of only two.
-  """
-  def zip_many(lists) do
-    zip_many(lists, [], [[]])
-  end
-
-  defp zip_many([], [], [[] | acc]) do
-    map_reverse(acc, [], &Enum.reverse/1)
-  end
-
-  defp zip_many([], remain, [last | acc]) do
-    zip_many(Enum.reverse(remain), [], [[] | [last | acc]])
-  end
-
-  defp zip_many([[] | _], remain, [last | acc]) do
-    zip_many(Enum.reverse(remain), [], [last | acc])
-  end
-
-  defp zip_many([[elem | list1] | list2], remain, [last | acc]) do
-    zip_many(list2, [list1 | remain], [[elem | last] | acc])
-  end
-
-  defp map_reverse([], acc, _fun), do: acc
-  defp map_reverse([head | tail], acc, fun), do: map_reverse(tail, [fun.(head) | acc], fun)
 end
@@ -11,44 +11,14 @@ defmodule Module.Types.Of do
  import Module.Types.Helpers
  import Module.Types.Unify

-  # There are important assumptions on how we work with maps.
-  #
-  # First, the keys in the map must be ordered by subtyping.
-  #
-  # Second, optional keys must be a superset of the required
-  # keys, i.e. %{required(atom) => integer, optional(:foo) => :bar}
-  # is forbidden.
-  #
-  # Third, in order to preserve co/contra-variance, a supertype
-  # must satisfy its subtypes. I.e. %{foo: :bar, atom() => :baz}
-  # is forbidden, it must be %{foo: :bar, atom() => :baz | :bar}.
-  #
-  # Once we support user declared maps, we need to validate these
-  # assumptions.
-
  @doc """
  Handles open maps (with dynamic => dynamic).
  """
-  def open_map(args, stack, context, of_fun) do
-    with {:ok, pairs, context} <- map_pairs(args, stack, context, of_fun) do
-      # If we match on a map such as %{"foo" => "bar"}, we cannot
-      # assert that %{binary() => binary()}, since we are matching
-      # only a single binary of infinite possible values. Therefore,
-      # the correct would be to match it to %{binary() => binary() | var}.
-      #
-      # We can skip this in two cases:
-      #
-      #   1. If the key is a singleton, then we know that it has no
-      #      other value than the current one
-      #
-      #   2. If the value is a variable, then there is no benefit in
-      #      creating another variable, so we can skip it
-      #
-      # For now, we skip generating the var itself and introduce
-      # :dynamic instead.
+  def open_map(args, stack, context, fun) do
+    with {:ok, pairs, context} <- map_pairs(args, stack, context, fun) do
      pairs =
        for {key, value} <- pairs, not has_unbound_var?(key, context) do
-          if singleton?(key, context) or match?({:var, _}, value) do
+          if singleton?(key, context) do
            {key, value}
          else
            {key, to_union([value, :dynamic], context)}
@@ -63,16 +33,16 @@ defmodule Module.Types.Of do
  @doc """
  Handles closed maps (without dynamic => dynamic).
  """
-  def closed_map(args, stack, context, of_fun) do
-    with {:ok, pairs, context} <- map_pairs(args, stack, context, of_fun) do
+  def closed_map(args, stack, context, fun) do
+    with {:ok, pairs, context} <- map_pairs(args, stack, context, fun) do
      {:ok, {:map, closed_to_unions(pairs, context)}, context}
    end
  end

-  defp map_pairs(pairs, stack, context, of_fun) do
+  defp map_pairs(pairs, stack, context, fun) do
    map_reduce_ok(pairs, context, fn {key, value}, context ->
-      with {:ok, key_type, context} <- of_fun.(key, :dynamic, stack, context),
-           {:ok, value_type, context} <- of_fun.(value, :dynamic, stack, context),
+      with {:ok, key_type, context} <- fun.(key, stack, context),
+           {:ok, value_type, context} <- fun.(value, stack, context),
           do: {:ok, {key_type, value_type}, context}
    end)
  end
@@ -143,39 +113,39 @@ defmodule Module.Types.Of do
  In the stack, we add nodes such as <<expr>>, <<..., expr>>, etc,
  based on the position of the expression within the binary.
  """
-  def binary([], _stack, context, _of_fun) do
+  def binary([], _stack, context, _fun) do
    {:ok, context}
  end

-  def binary([head], stack, context, of_fun) do
+  def binary([head], stack, context, fun) do
    head_stack = push_expr_stack({:<<>>, get_meta(head), [head]}, stack)
-    binary_segment(head, head_stack, context, of_fun)
+    binary_segment(head, head_stack, context, fun)
  end

-  def binary([head | tail], stack, context, of_fun) do
+  def binary([head | tail], stack, context, fun) do
    head_stack = push_expr_stack({:<<>>, get_meta(head), [head, @suffix]}, stack)

-    case binary_segment(head, head_stack, context, of_fun) do
-      {:ok, context} -> binary_many(tail, stack, context, of_fun)
+    case binary_segment(head, head_stack, context, fun) do
+      {:ok, context} -> binary_many(tail, stack, context, fun)
      {:error, reason} -> {:error, reason}
    end
  end

-  defp binary_many([last], stack, context, of_fun) do
+  defp binary_many([last], stack, context, fun) do
    last_stack = push_expr_stack({:<<>>, get_meta(last), [@prefix, last]}, stack)
-    binary_segment(last, last_stack, context, of_fun)
+    binary_segment(last, last_stack, context, fun)
  end

-  defp binary_many([head | tail], stack, context, of_fun) do
+  defp binary_many([head | tail], stack, context, fun) do
    head_stack = push_expr_stack({:<<>>, get_meta(head), [@prefix, head, @suffix]}, stack)

-    case binary_segment(head, head_stack, context, of_fun) do
-      {:ok, context} -> binary_many(tail, stack, context, of_fun)
+    case binary_segment(head, head_stack, context, fun) do
+      {:ok, context} -> binary_many(tail, stack, context, fun)
      {:error, reason} -> {:error, reason}
    end
  end

-  defp binary_segment({:"::", _meta, [expr, specifiers]}, stack, context, of_fun) do
+  defp binary_segment({:"::", _meta, [expr, specifiers]}, stack, context, fun) do
    expected_type =
      collect_binary_specifier(specifiers, &binary_type(stack.context, &1)) || :integer

@@ -192,7 +162,7 @@ defmodule Module.Types.Of do
        {:ok, context}

      true ->
-        with {:ok, type, context} <- of_fun.(expr, expected_type, stack, context),
+        with {:ok, type, context} <- fun.(expr, stack, context),
             {:ok, _type, context} <- unify(type, expected_type, stack, context),
             do: {:ok, context}
    end
@@ -237,7 +207,7 @@ defmodule Module.Types.Of do
  def remote(module, fun, arity, meta, context) when is_atom(module) do
    # TODO: In the future we may want to warn for modules defined
    # in the local context
-    if Keyword.get(meta, :context_module, false) do
+    if Keyword.get(meta, :context_module, false) and context.module != module do
      context
    else
      ParallelChecker.preload_module(context.cache, module)
@@ -249,12 +219,12 @@ defmodule Module.Types.Of do

  defp check_export(module, fun, arity, meta, context) do
    case ParallelChecker.fetch_export(context.cache, module, fun, arity) do
-      {:ok, mode, :def, reason} ->
-        check_deprecated(mode, module, fun, arity, reason, meta, context)
+      {:ok, :def, reason} ->
+        check_deprecated(module, fun, arity, reason, meta, context)

-      {:ok, mode, :defmacro, reason} ->
+      {:ok, :defmacro, reason} ->
        context = warn(meta, context, {:unrequired_module, module, fun, arity})
-        check_deprecated(mode, module, fun, arity, reason, meta, context)
+        check_deprecated(module, fun, arity, reason, meta, context)

      {:error, :module} ->
        if warn_undefined?(module, fun, arity, context) do
@@ -273,7 +243,7 @@ defmodule Module.Types.Of do
    end
  end

-  defp check_deprecated(:elixir, module, fun, arity, reason, meta, context) do
+  defp check_deprecated(module, fun, arity, reason, meta, context) do
    if reason do
      warn(meta, context, {:deprecated, module, fun, arity, reason})
    else
@@ -281,22 +251,6 @@ defmodule Module.Types.Of do
    end
  end

-  defp check_deprecated(:erlang, module, fun, arity, _reason, meta, context) do
-    case :otp_internal.obsolete(module, fun, arity) do
-      {:deprecated, string} when is_list(string) ->
-        reason = string |> List.to_string() |> String.capitalize()
-        warn(meta, context, {:deprecated, module, fun, arity, reason})
-
-      {:deprecated, string, removal} when is_list(string) and is_list(removal) ->
-        reason = string |> List.to_string() |> String.capitalize()
-        reason = "It will be removed in #{removal}. #{reason}"
-        warn(meta, context, {:deprecated, module, fun, arity, reason})
-
-      _ ->
-        context
-    end
-  end
-
  # The protocol code dispatches to unknown modules, so we ignore them here.
  #
  #     try do
@@ -327,7 +281,7 @@ defmodule Module.Types.Of do
    %{context | warnings: [{__MODULE__, warning, location} | context.warnings]}
  end

-  ## Warning formatting
+  ## Warning formating

  def format_warning({:undefined_module, module, fun, arity}) do
    [
@@ -10,8 +10,8 @@ defmodule Module.Types.Pattern do
  def of_head(patterns, guards, stack, context) do
    with {:ok, types, context} <-
           map_reduce_ok(patterns, context, &of_pattern(&1, stack, &2)),
-         # TODO: Check that of_guard/4 returns boolean() | :fail
-         {:ok, _, context} <- of_guard(guards_to_or(guards), :dynamic, stack, context),
+         # TODO: Check that of_guard/3 returns boolean() | :fail
+         {:ok, _, context} <- of_guard(guards_to_or(guards), stack, context),
         do: {:ok, types, context}
  end

@@ -57,9 +57,8 @@ defmodule Module.Types.Pattern do
      )
      when is_atom(var_context) do
    stack = push_expr_stack(expr, stack)
-    expected_fun = fn arg, _expected, stack, context -> of_pattern(arg, stack, context) end

-    with {:ok, {:map, pairs}, context} <- Of.open_map(args, stack, context, expected_fun) do
+    with {:ok, {:map, pairs}, context} <- Of.open_map(args, stack, context, &of_pattern/3) do
      {:ok, {:map, [{:required, {:atom, :__struct__}, :atom} | pairs]}, context}
    end
  end
@@ -68,11 +67,10 @@ defmodule Module.Types.Pattern do
  def of_pattern({:%, _meta1, [var, {:%{}, _meta2, args}]} = expr, stack, context)
      when not is_atom(var) do
    stack = push_expr_stack(expr, stack)
-    expected_fun = fn arg, _expected, stack, context -> of_pattern(arg, stack, context) end

    with {:ok, var_type, context} = of_pattern(var, stack, context),
         {:ok, _, context} <- unify(var_type, :atom, stack, context),
-         {:ok, {:map, pairs}, context} <- Of.open_map(args, stack, context, expected_fun) do
+         {:ok, {:map, pairs}, context} <- Of.open_map(args, stack, context, &of_pattern/3) do
      {:ok, {:map, [{:required, {:atom, :__struct__}, var_type} | pairs]}, context}
    end
  end
@@ -81,80 +79,78 @@ defmodule Module.Types.Pattern do
    of_shared(expr, stack, context, &of_pattern/3)
  end

+  def unify_kinds(:required, _), do: :required
+  def unify_kinds(_, :required), do: :required
+  def unify_kinds(:optional, :optional), do: :optional
+
  ## GUARDS

  # TODO: Some guards can be changed to intersection types or higher order types
  @boolean {:union, [{:atom, true}, {:atom, false}]}
  @number {:union, [:integer, :float]}
-  @unary_number_fun [{[:integer], :integer}, {[@number], :float}]
-  @binary_number_fun [
-    {[:integer, :integer], :integer},
-    {[:float, @number], :float},
-    {[@number, :float], :float}
-  ]

  @guard_functions %{
-    {:is_atom, 1} => [{[:atom], @boolean}],
-    {:is_binary, 1} => [{[:binary], @boolean}],
-    {:is_bitstring, 1} => [{[:binary], @boolean}],
-    {:is_boolean, 1} => [{[@boolean], @boolean}],
-    {:is_float, 1} => [{[:float], @boolean}],
-    {:is_function, 1} => [{[:fun], @boolean}],
-    {:is_function, 2} => [{[:fun, :integer], @boolean}],
-    {:is_integer, 1} => [{[:integer], @boolean}],
-    {:is_list, 1} => [{[{:list, :dynamic}], @boolean}],
-    {:is_map, 1} => [{[{:map, [{:optional, :dynamic, :dynamic}]}], @boolean}],
-    {:is_map_key, 2} => [{[:dynamic, {:map, [{:optional, :dynamic, :dynamic}]}], :dynamic}],
-    {:is_number, 1} => [{[@number], @boolean}],
-    {:is_pid, 1} => [{[:pid], @boolean}],
-    {:is_port, 1} => [{[:port], @boolean}],
-    {:is_reference, 1} => [{[:reference], @boolean}],
-    {:is_tuple, 1} => [{[:tuple], @boolean}],
-    {:<, 2} => [{[:dynamic, :dynamic], @boolean}],
-    {:"=<", 2} => [{[:dynamic, :dynamic], @boolean}],
-    {:>, 2} => [{[:dynamic, :dynamic], @boolean}],
-    {:>=, 2} => [{[:dynamic, :dynamic], @boolean}],
-    {:"/=", 2} => [{[:dynamic, :dynamic], @boolean}],
-    {:"=/=", 2} => [{[:dynamic, :dynamic], @boolean}],
-    {:==, 2} => [{[:dynamic, :dynamic], @boolean}],
-    {:"=:=", 2} => [{[:dynamic, :dynamic], @boolean}],
-    {:*, 2} => @binary_number_fun,
-    {:+, 1} => @unary_number_fun,
-    {:+, 2} => @binary_number_fun,
-    {:-, 1} => @unary_number_fun,
-    {:-, 2} => @binary_number_fun,
-    {:/, 2} => @binary_number_fun,
-    {:abs, 1} => @unary_number_fun,
-    {:ceil, 1} => [{[@number], :integer}],
-    {:floor, 1} => [{[@number], :integer}],
-    {:round, 1} => [{[@number], :integer}],
-    {:trunc, 1} => [{[@number], :integer}],
-    {:element, 2} => [{[:integer, :tuple], :dynamic}],
-    {:hd, 1} => [{[{:list, :dynamic}], :dynamic}],
-    {:length, 1} => [{[{:list, :dynamic}], :integer}],
-    {:map_get, 2} => [{[:dynamic, {:map, [{:optional, :dynamic, :dynamic}]}], :dynamic}],
-    {:map_size, 1} => [{[{:map, [{:optional, :dynamic, :dynamic}]}], :integer}],
-    {:tl, 1} => [{[{:list, :dynamic}], :dynamic}],
-    {:tuple_size, 1} => [{[:tuple], :integer}],
-    {:node, 1} => [{[{:union, [:pid, :reference, :port]}], :atom}],
-    {:binary_part, 3} => [{[:binary, :integer, :integer], :binary}],
-    {:bit_size, 1} => [{[:binary], :integer}],
-    {:byte_size, 1} => [{[:binary], :integer}],
-    {:size, 1} => [{[{:union, [:binary, :tuple]}], @boolean}],
-    {:div, 2} => [{[:integer, :integer], :integer}],
-    {:rem, 2} => [{[:integer, :integer], :integer}],
-    {:node, 0} => [{[], :atom}],
-    {:self, 0} => [{[], :pid}],
-    {:bnot, 1} => [{[:integer], :integer}],
-    {:band, 2} => [{[:integer, :integer], :integer}],
-    {:bor, 2} => [{[:integer, :integer], :integer}],
-    {:bxor, 2} => [{[:integer, :integer], :integer}],
-    {:bsl, 2} => [{[:integer, :integer], :integer}],
-    {:bsr, 2} => [{[:integer, :integer], :integer}],
-    {:or, 2} => [{[@boolean, @boolean], @boolean}],
-    {:and, 2} => [{[@boolean, @boolean], @boolean}],
-    {:xor, 2} => [{[@boolean, @boolean], @boolean}],
-    {:not, 1} => [{[@boolean], @boolean}]
+    {:is_atom, 1} => {[:atom], @boolean},
+    {:is_binary, 1} => {[:binary], @boolean},
+    {:is_bitstring, 1} => {[:binary], @boolean},
+    {:is_boolean, 1} => {[@boolean], @boolean},
+    {:is_float, 1} => {[:float], @boolean},
+    {:is_function, 1} => {[:fun], @boolean},
+    {:is_function, 2} => {[:fun, :integer], @boolean},
+    {:is_integer, 1} => {[:integer], @boolean},
+    {:is_list, 1} => {[{:list, :dynamic}], @boolean},
+    {:is_map, 1} => {[{:map, [{:optional, :dynamic, :dynamic}]}], @boolean},
+    {:is_map_key, 2} => {[:dynamic, {:map, [{:optional, :dynamic, :dynamic}]}], :dynamic},
+    {:is_number, 1} => {[@number], @boolean},
+    {:is_pid, 1} => {[:pid], @boolean},
+    {:is_port, 1} => {[:port], @boolean},
+    {:is_reference, 1} => {[:reference], @boolean},
+    {:is_tuple, 1} => {[:tuple], @boolean},
+    {:<, 2} => {[:dynamic, :dynamic], @boolean},
+    {:"=<", 2} => {[:dynamic, :dynamic], @boolean},
+    {:>, 2} => {[:dynamic, :dynamic], @boolean},
+    {:>=, 2} => {[:dynamic, :dynamic], @boolean},
+    {:"/=", 2} => {[:dynamic, :dynamic], @boolean},
+    {:"=/=", 2} => {[:dynamic, :dynamic], @boolean},
+    {:==, 2} => {[:dynamic, :dynamic], @boolean},
+    {:"=:=", 2} => {[:dynamic, :dynamic], @boolean},
+    {:*, 2} => {[@number, @number], @number},
+    {:+, 1} => {[@number], @number},
+    {:+, 2} => {[@number, @number], @number},
+    {:-, 1} => {[@number], @number},
+    {:-, 2} => {[@number, @number], @number},
+    {:/, 2} => {[@number, @number], @number},
+    {:abs, 1} => {[@number], @number},
+    {:ceil, 1} => {[@number], :integer},
+    {:floor, 1} => {[@number], :integer},
+    {:round, 1} => {[@number], :integer},
+    {:trunc, 1} => {[@number], :integer},
+    {:element, 2} => {[:integer, :tuple], :dynamic},
+    {:hd, 1} => {[{:list, :dynamic}], :dynamic},
+    {:length, 1} => {[{:list, :dynamic}], :integer},
+    {:map_get, 2} => {[:dynamic, {:map, [{:optional, :dynamic, :dynamic}]}], :dynamic},
+    {:map_size, 1} => {[{:map, [{:optional, :dynamic, :dynamic}]}], :integer},
+    {:tl, 1} => {[{:list, :dynamic}], :dynamic},
+    {:tuple_size, 1} => {[:tuple], :integer},
+    {:node, 1} => {[{:union, [:pid, :reference, :port]}], :atom},
+    {:binary_part, 3} => {[:binary, :integer, :integer], :binary},
+    {:bit_size, 1} => {[:binary], :integer},
+    {:byte_size, 1} => {[:binary], :integer},
+    {:size, 1} => {[{:union, [:binary, :tuple]}], @boolean},
+    {:div, 2} => {[:integer, :integer], :integer},
+    {:rem, 2} => {[:integer, :integer], :integer},
+    {:node, 0} => {[], :atom},
+    {:self, 0} => {[], :pid},
+    {:bnot, 1} => {[:integer], :integer},
+    {:band, 2} => {[:integer, :integer], :integer},
+    {:bor, 2} => {[:integer, :integer], :integer},
+    {:bxor, 2} => {[:integer, :integer], :integer},
+    {:bsl, 2} => {[:integer, :integer], :integer},
+    {:bsr, 2} => {[:integer, :integer], :integer},
+    {:or, 2} => {[@boolean, @boolean], @boolean},
+    {:and, 2} => {[@boolean, @boolean], @boolean},
+    {:xor, 2} => {[@boolean, @boolean], @boolean},
+    {:not, 1} => {[@boolean], @boolean}

    # Following guards are matched explicitly to handle
    # type guard functions such as is_atom/1
@@ -169,6 +165,7 @@ defmodule Module.Types.Pattern do
    :is_boolean,
    :is_float,
    :is_function,
+    :is_function,
    :is_integer,
    :is_list,
    :is_map,
@@ -183,36 +180,29 @@ defmodule Module.Types.Pattern do
  Refines the type variables in the typing context using type check guards
  such as `is_integer/1`.
  """
-  def of_guard(expr, expected, %{context: stack_context} = stack, context)
-      when stack_context != :pattern do
-    of_guard(expr, expected, %{stack | context: :pattern}, context)
+  def of_guard(expr, %{context: stack_context} = stack, context) when stack_context != :pattern do
+    of_guard(expr, %{stack | context: :pattern}, context)
  end

-  def of_guard({{:., _, [:erlang, :andalso]}, _, [left, right]} = expr, _expected, stack, context) do
+  def of_guard({{:., _, [:erlang, :andalso]}, _, [left, right]} = expr, stack, context) do
    stack = push_expr_stack(expr, stack)
+    fresh_context = fresh_context(context)

-    with {:ok, left_type, context} <- of_guard(left, @boolean, stack, context),
+    with {:ok, left_type, left_context} <- of_guard(left, stack, fresh_context),
+         {:ok, right_type, right_context} <- of_guard(right, stack, fresh_context),
+         {:ok, context} <- merge_context_and(context, stack, left_context, right_context),
         {:ok, _, context} <- unify(left_type, @boolean, stack, context),
-         {:ok, right_type, context} <- of_guard(right, :dynamic, keep_guarded(stack), context),
-         do: {:ok, to_union([@boolean, right_type], context), context}
+         {:ok, _, context} <- unify(right_type, @boolean, stack, context),
+         do: {:ok, @boolean, context}
  end

-  def of_guard({{:., _, [:erlang, :orelse]}, _, [left, right]} = expr, _expected, stack, context) do
+  def of_guard({{:., _, [:erlang, :orelse]}, _, [left, right]} = expr, stack, context) do
    stack = push_expr_stack(expr, stack)
-    left_indexes = collect_var_indexes_from_expr(left, context)
-    right_indexes = collect_var_indexes_from_expr(right, context)
+    fresh_context = fresh_context(context)

-    with {:ok, left_type, left_context} <- of_guard(left, @boolean, stack, context),
-         {:ok, _right_type, right_context} <- of_guard(right, :dynamic, stack, context),
-         context =
-           merge_context_or(
-             left_indexes,
-             right_indexes,
-             context,
-             stack,
-             left_context,
-             right_context
-           ),
+    with {:ok, left_type, left_context} <- of_guard(left, stack, fresh_context),
+         {:ok, _right_type, right_context} <- of_guard(right, stack, fresh_context),
+         {:ok, context} <- merge_context_or(context, stack, left_context, right_context),
         {:ok, _, context} <- unify(left_type, @boolean, stack, context),
         do: {:ok, @boolean, context}
  end
@@ -220,406 +210,218 @@ defmodule Module.Types.Pattern do
  # The unary operators + and - are special cased to avoid common warnings until
  # we add support for intersection types for the guard functions
  # -integer / +integer
-  def of_guard({{:., _, [:erlang, guard]}, _, [integer]}, _expected, _stack, context)
+  def of_guard({{:., _, [:erlang, guard]}, _, [integer]}, _stack, context)
      when guard in [:+, :-] and is_integer(integer) do
    {:ok, :integer, context}
  end

  # -float / +float
-  def of_guard({{:., _, [:erlang, guard]}, _, [float]}, _expected, _stack, context)
+  def of_guard({{:., _, [:erlang, guard]}, _, [float]}, _stack, context)
      when guard in [:+, :-] and is_float(float) do
    {:ok, :float, context}
  end

-  # tuple_size(arg) == integer
-  def of_guard(
-        {{:., _, [:erlang, :==]}, _, [{{:., _, [:erlang, :tuple_size]}, _, [var]}, size]} = expr,
-        expected,
-        stack,
-        context
-      )
-      when is_var(var) and is_integer(size) do
-    of_tuple_size(var, size, expr, expected, stack, context)
-  end
-
-  # integer == tuple_size(arg)
-  def of_guard(
-        {{:., _, [:erlang, :==]}, _, [size, {{:., _, [:erlang, :tuple_size]}, _, [var]}]} = expr,
-        expected,
-        stack,
-        context
-      )
-      when is_var(var) and is_integer(size) do
-    of_tuple_size(var, size, expr, expected, stack, context)
-  end
-
  # fun(args)
-  def of_guard({{:., _, [:erlang, guard]}, _, args} = expr, expected, stack, context) do
+  def of_guard({{:., _, [:erlang, guard]}, _, args} = expr, stack, context) do
+    stack = push_expr_stack(expr, stack)
+    {param_types, return_type} = guard_signature(guard, length(args))
    type_guard? = type_guard?(guard)
-    {consider_type_guards?, keep_guarded?} = stack.type_guards
-    signature = guard_signature(guard, length(args))

    # Only check type guards in the context of and/or/not,
    # a type guard in the context of is_tuple(x) > :foo
    # should not affect the inference of x
-    if not type_guard? or consider_type_guards? do
-      stack = push_expr_stack(expr, stack)
-      expected_clauses = filter_clauses(signature, expected, stack, context)
-      param_unions = signature_to_param_unions(expected_clauses, context)
-      arg_stack = %{stack | type_guards: {false, keep_guarded?}}
-      mfa = {:erlang, guard, length(args)}
+    if not type_guard? or stack.type_guards_enabled? do
+      arg_stack = %{stack | type_guards_enabled?: type_guard?}

      with {:ok, arg_types, context} <-
-             map_reduce_ok(Enum.zip(args, param_unions), context, fn {arg, param}, context ->
-               of_guard(arg, param, arg_stack, context)
-             end),
-           {:ok, return_type, context} <-
-             unify_call(
-               arg_types,
-               expected_clauses,
-               expected,
-               mfa,
-               signature,
-               stack,
-               context,
-               type_guard?
-             ) do
-        guard_sources = guard_sources(arg_types, type_guard?, keep_guarded?, context)
+             map_reduce_ok(args, context, &of_guard(&1, arg_stack, &2)),
+           {:ok, context} <- unify_call(arg_types, param_types, stack, context) do
+        {arg_types, guard_sources} =
+          case arg_types do
+            [{:var, index} | rest_arg_types] when type_guard? ->
+              guard_sources =
+                Map.update(context.guard_sources, index, [:guarded], &[:guarded | &1])
+
+              {rest_arg_types, guard_sources}
+
+            _ ->
+              {arg_types, context.guard_sources}
+          end
+
+        guard_sources =
+          Enum.reduce(arg_types, guard_sources, fn
+            {:var, index}, guard_sources ->
+              Map.update(guard_sources, index, [:fail], &[:fail | &1])
+
+            _, guard_sources ->
+              guard_sources
+          end)
+
        {:ok, return_type, %{context | guard_sources: guard_sources}}
      end
    else
-      # Assume that type guards always return boolean
-      boolean = {:union, [atom: true, atom: false]}
-      [{_params, ^boolean}] = signature
-      {:ok, boolean, context}
+      {:ok, return_type, context}
    end
  end

  # map.field
-  def of_guard({{:., meta1, [map, field]}, meta2, []}, expected, stack, context) do
-    of_guard({{:., meta1, [:erlang, :map_get]}, meta2, [field, map]}, expected, stack, context)
+  def of_guard({{:., meta1, [map, field]}, meta2, []}, stack, context) do
+    of_guard({{:., meta1, [:erlang, :map_get]}, meta2, [field, map]}, stack, context)
  end

  # var
-  def of_guard(var, _expected, _stack, context) when is_var(var) do
-    {:ok, get_var!(var, context), context}
+  def of_guard(var, _stack, context) when is_var(var) do
+    type = Map.fetch!(context.vars, var_name(var))
+    {:ok, type, context}
  end

-  def of_guard(expr, _expected, stack, context) do
-    of_shared(expr, stack, context, &of_guard(&1, :dynamic, &2, &3))
+  def of_guard(expr, stack, context) do
+    of_shared(expr, stack, context, &of_guard/3)
  end

-  defp of_tuple_size(var, size, expr, _expected, stack, context) do
-    {consider_type_guards?, _keep_guarded?} = stack.type_guards
+  defp fresh_context(context) do
+    types = Map.new(context.types, fn {var, _} -> {var, :unbound} end)
+    traces = Map.new(context.traces, fn {var, _} -> {var, []} end)
+    %{context | types: types, traces: traces}
+  end

-    result =
-      if consider_type_guards? do
-        stack = push_expr_stack(expr, stack)
-        tuple_elems = Enum.map(1..size//1, fn _ -> :dynamic end)
+  defp unify_call(args, params, stack, context) do
+    reduce_ok(Enum.zip(args, params), context, fn {arg, param}, context ->
+      case unify(arg, param, stack, context) do
+        {:ok, _, context} -> {:ok, context}
+        {:error, reason} -> {:error, reason}
+      end
+    end)
+  end

-        with {:ok, type, context} <- of_guard(var, :dynamic, stack, context),
-             {:ok, _type, context} <- unify({:tuple, size, tuple_elems}, type, stack, context),
-             do: {:ok, context}
-      else
+  defp merge_context_and(context, stack, left, right) do
+    with {:ok, context} <- unify_new_types(context, stack, left),
+         {:ok, context} <- unify_new_types(context, stack, right) do
+      guard_sources = and_guard_sources(left.guard_sources, right.guard_sources)
+      guard_sources = merge_guard_sources([context.guard_sources, guard_sources])
+      {:ok, %{context | guard_sources: guard_sources}}
+    end
+  end
+
+  defp unify_new_types(context, stack, new_context) do
+    context = merge_traces(context, new_context)
+
+    reduce_ok(Map.to_list(new_context.types), context, fn
+      {_index, :unbound}, context ->
        {:ok, context}
-      end

-    case result do
-      {:ok, context} ->
-        boolean = {:union, [atom: true, atom: false]}
-        {:ok, boolean, context}
+      {index, new_type}, context ->
+        case unify({:var, index}, new_type, %{stack | trace: false}, context) do
+          {:ok, _, context} ->
+            {:ok, context}

-      {:error, reason} ->
-        {:error, reason}
-    end
-  end
-
-  defp signature_to_param_unions(signature, context) do
-    signature
-    |> Enum.map(fn {params, _return} -> params end)
-    |> zip_many()
-    |> Enum.map(&to_union(&1, context))
-  end
-
-  # Collect guard sources from argument types, see type context documentation
-  # for more information
-  defp guard_sources(arg_types, type_guard?, keep_guarded?, context) do
-    {arg_types, guard_sources} =
-      case arg_types do
-        [{:var, index} | rest_arg_types] when type_guard? ->
-          guard_sources = Map.put_new(context.guard_sources, index, :guarded)
-          {rest_arg_types, guard_sources}
-
-        _ ->
-          {arg_types, context.guard_sources}
-      end
-
-    Enum.reduce(arg_types, guard_sources, fn
-      {:var, index}, guard_sources ->
-        Map.update(guard_sources, index, :fail, &guarded_if_keep_guarded(&1, keep_guarded?))
-
-      _, guard_sources ->
-        guard_sources
-    end)
-  end
-
-  defp collect_var_indexes_from_expr(expr, context) do
-    {_, vars} =
-      Macro.prewalk(expr, %{}, fn
-        var, acc when is_var(var) ->
-          var_name = var_name(var)
-          %{^var_name => type} = context.vars
-          {var, collect_var_indexes(type, context, acc)}
-
-        other, acc ->
-          {other, acc}
-      end)
-
-    Map.keys(vars)
-  end
-
-  defp unify_call(args, clauses, _expected, _mfa, _signature, stack, context, true = _type_guard?) do
-    unify_type_guard_call(args, clauses, stack, context)
-  end
-
-  defp unify_call(args, clauses, expected, mfa, signature, stack, context, false = _type_guard?) do
-    unify_call(args, clauses, expected, mfa, signature, stack, context)
-  end
-
-  defp unify_call([], [{[], return}], _expected, _mfa, _signature, _stack, context) do
-    {:ok, return, context}
-  end
-
-  defp unify_call(args, clauses, expected, mfa, signature, stack, context) do
-    # Given the arguments:
-    # foo | bar, {:ok, baz | bat}
-
-    # Expand unions in arguments:
-    # foo | bar, {:ok, baz} | {:ok, bat}
-
-    # Permute arguments:
-    # foo, {:ok, baz}
-    # foo, {:ok, bat}
-    # bar, {:ok, baz}
-    # bar, {:ok, bat}
-
-    flatten_args = Enum.map(args, &flatten_union(&1, context))
-    cartesian_args = cartesian_product(flatten_args)
-
-    # Remove clauses that do not match the expected type
-    # Ignore type variables in parameters by changing them to dynamic
-
-    clauses =
-      clauses
-      |> filter_clauses(expected, stack, context)
-      |> Enum.map(fn {params, return} ->
-        {Enum.map(params, &var_to_dynamic/1), return}
-      end)
-
-    # For each permuted argument find the clauses they match
-    # All arguments must match at least one clause, but all clauses
-    # do not need to match
-    # Collect the return values from clauses that matched and collect
-    # the type contexts from unifying argument and parameter to
-    # infer type variables in arguments
-    result =
-      flat_map_ok(cartesian_args, fn cartesian_args ->
-        result =
-          Enum.flat_map(clauses, fn {params, return} ->
-            result =
-              map_ok(Enum.zip(cartesian_args, params), fn {arg, param} ->
-                case unify(arg, param, stack, context) do
-                  {:ok, _type, context} -> {:ok, context}
-                  {:error, reason} -> {:error, reason}
-                end
-              end)
-
-            case result do
-              {:ok, contexts} -> [{return, contexts}]
-              {:error, _reason} -> []
-            end
-          end)
-
-        if result != [] do
-          {:ok, result}
-        else
-          {:error, args}
+          {:error, reason} ->
+            {:error, reason}
        end
-      end)
-
-    case result do
-      {:ok, returns_contexts} ->
-        {success_returns, contexts} = Enum.unzip(returns_contexts)
-        contexts = Enum.concat(contexts)
-
-        indexes =
-          for types <- flatten_args,
-              type <- types,
-              index <- collect_var_indexes_from_type(type),
-              do: index,
-              uniq: true
-
-        # Build unions from collected type contexts to unify with
-        # type variables from arguments
-        result =
-          map_reduce_ok(indexes, context, fn index, context ->
-            union =
-              contexts
-              |> Enum.map(&Map.fetch!(&1.types, index))
-              |> Enum.reject(&(&1 == :unbound))
-
-            if union == [] do
-              {:ok, {:var, index}, context}
-            else
-              unify({:var, index}, to_union(union, context), stack, context)
-            end
-          end)
-
-        case result do
-          {:ok, _types, context} -> {:ok, to_union(success_returns, context), context}
-          {:error, reason} -> {:error, reason}
-        end
-
-      {:error, args} ->
-        error(:unable_apply, {mfa, args, expected, signature, stack}, context)
-    end
-  end
-
-  defp unify_type_guard_call(args, [{params, return}], stack, context) do
-    result =
-      reduce_ok(Enum.zip(args, params), context, fn {arg, param}, context ->
-        case unify(arg, param, stack, context) do
-          {:ok, _, context} -> {:ok, context}
-          {:error, reason} -> {:error, reason}
-        end
-      end)
-
-    case result do
-      {:ok, context} -> {:ok, return, context}
-      {:error, reason} -> {:error, reason}
-    end
-  end
-
-  defp cartesian_product(lists) do
-    List.foldr(lists, [[]], fn list, acc ->
-      for elem_list <- list,
-          list_acc <- acc,
-          do: [elem_list | list_acc]
-    end)
-  end
-
-  defp var_to_dynamic(type) do
-    {type, _acc} =
-      walk(type, :ok, fn
-        {:var, _index}, :ok ->
-          {:dynamic, :ok}
-
-        other, :ok ->
-          {other, :ok}
-      end)
-
-    type
-  end
-
-  defp collect_var_indexes_from_type(type) do
-    {_type, indexes} =
-      walk(type, [], fn
-        {:var, index}, indexes ->
-          {{:var, index}, [index | indexes]}
-
-        other, indexes ->
-          {other, indexes}
-      end)
-
-    indexes
-  end
-
-  defp merge_context_or(left_indexes, right_indexes, context, stack, left, right) do
-    left_different = filter_different_indexes(left_indexes, left, right)
-    right_different = filter_different_indexes(right_indexes, left, right)
-
-    case {left_different, right_different} do
-      {[index], [index]} -> merge_context_or_equal(index, stack, left, right)
-      {_, _} -> merge_context_or_diff(left_different, context, left)
-    end
-  end
-
-  defp filter_different_indexes(indexes, left, right) do
-    Enum.filter(indexes, fn index ->
-      %{^index => left_type} = left.types
-      %{^index => right_type} = right.types
-      left_type != right_type
-    end)
-  end
-
-  defp merge_context_or_equal(index, stack, left, right) do
-    %{^index => left_type} = left.types
-    %{^index => right_type} = right.types
-
-    cond do
-      left_type == :unbound ->
-        refine_var!(index, right_type, stack, left)
-
-      right_type == :unbound ->
-        left
-
-      true ->
-        # Only include right side if left side is from type guard such as is_list(x),
-        # do not refine in case of length(x)
-        if left.guard_sources[index] == :fail do
-          guard_sources = Map.put(left.guard_sources, index, :fail)
-          left = %{left | guard_sources: guard_sources}
-          refine_var!(index, left_type, stack, left)
-        else
-          guard_sources = merge_guard_sources([left.guard_sources, right.guard_sources])
-          left = %{left | guard_sources: guard_sources}
-          refine_var!(index, to_union([left_type, right_type], left), stack, left)
-        end
-    end
-  end
-
-  # If the variable failed, we can keep them from the left side as is.
-  # If they didn't fail, then we need to restore them to their original value.
-  defp merge_context_or_diff(indexes, old_context, new_context) do
-    Enum.reduce(indexes, new_context, fn index, context ->
-      if new_context.guard_sources[index] == :fail do
-        context
-      else
-        restore_var!(index, new_context, old_context)
-      end
    end)
  end

  defp merge_guard_sources(sources) do
    Enum.reduce(sources, fn left, right ->
-      Map.merge(left, right, fn
-        _index, :guarded, :guarded -> :guarded
-        _index, _, _ -> :fail
-      end)
+      Map.merge(left, right, fn _index, left, right -> join_guard_source(left, right) end)
    end)
  end

-  defp guarded_if_keep_guarded(:guarded, true), do: :guarded
-  defp guarded_if_keep_guarded(_, _), do: :fail
+  defp join_guard_source(left, right) do
+    sources = left ++ right

-  defp keep_guarded(%{type_guards: {consider?, _}} = stack),
-    do: %{stack | type_guards: {consider?, true}}
+    cond do
+      :fail in sources -> [:fail]
+      :guarded in sources -> [:guarded]
+      true -> []
+    end
+  end

-  defp filter_clauses(signature, expected, stack, context) do
-    Enum.filter(signature, fn {_params, return} ->
-      match?({:ok, _type, _context}, unify(return, expected, stack, context))
+  defp and_guard_sources(left, right) do
+    Map.merge(left, right, fn _index, left, right ->
+      # When the failing guard function wont fail due to type check function before it,
+      # for example: is_list(x) and length(x)
+      if :guarded in left and :fail in right do
+        [:guarded]
+      else
+        join_guard_source(left, right)
+      end
    end)
  end

-  Enum.each(@guard_functions, fn {{name, arity}, signature} ->
-    defp guard_signature(unquote(name), unquote(arity)), do: unquote(Macro.escape(signature))
-  end)
+  defp merge_traces(context, new_context) do
+    traces =
+      :maps.fold(
+        fn index, new_traces, traces ->
+          :maps.update_with(index, &(new_traces ++ &1), new_traces, traces)
+        end,
+        context.traces,
+        new_context.traces
+      )

-  Enum.each(@type_guards, fn name ->
-    defp type_guard?(unquote(name)), do: true
-  end)
+    %{context | traces: traces}
+  end

-  defp type_guard?(name) when is_atom(name), do: false
+  defp merge_context_or(context, stack, left, right) do
+    context =
+      case {Map.to_list(left.types), Map.to_list(right.types)} do
+        {[{index, :unbound}], [{index, type}]} ->
+          refine_var(index, type, stack, context)
+
+        {[{index, type}], [{index, :unbound}]} ->
+          refine_var(index, type, stack, context)
+
+        {[{index, left_type}], [{index, right_type}]} ->
+          # Only include right side if left side is from type guard such as is_list(x),
+          # do not refine in case of length(x)
+          left_guard_sources = Map.get(left.guard_sources, index, [])
+
+          if :fail in left_guard_sources do
+            guard_sources = Map.put(context.guard_sources, index, [:fail])
+            context = %{context | guard_sources: guard_sources}
+            refine_var(index, left_type, stack, context)
+          else
+            guard_sources =
+              merge_guard_sources([
+                context.guard_sources,
+                left.guard_sources,
+                right.guard_sources
+              ])
+
+            context = %{context | guard_sources: guard_sources}
+            refine_var(index, to_union([left_type, right_type], context), stack, context)
+          end
+
+        {left_types, _right_types} ->
+          Enum.reduce(left_types, context, fn {index, left_type}, context ->
+            left_guard_sources = Map.get(left.guard_sources, index, [])
+
+            if :fail in left_guard_sources do
+              guard_sources =
+                merge_guard_sources([
+                  context.guard_sources,
+                  left.guard_sources,
+                  right.guard_sources
+                ])
+
+              context = %{context | guard_sources: guard_sources}
+              refine_var(index, left_type, stack, context)
+            else
+              context
+            end
+          end)
+      end
+
+    {:ok, context}
+  end
+
+  defp guard_signature(name, arity) do
+    Map.fetch!(@guard_functions, {name, arity})
+  end
+
+  defp type_guard?(name) do
+    name in @type_guards
+  end

  ## Shared

@@ -645,9 +447,7 @@ defmodule Module.Types.Pattern do

  # <<...>>>
  defp of_shared({:<<>>, _meta, args}, stack, context, fun) do
-    expected_fun = fn arg, _expected, stack, context -> fun.(arg, stack, context) end
-
-    case Of.binary(args, stack, context, expected_fun) do
+    case Of.binary(args, stack, context, fun) do
      {:ok, context} -> {:ok, :binary, context}
      {:error, reason} -> {:error, reason}
    end
@@ -741,18 +541,16 @@ defmodule Module.Types.Pattern do
  # %{...}
  defp of_shared({:%{}, _meta, args} = expr, stack, context, fun) do
    stack = push_expr_stack(expr, stack)
-    expected_fun = fn arg, _expected, stack, context -> fun.(arg, stack, context) end
-    Of.open_map(args, stack, context, expected_fun)
+    Of.open_map(args, stack, context, fun)
  end

  # %Struct{...}
  defp of_shared({:%, meta1, [module, {:%{}, _meta2, args}]} = expr, stack, context, fun)
       when is_atom(module) do
    stack = push_expr_stack(expr, stack)
-    expected_fun = fn arg, _expected, stack, context -> fun.(arg, stack, context) end

    with {:ok, struct, context} <- Of.struct(module, meta1, context),
-         {:ok, map, context} <- Of.open_map(args, stack, context, expected_fun) do
+         {:ok, map, context} <- Of.open_map(args, stack, context, fun) do
      unify(map, struct, stack, context)
    end
  end
@@ -10,7 +10,6 @@ defmodule Module.Types.Unify do
  #   {:atom, atom} < :atom
  #   :integer
  #   :float
-  #   :binary
  #   :pid
  #   :port
  #   :reference
@@ -21,37 +20,65 @@ defmodule Module.Types.Unify do
  #   {:tuple, size, [type]} < :tuple
  #   {:union, [type]}
  #   {:map, [{:required | :optional, key_type, value_type}]}
-  #   {:fun, [{params, return}]}
  #
  # Once new types are added, they should be considered in:
  #
  #   * unify (all)
  #   * format_type (all)
  #   * subtype? (subtypes only)
+  #   * has_unbound_var? (composite only)
  #   * recursive_type? (composite only)
-  #   * collect_var_indexes (composite only)
-  #   * lift_types (composite only)
-  #   * flatten_union (composite only)
-  #   * walk (composite only)
  #

  @doc """
  Unifies two types and returns the unified type and an updated typing context
  or an error in case of a typing conflict.
  """
-  def unify(same, same, _stack, context) do
+  def unify(source, target, stack, context) do
+    case do_unify(source, target, stack, context) do
+      {:ok, type, context} ->
+        {:ok, type, context}
+
+      {:error, reason} ->
+        if stack.context == :pattern do
+          case do_unify(target, source, stack, context) do
+            {:ok, type, context} ->
+              {:ok, type, context}
+
+            {:error, _} ->
+              {:error, reason}
+          end
+        else
+          {:error, reason}
+        end
+    end
+  end
+
+  defp do_unify(same, same, _stack, context) do
    {:ok, same, context}
  end

-  def unify({:var, var}, type, stack, context) do
-    unify_var(var, type, stack, context, _var_source = true)
+  defp do_unify(type, {:var, var}, stack, context) do
+    case context.types do
+      %{^var => {:var, var_type}} ->
+        do_unify(type, {:var, var_type}, stack, context)
+
+      %{} ->
+        unify_var(var, type, stack, context, _var_source = false)
+    end
  end

-  def unify(type, {:var, var}, stack, context) do
-    unify_var(var, type, stack, context, _var_source = false)
+  defp do_unify({:var, var}, type, stack, context) do
+    case context.types do
+      %{^var => {:var, var_type}} ->
+        do_unify({:var, var_type}, type, stack, context)
+
+      %{} ->
+        unify_var(var, type, stack, context, _var_source = true)
+    end
  end

-  def unify({:tuple, n, sources}, {:tuple, n, targets}, stack, context) do
+  defp do_unify({:tuple, n, sources}, {:tuple, n, targets}, stack, context) do
    result =
      map_reduce_ok(Enum.zip(sources, targets), context, fn {source, target}, context ->
        unify(source, target, stack, context)
@@ -63,41 +90,33 @@ defmodule Module.Types.Unify do
    end
  end

-  def unify({:list, source}, {:list, target}, stack, context) do
+  defp do_unify({:list, source}, {:list, target}, stack, context) do
    case unify(source, target, stack, context) do
      {:ok, type, context} -> {:ok, {:list, type}, context}
      {:error, reason} -> {:error, reason}
    end
  end

-  def unify({:map, source_pairs}, {:map, target_pairs}, stack, context) do
+  defp do_unify({:map, source_pairs}, {:map, target_pairs}, stack, context) do
    unify_maps(source_pairs, target_pairs, stack, context)
  end

-  def unify(source, :dynamic, _stack, context) do
+  defp do_unify(source, :dynamic, _stack, context) do
    {:ok, source, context}
  end

-  def unify(:dynamic, target, _stack, context) do
+  defp do_unify(:dynamic, target, _stack, context) do
    {:ok, target, context}
  end

-  def unify({:union, types}, target, stack, context) do
-    unify_result =
-      map_reduce_ok(types, context, fn type, context ->
-        unify(type, target, stack, context)
-      end)
-
-    case unify_result do
-      {:ok, types, context} -> {:ok, to_union(types, context), context}
-      {:error, context} -> {:error, context}
-    end
-  end
-
-  def unify(source, target, stack, context) do
+  defp do_unify(source, target, stack, context) do
    cond do
-      # TODO: This condition exists to handle unions with unbound vars.
-      match?({:union, _}, target) and has_unbound_var?(target, context) ->
+      # This condition exists to handle unions with unbound vars.
+      # TODO: handle unions properly. Note we can easily unify
+      # "union < type" even if union has vars as the vars must be
+      # type
+      (match?({:union, _}, source) and has_unbound_var?(source, context)) or
+          (match?({:union, _}, target) and has_unbound_var?(target, context)) ->
        {:ok, source, context}

      subtype?(source, target, context) ->
@@ -108,14 +127,14 @@ defmodule Module.Types.Unify do
    end
  end

-  def unify_var(var, :dynamic, _stack, context, _var_source?) do
+  defp unify_var(var, :dynamic, _stack, context, _var_source?) do
    {:ok, {:var, var}, context}
  end

-  def unify_var(var, type, stack, context, var_source?) do
+  defp unify_var(var, type, stack, context, var_source?) do
    case context.types do
      %{^var => :unbound} ->
-        context = refine_var!(var, type, stack, context)
+        context = refine_var(var, type, stack, context)
        stack = push_unify_stack(var, stack)

        if recursive_type?(type, [], context) do
@@ -128,11 +147,6 @@ defmodule Module.Types.Unify do
          {:ok, {:var, var}, context}
        end

-      %{^var => {:var, _} = var_type} ->
-        # Do not recursively traverse type vars for now
-        # to avoid pathological cases related to performance.
-        {:ok, var_type, context}
-
      %{^var => var_type} ->
        # Only add trace if the variable wasn't already "expanded"
        context =
@@ -156,7 +170,7 @@ defmodule Module.Types.Unify do
            {:ok, {:var, var}, context}

          {:ok, res_type, context} ->
-            context = refine_var!(var, res_type, stack, context)
+            context = refine_var(var, res_type, stack, context)
            {:ok, {:var, var}, context}

          {:error, reason} ->
@@ -168,7 +182,7 @@ defmodule Module.Types.Unify do
  # * All required keys on each side need to match to the other side.
  # * All optional keys on each side that do not match must be discarded.

-  def unify_maps(source_pairs, target_pairs, stack, context) do
+  defp unify_maps(source_pairs, target_pairs, stack, context) do
    {source_required, source_optional} = split_pairs(source_pairs)
    {target_required, target_optional} = split_pairs(target_pairs)

@@ -199,7 +213,7 @@ defmodule Module.Types.Unify do
    end
  end

-  def unify_source_required(source_required, target_pairs, stack, context) do
+  defp unify_source_required(source_required, target_pairs, stack, context) do
    map_reduce_ok(source_required, context, fn {source_key, source_value}, context ->
      Enum.find_value(target_pairs, fn {target_kind, target_key, target_value} ->
        with {:ok, key, context} <- unify(source_key, target_key, stack, context) do
@@ -219,7 +233,7 @@ defmodule Module.Types.Unify do
    end)
  end

-  def unify_target_required(target_required, source_pairs, stack, context) do
+  defp unify_target_required(target_required, source_pairs, stack, context) do
    map_reduce_ok(target_required, context, fn {target_key, target_value}, context ->
      Enum.find_value(source_pairs, fn {source_kind, source_key, source_value} ->
        with {:ok, key, context} <- unify(source_key, target_key, stack, context) do
@@ -239,7 +253,7 @@ defmodule Module.Types.Unify do
    end)
  end

-  def unify_source_optional(source_optional, target_optional, stack, context) do
+  defp unify_source_optional(source_optional, target_optional, stack, context) do
    flat_map_reduce_ok(source_optional, context, fn {source_key, source_value}, context ->
      Enum.find_value(target_optional, fn {target_key, target_value} ->
        with {:ok, key, context} <- unify(source_key, target_key, stack, context) do
@@ -259,7 +273,7 @@ defmodule Module.Types.Unify do
    end)
  end

-  def unify_target_optional(target_optional, source_optional, stack, context) do
+  defp unify_target_optional(target_optional, source_optional, stack, context) do
    flat_map_reduce_ok(target_optional, context, fn {target_key, target_value}, context ->
      Enum.find_value(source_optional, fn {source_key, source_value} ->
        with {:ok, key, context} <- unify(source_key, target_key, stack, context) do
@@ -288,7 +302,7 @@ defmodule Module.Types.Unify do
    {required, optional}
  end

-  def error(type, reason, context), do: {:error, {type, reason, context}}
+  defp error(type, reason, context), do: {:error, {type, reason, context}}

  @doc """
  Push expression to stack.
@@ -359,11 +373,11 @@ defmodule Module.Types.Unify do
  end

  @doc """
-  Maybe resolves a variable.
+  Resolves a variable raising if it is unbound.
  """
  def resolve_var({:var, var}, context) do
    case context.types do
-      %{^var => :unbound} -> {:var, var}
+      %{^var => :unbound} -> raise "cannot resolve unbound var"
      %{^var => type} -> resolve_var(type, context)
    end
  end
@@ -392,21 +406,10 @@ defmodule Module.Types.Unify do
    %{stack | unify_stack: [var | stack.unify_stack]}
  end

-  @doc """
-  Restores the variable information from the old context into new context.
-  """
-  def restore_var!(var, new_context, old_context) do
-    %{^var => type} = old_context.types
-    %{^var => trace} = old_context.traces
-    types = Map.put(new_context.types, var, type)
-    traces = Map.put(new_context.traces, var, trace)
-    %{new_context | types: types, traces: traces}
-  end
-
  @doc """
  Set the type for a variable and add trace.
  """
-  def refine_var!(var, type, stack, context) do
+  def refine_var(var, type, stack, context) do
    types = Map.put(context.types, var, type)
    context = %{context | types: types}
    trace_var(var, type, stack, context)
@@ -468,68 +471,37 @@ defmodule Module.Types.Unify do
    end)
  end

-  defp recursive_type?({:fun, clauses}, parents, context) do
-    Enum.any?(clauses, fn {args, return} ->
-      Enum.any?([return | args], &recursive_type?(&1, [clauses | parents], context))
-    end)
-  end
-
  defp recursive_type?(_other, _parents, _context) do
    false
  end

-  @doc """
-  Collects all type vars recursively.
-  """
-  def collect_var_indexes(type, context, acc \\ %{}) do
-    {_type, indexes} =
-      walk(type, acc, fn
-        {:var, var}, acc ->
-          case acc do
-            %{^var => _} ->
-              {{:var, var}, acc}
-
-            %{} ->
-              case context.types do
-                %{^var => :unbound} ->
-                  {{:var, var}, Map.put(acc, var, true)}
-
-                %{^var => type} ->
-                  {{:var, var}, collect_var_indexes(type, context, Map.put(acc, var, true))}
-              end
-          end
-
-        other, acc ->
-          {other, acc}
-      end)
-
-    indexes
-  end
-
  @doc """
  Checks if the type has a type var.
  """
-  def has_unbound_var?(type, context) do
-    walk(type, :ok, fn
-      {:var, var}, acc ->
-        case context.types do
-          %{^var => :unbound} ->
-            throw(:has_unbound_var?)
-
-          %{^var => type} ->
-            has_unbound_var?(type, context)
-            {{:var, var}, acc}
-        end
-
-      other, acc ->
-        {other, acc}
-    end)
-
-    false
-  catch
-    :throw, :has_unbound_var? -> true
+  def has_unbound_var?({:var, var}, context) do
+    case context.types do
+      %{^var => :unbound} -> true
+      %{^var => type} -> has_unbound_var?(type, context)
+    end
  end

+  def has_unbound_var?({:tuple, _, args}, context),
+    do: Enum.any?(args, &has_unbound_var?(&1, context))
+
+  def has_unbound_var?({:union, args}, context),
+    do: Enum.any?(args, &has_unbound_var?(&1, context))
+
+  def has_unbound_var?({:list, arg}, context),
+    do: has_unbound_var?(arg, context)
+
+  def has_unbound_var?({:map, pairs}, context) do
+    Enum.any?(pairs, fn {_, key, value} ->
+      has_unbound_var?(key, context) or has_unbound_var?(value, context)
+    end)
+  end
+
+  def has_unbound_var?(_type, _context), do: false
+
  @doc """
  Returns true if it is a singleton type.

@@ -584,7 +556,7 @@ defmodule Module.Types.Unify do
  def subtype?({:tuple, n, left_types}, {:tuple, n, right_types}, context) do
    left_types
    |> Enum.zip(right_types)
-    |> Enum.all?(fn {left, right} -> subtype?(left, right, context) end)
+    |> Enum.any?(fn {left, right} -> subtype?(left, right, context) end)
  end

  def subtype?({:map, left_pairs}, {:map, right_pairs}, context) do
@@ -628,15 +600,17 @@ defmodule Module.Types.Unify do
  def to_union([type], _context), do: type

  def to_union(types, context) when types != [] do
-    case unique_super_types(unnest_unions(types), context) do
+    flat_types = flatten_union(types)
+
+    case unique_super_types(flat_types, context) do
      [type] -> type
      types -> {:union, types}
    end
  end

-  defp unnest_unions(types) do
+  defp flatten_union(types) do
    Enum.flat_map(types, fn
-      {:union, types} -> unnest_unions(types)
+      {:union, types} -> flatten_union(types)
      type -> [type]
    end)
  end
@@ -661,204 +635,6 @@ defmodule Module.Types.Unify do
    []
  end

-  ## Type lifting
-
-  @doc """
-  Lifts type variables to their inferred types from the context.
-  """
-  def lift_types(types, %{lifted_types: _} = context) do
-    Enum.map_reduce(types, context, &lift_type/2)
-  end
-
-  def lift_types(types, context) do
-    context = %{
-      types: context.types,
-      lifted_types: %{},
-      lifted_counter: 0
-    }
-
-    Enum.map_reduce(types, context, &lift_type/2)
-  end
-
-  # Lift type variable to its inferred (hopefully concrete) types from the context
-  defp lift_type({:var, var}, context) do
-    case context.lifted_types do
-      %{^var => lifted_var} ->
-        {{:var, lifted_var}, context}
-
-      %{} ->
-        case context.types do
-          %{^var => :unbound} ->
-            new_lifted_var(var, context)
-
-          %{^var => type} ->
-            if recursive_type?(type, [], context) do
-              new_lifted_var(var, context)
-            else
-              # Remove visited types to avoid infinite loops
-              # then restore after we are done recursing on vars
-              types = context.types
-              context = put_in(context.types[var], :unbound)
-              {type, context} = lift_type(type, context)
-              {type, %{context | types: types}}
-            end
-
-          %{} ->
-            new_lifted_var(var, context)
-        end
-    end
-  end
-
-  defp lift_type({:union, types}, context) do
-    {types, context} = Enum.map_reduce(types, context, &lift_type/2)
-    {{:union, types}, context}
-  end
-
-  defp lift_type({:tuple, n, types}, context) do
-    {types, context} = Enum.map_reduce(types, context, &lift_type/2)
-    {{:tuple, n, types}, context}
-  end
-
-  defp lift_type({:map, pairs}, context) do
-    {pairs, context} =
-      Enum.map_reduce(pairs, context, fn {kind, key, value}, context ->
-        {key, context} = lift_type(key, context)
-        {value, context} = lift_type(value, context)
-        {{kind, key, value}, context}
-      end)
-
-    {{:map, pairs}, context}
-  end
-
-  defp lift_type({:list, type}, context) do
-    {type, context} = lift_type(type, context)
-    {{:list, type}, context}
-  end
-
-  defp lift_type({:fun, clauses}, context) do
-    clauses =
-      Enum.map_reduce(clauses, context, fn {args, return}, context ->
-        {[return | args], context} = Enum.map_reduce([return | args], context, &lift_type/2)
-        {{args, return}, context}
-      end)
-
-    {{:fun, clauses}, context}
-  end
-
-  defp lift_type(other, context) do
-    {other, context}
-  end
-
-  defp new_lifted_var(original_var, context) do
-    types = Map.put(context.lifted_types, original_var, context.lifted_counter)
-    counter = context.lifted_counter + 1
-
-    type = {:var, context.lifted_counter}
-    context = %{context | lifted_types: types, lifted_counter: counter}
-    {type, context}
-  end
-
-  # TODO: Figure out function expansion
-
-  @doc """
-  Expand unions so that all unions are at the top level.
-
-      {integer() | float()} => {integer()} | {float()}
-  """
-  def flatten_union({:union, types}, context) do
-    Enum.flat_map(types, &flatten_union(&1, context))
-  end
-
-  def flatten_union(type, context) do
-    List.wrap(do_flatten_union(type, context))
-  end
-
-  def do_flatten_union({:tuple, num, types}, context) do
-    flatten_union_tuple(types, num, context, [])
-  end
-
-  def do_flatten_union({:list, type}, context) do
-    case do_flatten_union(type, context) do
-      {:union, union_types} -> Enum.map(union_types, &{:list, &1})
-      _type -> [{:list, type}]
-    end
-  end
-
-  def do_flatten_union({:map, pairs}, context) do
-    flatten_union_map(pairs, context, [])
-  end
-
-  def do_flatten_union({:var, var}, context) do
-    if looping_var?(var, context, []) do
-      {:var, var}
-    else
-      case context.types do
-        %{^var => :unbound} -> {:var, var}
-        %{^var => {:union, types}} -> Enum.map(types, &do_flatten_union(&1, context))
-        %{^var => type} -> do_flatten_union(type, context)
-      end
-    end
-  end
-
-  def do_flatten_union(type, _context) do
-    type
-  end
-
-  defp flatten_union_tuple([type | types], num, context, acc) do
-    case do_flatten_union(type, context) do
-      {:union, union_types} ->
-        Enum.flat_map(union_types, &flatten_union_tuple(types, num, context, [&1 | acc]))
-
-      type ->
-        flatten_union_tuple(types, num, context, [type | acc])
-    end
-  end
-
-  defp flatten_union_tuple([], num, _context, acc) do
-    [{:tuple, num, Enum.reverse(acc)}]
-  end
-
-  defp flatten_union_map([{kind, key, value} | pairs], context, acc) do
-    case do_flatten_union(key, context) do
-      {:union, union_types} ->
-        Enum.flat_map(union_types, &flatten_union_map_value(kind, &1, value, pairs, context, acc))
-
-      type ->
-        flatten_union_map_value(kind, type, value, pairs, context, acc)
-    end
-  end
-
-  defp flatten_union_map([], _context, acc) do
-    [{:map, Enum.reverse(acc)}]
-  end
-
-  defp flatten_union_map_value(kind, key, value, pairs, context, acc) do
-    case do_flatten_union(value, context) do
-      {:union, union_types} ->
-        Enum.flat_map(union_types, &flatten_union_map(pairs, context, [{kind, key, &1} | acc]))
-
-      value ->
-        flatten_union_map(pairs, context, [{kind, key, value} | acc])
-    end
-  end
-
-  defp looping_var?(var, context, parents) do
-    case context.types do
-      %{^var => :unbound} ->
-        false
-
-      %{^var => {:var, type}} ->
-        if var in parents do
-          true
-        else
-          looping_var?(type, context, [var | parents])
-        end
-
-      %{^var => _type} ->
-        false
-    end
-  end
-
  @doc """
  Formats types.

@@ -868,7 +644,7 @@ defmodule Module.Types.Unify do
  def format_type({:map, pairs}, true) do
    case List.keyfind(pairs, {:atom, :__struct__}, 1) do
      {:required, {:atom, :__struct__}, {:atom, struct}} ->
-        ["%", inspect(struct), "{}"]
+        "%#{inspect(struct)}{}"

      _ ->
        "map()"
@@ -876,31 +652,24 @@ defmodule Module.Types.Unify do
  end

  def format_type({:union, types}, simplify?) do
-    types
-    |> Enum.map(&format_type(&1, simplify?))
-    |> Enum.intersperse(" | ")
+    "#{Enum.map_join(types, " | ", &format_type(&1, simplify?))}"
  end

  def format_type({:tuple, _, types}, simplify?) do
-    format =
-      types
-      |> Enum.map(&format_type(&1, simplify?))
-      |> Enum.intersperse(", ")
-
-    ["{", format, "}"]
+    "{#{Enum.map_join(types, ", ", &format_type(&1, simplify?))}}"
  end

  def format_type({:list, type}, simplify?) do
-    ["[", format_type(type, simplify?), "]"]
+    "[#{format_type(type, simplify?)}]"
  end

  def format_type({:map, pairs}, false) do
    case List.keytake(pairs, {:atom, :__struct__}, 1) do
      {{:required, {:atom, :__struct__}, {:atom, struct}}, pairs} ->
-        ["%", inspect(struct), "{", format_map_pairs(pairs), "}"]
+        "%#{inspect(struct)}{#{format_map_pairs(pairs)}}"

      _ ->
-        ["%{", format_map_pairs(pairs), "}"]
+        "%{#{format_map_pairs(pairs)}}"
    end
  end

@@ -909,84 +678,26 @@ defmodule Module.Types.Unify do
  end

  def format_type({:var, index}, _simplify?) do
-    ["var", Integer.to_string(index + 1)]
-  end
-
-  def format_type({:fun, clauses}, simplify?) do
-    format =
-      Enum.map(clauses, fn {params, return} ->
-        params = Enum.intersperse(Enum.map(params, &format_type(&1, simplify?)), ", ")
-        params = if params == [], do: params, else: [params, " "]
-        return = format_type(return, simplify?)
-        [params, "-> ", return]
-      end)
-
-    ["(", Enum.intersperse(format, "; "), ")"]
+    "var#{index}"
  end

  def format_type(atom, _simplify?) when is_atom(atom) do
-    [Atom.to_string(atom), "()"]
+    "#{atom}()"
  end

  defp format_map_pairs(pairs) do
    {atoms, others} = Enum.split_with(pairs, &match?({:required, {:atom, _}, _}, &1))
    {required, optional} = Enum.split_with(others, &match?({:required, _, _}, &1))

-    (atoms ++ required ++ optional)
-    |> Enum.map(fn
+    Enum.map_join(atoms ++ required ++ optional, ", ", fn
      {:required, {:atom, atom}, right} ->
-        [Atom.to_string(atom), ": ", format_type(right, false)]
+        "#{atom}: #{format_type(right, false)}"

      {:required, left, right} ->
-        [format_type(left, false), " => ", format_type(right, false)]
+        "#{format_type(left, false)} => #{format_type(right, false)}"

      {:optional, left, right} ->
-        ["optional(", format_type(left, false), ") => ", format_type(right, false)]
+        "optional(#{format_type(left, false)}) => #{format_type(right, false)}"
    end)
-    |> Enum.intersperse(", ")
-  end
-
-  @doc """
-  Performs a depth-first, pre-order traversal of the type tree using an accumulator.
-  """
-  def walk({:map, pairs}, acc, fun) do
-    {pairs, acc} =
-      Enum.map_reduce(pairs, acc, fn {kind, key, value}, acc ->
-        {key, acc} = walk(key, acc, fun)
-        {value, acc} = walk(value, acc, fun)
-        {{kind, key, value}, acc}
-      end)
-
-    fun.({:map, pairs}, acc)
-  end
-
-  def walk({:union, types}, acc, fun) do
-    {types, acc} = Enum.map_reduce(types, acc, &walk(&1, &2, fun))
-    fun.({:union, types}, acc)
-  end
-
-  def walk({:tuple, num, types}, acc, fun) do
-    {types, acc} = Enum.map_reduce(types, acc, &walk(&1, &2, fun))
-    fun.({:tuple, num, types}, acc)
-  end
-
-  def walk({:list, type}, acc, fun) do
-    {type, acc} = walk(type, acc, fun)
-    fun.({:list, type}, acc)
-  end
-
-  def walk({:fun, clauses}, acc, fun) do
-    {clauses, acc} =
-      Enum.map_reduce(clauses, acc, fn {params, return}, acc ->
-        {params, acc} = Enum.map_reduce(params, acc, &walk(&1, &2, fun))
-        {return, acc} = walk(return, acc, fun)
-        {{params, return}, acc}
-      end)
-
-    fun.({:fun, clauses}, acc)
-  end
-
-  def walk(type, acc, fun) do
-    fun.(type, acc)
  end
 end
@@ -257,36 +257,6 @@ defmodule Node do
    :erlang.spawn_link(node, module, fun, args)
  end

-  @doc """
-  Spawns the given function on a node, monitors it and returns its PID
-  and monitoring reference.
-
-  This functionality was added on Erlang/OTP 23. Using this function to
-  communicate with nodes running on earlier versions will fail.
-
-  Inlined by the compiler.
-  """
-  @doc since: "1.14.0"
-  @spec spawn_monitor(t, (() -> any)) :: {pid, reference}
-  def spawn_monitor(node, fun) do
-    :erlang.spawn_monitor(node, fun)
-  end
-
-  @doc """
-  Spawns the given module and function passing the given args on a node,
-  monitors it and returns its PID and monitoring reference.
-
-  This functionality was added on Erlang/OTP 23. Using this function
-  to communicate with nodes running on earlier versions will fail.
-
-  Inlined by the compiler.
-  """
-  @doc since: "1.14.0"
-  @spec spawn_monitor(t, module, atom, [any]) :: {pid, reference}
-  def spawn_monitor(node, module, fun, args) do
-    :erlang.spawn_monitor(node, module, fun, args)
-  end
-
  @doc """
  Sets the magic cookie of `node` to the atom `cookie`.

--- a/Show More
+++ b/Show More
Author	SHA1	Message	Date
José Valim	4e6d67c169	Add branch docs publishing	2023-05-30 11:41:49 +02:00
jendis	614ae049e6	Fix elixir test assertion for erlang >=OTP-24.1 (#11311 )	2021-10-14 16:43:34 +02:00
MatteoandJosé Valim	b1492cb0cf	Fix logger translator with otp-24 (#11222 ) * Handle new significant key in sasl reports * Add OTP-24.0 to CI matrix Co-authored-by: José Valim <jose.valim@dashbit.co>	2021-08-31 23:46:27 +02:00
Wojtek Mach	237a71311c	Update warnings for OTP master (#10807 )	2021-08-31 19:27:51 +02:00
José Valim	e40b280fd8	Print task times on MIX_DEBUG=1	2021-06-01 11:43:49 +02:00
José Valim	308255bda8	Release v1.11.4	2021-03-16 12:25:59 +01:00
José Valim	1e81a5b9a5	Run formatter	2021-02-28 01:33:19 +01:00
José Valim	0627d7b0d4	Pass env and target to Mix.Config readers	2021-02-27 21:52:56 +01:00
Wojtek Mach	99ec7522d3	Backport OTP 24 compatibility patches to v1.11 (#10743 ) * Update Erlang warnings translation (#10694) Since https://github.com/erlang/otp/commit/8ecc648df22dbfe9dd68a3e2b968ba2b6a2ca7fe instead of `{eval_failure, Reason}` we'd get `{eval_failure, Call, Reason}` * Fix translating erl compiler errors to diagnostics on OTP 24 (#10719) The compiler previously emitted just `line` and now emits `{line, column}`. The diagnostic struct accepts as position either: nil line {start_line, start_col, end_line, end_col} so we could have used the `column` to create the 4-tuple but we don't have enough information to do that correctly, we don't know where the line ends. * Fix remaining warning translations for OTP 24 (#10720) Yecc error message changed so we need to loosen up our assertion: OTP 23 iex> iex Erlang/OTP 23 [erts-11.1.7] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] Interactive Elixir (1.11.3) - press Ctrl+C to exit (type h() ENTER for help) iex(1)> :yecc.file('f.yrl') f.yrl:1: syntax error before: '.' :error OTP 24 iex> iex Erlang/OTP 24 [DEVELOPMENT] [erts-11.1.7] [source-802d2c5083] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] Interactive Elixir (1.12.0-dev) - press Ctrl+C to exit (type h() ENTER for help) iex(1)> :yecc.file('f.yrl') f.yrl:1:5: syntax error before: . :error * Support 16bit floats in bitstrings (#10740) On OTP 24: iex> <<x::float-16>> = <<60, 0>> iex> x 1.0 iex> <<x::float-16>> <<60, 0>> Before OTP 24 we'd get errors or wouldn't match: iex> <<1.0::float-16>> (ArgumentError) argument error while evaluating iex at line 1 <<x::float-16>> = <<60, 0>> (MatchError) no match of right hand side value: <<60, 0>> iex> (fn <<x::float-16>> -> x; _ -> :nomatch end).(<<60, 0>>) :nomatch * Handle :compile.file/2 returning :error on OTP 24 (#10742) Before OTP 24 when given invalid args, :compile.file/2 would return: iex(1)> :compile.file('a.erl', [{:d, 'foo', 'bar'}, :report]) {:error, :badarg} On OTP 24: iex(1)> :compile.file('a.erl', [{:d, 'foo', 'bar'}, :report]) * Internal compiler error * exception error: bad argument in function io_lib:format/2 called as io_lib:format("badly formed '~s'",[{"foo","bar"}]) in call from sys_messages:list_errors/3 (sys_messages.erl, line 53) in call from lists:foreach/2 (lists.erl, line 1342) in call from compile:comp_ret_err/1 (compile.erl, line 546) in call from compile:'-internal_fun/2-anonymous-0-'/2 (compile.erl, line 229) in call from compile:'-do_compile/2-anonymous-0-'/1 (compile.erl, line 219) :error	2021-02-20 14:33:11 +01:00
José Valim	d30c5c0185	Release v1.11.3	2021-01-04 16:47:18 +01:00
José Valim	3fc334ebc3	Support all literals in guards, closes #10613	2021-01-02 17:19:30 +01:00
Julian Doherty	df8955c0dd	Improve Enum.chunk_while/4 docs to clarify `after_fun` semantics (#10595 ) - add `{:halt, acc}` tuple return doc for `chunk_fun` - explain `after_fun` semantics in more detail - format return tuples for `chunk_fun` and `after_fun` as markdown lists - added note that `acc` in `after_fun` return tuple is ignored - note that `Enum.chunk_while/4` returns a list of chunks, not a list of lists (emitted chunks can be anything, not necessarily just lists)	2021-01-02 17:09:25 +01:00
José Valim	6b87a54825	Clarify writing documentation guide, closes #10610	2021-01-02 17:09:20 +01:00
José Valim	72ec902554	Revert "Add support for new rebar3 output env option (#10018 )" This option will be enabled on Elixir v1.12 instead. This reverts commit `fc9f7690c1`.	2020-12-21 13:01:34 +01:00
José Valim	2c9fff0f93	Update CHANGELOG	2020-12-17 13:23:40 +01:00
José Valim	c42f7af02b	Do not match on error_info on OTP 24	2020-12-17 13:21:32 +01:00
José Valim	9c77960a26	Consider macros and module attributes on the left side of ++ on ExUnit.Diff Closes #10520	2020-12-17 13:17:19 +01:00
José Valim	a20f413841	Do not warn for attributes used in after_compile Closes #10579.	2020-12-17 13:08:07 +01:00
José Valim	ffbae20014	Improve xref error message, closes #10582	2020-12-17 08:18:16 +01:00
José Valim	9c81578ab5	Update CHANGELOG	2020-12-13 09:24:38 +01:00
José Valim	a9f7b8e18c	Run formatter	2020-12-13 09:15:02 +01:00
José Valim	61c3c34f44	Do not discard context from with, closes #10538	2020-12-13 09:14:39 +01:00
José Valim	d8faf5bb7b	Fix bootstrapping	2020-12-13 09:13:47 +01:00
José Valim	9d03032cfd	Add line and column to EEx tokenizer	2020-12-13 09:06:15 +01:00
José Valim	3c4c68b3d5	Fix variable overriding in records, closes #10540	2020-12-13 09:05:09 +01:00
José Valim	bed0a68176	Do not use unicode chars if ANSI is disabled See https://github.com/elixir-lang/elixir/issues/10481#issuecomment-742448132	2020-12-10 12:19:19 +01:00
José Valim	60642c340d	Improve error message on do-block in module attr, closes #10544	2020-12-10 12:19:14 +01:00
Eric Meadows-Jönsson	35e4263934	Fix docs tests on OTP 23 (#10510 )	2020-11-29 10:19:53 +01:00
José Valim	43327512da	Do not use private and removed ram_file:compress/1 (#10439 )	2020-11-29 10:19:22 +01:00
José Valim	32692f14ff	Fix test on Erlang master	2020-11-29 09:51:00 +01:00
Eric Meadows-Jönsson	f80bd3c478	Fix intermittent test failure caused by archive warning (#10493 )	2020-11-29 09:43:36 +01:00
José Valim	23934b48ba	Fix failure on Erlang/OTP master	2020-11-29 09:43:28 +01:00
Dominic Letz	c370a8a724	Add :compressed to stream_modes spec (#10490 ) :compressed is already supported here so that gzipped files can be streamed `File.stream!("log.gz", [:compressed])`.	2020-11-29 09:43:17 +01:00
José Valim	8c2237f80d	Handle in memory modules in Xref.calls, closes #10502	2020-11-21 08:34:30 +01:00
José Valim	a5e9c39023	Do not raise when checking for ambiguity with static_atoms_encoder, closes #10501	2020-11-20 12:43:14 +01:00
José Valim	6d918f5fb4	Wrap around :file instead of calling internals	2020-11-20 07:14:43 +01:00
Eksperimental	4347468d8a	Update GitHub actions/checkout to v2 (#10496 )	2020-11-18 13:21:49 +01:00
José Valim	f044def5a1	Handle recursive vars in map values (#10498 )	2020-11-18 12:42:23 +01:00
José Valim	05c9ccad12	Check for stacktrace at compile-time and runtime	2020-11-03 20:18:50 +01:00
José Valim	7533e56c1b	Release v1.11.2	2020-11-03 15:23:56 +01:00
José Valim	3f083795b6	Do not trace protocol impl checks A more complete solution is found in master but this approach is less disruptive in the v1.11 branch.	2020-11-02 11:35:51 +01:00
José Valim	1bbc959d1a	Prune tracers when fetching __ENV__ inside functions, closes #10466	2020-10-30 13:30:17 +01:00
José Valim	1603f21b0a	Fix race condition when loading test helper, closes #10464	2020-10-29 19:29:06 +01:00
José Valim	02c3957667	Clarify wording about siblings in umbrella	2020-10-22 10:53:14 +02:00
José Valim	eeab9f5aa1	Ensure manually set tracers are kept on compilation Closes #10451.	2020-10-22 08:50:10 +02:00
José Valim	3f3e987a23	Handle aliases with code recursion It addresses a regression introduced in `97e8b0242d`. Closes https://github.com/nerves-project/nerves/issues/557.	2020-10-20 20:33:58 +02:00
José Valim	53c8b27ee2	Fix bootstrap issue in Code module	2020-10-17 20:10:26 +02:00
José Valim	3550dd10af	Do not crash when getting docs for missing erts appdir Closes #10437.	2020-10-17 19:46:51 +02:00
José Valim	7e44b88122	Raise for is_record guards, closes #10436	2020-10-17 19:33:10 +02:00
José Valim	5c5259826f	Release v1.11.1	2020-10-16 09:31:35 +02:00
Xavier Noria	ccdefd904f	Improves the docs of config/runtime.exs and Config.config_env/0 (#10414 )	2020-10-16 09:23:13 +02:00
José Valim	ff95a59ec0	Add :append to stream_mode, closes #10421	2020-10-16 09:22:44 +02:00
José Valim	4081590742	Add inet6 fallback to Mix usage of httpc, closes #10423	2020-10-16 09:22:16 +02:00
José Valim	693df5fe8c	Properly handle tags inside typespec in Erlang docs, closes #10430	2020-10-16 09:22:11 +02:00
José Valim	b4605374b5	Do not deadlock Logger if handler crashes on sync mode, closes #10420	2020-10-12 09:27:32 +02:00
Eksperimental	36ec08e0c8	Fix warning message in app requirement (#10417 ) It was missing a closing square bracket. Previously it was saying 3. In case you don't want to add a requirement to :crypto, you may optionally skip this warning by adding [xref: [exclude: :crypto] to your "def project" in mix.exs Now 3. In case you don't want to add a requirement to :crypto, you may optionally skip this warning by adding [xref: [exclude: :crypto]] to your "def project" in mix.exs	2020-10-11 00:15:59 +02:00
José Valim	ae0ac9b3c9	Ignore tracers if lexical tracker is dead or explicitly nil	2020-10-11 00:15:41 +02:00
Milton Mazzarri	e3479831ba	Do not show warning when `super` is in `GenServer.child_spec/1` (#10418 ) The original goal[1] was to deprecate the usage of `super` on every `GenServer` callback, but `child_spec/1` is not a callback, it's a default implementation that can be re-implemented. This commit removes the _deprecation warning_ when someone use `super` in `GenServer.child_spec/1`. Fixes: #10415 [1] https://github.com/elixir-lang/elixir/commit/c024b0eeb2dc69a759fe5ceeb1c8216d58ae9386#diff-ed0344c13ed25389035f337d94902894R301-R316	2020-10-11 00:15:40 +02:00
José Valim	ffbcc004ec	Do not crash when :reduce is set to nil in comprehensions, closes #10411	2020-10-08 15:37:53 +02:00
José Valim	e0d61c7875	Fix order dependent tests in logger suite	2020-10-08 09:43:51 +02:00
Michał Łępicki	b2059031a6	Fix returning errors in Module.Types.Expr.of_expr (#10410 )	2020-10-08 09:37:13 +02:00
José Valim	ed2829d8ea	Keep warnings when traversing clauses	2020-10-07 23:53:23 +02:00
José Valim	081f99cd37	Consider targets when filtering apps, closes #10405	2020-10-06 19:31:36 +02:00
José Valim	7837cc5c59	Release v1.11.0	2020-10-06 15:43:09 +02:00
Daniil Fedotov	b96fc39422	Restrict Logger.configure on config_change callback (#10388 ) The `config_change` callback is called from `application_controller` process, which is receiving env updates on releases. `Logger.configure` does a blocking call to the `Logger` process, which calls `Application.put_env` This causes a crash on logger config update. The fix is to call `Logger.configure` only for the config that have not yet been persisted.	2020-10-03 08:33:31 +02:00
Waldemar Rachwał	e1cb898198	Take --dot-iex into account after shell respawn (#10384 )	2020-10-01 20:36:14 +02:00
Dave Lucia	88e2894925	Enum.max_by/3 and Enum.min_by/3 dialyzer fixes (#10383 )	2020-10-01 13:23:19 +02:00
José Valim	f7cb5ae053	Fix inference of open maps with non-singleton keys Closes #10371.	2020-09-29 13:11:22 +02:00
José Valim	b4845e6854	Update iso.ex	2020-09-25 13:34:38 +02:00
José Valim	0f1200f99b	Add a note on async_stream+take	2020-09-25 13:33:15 +02:00
José Valim	cec1a7190b	Make config/runtime.exs deep merge, closes #10365	2020-09-25 13:32:54 +02:00
Gabriel Alves	53d1b98a05	Raise instead of crashing on when trying to use list operators in guards (#10363 )	2020-09-23 14:30:39 +02:00
José Valim	4828f11cd2	Keep invoking loadconfig on cli boot	2020-09-22 15:47:35 +02:00
José Valim	501271cad0	Make replace and replace! in Keyword consistent, closes #10345	2020-09-18 16:13:16 +02:00
José Valim	fd4a6ad5cf	Handle empty map in other places, closes #10343	2020-09-18 10:53:56 +02:00
José Valim	196aab87ca	Align doc chunks return with EEP 48	2020-09-18 10:41:39 +02:00
José Valim	59b266506a	Append space on middle and start expr if necessary, closes #10340	2020-09-17 17:11:28 +02:00
José Valim	1c8e625d77	Speed up compilation with multiple describe	2020-09-17 14:24:54 +02:00
José Valim	f9d7adbfdf	Introduce register_test/6 to speed up test definition	2020-09-17 10:57:00 +02:00
José Valim	f1721c8a58	Reduce amount of injected code in case	2020-09-17 10:29:40 +02:00
José Valim	57abca4c16	Properly handle reduce in types, closes #10224	2020-09-14 23:02:07 +02:00
José Valim	8e9ece0d62	More typing improvements (#10333 ) 1. Move push_expr_stack to unify and keep helpers typing free 2. Add get_var! when accessing variables so it helps us find variables that have not been properly processed 3. Properly process all variables found missing on step 2	2020-09-14 22:45:34 +02:00
José Valim	54ba096d34	Remove boolean and number as builtin types (#10329 )	2020-09-14 22:45:34 +02:00
José Valim	6042fd0bcc	Infer -> Unify	2020-09-14 22:45:34 +02:00
Eksperimental	475b73b46f	Use proper casing in CHANGELOG (#10331 )	2020-09-14 15:24:51 +02:00
José Valim	3cf6069ad9	Fix typo in CHANGELOG	2020-09-14 09:43:19 +02:00
José Valim	48cee5aaa5	Release v1.11.0-rc.0	2020-09-14 09:16:34 +02:00
@@ -1 +1 @@
 .14.5
 .11.4