https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56389
--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> --- (In reply to Andrew Pinski from comment #4) > Fixed for GCC 11. I cannot figure out which patch fixed it though. > There has been a bunch of fixes dealing with return types dealing with C++20 > concepts. For an example PR 96443.