[1.11 Regression] partial plugin doesn't respect TypeVar bounds when deciding if something can be passed to partial

[AlexWaygood]

Bug Report

from typing import Callable, TypeVar
import functools

T = TypeVar("T", bound=Callable[[str, int], str])
S = TypeVar("S", bound=type[str])

def foo(f: T) -> T:
    g = functools.partial(f, "foo")  # error: "T" not callable  [misc]
    return f

def bar(f: S) -> S:
    g = functools.partial(f, "foo")  # error: "S" not callable  [misc]
    return f

https://mypy-play.net/?mypy=master&python=3.12&gist=93876fe629e5320a88349da7a9f65188

Mypy should understand both T and S to be callable due to the fact that the TypeVars have Callable and type as their respective upper bounds. We're hitting this in our attempt to upgrade mypy to 1.11.1 for Argument Clinic over at CPython in python/cpython#122550.

Cc. @hauntsaninja

Your Environment

• Mypy version used: 1.12.0+dev.9d56820a63d5b47b53ff0ab6e96ce0951c774ae5 (compiled: no)

[AlexWaygood]

#17659 notes that this also causes issues for Self (which is internally just a special kind of TypeVar)

[hauntsaninja]

I'm going to very disappointingly fix this in #17660

• This will fix your first example.
• It would also fix the type[str] example, except it doesn't yet because str has overloaded constructor and overloads don't really work (mostly due to preexisting missing logic), see partial plugin does not handle overloads #17585
• It will also not fix 1.11 Regression: Self in classmethod causes "type[Self] not callable" error #17659 so I've reopened that. If I make mypy eagerly resolve the Self to its upper bound there, then it would introduce a complaint on the next line. So something cleverer needs to happen.

[AlexWaygood]

That all makes sense; thanks for the explanation!