fixed match-case against typing.Callable

[randolf-scholz]

Fixes #14014

Added an extra elif branch that checks if we are matching against typing.Callable, and uses callable_with_ellipsis to treat it as a Callable[..., Any].

[randolf-scholz]

these two conditions are also checked in the elif before and below, but I did not bother to try to optimize them away.

[randolf-scholz]

I am not sure if this is the right type of Any; I was guessing based on the description.

[randolf-scholz]

Hm, this probably can be improved quite a bit, since currently it always infers Callalbe[..., Any], but better would be to get the same inference as in a case fn if callable(fn) branch.

[randolf-scholz]

I found a solution now to get more precise narrowing, e.g.

def int_fun(x: int) -> int: return x+1

match int_fun:
    case Callable() as fn:
        reveal_type(fn)  # N: Revealed type is "def (x: builtins.int) -> builtins.int"

I'm sure there's a more elegant way to do it, but this is the only thing I came up with.

[randolf-scholz]

Hm, this doesn't work as desired when e.g. x: Callable[[int], int] | str, we get Callable[..., Any] and not Callable[[int], int].

I guess we need to patch the conditional_types_with_intersection function instead?

[randolf-scholz]

Closing temporarily to find a better solution that yields correct narrowing logic.

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅