1  template<typename T>
       2  struct make_signed 
       3  {
       4    using type = int;
       5  };
       6  
       7  template<typename S>
       8  using make_signed_t = typename make_signed<S>::type;
       9  
      10  template<typename U>
      11  auto ssize (U &parm) -> make_signed_t<decltype(parm.call())>;