Bug?: Passing unpacked Dict fails unless all func args support all dict types?

[neiljp]

I have the following test-case inspired by real code similar to x and func.

from typing import Optional
x = dict(a=5, b=None)
y = dict(a=5, b=6)

def func(*, a: int, b: Optional[int]) -> None:
    print(a, b)
 def func2(*, a: Optional[int], b: Optional[int]) -> None:
    print(a, b)

func(**x)  # Only call to fail mypy; expect this to pass, or is extra annotation needed?
func(**y)
func2(**x)
func2(**y)

Output:

error: Argument 1 to "func" has incompatible type "**Dict[str, Optional[int]]"; expected "int"

Version 0.641, extensions 0.4.1. No explicit flags.

[ilevkivskyi]

Yes, you need to annotate this as a typed dict. By default mypy assumes all keys have the same types, like Dict[str, int].

But beware there is another issue #5198 that may give you false negatives. Anyway, this is essentially a duplicate of #5382, so closing.

[neiljp]

@ilevkivskyi Thanks for the pointer, using a TypedDict enables the code to pass mypy here.