Do not delete enforce_keys on defstruct, closes #12126

Author: josevalim

lib/elixir/lib/kernel/utils.ex

@@ -138,10 +138,10 @@ defmodule Kernel.Utils do
     fields = :lists.map(mapper, fields)
 
     enforce_keys =
-      case :ets.take(set, :enforce_keys) do
-        [{_, enforce_keys, _, _}] when is_list(enforce_keys) -> enforce_keys
-        [{_, enforce_key, _, _}] -> [enforce_key]
-        [] -> []
+      case Module.get_attribute(module, :enforce_keys) do
+        nil -> []
+        enforce_keys when is_list(enforce_keys) -> enforce_keys
+        enforce_key -> [enforce_key]
       end
 
     # TODO: Make it raise on v2.0

lib/elixir/test/elixir/map_test.exs

@@ -393,6 +393,10 @@ defmodule MapTest do
       defmodule TestMod do
         @enforce_keys :foo
         defstruct [:foo]
+
+        # Verify it remain set afterwards
+        :foo = @enforce_keys
+
         def foo do
           %TestMod{}
         end