type signature in generic subclass

[oraluben]

from typing import Generic, Callable, TypeVar, Iterator

T = TypeVar('T')


class Box(Generic[T]):
    @classmethod
    def wrap(cls, generator: Callable[[], T]) -> 'Box[T]':
        pass


class IteratorBox(Box[Iterator[T]],
                  Generic[T]):
    pass


def g() -> int:
    return 0


r = IteratorBox.wrap(g)

b: IteratorBox = IteratorBox
reveal_type(b.wrap)
reveal_type(IteratorBox.wrap)
reveal_type(IteratorBox.wrap(g))

output of mypy is

as type "IteratorBox[Any]")
test.py:24: error: Revealed type is 'def (generator: def () -> typing.Iterator*[Any]) -> test.Box[typing.Iter
ator*[Any]]'
test.py:25: error: Revealed type is 'def [T] (generator: def () -> T`1) -> test.Box[T`1]'
test.py:26: error: Revealed type is 'test.Box[builtins.int*]'

I was expecting that mypy will find type mismatch to call IteratorBox.wrap(g), which it didn't.
And reveal_type(IteratorBox.wrap) just return the type of the method in base class.

[ilevkivskyi]

This is a known issue, see #3645, but I don't want to close this because I want to collect all the use cases for type variables in class methods, so that we can understand what is actually desired and test our solution properly.

[oraluben]

Thanks for your reply! I have tried the PR and found a code may get wrong checking result. If it's ok to put my repro in the PR?