Binder doesn't work well with Type[...]

[ilevkivskyi]

This code:

from typing import Union, Type

class C: ...

x: Union[C, Type[C]]

if isinstance(x, type) and issubclass(x, C):
    reveal_type(x)

Shows that the type of x is builtins.type. Ideally it should be Type[C].

[andrewbaxter]

Is this the same as:

class A:
    x = 4


i: type = A
assert issubclass(i, A)
print(i.x)

which fails with:

7: error: "type" has no attribute "x"

?

mypy 0.590

It looks like issubclass doesn't imply anything AFAICT, unlike isinstance.

There's this workaround:

i: type = A
j: Type[A] = i
print(j.x)

but since this isn't in assertion format it seems more like a static check omission.

[ilevkivskyi]

Yes, this is the same bug.

[chadrik]

Just got bit by this one.

[ilevkivskyi]

(Removing unions tag since there are repros without unions, and increasing priority to high since this appeared several times again.)