Callable protocol has no attribute __name__

[Cheaterman]

Bug Report

Hello and apologies in advance if this is somewhat normal and/or I missed the proper way to type-hint this, but my gut instinct says that this should work: https://mypy-play.net/?mypy=latest&python=3.10&gist=19147e0d445ef5a57cb6a3fecb346436&flags=show-error-codes

The reason being, the documentation states « Callback protocols and Callable types can be used interchangeably. » ; which I naively interpret as "P is a Callable" (for most intents and purposes) which should make this error message impossible.

To Reproduce

Check mypy-play link above, but given I don't know how long these last, see following example:

import typing


class P(typing.Protocol):
    __name__: str

    def __call__(self) -> None:
        return


def DEFAULT_P() -> None: ...


def f(o: P) -> None:
    o()
    o.__name__

f(DEFAULT_P)

Expected Behavior

No error, given P is a Callable?

Actual Behavior

An error that (IMHO) seems to go against what the documentation hints to. (I insist on that point because it could simply be that documentation needs a fix, not implementation)

main.py:19: error: Argument 1 to "f" has incompatible type "Callable[[], None]"; expected "P" [arg-type]

Your Environment

• Mypy version used: 0.931 & mypy-play
• Mypy command-line flags: --strict .
• Mypy configuration options from mypy.ini (and other config files): -
• Python version used: 3.9
• Operating system and version: Gentoo

[JelleZijlstra]

The error message is correct because Callable does not provide a __name__ attribute, and indeed it is possible to have Callables without a __name__.

But you are passing a function object, which does have a __name__. We should fix this issue by making the fallback type for functions better.

[pranavrajpal]

I think this is a duplicate of #10403.

[Cheaterman]

It totally is! My apologies... I found several similar mentions when Googling but missed #10403 . Thanks!