gh-146553: Fix infinite loop in typing.get_type_hints() on circular __wrapped__ (#148595)

Author: ashm-dev

Lib/test/test_typing.py

@@ -6888,6 +6888,24 @@ def test_get_type_hints_wrapped_decoratored_func(self):
         self.assertEqual(gth(ForRefExample.func), expects)
         self.assertEqual(gth(ForRefExample.nested), expects)
 
+    def test_get_type_hints_wrapped_cycle_self(self):
+        # gh-146553: __wrapped__ self-reference must raise ValueError,
+        # not loop forever.
+        def f(x: int) -> str: ...
+        f.__wrapped__ = f
+        with self.assertRaisesRegex(ValueError, 'wrapper loop'):
+            get_type_hints(f)
+
+    def test_get_type_hints_wrapped_cycle_mutual(self):
+        # gh-146553: mutual __wrapped__ cycle (a -> b -> a) must raise
+        # ValueError, not loop forever.
+        def a(): ...
+        def b(): ...
+        a.__wrapped__ = b
+        b.__wrapped__ = a
+        with self.assertRaisesRegex(ValueError, 'wrapper loop'):
+            get_type_hints(a)
+
     def test_get_type_hints_annotated(self):
         def foobar(x: List['X']): ...
         X = Annotated[int, (1, 10)]

Lib/typing.py

@@ -2486,8 +2486,12 @@ def get_type_hints(obj, globalns=None, localns=None, include_extras=False,
         else:
             nsobj = obj
             # Find globalns for the unwrapped object.
+            seen = {id(nsobj)}
             while hasattr(nsobj, '__wrapped__'):
                 nsobj = nsobj.__wrapped__
+                if id(nsobj) in seen:
+                    raise ValueError(f'wrapper loop when unwrapping {obj!r}')
+                seen.add(id(nsobj))
             globalns = getattr(nsobj, '__globals__', {})
         if localns is None:
             localns = globalns

Misc/NEWS.d/next/Library/2026-04-15-11-00-39.gh-issue-146553.VGOsoP.rst

@@ -0,0 +1,2 @@
+Fix infinite loop in :func:`typing.get_type_hints` when ``__wrapped__``
+forms a cycle. Patch by Shamil Abdulaev.