cannot inherit from a parameters

[samsja]

Bug Report

It seems that mypy does not allow to inherit from a parameter when creating a function on the fly.

To Reproduce

from typing import Type


def f(cls: Type) -> Type:


    class A(cls):
        ...
    
    return A

>>>file.py:6: error: Variable "cls" is not valid as a type  [valid-type]
>>>file.py:6: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#variables-vs-type-aliases
>>>file.py:6: error: Invalid base class "cls"  [misc]

Expected Behavior

Mypy should not complain

Actual Behavior

Mypy complain and say

>>>file.py:6: error: Variable "cls" is not valid as a type  [valid-type]
>>>file.py:6: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#variables-vs-type-aliases
>>>file.py:6: error: Invalid base class "cls"  [misc]

Your Environment

• Mypy version used:`0.990
• Python version used: 3.9.10

[tmke8]

I believe that's fixed by #14135 which has been merged to master but hasn't been released yet.

(I haven't tried it out though.)

[AlexWaygood]

I believe that's fixed by #14135 which has been merged to master but hasn't been released yet.

(I haven't tried it out though.)

Correct, this is already fixed on master. I can reproduce with c660354, but not with 3c5f368. The fix will be released as part of mypy 1.0, coming soon!

[samsja]

Just tried with this version it work indeed. Thanks for the amazing work !

[AlexWaygood]

Just tried with this version it work indeed. Thanks for the amazing work !

You have @ilevkivskyi to thank :)