Support bitstring specifies as map keys in pattern, closes #12586

lib/elixir/src/elixir_map.erl

@@ -62,6 +62,8 @@ clean_struct_key_from_map_assocs(Meta, Assocs, E) ->
 
 validate_match_key(Meta, {Name, _, Context}, E) when is_atom(Name), is_atom(Context) ->
   file_error(Meta, E, ?MODULE, {invalid_variable_in_map_key_match, Name});
+validate_match_key(Meta, {'::', _, [Left, _]}, E) ->
+  validate_match_key(Meta, Left, E);
 validate_match_key(_, {'^', _, [{Name, _, Context}]}, _) when is_atom(Name), is_atom(Context) ->
   ok;
 validate_match_key(_, {'%{}', _, [_ | _]}, _) ->

lib/elixir/test/elixir/kernel/expansion_test.exs

@@ -483,7 +483,7 @@ defmodule Kernel.ExpansionTest do
                quote(do: %{a: after_expansion = 1, b: a()})
     end
 
-    test "with variables on keys" do
+    test "with variables on keys inside patterns" do
       ast =
         quote do
           %{(x = 1) => 1}
@@ -516,6 +516,34 @@ defmodule Kernel.ExpansionTest do
       end)
     end
 
+    test "with binaries in keys inside patterns" do
+      before_ast =
+        quote do
+          %{<<0>> => nil} = %{<<0>> => nil}
+        end
+
+      after_ast =
+        quote do
+          %{<<0::integer>> => nil} = %{<<0::integer>> => nil}
+        end
+
+      assert expand(before_ast) |> clean_meta([:alignment]) == clean_bit_modifiers(after_ast)
+      assert expand(after_ast) |> clean_meta([:alignment]) == clean_bit_modifiers(after_ast)
+
+      ast =
+        quote do
+          x = 8
+          %{<<0::integer-size(x)>> => nil} = %{<<0::integer>> => nil}
+        end
+
+      assert expand(ast) |> clean_meta([:alignment]) ==
+               clean_bit_modifiers(ast) |> clean_meta([:context, :imports])
+
+      assert_compile_error(~r"cannot use variable x as map key inside a pattern", fn ->
+        expand(quote(do: %{<<x::integer>> => 1} = %{}), [])
+      end)
+    end
+
     test "expects key-value pairs" do
       assert_compile_error(~r"expected key-value pairs in a map, got: :foo", fn ->
         expand(quote(do: unquote({:%{}, [], [:foo]})))