Type inference problem with generic function with type variable type as return type

[JukkaL]

Consider this code:

from typing import typevar, List
T = typevar('T')
def f(x: List[T]) -> T: return x[0]
def g(y: object) -> None: pass
a = [1]
g(f(a))  # Argument 1 to "f" has incompatible type List[int]; expected List[object]

The code should not be rejected. We should not infer T from the context of the f invocation.

This is a generalization of #360.