Add broken Callable check

[cdce8p]

Type of Changes

	Type
✓	✨ New feature

Description

Similar to the broken NoReturn check - #5304, however this time for Callable.
Using collections.abc.Callable inside Optional and Union is broken in Python 3.9.0 and 3.9.1.

This one is a bit more difficult as we currently currently suggest replacing the deprecated typing.Callable with collections.abc.Callable. Doing that can result in unexpected errors. The PR will change that behavior and not emit deprecated-typing-alias for typing.Callable if py-version < (3, 9, 2). In addition it adds a new check to warn about potential errors.

Example broken code

from collections.abc import Callable
from typing import Optional, Union

Alias1 = Optional[Callable[[int], None]
Alias2 = Union[Callable[[int], None], None]

When exactly is it broken?

• Python 3.9.0 or 3.9.1
• And collections.abc.Callable as part of Optional or Union
• And argument list for Callable, e.g. [int].

https://bugs.python.org/issue42965

[coveralls]

Pull Request Test Coverage Report for Build 1965675033

• 39 of 39 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.01%) to 94.019%

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Totals
Change from base Build 1964199132:	0.01%
Covered Lines:	14996
Relevant Lines:	15950

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💛 - Coveralls

[Pierre-Sassoulas]

Looks good already!

[Pierre-Sassoulas]

This line is not covered by the tests.

[cdce8p]

Saw that too. Seems like my previous filter steps are quite good already. Took me a moment to find something that would run this line.

[Pierre-Sassoulas]

Suggested change

	args=(msg.qname, msg.alias),
	args=(msg.qname, msg.alias),
	confidence=interfaces.INFERENCE,

AFAIK because of inferred.qname() line 275 / 282 ?

[cdce8p]

Let's do that separately. It would change existing tests.

[Pierre-Sassoulas]

👌