Add type overload with filter(None, iter)

[dishang-le]

The built-in sync filter has a overload type hint to infer that the return type of filter(None, iter) is not None, can you add similar type overload?

e.g.

maybe_none: Iterable[int | None] = [1, 2, None]
not_none: Iterable[int] = filter(None, maybe_none) # it knows not_none is type Iterable[int] without cast

[maxfischer2781]

Indeed the typeshed annotations for filter handle more cases. Good catch, thanks for the report.

class filter(Iterator[_T]):
    @overload
    def __new__(cls, __function: None, __iterable: Iterable[_T | None]) -> Self: ...
    @overload
    def __new__(cls, __function: Callable[[_S], TypeGuard[_T]], __iterable: Iterable[_S]) -> Self: ...
    @overload
    def __new__(cls, __function: Callable[[_T], Any], __iterable: Iterable[_T]) -> Self: ...
    def __iter__(self) -> Self: ...
    def __next__(self) -> _T: ...