Class C

Lib/test/test_class.py:699–706

            y = 0
            __slots__ = ('z',)
        class C:
            __slots__ = ("y",)

            def __setattr__(self, name, value) -> None:
                if name == "z":
                    super().__setattr__("y", 1)
                else:
                    super().__setattr__(name, value)

        error_msg = "'A' object has no attribute 'x'"
        with self.assertRaisesRegex(AttributeError, error_msg):