Argument Clinic crashes with ValueError for an optional group before a var-positional parameter

[serhiy-storchaka]

/*[clinic input]
module foo
foo.bar
    [
    a: int
    ]
    *args: tuple
[clinic start generated code]*/

fails with ValueError: required is empty but left is not, raised by permute_optional_groups(), instead of a ClinicError pointing at the offending line.

The opposite order, *args: tuple / [a: int], reports You cannot use optional groups ('[' and ']') unless all parameters are positional-only ('/'), but this is confusing because *args also only accepts positional arguments.

Linked PRs

• gh-158320: Reject optional groups with a var-positional parameter in Argument Clinic #158323
• gh-158320: Remove a file added by mistake #158347