no-any-explicit false positive with type parameter default Any

[jorenham]

Describe the problem

There's no explicit Any here:

a = slice(None)
b: slice = a

But the following error is reported:

Explicit "Any" is not allowed (no-any-explicit) [Ln 2, Col 1]

I'm guessing this is because the type parameters of slice default to Any. But I don't see why such an implicit Any should be considered as explicit.

Gist to reproduce

a = slice(None)
b: slice = a

Severity

annoying but workaround is available

Your Environment

basedmypy 2.9.1 (compiled: yes)
Based on mypy 1.14.1

[jorenham]

And the weirdest thing is that in this example, it occurs twice:

from typing import Generic, TypeVar

T = TypeVar("T", bound=int | slice)  # E: no-any-explicit

class A(Generic[T]): ...  # <no error>
class B(A[T]): ...  # E: no-any-explicit

So with A it doesn't report an error, but with B it does?

[jorenham]

For a real life example, see e.g. optype/numpy/_to.py, which doesn't even import Any, yet there are 62 no-any-explicit errors reported, forcing me to use # mypy: disable-error-code="no-any-explicit".

[KotlinIsland]

I'm guessing this is because the type parameters of slice default to Any. But I don't see why such an implicit Any should be considered as explicit.

so this is more about understandability? or would you not want an error here at all?

[jorenham]

I don't think it's useful in this case, because the Any is out of your control. I also don't think that it's useful to report the same error about the same Any on multiple occasions. Given the name of the error, I expected it to only be reported once I explicitly write "Any", so that I can actually see that it's there.

I might be wrong here, but I thought that that's also the way that bpr's reportExplicitAny works 🤷🏻