Alias that is generic over a ParamSpec is not hashable when using a list as parameters_expression

Bug report

Bug description:

This is slightly related to #124445, but a different issue, maybe it can be solved at the same time?

Consider the following code where [T] is a parameters_expression according to PEP 612. Similar to using Callable or using Generic[P] or Protocol[P] I would expect the following code to work and receive a hashable variable:

from typing import TypeVar
from collections.abc import Callable
type X[**P] = Callable[P, int]
T = TypeVar("T")
hash(X[[T]])
# ~~~~^^^^^^^^
# TypeError: unhashable type: 'list'

Cause:

The problem is that X[[T]].__args__ == ([T],) which cannot be hashed. I think the list should either be turned into a tuple. Either a nested one as its done for Generic and Protocol or joined like for Callable[P, str][[int]].__args__.

Discussion:

I've opened a parallel topic on discuss

CPython versions tested on:

3.13.0.rc2

Operating systems tested on:

Linux

EDIT: A thought, should this be changed for whole class in general?

Inizia con il riproduttore nell’issue e confronta il comportamento dell’alias ParamSpec con i casi Generic, Protocol e Callable citati. Leggi PEP 612, l’issue #124445 e la discussione collegata per stabilire se i parametri lista debbano diventare tuple annidate o essere uniti. Il lavoro è completato quando hash(X[[T]]) funziona senza una lista non hashable, preservando gli argomenti previsti.