Subclassing generic class using `ParamSpec` fails depending on how base class is referenced

[keosak]

Bug Report
Mypy reports an issue with subclassing generic class using ParamSpec, but only when the base class is referenced via module attribute access.

To Reproduce

File test1.py

from typing import Generic, ParamSpec

P = ParamSpec("P")

class Base(Generic[P]):
    def test(self, *args: P.args, **kwargs: P.kwargs):
        raise NotImplementedError

File test2_good.py

from test1 import Base

class Derived(Base[[int]]):
    def test(self, x: int):
        print(x)

File test2_bad.py

import test1

class Derived(test1.Base[[int]]):
    def test(self, x: int):
        print(x)

Expected Behavior
When running Mypy against the test2_good.py file, no issues are reported. This is what I expect.

(venv) debian@25081d5e7e53:/workspace$ mypy test2_good.py 
Success: no issues found in 1 source file

Actual Behavior
When running Mypy against the test2_bad.py file, an issue is reported. The only difference is how the base class is specified.

(venv) debian@25081d5e7e53:/workspace$ mypy test2_bad.py 
test2_bad.py:4: error: Bracketed expression "[...]" is not valid as a type  [valid-type]
test2_bad.py:4: note: Did you mean "List[...]"?
Found 1 error in 1 file (checked 1 source file)

Your Environment

• Mypy version used: 1.0.1 (compiled: yes)
• Mypy command-line flags: None
• Mypy configuration options from mypy.ini (and other config files): None
• Python version used: 3.10.8 from the official Docker image

[keosak]

Still there as of Mypy 1.1.1.

[keosak]

Still there as of Mypy 1.2.0.

[keosak]

This is still happening in version 1.4.1. No reaction from anyone?

[hauntsaninja]

@keosak is the project you were running into this on open source?

[keosak]

Glad to see this fixed. I will test it with our code when the next version of Mypy is released.

@hauntsaninja No, it's not open source.