Fix TypeError on nested Annotated types where the inner type has unhashable metadata (#417)

Author: AlexWaygood

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 - Preliminary changes for compatibility with the draft implementation
   of PEP 649 in Python 3.14.
+- Fix regression in v4.12.0 where nested `Annotated` types would cause
+  `TypeError` to be raised if the nested `Annotated` type had unhashable
+  metadata.
 
 # Release 4.12.0 (May 23, 2024)
 

src/test_typing_extensions.py

@@ -4769,6 +4769,14 @@ def test_annotated_in_other_types(self):
         X = List[Annotated[T, 5]]
         self.assertEqual(X[int], List[Annotated[int, 5]])
 
+    def test_nested_annotated_with_unhashable_metadata(self):
+        X = Annotated[
+            List[Annotated[str, {"unhashable_metadata"}]],
+            "metadata"
+        ]
+        self.assertEqual(X.__origin__, List[Annotated[str, {"unhashable_metadata"}]])
+        self.assertEqual(X.__metadata__, ("metadata",))
+
 
 class GetTypeHintsTests(BaseTestCase):
     def test_get_type_hints(self):

src/typing_extensions.py

@@ -2958,9 +2958,9 @@ def _has_generic_or_protocol_as_origin() -> bool:
     except AttributeError:
         return False  # err on the side of leniency
     else:
-        return frame.f_locals.get("origin") in {
+        return frame.f_locals.get("origin") in (
             typing.Generic, Protocol, typing.Protocol
-        }
+        )
 
 
 _TYPEVARTUPLE_TYPES = {TypeVarTuple, getattr(typing, "TypeVarTuple", None)}