[3.11] gh-115165: Fix typing.Annotated for immutable types (GH-115213) (#115228)

gh-115165: Fix `typing.Annotated` for immutable types (GH-115213)

The return value from an annotated callable can raise any exception from
__setattr__ for the `__orig_class__` property.
(cherry picked from commit 564385612c)

Co-authored-by: dave-shawley <daveshawley@gmail.com>

Lib/test/test_typing.py

@@ -3665,6 +3665,17 @@ class GenericTests(BaseTestCase):
         c.bar = 'abc'
         self.assertEqual(c.__dict__, {'bar': 'abc'})
 
+    def test_setattr_exceptions(self):
+        T = TypeVar("T")
+        class Immutable(Generic[T]):
+            def __setattr__(self, key, value):
+                raise RuntimeError("immutable")
+
+        # gh-115165: This used to cause RuntimeError to be raised
+        # when we tried to set `__orig_class__` on the `Immutable` instance
+        # returned by the `Immutable[int]()` call
+        self.assertIsInstance(Immutable[int](), Immutable)
+
     def test_subscripted_generics_as_proxies(self):
         T = TypeVar('T')
         class C(Generic[T]):
@@ -7397,6 +7408,17 @@ class AnnotatedTests(BaseTestCase):
         self.assertEqual(MyCount([4, 4, 5]), {4: 2, 5: 1})
         self.assertEqual(MyCount[int]([4, 4, 5]), {4: 2, 5: 1})
 
+    def test_instantiate_immutable(self):
+        class C:
+            def __setattr__(self, key, value):
+                raise Exception("should be ignored")
+
+        A = Annotated[C, "a decoration"]
+        # gh-115165: This used to cause RuntimeError to be raised
+        # when we tried to set `__orig_class__` on the `C` instance
+        # returned by the `A()` call
+        self.assertIsInstance(A(), C)
+
     def test_cannot_instantiate_forward(self):
         A = Annotated["int", (5, 6)]
         with self.assertRaises(TypeError):