        self_t& ssl(T&&)
        {
            // We can't call .ssl() member function unless CROW_ENABLE_SSL is defined.
            static_assert(
              // make static_assert dependent to T; always false
              std::is_base_of<T, void>::value,
              "Define CROW_ENABLE_SSL to enable ssl support.");
            return *this;
        }
        self_t& ssl(T&&)
        {
             
            static_assert(
               
              std::is_base_of<T, void>::value,
              "Define CROW_ENABLE_SSL to enable ssl support.");
            return *this;
        }