https://gcc.gnu.org/bugzilla/show_bug.cgi?id=46589
--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> --- This code was made ill-formed by https://wg21.link/p1766r1 (new in C++20 but a DR against previous standards). So GCC should just reject it (maybe with a switch to allow the old behaviour). See PR 97475.
