Issue found while trying to write tests for  https://bugs.python.org/issue30592 .

Issue related to http://bugs.python.org/issue30534 .

The following code:

    [].index(x=2)

should raise the following error:

    TypeError: index() takes no keyword arguments

but currently raises:

    TypeError: index() takes at least 1 argument (0 given)


This is easily reproduced with the following unit test:

    # AssertionError: "^index\(\) takes no keyword arguments$" does not match "index() takes at least 1 argument (0 given)"
    def test_varargs4_kw(self):
        msg = r"^index\(\) takes no keyword arguments$"
        self.assertRaisesRegex(TypeError, msg, [].index, x=2)

Good catch! This issue is similar to issue30534, but caused by generated code.

The solution is easy: make Argument Clinic (Tools/clinic/clinic.py) generating _PyArg_NoStackKeywords() before _PyArg_ParseStack() and regenerate all generated by Argument Clinic code (make clinic).

Can I give this a try or is anyone working on this already ?

Yes, pleas do this.

Thanks Serhiy Storchaka for the tip! I am currently investigating how the argument clinic works. I have used git bisect to find when the issue got introduced.

commit fdd42c481edba4261f861fc1dfe24bbd79b5a17a
bpo-20185: Convert list object implementation to Argument Clinic. (#542)

This commit only exposed existing bug in Argument Clinic. The same bug should be exposed for other methods that takes no keyword arguments converted to Argument Clinic.

New changeset 7445381c606faf20e253da42656db478a4349f8e by Serhiy Storchaka (Sylvain) in branch 'master':
bpo-30600: Fix error messages (condition order in Argument Clinic) (#2051)
https://github.com/python/cpython/commit/7445381c606faf20e253da42656db478a4349f8e

The PR LGTM. Thank you for your contribution SylvainDe!