ParamSpec seems to get lost with partial()

[Dreamsorcerer]

Bug Report

Trying to get ParamSpec working for async-lru, and currently testing out the new partial() support added last year, but it doesn't seem to work with our wrapper class.

To Reproduce

from typing import Any, Callable, Coroutine, Generic, ParamSpec, TypeVar

_R = TypeVar("_R")
_P = ParamSpec("_P")

class Wrapper(Generic[_P, _R]):
    def __init__(self, fn: Callable[_P, Coroutine[Any, Any, _R]]) -> None:
        self.fn = fn

    async def __call__(self, *args: _P.args, **kwargs: _P.kwargs) -> _R:
        return await self.fn(*args, **kwargs)

async def coro(val: int) -> int:
    return val

async def test() -> None:
    coro_wrapped = Wrapper(coro)
    reveal_type(coro_wrapped)  # Revealed type is "Wrapper[[val: builtins.int], builtins.int]"
    await coro_wrapped(3, 2)  # error: Too many arguments for "__call__" of "Wrapper"  [call-arg]

    partial_wrapped = Wrapper(partial(coro, 2))
    reveal_type(partial_wrapped)  # Revealed type is "Wrapper[[*args: Any, **kwargs: Any], builtins.int]"
    await partial_wrapped(4)  # XXX: Should be an error here.

Your Environment

• Mypy version used: 1.14.1
• Python version used: 3.9

[A5rocks]

For the record, this is a manifestation of #3832 because inferring signatures does not call the functools plugin for the functools.partial.__call__ signature.