Join of two type concrete type objects may be considered abstract

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Issue 类型
缺陷
描述清晰度
基本清楚
活跃度
停滞
技术栈
python
领域
devtools

调研方向

Start with the reproducer in the issue and inspect how mypy computes joins of callable type objects representing A and B. Determine whether t0 should be accepted without the abstract-class error, and assess whether the same behavior needs correction for meets.

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描述

bug false-positive priority-1-normal topic-join-v-union

Mypy complains about the following code even though it looks fine:

from abc import abstractmethod

class Base:
    @abstractmethod
    def f(self) -> None: pass
class A(Base):
    def f(self) -> None: pass
class B(Base):
    def f(self) -> None: pass

t = [A, B]

t[0]()  # Cannot instantiate abstract class 'Base' with abstract attribute 'f'

It looks like the join of two callables representing type objects should perhaps be Type[x] instead of another callable, since mypy basically assumes that a callable represents a specific type object, not something that can also be any subclass. The same issue probably applies to meets as well.

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