New submission from Erez Zinman <erezinman.program...@gmail.com>:
Consider the following example: ``` from abc import ABCMeta, ABC class MetaclassMixin(ABC): pass class Meta(MetaclassMixin, ABCMeta): pass class A(metaclass=Meta): pass ``` Then the call `isinstance(A, Meta)` returns `True` but `isinstance(1, Meta)` raises >>> TypeError: __subclasscheck__() missing 1 required positional argument: >>> 'subclass' Checked on 3.6.9, 3.8.0 & 3.8.8 ---------- components: Library (Lib) messages: 389314 nosy: erezinman priority: normal severity: normal status: open title: A metaclass that inherits both `ABC` and `ABCMeta` breaks on `__subclasscheck__` versions: Python 3.6, Python 3.8 _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue43594> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com