[Bug c++/71794] Std::array as an incomplete type in nested name specifier.

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71794

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
VC++ accepts it too, so it's two for and two against.

Reduced:

template<unsigned N> struct X { };

template<typename T> struct Y;

template<int N> struct Y<X<N>> { };

template<typename T> Y<T> f() { return {}; }

auto x = f< X<1> >();