Special-case .pop() on TypedDict

[Lancetnik]

Mypy doesn't respect TypedDict object changes. As an example, the following snippet

from typing import TypedDict

class A(TypedDict, total=False):
    a: str

def func(a: str) -> None:
    pass

data: A = {"a": "a"}
a = data.pop("a", "")
func(a, **data)

Raises the error:

error: "func" gets multiple values for keyword argument "a" [misc]

Formally, it is correctly, but it will be nice if mypy respects object keys changes. Especially in Unpack case:

from typing import Unpack, TypedDict

class A(TypedDict, total=False):
    a: str
    
def func(a: str) -> None:
    pass
    
def func2(**data: Unpack[A]) -> None:
    a = data.pop("a", "")
    func(a, **data) 

[JelleZijlstra]

This would require special-casing .pop() to change the type of the TypedDict to some custom type. Not impossible to do, but it would require significant complexity so it's unlikely we'll add this.

[Lancetnik]

I expected, but had to try 😄