resetter.h

#include <utility>

template <typename T, typename U = T>
class ScopedRestore {
 public:
    explicit ScopedRestore(T* it):
        ref_(*it), old_val_(*it) {}
    ~ScopedRestore() noexcept(noexcept(this->ref_ = std::move(this->old_val_))) {
        using std::move;
        ref_ = move(old_val_);
    }

 private:
    T& ref_;
    U old_val_;
};