Tag / as an operator in fragments, closes #14643

lib/elixir/lib/code/fragment.ex

@@ -302,7 +302,8 @@ defmodule Code.Fragment do
       {{:local_or_var, acc}, count} -> {{:local_arity, acc}, count}
       {{:dot, base, acc}, count} -> {{:dot_arity, base, acc}, count}
       {{:operator, acc}, count} -> {{:operator_arity, acc}, count}
-      {_, _} -> {:none, 0}
+      {{:sigil, _}, _} -> {:none, 0}
+      {_, _} -> {{:operator, ~c"/"}, 1}
     end
   end
 

lib/elixir/test/elixir/code_fragment_test.exs

@@ -302,6 +302,7 @@ defmodule CodeFragmentTest do
     end
 
     test "operators" do
+      assert CF.cursor_context("/") == {:operator, ~c"/"}
       assert CF.cursor_context("+") == {:operator, ~c"+"}
       assert CF.cursor_context("++") == {:operator, ~c"++"}
       assert CF.cursor_context("!") == {:operator, ~c"!"}
@@ -361,6 +362,15 @@ defmodule CodeFragmentTest do
       assert CF.cursor_context("~r/") == :none
       assert CF.cursor_context("~r<") == :none
 
+      assert CF.cursor_context("~r''") == :none
+      assert CF.cursor_context("~r' '") == :none
+      assert CF.cursor_context("~r'foo'") == :none
+
+      # The slash is used in sigils, arities, and operators, so there is ambiguity
+      assert CF.cursor_context("~r//") == {:operator, ~c"/"}
+      assert CF.cursor_context("~r/ /") == {:operator, ~c"/"}
+      assert CF.cursor_context("~r/foo/") == {:local_arity, ~c"foo"}
+
       assert CF.cursor_context("~R") == {:sigil, ~c"R"}
       assert CF.cursor_context("~R/") == :none
       assert CF.cursor_context("~R<") == :none