Type inference in high level function

For fully valid code got:
error: Argument 1 to "map" has incompatible type overloaded function; expected "Callable[[Iterator[_T], int, None], Iterator[_T]].

In foo.py:

from typing import Generic, Iterable, Iterator, Sequence, TypeVar
_T = TypeVar('_T')

class Windowed(Generic[_T]):
    def __init__(self, it: Iterable[_T], size: int) -> None:
        self.it = it
        self.size = size

    def __iter__(self) -> Iterator[Sequence[_T]]:
        iters = tee(self.it, self.size)
        slices = map(islice, iters, count(0), repeat(None))
        return zip(*slices)

However islice has overload:

def islice(iterable: Iterable[_T], start: Optional[int], stop: Optional[int],
           step: Optional[int] = ...) -> Iterator[_T]: ...

Using mypy 0.750 from PyPI, on python 3.7.5. Running it via mypy foo.py

Reproduce el diagnóstico de foo.py con mypy 0.750 en Python 3.7.5, centrándote en la llamada map(islice, iters, count(0), repeat(None)) y en la sobrecarga de islice mostrada en el issue. Rastrea la inferencia de tipos de la función sobrecargada y verifica que el ejemplo válido ya no informe de un error de argumento incompatible.