[Bug c++/110349] [C++26] P2169R4 - Placeholder variables with no name

["jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110349

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |jakub at gcc dot gnu.org

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 55725
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55725&action=edit
gcc14-pr110349-wip.patch

I've played with this a little bit so far, but am a little bit stuck.
When lookup_name reports error on ambiguous _ because 2+ declarations with the
_ name are in the same scope (counting function overloads as one obviously),
the error is reported too many times, even from tentative parsing.
And also unsure if it should return error_mark_node in that case or not, if I
return error_mark_node I get some extra error recovery errors as well (though
if the error is avoided during tentative parsing, I guess we have to return
error_mark_node in that case.