Ignore additional callbacks in protocol implementation, closes #15456

lib/elixir/lib/module/types.ex

@@ -136,8 +136,8 @@ defmodule Module.Types do
   defp impl_for(attrs) do
     case List.keyfind(attrs, :__impl__, 0) do
       {:__impl__, [protocol: protocol, for: for]} ->
-        if Code.ensure_loaded?(protocol) and function_exported?(protocol, :behaviour_info, 1) do
-          {for, protocol.behaviour_info(:callbacks)}
+        if Code.ensure_loaded?(protocol) and function_exported?(protocol, :__protocol__, 1) do
+          {for, protocol.__protocol__(:functions)}
         else
           nil
         end

lib/elixir/test/elixir/module/types/integration_test.exs

@@ -154,6 +154,50 @@ defmodule Module.Types.IntegrationTest do
 
       assert itself_arg.(Itself.Unknown) == dynamic(open_map(__struct__: atom([Unknown])))
     end
+
+    test "ignores additional callbacks on implementations" do
+      files = %{
+        "p.ex" => """
+        defmodule InjectCallback do
+          defmacro __before_compile__(_env) do
+            quote do
+              @callback extra() :: term()
+            end
+          end
+        end
+
+        defprotocol Injected do
+          @before_compile InjectCallback
+          def f(x)
+        end
+
+        defimpl Injected, for: Atom do
+          def f(_), do: :ok
+          def extra(), do: :extra
+        end
+
+        defprotocol Explicit do
+          @callback extra() :: term()
+          def f(x)
+        end
+
+        defimpl Explicit, for: Atom do
+          def f(_), do: :ok
+          def extra(), do: :extra
+        end
+        """
+      }
+
+      assert capture_compile_warnings(files, []) == """
+                 warning: cannot define @callback extra/0 inside protocol, use def/1 to outline your protocol definition
+                 │
+              20 │   @callback extra() :: term()
+                 │   ~~~~~~~~~~~~~~~~~~~~~~~~~~~
+                 │
+                 └─ p.ex:20: Explicit (module)
+
+             """
+    end
   end
 
   describe "type checking" do