[Bug libstdc++/59712] unordered_map : clang fails with "member access into incomplete type"

["oparcollet.triqs at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59712

--- Comment #2 from Olivier Parcollet <oparcollet.triqs at gmail dot com> ---
I am not sure.

If I understood correctly, clang is stricter on this sort of issue than gcc,
but I do not know what the standard says.

A minimal version of such code is (from hashtable.h) : 

#include <utility>

template<typename T> class A {
 int f(int i) const noexcept { return i + 1; }
 static_assert(noexcept(std::declval<const A&>().f(0)),"bla bla");
};

int main() {
 A<int> a;
}

again gcc compiles it, not clang (same error as before).

Which one is right ?
(even though I don't really see the point of this static_assert in the first
place...).