Function "issubclass()" incorrectly narrows down a type of variable. Generic. TypeVar. Subclass.

Bug Report

Function "issubclass()" does not narrow down a type of variable.

To Reproduce

from typing import Any, Generic, TypeVar, cast

R = TypeVar("R", "FooResponse", "BarResponse")


class BaseResponse:
    def __str__(self) -> str:
        return "<{}: {}>".format(self.__class__.__name__, self.__dict__)


class FooResponse(BaseResponse):
    def __init__(self, val: str) -> None:
        self.foo1 = val


class BarResponse(BaseResponse):
    def __init__(self, val1: str, val2: str) -> None:
        self.bar1 = val1
        self.bar2 = val2


class BaseRequest(Generic[R]):
    response_class: type[R]


class FooRequest(BaseRequest[FooResponse]):
    response_class = FooResponse


class BarRequest(BaseRequest[BarResponse]):
    response_class = BarResponse


def build_data(response_class: type[R]) -> R:
    if issubclass(response_class, FooResponse):
        reveal_type(response_class)
        return FooResponse("FOO")
    raise ValueError("Unsupported type: {}".format(response_class))


def query(req: BaseRequest[R]) -> R:
    return build_data(req.response_class)


def main(**_kwargs: Any) -> None:
    print(query(FooRequest()))

I expect mypy does not throw any error while validating the source code.

Actual Behavior

I got this output:

script/test_union.py:36: note: Revealed type is "Type[script.test_union.FooResponse]"
script/test_union.py:36: note: Revealed type is "Type[script.test_union.<subclass of "BarResponse" and "FooResponse">]"
script/test_union.py:37: error: Incompatible return value type (got "FooResponse", expected "BarResponse")  [return-value]

Your Environment

Versions:

Python 3.11.1
mypy==1.2.0
mypy-extensions==1.0.0

Mypy command: mypy --strict mysourcecode.py

Commencez par le reproducer Python inline et exécutez-le avec mypy --strict mysourcecode.py sous les versions indiquées. Comparez les types révélés et l’erreur de valeur de retour avec le comportement attendu ; c’est terminé lorsque le reproducer se valide sans l’erreur de retour incompatible tout en préservant le narrowing générique correct.