3284 struct nullopt_t {  struct
3285   constexpr explicit nullopt_t(int) {}  in nullopt_t()  argument
3681   constexpr Optional(nullopt_t) {}  // NOLINT(runtime/explicit)  in Optional()  argument
3770   Optional& operator=(nullopt_t) {  in operator =()  argument
3991 constexpr bool operator==(const Optional<T>& opt, nullopt_t) {  in operator ==()  argument
3996 constexpr bool operator==(nullopt_t, const Optional<T>& opt) {  in operator ==()  argument
4001 constexpr bool operator!=(const Optional<T>& opt, nullopt_t) {  in operator !=()  argument
4006 constexpr bool operator!=(nullopt_t, const Optional<T>& opt) {  in operator !=()  argument
4011 constexpr bool operator<(const Optional<T>&, nullopt_t) {  in operator <()  argument
4016 constexpr bool operator<(nullopt_t, const Optional<T>& opt) {  in operator <()  argument
4021 constexpr bool operator<=(const Optional<T>& opt, nullopt_t) {  in operator <=()  argument
4026 constexpr bool operator<=(nullopt_t, const Optional<T>&) {  in operator <=()  argument
4031 constexpr bool operator>(const Optional<T>& opt, nullopt_t) {  in operator >()  argument
4036 constexpr bool operator>(nullopt_t, const Optional<T>&) {  in operator >()  argument
4041 constexpr bool operator>=(const Optional<T>&, nullopt_t) {  in operator >=()  argument
4046 constexpr bool operator>=(nullopt_t, const Optional<T>& opt) {  in operator >=()  argument