gh-90562: Update __class__ in function closures for dataclasses with slots=True

Lib/dataclasses.py

@@ -1221,16 +1221,46 @@ def _add_slots(cls, is_frozen, weakref_slot):
 
     # And finally create the class.
     qualname = getattr(cls, '__qualname__', None)
-    cls = type(cls)(cls.__name__, cls.__bases__, cls_dict)
+    new_cls = type(cls)(cls.__name__, cls.__bases__, cls_dict)
     if qualname is not None:
-        cls.__qualname__ = qualname
+        new_cls.__qualname__ = qualname
 
     if is_frozen:
         # Need this for pickling frozen classes with slots.
-        cls.__getstate__ = _dataclass_getstate
-        cls.__setstate__ = _dataclass_setstate
+        new_cls.__getstate__ = _dataclass_getstate
+        new_cls.__setstate__ = _dataclass_setstate
+
+    # References to the old class may still be stored in class function __closure__s.
+    # Try and replace them with the new class so, for example, super() will work.
+    for cls_attribute in cls_dict.values():
+        # Unwrap classmethods, staticmethods, and decorators made using @functools.wraps.
+        cls_attribute = inspect.unwrap(cls_attribute)
+
+        if isinstance(cls_attribute, property):
+            # Special case to support property.
+            for func in (cls_attribute.fget, cls_attribute.fset, cls_attribute.fdel):
+                _update_class_cell(cls, new_cls, func)
+        else:
+            _update_class_cell(cls, new_cls, cls_attribute)
 
-    return cls
+    return new_cls
+
+
+def _update_class_cell(old_cls, new_cls, function):
+    # Ignore if the object isn't actually a function.
+    if not inspect.isfunction(function):
+        return
+
+    # Function does not use __class__ or super(), ignore.
+    if function.__closure__ is None:
+        return
+
+    # Look through function closure to find the __class__ cell, and update
+    # it with the new class if it previously contained the old class.
+    for name, cell in zip(function.__code__.co_freevars, function.__closure__):
+        if name == "__class__" and cell.cell_contents is old_cls:
+            cell.cell_contents = new_cls
+            break
 
 
 def dataclass(cls=None, /, *, init=True, repr=True, eq=True, order=False,

Lib/test/test_dataclasses.py

@@ -3331,6 +3331,100 @@ class A(Base):
         a_ref = weakref.ref(a)
         self.assertIs(a.__weakref__, a_ref)
 
+    def test_slots_super(self):
+        @dataclass(slots=True)
+        class Base:
+            a: int
+            def b(self):
+                return 2
+
+            def c(self):
+                return 3
+
+        @dataclass(slots=True)
+        class A(Base):
+            def b(self):
+                return super().b()
+
+            def d(self):
+                return 4
+
+        a = A(1)
+        self.assertEqual(a.a, 1)
+        self.assertEqual(a.b(), 2)
+        self.assertEqual(a.c(), 3)
+        self.assertEqual(a.d(), 4)
+
+    def test_slots_dunder_class(self):
+        class Base:
+            def foo(self):
+                return 1
+
+        class OtherClass(Base):
+            def foo(self):
+                return __class__
+
+        @dataclass(slots=True)
+        class A:
+            foo = OtherClass.foo
+
+            def bar(self):
+                return __class__
+
+        a = A()
+        self.assertEqual(a.foo(), OtherClass)
+        self.assertEqual(a.bar(), A)
+
+    def test_slots_dunder_class_decorated(self):
+        import functools
+
+        def deco(f):
+            @functools.wraps(f)
+            def wrapper(*args, **kwargs):
+                return f(*args, **kwargs)
+            return wrapper
+
+        @dataclass(slots=True)
+        class A():
+            @classmethod
+            @deco
+            def b(cls):
+                return __class__
+
+        a = A()
+        self.assertEqual(a.b(), A)
+
+    def test_slots_dunder_class_property_getter(self):
+        @dataclass(slots=True)
+        class A:
+            @property
+            def foo(slf):
+                return __class__
+
+        a = A()
+        self.assertEqual(a.foo, A)
+
+    def test_slots_dunder_class_property_setter(self):
+        @dataclass(slots=True)
+        class A:
+            foo = property()
+            @foo.setter
+            def foo(slf, val):
+                self.assertEqual(__class__, type(slf))
+
+        a = A()
+        a.foo = 4
+
+    def test_slots_dunder_class_property_deleter(self):
+        @dataclass(slots=True)
+        class A:
+            foo = property()
+            @foo.deleter
+            def foo(slf):
+                self.assertEqual(__class__, type(slf))
+
+        a = A()
+        del a.foo
 
 class TestDescriptors(unittest.TestCase):
     def test_set_name(self):