Type variable re-scoping doesn't work under certain circumstances with higher-order functions

[LeeeeT]

Prior to version 1.1.357 the following code was type checked as I expected.

from collections.abc import Callable


def d[T, R](c: Callable[[T], R]) -> Callable[[T], R]: ...


@d
def f[A, B](c: Callable[[list[A]], list[B]]) -> tuple[A, B]: ...


def id[T](value: T) -> T: ...


reveal_type(f(id))

The revealed type is tuple[A@f, A@f].

Starting with version 1.1.358, pyright is no longer able to determine the correct type of f(id), it is now tuple[Unknown, A@f]. I presume the regression was introduced by #7630 or #7634.

A few observations:

• If you remove the @d decorator, it stops working on 1.1.357 either, although it doesn't change the type of the f function itself.
• Wrapping A and B in list[] (or any other generic) in the f's signature prevents pyright from successfully re-scoping type variables; if you rewrite f as def f[A, B](c: Callable[[A], B]) -> tuple[A, B] it works.

I understand I'm in a gray area of the typing spec. Feel free to close this. 😔

[erictraut]

Closing this as "won't fix".