Bug: `TypeVar` `default` don't work in runtime

[IvanKirpichnikov]

MRE:

from typing import Generic

from typing_extensions import TypeVar

G = TypeVar("G")
T = TypeVar("T", default=int)

class MRE(Generic[G, T]): ...

MRE[int]

Error:

TypeError: Too few arguments for <class '__main__.MRE'>; actual 1, expected 2

Expected behavior:

Working code is as of 3.13.

Note.

When using typing_extensions, the same error occurs.

Intended solution

Implement your own Generic class, which will be used until version 3.13.

---

With your permission, I would like to provide a Pull Request to fix this bug.

[JelleZijlstra]

This works for me if you do from typing_extensions import Generic.

If there is something we can do in typing_extensions to make this work with from typing import Generic too, I'd consider it. I hope the approach doesn't involve monkeypatching typing.Generic though.

[IvanKirpichnikov]

Это работает для меня, если вы это сделаете from typing_extensions import Generic.

What is your python and typing_extensions version?
i have versions 3.11 and typing-extensions==4.14.1 and it doesn't work for me with from typing_extensions import Generic

[IvanKirpichnikov]

Ah, my mistake. The package has not been updated to the latest version.

Everything is working now

[IvanKirpichnikov]

thank you for your help