Untyped decorator causes "signature incompatible with supertype"

[ddfisher]

Here's a minimal repro:

from typing import *

# untyped decorator
def deco(f): pass

class A:
    @deco
    def f(self) -> Any:
        pass

class B(A):
    @deco
    def f(self) -> Any:  # E:  Signature of "f" incompatible with supertype "A"
        pass

[ddfisher]

@sixolet I think this may be related to your recent Callable improvements?