https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70528
--- Comment #1 from Ville Voutilainen <ville.voutilainen at gmail dot com> --- A shorter reproducer for the funny part where the error arises: template <class T, class U = decltype(T())> struct I { }; struct J { struct K { int First = 0; }; I<K> FunctionMDInfo; };