How can the stub for functools.partial be made to work?

[gvanrossum]

The 2.7 stub for functools contains this elaborate definition for functools.partial:

class partial(Generic[_T]):
    func = ...  # Callable[..., _T]
    args = ...  # type: Tuple[Any, ...]
    keywords = ...  # type: Dict[str, Any]
    def __init__(self, func: Callable[..., _T], *args: Any, **kwargs: Any) -> None: ...
    def __call__(self, *args: Any, **kwargs: Any) -> _T: ...

However, despite the presence of a __call__ method, this isn't compatible with Callable -- e.g. this gives an error:

from typing import *
from functools import partial
def foo(a: int) -> int:
    return a
bar = partial(foo, 42)  # type: Callable[[], int]

The error is on the last line:

t.py:5: error: Incompatible types in assignment (expression has type partial[int], variable has type Callable[[], int])

I can shut it up with a cast but that's ugly. I'd like the checker to at least understand that class partial as given is callable.

[JukkaL]

The reason for this is that mypy doesn't consider partial to be a subtype of Callable, even though it obviously should be. This is a bug in mypy, and there already is an open issue for this: #797

[gvanrossum]

Duplicate of #797.