- std::pair<iterator, bool> insert(const key_type &data) {
- auto ret = sl_->addOrGetData(data);
+ template<typename U,
+ typename=typename std::enable_if<std::is_convertible<U, T>::value>::type>
+ std::pair<iterator, bool> insert(U&& data) {
+ auto ret = sl_->addOrGetData(std::forward<U>(data));