Vararg decorator failed to deduce type

[eiva]

I need to create decorator with customization.
and found curious problem:

def log_call(**opt: Any) -> Callable[[Callable[[I], O]], Callable[[I], O]]:
    def decorator(f: Callable[[I], O]) -> Callable[[I], O]:
        def log_call_wrapper(*args: I, **kwargs:Any) -> O:
            return cast(Any, f)(*args, **kwargs)
        return log_call_wrapper
    return decorator

@log_call()
def test(a: int)->str:
   return str(a)

test(2)

Produce following error:

test.py:30: error: Argument 1 has incompatible type Callable[[int], str]; expected Callable[[None], None]
test.py:34: error: Argument 1 to "test" has incompatible type "int"; expected None

What is wrang (looks like mypy wrongly treat @dec() as @dec and infere function type as parameters...

This:

def log_call(f: Callable[[I], O]) -> Callable[[I], O]:
    def log_call_wrapper(*args: I, **kwargs:Any) -> O:
        return cast(Any, f)(*args, **kwargs)
    return log_call_wrapper

@log_call
def test(a: int)->str:
   return str(a)

test(2)

Works good and point me to mistake with argument type.

[gvanrossum]

This is a known problem, #1551 -- I'm closing this as a duplicate.