Possible regression in mypy 0.981: Generics don't work when TypeVar are previously used in a TypedDict

[jzazo]

Bug Report

When pulling the example of Generics from the documentation and specifying a generic TypedDict following the blog post, I get an error on simple Generic example.

To Reproduce

from typing import Generic, TypeVar
from typing_extensions import TypedDict  # I am using python 3.10.4

T = TypeVar("T")
MyDict = TypedDict("MyDict", {"foo": T})

class Stack(Generic[T]):  # mypy error: Free type variable expected in Generic[...]  [misc]
    def __init__(self) -> None:
        pass

Commenting line 5 removes the error. Moving line 5 after the declaration of Stack also works.

Expected Behavior
That class Stack is a correct Generic and mypy should not error.

Your Environment

• Mypy version used: 0.981
• Python version used: 3.10.4

[AlexWaygood]

Reproduced: https://mypy-play.net/?mypy=latest&python=3.10&gist=f60adc581fff2b54cb71c860ada20577

@ilevkivskyi, one for you? :)

[jzazo]

Another example that may originate from the same issue. Commenting MyDict1 declaration removes the error.

from typing import Sequence, TypeVar
from typing_extensions import TypedDict

T = TypeVar("T")

MyDict1 = TypedDict("MyDict1", {"foo": Sequence[T]})
MyDict2 = TypedDict("MyDict2", {"foo": Sequence[T]})

MyDict1[int]  # ok
MyDict2[int]  # mypy(error): The type "Type[MyDict2]" is not generic and not indexable  [misc]

[ilevkivskyi]

This is not really a regression, as previously you would still get an error (in a different place). It is however indeed a bug, you should be able to reuse the type variable. Unless I am missing something, should be a simple fix.

[ilevkivskyi]

Oh, actually both examples work correctly on master. It looks like @Michael0x2a already added the missing TypeVar scope frame in #13678 (and also fixed a docstring for me, thank you!)

[ilevkivskyi]

(btw it was one of rare cases where git blame was used as git gratitude)