Support PEP 612: Parameter Specification Variables

[rchen152]

PEP: https://www.python.org/dev/peps/pep-0612/

As a simple first step, we should add ParamSpec and Concatenate to the typing stub so typeshed can start using them (python/typeshed#4827).

[rchen152]

Assigning to myself to implement the "first step" described above, to unblock typeshed.

[rchen152]

It's now possible to use a ParamSpec or Concatenate as the first argument to a Callable in type stubs.

[cebtenzzre]

If the test_paramspec_args testcase is expanded slightly to actually use the arguments, pytype-single prints ERROR:pytype.matcher Invalid type: <class 'pytype.abstract.function.ParamSpecMatch'> and then raises NotImplementedError: ParamSpecArgs. This is with pytype 2024.10.11. Is this the expected behavior?

from typing import Callable, ParamSpec, TypeVar
P = ParamSpec("P")
T = TypeVar("T")

def f(x: Callable[P, T], /, *args: P.args, **kwargs: P.kwargs) -> T:
    return x(*args, **kwargs)

def foo():
    pass

f(foo)

[h-joo]

Hi, thank you for your report. Google is shifting its effort to a different approach for type checking apart from pytype, and we're not planning to put in any effort in the near future in pytype, so we'll close this issue. Please see the announcement here.