[Bug c++/70528] [5/6 Regression] bogus error: constructor required before non-static data member

[ville.voutilainen at gmail dot com]

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;
};