[Bug libstdc++/51365] cannot use final empty class in std::tuple

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51365

--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-12-01 
01:07:27 UTC ---
Here's another testcase:

#include <future>
#include <memory>

template<typename T>
struct final_allocator final : std::allocator<T>
{
  final_allocator() = default;

  template<typename U>
    final_allocator(const final_allocator<U>&) { }

  template<typename U>
    struct rebind { typedef final_allocator<U> other; };
};

final_allocator<int> a;

std::promise<int> p(std::allocator_arg, a);