bpo-35992: Use PySequence_GetItem only if sq_item is not NULL (GH-11857)

Not using `__class_getitem__()` fallback if there is a non-subcriptable metaclass was caused by a certain asymmetry between how `PySequenceMethods` and `PyMappingMethods` are used in `PyObject_GetItem`. This PR removes this asymmetry. No tests failed, so I assume it was not intentional.

1 files changed, 8 insertions, 1 deletions

diff --git a/Lib/test/test_genericclass.py b/Lib/test/test_genericclass.py
index 37e755b..37a87bc 100644
--- a/Lib/test/test_genericclass.py
+++ b/Lib/test/test_genericclass.py
@@ -248,7 +248,14 @@ class TestClassGetitem(unittest.TestCase):
                 return f'{cls.__name__}[{item.__name__}]'
         self.assertEqual(Meta[int], 'Meta[int]')
 
-    def test_class_getitem_metaclass_2(self):
+    def test_class_getitem_with_metaclass(self):
+        class Meta(type): pass
+        class C(metaclass=Meta):
+            def __class_getitem__(cls, item):
+                return f'{cls.__name__}[{item.__name__}]'
+        self.assertEqual(C[int], 'C[int]')
+
+    def test_class_getitem_metaclass_first(self):
         class Meta(type):
             def __getitem__(cls, item):
                 return 'from metaclass'