Support inferring a call to `dict(...)` in TypedDict context

[carljm]

Originally reported at https://www.reddit.com/r/Python/comments/1podix2/comment/nuhhob3/

from typing import TypedDict

class TD(TypedDict):
    x: int

t: TD = dict(x=1) # error: "Object of type `dict[str, int]` is not assignable to `TD`"

https://play.ty.dev/63687f42-6944-4a20-b04f-94a38b171e73

[Hugo-Polloli]

I'm going to try this over the weekend if that's ok :)

[mflova]

Despite the recommenation of not using mutable data structures as default input arguments, the following code snippet would not be working despite the fix. Is this expected?

def func(foo: TD = dict(x=1)) -> None:
    ...

(or even with the {"x": 1})