Incorrect syntax error message for incorrect argument unpacking

[thatbirdguythatuknownot]

Bug report

Bug description:

I don't think SyntaxError: iterable argument unpacking follows keyword argument unpacking should be present in a case like this (minimal reproducible example):

>>> func(t, *:)
  File "<stdin>", line 1
    func(t, *:)
         ^
SyntaxError: iterable argument unpacking follows keyword argument unpacking

So it seems like if * is followed by code that triggers a generic SyntaxError: invalid syntax error, the former error triggers and overshadows the generic error. This has somewhat made checking the error in the expression following that * a bit harder.
I have another question. func(a=5, *b) is apparently allowed but from the error func(**{'a': 7}, *b) isn't? I don't know what the PEP is for this so I'll try to search it up later.

CPython versions tested on:

3.12

Operating systems tested on:

Windows

Linked PRs

• gh-110696: Fix incorrect syntax error message for incorrect argument unpacking #110706
• [3.12] gh-110696: Fix incorrect syntax error message for incorrect argument unpacking (GH-110706) #110765
• [3.11] gh-110696: Fix incorrect syntax error message for incorrect argument unpacking (GH-110706) #110766

[Eclips4]

cc @pablogsal

[thatbirdguythatuknownot]

As for my question, it seems that func(a=5, *b) shouldn't be valid? All the other alternative ways to write it are invalid syntax.

# not allowed
func(a=5, 1, 2)
func(**{'a': 5}, 1, 2)
func(**{'a': 5}, *(1, 2))
# allowed
func(a=7, *(1, 2))

I might have to follow this up with a different issue.

[pablogsal]

As for my question, it seems that func(a=5, *b) shouldn't be valid? All the other alternative ways to write it are invalid syntax.

It was valid before (3.9 and older) so we cannot just make invalid now for backwards compatibility reasons.