`filter` does not narrow `TypeVar` used in `TypeGuard` signature

Bug Report

Using filter with a TypeGuard, the TypeVar used in the TypeGuard signature is not properly narrowed.

To Reproduce

# tmp.py
from typing import Iterator, Optional, TypeVar

from typing_extensions import TypeGuard

T = TypeVar("T")


def is_not_none(x: Optional[T]) -> TypeGuard[T]:
    return x is not None


maybe_ints: list[Optional[int]] = [1, None, 2]
ints: Iterator[int] = filter(is_not_none, maybe_ints)

$ mypy tmp.py
tmp.py:14: error: Argument 1 to "filter" has incompatible type "Callable[[Optional[T]], TypeGuard[T]]"; expected "Callable[[Optional[int]], TypeGuard[int]]"
Found 1 error in 1 file (checked 1 source file)

Expected Behavior

I wouldn't expect any error. Since the second argument to filter is typed as list[Optional[int]], mypy should narrow the TypeVar T appropriately.

Your Environment

• Mypy version used: mypy 0.950
• Mypy command-line flags: none
• Mypy configuration options from mypy.ini (and other config files): none
• Python version used: 3.10

This may be related to https://github.com/python/mypy/issues/12682. I decided to open a new ticket instead of commenting on that issue because the repro above feels different from the one reported on that issue.

Start by reproducing the report with tmp.py and mypy 0.950 or the current version, focusing on filter with is_not_none and the TypeGuard TypeVar. Trace the type-checking path for filter callback inference and TypeGuard narrowing; done means the example type-checks and ints is accepted as Iterator[int].