Kwargs after ParamSpec.args should be tolerated

Bug Report
I believe mypy's handling of ParamSpecs is slightly too restrictive. Currently, it validates that there are no args or kwargs after a ParamSpec.args argument other than **kwargs. I believe it's tolerable to have kwargs follow a ParamSpec.args

Related to #18278

To Reproduce

def f5(f: Callable[P, int], *args: P.args, extra_regular_arg: int, **kwargs: P.kwargs) -> int: ...  # E: Arguments not allowed after ParamSpec.args

def f6(f: Callable[P, int], *args: P.args, extra_kwarg: int = 123, **kwargs: P.kwargs) -> int: ...  # E: Arguments not allowed after ParamSpec.args

Expected Behavior
The first function above should continue to fail, while the second function should not throw an error

Thanks for the issue! However, the behavior you suggest is not permitted by the typing spec, which states:

Placing keyword-only parameters between the *args and **kwargs is forbidden.

Both extra_regular_arg in f5 and extra_kwarg in f6 are keyword-only parameters, so mypy is correct to reject them. The reason for this restriction explained in the Rejected Alternatives section of the original PEP: https://peps.python.org/pep-0612/#concatenating-keyword-parameters

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Kwargs after ParamSpec.args should be tolerated #19506

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Kwargs after ParamSpec.args should be tolerated #19506

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brianschubert commented on Jul 25, 2025

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