support auto ParamSpec

[asukaminato0721]

Describe the Bug

For decorator, maybe add option for auto infer [**P] P.args P.kwargs if possible.

Sandbox Link

No response

(Only applicable for extension issues) IDE Information

No response

[yangdanny97]

I remember trying to do auto-generic and infer the first argument as T, but I don't think it had good results. This could be something interesting to try, but we'd need to figure out whether the un-annotated decorator intends to accept a callable or not

[asukaminato0721]

how about if find @functools.wraps(func) then assume this is a decorator.

[OutSquareCapital]

Is this why pyrefly currently can't make this work?

from collections.abc import Callable, Iterable, Iterator
from typing import Any, Concatenate, override


class MyIterator[T](Iterator[T]):
    def __init__(self, iterable: Iterable[T]) -> None:
        self._iterable: Iterable[T] = iterable

    @override
    def __iter__(self) -> Iterator[T]:
        return iter(self._iterable)

    @override
    def __next__(self) -> T:
        return next(iter(self._iterable))

    def for_each[**P](
        self,
        func: Callable[Concatenate[T, P], Any],
        *args: P.args,
        **kwargs: P.kwargs,
    ) -> None:
        for item in self:
            _ = func(item, *args, **kwargs)


def foo(*args: int) -> None:
    print(args)


MyIterator([1]).for_each(foo, 2, 3)

output:

(1, 2, 3)

pyrefly check, latest version:

ERROR Expected 1 positional argument, got 3 in function `MyIterator.for_each` [bad-argument-count]
  --> t.py:34:31
   |
34 | MyIterator([1]).for_each(foo, 2, 3)

Basedpyright has not issues here, nor ty.