inherited ClassVar

[beauxq]

In the pyrefly playground, I tried this:

from typing import ClassVar


class B:
    x: ClassVar[int | str] = 0


class C(B):
    x = "random"  # pyrefly reports error here "Class member `x` overrides parent class `B` in an inconsistent manner"

But it is not inconsistent with what B declares. - x should be ok as a str

If you want to go further, this is also an opportunity to be better than mypy and pyright:

from typing import ClassVar, reveal_type


class B:
    x: ClassVar[int | str] = 0


class C(B):
    x = "random"


class D(C):
    x = 1  # mypy complains where it shouldn't


class E(D):
    x = b"3"  # pyright doesn't complain where it should


def foo(b: type[B]) -> None:
    x = b.x
    reveal_type(x)
    if isinstance(x, int):
        print(x + 8)
    else:
        print(x + "8")


foo(E)

The annotation of x in B should apply to all subclasses

[yangdanny97]

Thanks for the report! Fully supporting ClassVar is on our list of TODOs here: #16

[samwgoldman]

Is this behavior described anywhere? If not in the spec, is this something that mypy and/or pyright do? Based on the spec alone, it’s not clear to me why ClassVar annotations would be implicitly inherited. Maybe I missed the part of the spec that mentions this behavior?