message: Fixes mpl.h compilation error in Clang raised by -Wreturn-std-move
diff: @@ -114,7 +114,7 @@ inline auto try_apply(F&& f, const list<T, U, R...>&)
  {
  if (auto&& result = f(identity<T>{}))
  {
  - return result;
  + return std::move(result);
  }
  return try_apply(std::forward<F>(f), list<U, R...>{});
  