https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102007
--- Comment #1 from 康桓瑋 <hewillk at gmail dot com> --- Please note that this bug comes from the following ill-formed code that GCC accepts. template<class> concept A = true; template<class T = A> concept B = true; static_assert(B<>); https://godbolt.org/z/7d54sYhv3
