This issue also pertains to total_ordering (and perhaps other std library class-decorators I haven't thought of), not to mention 3rd party decorators that could have this problem (attrs, for example, does not cover this case). Updating  __abstractmethods__ inside each of these decorators would solve the problem, but does seem like a pain for 3rd-party. Maybe a meta-decorator could be added to make this easier?

    @update_abstractmethods

    def dataclass(...):

        ...