The result of `get_origin()` on a `GenericAlias` variable "is not indexable"

[mgorny]

Bug Report

Consider the following minimal snippet:

from types import GenericAlias
from typing import get_origin


def test(expected_type: GenericAlias) -> None:
    list_type = get_origin(expected_type)
    list_type[int]

mypy seems to consider list_type[int] invalid here:

$ mypy foo.py 
foo.py:7: error: Value of type "type" is not indexable  [index]
Found 1 error in 1 file (checked 1 source file)

To Reproduce

https://mypy-play.net/?mypy=latest&python=3.12&gist=d8185597c8fe9a327a276508cc1fa4d3

Actual Behavior

$ mypy foo.py 
foo.py:7: error: Value of type "type" is not indexable  [index]
Found 1 error in 1 file (checked 1 source file)

Your Environment

• Mypy version used: 1.15.0
• Mypy command-line flags: (none)
• Mypy configuration options from mypy.ini (and other config files): (none)
• Python version used: 3.13.2

[A5rocks]

I think this is moreso a typeshed thing. Probably they just need to add an overload or two?

[hauntsaninja]

Yeah, if there is a bug here, it should be handled in typeshed. In general, static type checking of runtime typing is kind of hard to do in Python