bpo-44524: Don't modify MRO when inheriting from typing.Annotated (GH-27841)

Fidget-Spinner · web-flow · commit 23384a174935 · 2021-08-25T21:13:59.000+03:00
diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
@@ -4568,6 +4568,11 @@ def test_annotated_in_other_types(self):
         X = List[Annotated[T, 5]]
         self.assertEqual(X[int], List[Annotated[int, 5]])
 
+    def test_annotated_mro(self):
+        class X(Annotated[int, (1, 10)]): ...
+        self.assertEqual(X.__mro__, (X, int, object),
+                         "Annotated should be transparent.")
+
 
 class TypeAliasTests(BaseTestCase):
     def test_canonical_usage_with_variable_annotation(self):
diff --git a/Lib/typing.py b/Lib/typing.py
@@ -1575,7 +1575,7 @@ def __init__(self, origin, metadata):
         if isinstance(origin, _AnnotatedAlias):
             metadata = origin.__metadata__ + metadata
             origin = origin.__origin__
-        super().__init__(origin, origin, name="Annotated")
+        super().__init__(origin, origin)
         self.__metadata__ = metadata
 
     def copy_with(self, params):
@@ -1603,6 +1603,11 @@ def __eq__(self, other):
     def __hash__(self):
         return hash((self.__origin__, self.__metadata__))
 
+    def __getattr__(self, attr):
+        if attr in {'__name__', '__qualname__'}:
+            return 'Annotated'
+        return super().__getattr__(attr)
+
 
 class Annotated:
     """Add context specific metadata to a type.
