EEP 52: Allow pins inside map keys in matches (#11544)

3 files changed, 16 insertions, 19 deletions

diff --git a/lib/elixir/src/elixir_map.erl b/lib/elixir/src/elixir_map.erl
index 3da517ae8..560b7a437 100644
--- a/lib/elixir/src/elixir_map.erl
+++ b/lib/elixir/src/elixir_map.erl
@@ -60,10 +60,10 @@ clean_struct_key_from_map_assocs(Meta, Assocs, E) ->
       Assocs
   end.
 
-validate_match_key(Meta, {'^', _, [{Name, _, Context}]}, E) when is_atom(Name), is_atom(Context) ->
-  form_error(Meta, E, ?MODULE, {invalid_pin_in_map_key_match, Name});
 validate_match_key(Meta, {Name, _, Context}, E) when is_atom(Name), is_atom(Context) ->
   form_error(Meta, E, ?MODULE, {invalid_variable_in_map_key_match, Name});
+validate_match_key(_, {'^', _, [{Name, _, Context}]}, _) when is_atom(Name), is_atom(Context) ->
+  ok;
 validate_match_key(_, {'%{}', _, [_ | _]}, _) ->
   ok;
 validate_match_key(Meta, {Left, _, Right}, E) ->
@@ -102,8 +102,6 @@ is_literal(_) -> true.
 
 validate_kv(Meta, KV, Original, #{context := Context} = E) ->
   lists:foldl(fun
-    ({{'^', _, [_]}, _}, {Index, Used}) ->
-      {Index + 1, Used};
     ({K, _V}, {Index, Used}) ->
       (Context == match) andalso validate_match_key(Meta, K, E),
       NewUsed = validate_not_repeated(Meta, K, Used, E),
@@ -202,11 +200,6 @@ format_error({invalid_struct_name_in_match, Expr}) ->
 format_error({invalid_struct_name, Expr}) ->
   Message = "expected struct name to be a compile time atom or alias, got: ~ts",
   io_lib:format(Message, ['Elixir.Macro':to_string(Expr)]);
-format_error({invalid_pin_in_map_key_match, Name}) ->
-  Message =
-    "cannot use pin operator ^~ts inside a data structure as a map key in a pattern. "
-    "The pin operator can only be used as the whole key",
-  io_lib:format(Message, [Name]);
 format_error({invalid_variable_in_map_key_match, Name}) ->
   Message =
     "cannot use variable ~ts as map key inside a pattern. Map keys in patterns can only be literals "
diff --git a/lib/elixir/test/elixir/kernel/expansion_test.exs b/lib/elixir/test/elixir/kernel/expansion_test.exs
index 360058d4a..8282a094d 100644
--- a/lib/elixir/test/elixir/kernel/expansion_test.exs
+++ b/lib/elixir/test/elixir/kernel/expansion_test.exs
@@ -475,16 +475,13 @@ defmodule Kernel.ExpansionTest do
 
       assert expand(ast) == ast
 
-      assert_raise CompileError,
-                   ~r"cannot use pin operator \^x inside a data structure as a map key in a pattern",
-                   fn ->
-                     expand(
-                       quote do
-                         x = 1
-                         %{{^x} => 1} = %{}
-                       end
-                     )
-                   end
+      ast =
+        quote do
+          x = 1
+          %{{^x} => 1} = %{{1} => 1}
+        end
+
+      assert expand(ast) == ast
 
       assert_raise CompileError, ~r"cannot use variable x as map key inside a pattern", fn ->
         expand(quote(do: %{x => 1} = %{}))
diff --git a/lib/elixir/test/elixir/module/types/map_test.exs b/lib/elixir/test/elixir/module/types/map_test.exs
index f416d77da..5324c8453 100644
--- a/lib/elixir/test/elixir/module/types/map_test.exs
+++ b/lib/elixir/test/elixir/module/types/map_test.exs
@@ -160,6 +160,13 @@ defmodule Module.Types.MapTest do
              )
            ) == {:ok, {:map, [{:required, {:atom, :a}, {:atom, :b}}]}}
 
+    assert quoted_expr(
+             (
+               a = :a
+               %{{^a, :b} => :c} = %{{:a, :b} => :c}
+             )
+           ) == {:ok, {:map, [{:required, {:tuple, 2, [{:atom, :a}, {:atom, :b}]}, {:atom, :c}}]}}
+
     assert {:error,
             {:unable_unify,
              {{:map, [{:required, {:atom, :c}, {:atom, :d}}]},