[Bug c++/110608] New: error on evaluation of concept three_way_comparable on recursive variant

[Bug c++/110608] New: error on evaluation of concept three_way_comparable on recursive variant

[walim at gmx dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110608

            Bug ID: 110608
           Summary: error on evaluation of concept three_way_comparable on
                    recursive variant
           Product: gcc
           Version: 13.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: walim at gmx dot net
  Target Milestone: ---

Created attachment 55508
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55508&action=edit
reduced demo of the error situation (-std=c++20 or higher must be active to
reproduce the error)

A recursiv variant type with its data type as base will not compile in g++ with
-std=c++20 or higher, because of problems evaluating the concept
three_way_comparable

Found on g++ 13.2 on some linux installations and reproduced in compiler
explorer.
(No such error in clang++ and vc)

[Bug c++/110608] error on evaluation of concept three_way_comparable on recursive variant

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110608

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I think GCC is correct here ...

GCC is the only compiler which implements the `satisfaction of atomic
constraint not depending on itself` part of the C++ standard (there are a few
open bugs dealing with that but just left open because maybe the C++ standard
will change).