Remove unnecessary specs for funs with default arguments (#6095)

The command used to detect these lines is:
$ ag "(\@spec\s+[a-zA-Z0-9_?!]+\()[^\n]*\s*\1" -A2

lib/elixir/lib/base.ex

@@ -170,7 +170,6 @@ defmodule Base do
       "666f6f626172"
 
   """
-  @spec encode16(binary) :: binary
   @spec encode16(binary, Keyword.t) :: binary
   def encode16(data, opts \\ []) when is_binary(data) do
     case = Keyword.get(opts, :case, :upper)
@@ -204,7 +203,6 @@ defmodule Base do
       {:ok, "foobar"}
 
   """
-  @spec decode16(binary) :: {:ok, binary} | :error
   @spec decode16(binary, Keyword.t) :: {:ok, binary} | :error
   def decode16(string, opts \\ []) do
     {:ok, decode16!(string, opts)}
@@ -242,7 +240,6 @@ defmodule Base do
       "foobar"
 
   """
-  @spec decode16!(binary) :: binary
   @spec decode16!(binary, Keyword.t) :: binary
   def decode16!(string, opts \\ [])
 
@@ -273,7 +270,6 @@ defmodule Base do
       "Zm9vYg"
 
   """
-  @spec encode64(binary) :: binary
   @spec encode64(binary, Keyword.t) :: binary
   def encode64(data, opts \\ []) when is_binary(data) do
     pad? = Keyword.get(opts, :padding, true)
@@ -304,7 +300,6 @@ defmodule Base do
       {:ok, "foob"}
 
   """
-  @spec decode64(binary) :: {:ok, binary} | :error
   @spec decode64(binary, Keyword.t) :: {:ok, binary} | :error
   def decode64(string, opts \\ []) when is_binary(string) do
     {:ok, decode64!(string, opts)}
@@ -339,7 +334,6 @@ defmodule Base do
       "foob"
 
   """
-  @spec decode64!(binary) :: binary
   @spec decode64!(binary, Keyword.t) :: binary
   def decode64!(string, opts \\ []) when is_binary(string) do
     pad? = Keyword.get(opts, :padding, true)
@@ -362,7 +356,6 @@ defmodule Base do
       "_3_-_A"
 
   """
-  @spec url_encode64(binary) :: binary
   @spec url_encode64(binary, Keyword.t) :: binary
   def url_encode64(data, opts \\ []) when is_binary(data) do
     pad? = Keyword.get(opts, :padding, true)
@@ -391,7 +384,6 @@ defmodule Base do
       {:ok, <<255, 127, 254, 252>>}
 
   """
-  @spec url_decode64(binary) :: {:ok, binary} | :error
   @spec url_decode64(binary, Keyword.t) :: {:ok, binary} | :error
   def url_decode64(string, opts \\ []) when is_binary(string) do
     {:ok, url_decode64!(string, opts)}
@@ -424,7 +416,6 @@ defmodule Base do
       <<255, 127, 254, 252>>
 
   """
-  @spec url_decode64!(binary) :: binary
   @spec url_decode64!(binary, Keyword.t) :: binary
   def url_decode64!(string, opts \\ []) when is_binary(string)  do
     pad? = Keyword.get(opts, :padding, true)
@@ -463,7 +454,6 @@ defmodule Base do
       "MZXW6YTBOI"
 
   """
-  @spec encode32(binary) :: binary
   @spec encode32(binary, Keyword.t) :: binary
   def encode32(data, opts \\ []) when is_binary(data) do
     case = Keyword.get(opts, :case, :upper)
@@ -507,7 +497,6 @@ defmodule Base do
       {:ok, "foobar"}
 
   """
-  @spec decode32(binary) :: {:ok, binary} | :error
   @spec decode32(binary, Keyword.t) :: {:ok, binary} | :error
   def decode32(string, opts \\ []) do
     {:ok, decode32!(string, opts)}
@@ -554,7 +543,6 @@ defmodule Base do
       "foobar"
 
   """
-  @spec decode32!(binary) :: binary
   @spec decode32!(binary, Keyword.t) :: binary
   def decode32!(string, opts \\ []) when is_binary(string) do
     case = Keyword.get(opts, :case, :upper)
@@ -595,7 +583,6 @@ defmodule Base do
       "CPNMUOJ1E8"
 
   """
-  @spec hex_encode32(binary) :: binary
   @spec hex_encode32(binary, Keyword.t) :: binary
   def hex_encode32(data, opts \\ []) when is_binary(data) do
     case = Keyword.get(opts, :case, :upper)
@@ -640,7 +627,6 @@ defmodule Base do
       {:ok, "foobar"}
 
   """
-  @spec hex_decode32(binary) :: {:ok, binary} | :error
   @spec hex_decode32(binary, Keyword.t) :: {:ok, binary} | :error
   def hex_decode32(string, opts \\ []) do
     {:ok, hex_decode32!(string, opts)}
@@ -688,7 +674,6 @@ defmodule Base do
       "foobar"
 
   """
-  @spec hex_decode32!(binary) :: binary
   @spec hex_decode32!(binary, Keyword.t) :: binary
   def hex_decode32!(string, opts \\ []) when is_binary(string) do
     case = Keyword.get(opts, :case, :upper)

lib/elixir/lib/enum.ex

@@ -226,7 +226,6 @@ defmodule Enum do
       false
 
   """
-  @spec all?(t) :: boolean
   @spec all?(t, (element -> as_boolean(term))) :: boolean
 
   def all?(enumerable, fun \\ fn(x) -> x end)
@@ -264,7 +263,6 @@ defmodule Enum do
       true
 
   """
-  @spec any?(t) :: boolean
   @spec any?(t, (element -> as_boolean(term))) :: boolean
 
   def any?(enumerable, fun \\ fn(x) -> x end)
@@ -2650,7 +2648,6 @@ defmodule Enum do
       [a: 3, b: 4, c: 5]
 
   """
-  @spec with_index(t) :: [{element, index}]
   @spec with_index(t, integer) :: [{element, index}]
   def with_index(enumerable, offset \\ 0) do
     map_reduce(enumerable, offset, fn x, acc ->

lib/elixir/lib/keyword.ex

@@ -174,7 +174,6 @@ defmodule Keyword do
       3
 
   """
-  @spec get(t, key) :: value
   @spec get(t, key, value) :: value
   def get(keywords, key, default \\ nil) when is_list(keywords) and is_atom(key) do
     case :lists.keyfind(key, 1, keywords) do

lib/elixir/lib/macro.ex

@@ -504,7 +504,6 @@ defmodule Macro do
       1
 
   """
-  @spec escape(term) :: Macro.t
   @spec escape(term, Keyword.t) :: Macro.t
   def escape(expr, opts \\ []) do
     elem(:elixir_quote.escape(expr, Keyword.get(opts, :unquote, false)), 0)
@@ -682,7 +681,6 @@ defmodule Macro do
       "one + two"
 
   """
-  @spec to_string(Macro.t) :: String.t
   @spec to_string(Macro.t, (Macro.t, String.t -> String.t)) :: String.t
   def to_string(tree, fun \\ fn(_ast, string) -> string end)
 

lib/elixir/lib/map.ex

@@ -398,7 +398,6 @@ defmodule Map do
       3
 
   """
-  @spec get(map, key) :: value
   @spec get(map, key, value) :: value
   def get(map, key, default \\ nil) do
     case fetch(map, key) do

lib/elixir/lib/process.ex

@@ -40,7 +40,6 @@ defmodule Process do
   Returns the value for the given `key` in the process dictionary,
   or `default` if `key` is not set.
   """
-  @spec get(term) :: term
   @spec get(term, default :: term) :: term
   def get(key, default \\ nil) do
     case :erlang.get(key) do
@@ -399,7 +398,6 @@ defmodule Process do
 
   Inlined by the compiler.
   """
-  @spec demonitor(reference) :: true
   @spec demonitor(reference, options :: [:flush | :info]) :: boolean
   defdelegate demonitor(monitor_ref, options \\ []), to: :erlang
 

lib/elixir/lib/stream.ex

@@ -155,7 +155,6 @@ defmodule Stream do
       [[1, 2, 3], [4, 5, 6]]
 
   """
-  @spec chunk(Enumerable.t, pos_integer, pos_integer) :: Enumerable.t
   @spec chunk(Enumerable.t, pos_integer, pos_integer, Enumerable.t | nil) :: Enumerable.t
   def chunk(enum, n, step, leftover \\ nil)
       when is_integer(n) and n > 0 and is_integer(step) and step > 0 do
@@ -954,7 +953,6 @@ defmodule Stream do
       [{1, 3}, {2, 4}, {3, 5}]
 
   """
-  @spec with_index(Enumerable.t) :: Enumerable.t
   @spec with_index(Enumerable.t, integer) :: Enumerable.t
   def with_index(enum, offset \\ 0) do
     lazy enum, offset, fn(f1) -> R.with_index(f1) end

lib/elixir/lib/string.ex

@@ -347,7 +347,6 @@ defmodule String do
       ["1", "2", "3", "4"]
 
   """
-  @spec split(t, pattern | Regex.t) :: [t]
   @spec split(t, pattern | Regex.t, Keyword.t) :: [t]
   def split(string, pattern, options \\ [])
 

lib/elixir/lib/supervisor.ex

@@ -318,7 +318,6 @@ defmodule Supervisor do
   name, the supported values are described in the "Name registration"
   section in the `GenServer` module docs.
   """
-  @spec start_link(module, term) :: on_start
   @spec start_link(module, term, options) :: on_start
   def start_link(module, arg, options \\ []) when is_list(options) do
     case Keyword.get(options, :name) do

lib/elixir/lib/system.ex

@@ -462,7 +462,6 @@ defmodule System do
       System.halt(:abort)
 
   """
-  @spec halt() :: no_return
   @spec halt(non_neg_integer | binary | :abort) :: no_return
   def halt(status \\ 0)
 
@@ -494,7 +493,6 @@ defmodule System do
       System.stop(1)
 
   """
-  @spec stop() :: no_return
   @spec stop(non_neg_integer | binary) :: no_return
   def stop(status \\ 0)
 

lib/iex/test/iex/helpers_test.exs

@@ -188,16 +188,16 @@ defmodule IEx.HelpersTest do
     assert capture_io(fn -> s IEx.Remsh end) == "No specification for IEx.Remsh was found\n"
 
     # Test that it shows at least two specs
-    assert Enum.count(capture_io(fn -> s Enum end) |> String.split("\n"), fn line ->
+    assert Enum.count(capture_io(fn -> s Process end) |> String.split("\n"), fn line ->
       String.starts_with? line, "@spec"
     end) >= 2
 
-    assert Enum.count(capture_io(fn -> s Enum.all? end) |> String.split("\n"), fn line ->
+    assert Enum.count(capture_io(fn -> s Process.demonitor end) |> String.split("\n"), fn line ->
       String.starts_with? line, "@spec"
     end) >= 2
 
-    assert capture_io(fn -> s Enum.all?/1 end) ==
-           "@spec all?(t()) :: boolean()\n"
+    assert capture_io(fn -> s Process.register/2 end) ==
+           "@spec register(pid() | port(), atom()) :: true\n"
     assert capture_io(fn -> s struct end) ==
            "@spec struct(module() | struct(), Enum.t()) :: struct()\n"
   end