allow changing __class__ between a heaptype and non-heaptype in some cases (closes #22986)

Patch by Nathaniel Smith.

1 files changed, 16 insertions, 0 deletions

diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py
index 0c88fd2..595af4b 100644
--- a/Lib/test/test_descr.py
+++ b/Lib/test/test_descr.py
@@ -1026,6 +1026,22 @@ order (MRO) for bases """
         self.assertEqual(x.foo, 1)
         self.assertEqual(x.__dict__, {'foo': 1})
 
+    def test_object_class_assignment_between_heaptypes_and_nonheaptypes(self):
+        class SubType(types.ModuleType):
+            a = 1
+
+        m = types.ModuleType("m")
+        self.assertTrue(m.__class__ is types.ModuleType)
+        self.assertFalse(hasattr(m, "a"))
+
+        m.__class__ = SubType
+        self.assertTrue(m.__class__ is SubType)
+        self.assertTrue(hasattr(m, "a"))
+
+        m.__class__ = types.ModuleType
+        self.assertTrue(m.__class__ is types.ModuleType)
+        self.assertFalse(hasattr(m, "a"))
+
     def test_slots(self):
         # Testing __slots__...
         class C0(object):