Expand :for in protocols with the appropriate env

Author: josevalim

lib/elixir/lib/protocol.ex

@@ -931,7 +931,8 @@ defmodule Protocol do
           raise ArgumentError, "defimpl/3 expects a :for option when declared outside a module"
       end)
 
-    for = Macro.expand_literals(for, %{env | module: Kernel, function: {:defimpl, 3}})
+    for =
+      Macro.expand_literals(for, %{env | module: env.module || Elixir, function: {:__impl__, 1}})
 
     case opts do
       [] -> raise ArgumentError, "defimpl expects a do-end block"

lib/elixir/test/elixir/protocol_test.exs

@@ -74,6 +74,14 @@ defmodule ProtocolTest do
     end
   end
 
+  defmodule ImplStructExplicitFor do
+    defstruct a: 0, b: 0
+
+    defimpl Sample, for: __MODULE__ do
+      def ok(_struct), do: true
+    end
+  end
+
   test "protocol implementations without any" do
     assert is_nil(Sample.impl_for(:foo))
     assert is_nil(Sample.impl_for(fn x -> x end))
@@ -91,6 +99,7 @@ defmodule ProtocolTest do
     assert is_nil(Sample.impl_for(make_ref()))
 
     assert Sample.impl_for(%ImplStruct{}) == Sample.ProtocolTest.ImplStruct
+    assert Sample.impl_for(%ImplStructExplicitFor{}) == Sample.ProtocolTest.ImplStructExplicitFor
     assert Sample.impl_for(%NoImplStruct{}) == nil
   end