[Bug c++/67762] [C++1z] 'not a constant expression" errors only with -fsanitize=undefined

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67762

--- Comment #4 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
(In reply to Marek Polacek from comment #3)
> Not reducing anymore; creduce dies for me :(.

Yes, I was unsuccessful in reducing it with creduce, too.
(Well, clang doesn't support C++ concepts yet, so perhaps it is not
too surprising.)