Stop calling _clear_type_descriptors

Author: encukou

Lib/dataclasses.py

@@ -1283,10 +1283,6 @@ def _add_slots(cls, is_frozen, weakref_slot, defined_fields):
     if '__slots__' in cls.__dict__:
         raise TypeError(f'{cls.__name__} already specifies __slots__')
 
-    # gh-102069: Remove existing __weakref__ descriptor.
-    # gh-135228: Make sure the original class can be garbage collected.
-    sys._clear_type_descriptors(cls)
-
     # Create a new dict for our new class.
     cls_dict = dict(cls.__dict__)
     field_names = tuple(f.name for f in fields(cls))
@@ -1304,6 +1300,11 @@ def _add_slots(cls, is_frozen, weakref_slot, defined_fields):
         #  available in _MARKER.
         cls_dict.pop(field_name, None)
 
+    # Remove __dict__ and `__weakref__` descriptors.
+    # They'll be added back if applicable.
+    cls_dict.pop('__dict__', None)
+    cls_dict.pop('__weakref__', None)  # gh-102069
+
     # And finally create the class.
     qualname = getattr(cls, '__qualname__', None)
     newcls = type(cls)(cls.__name__, cls.__bases__, cls_dict)