template<class T, class D> void swap(unique_ptr<T, D>& x, unique_ptr<T, D>& y) noexcept;
template<class T1, class D1, class T2, class D2>
bool operator==(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);
template<class T1, class D1, class T2, class D2>
bool operator<(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);
template<class T1, class D1, class T2, class D2>
bool operator>(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);
template<class T1, class D1, class T2, class D2>
bool operator<=(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);
template<class T1, class D1, class T2, class D2>
bool operator>=(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);
template<class T1, class D1, class T2, class D2>
requires three_way_comparable_with<typename unique_ptr<T1, D1>::pointer,
typename unique_ptr<T2, D2>::pointer>
compare_three_way_result_t<typename unique_ptr<T1, D1>::pointer,
typename unique_ptr<T2, D2>::pointer>
operator<=>(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);
template<class T, class D>
bool operator==(const unique_ptr<T, D>& x, nullptr_t) noexcept;
template<class T, class D>
bool operator<(const unique_ptr<T, D>& x, nullptr_t);
template<class T, class D>
bool operator<(nullptr_t, const unique_ptr<T, D>& x);
template<class T, class D>
bool operator>(const unique_ptr<T, D>& x, nullptr_t);
template<class T, class D>
bool operator>(nullptr_t, const unique_ptr<T, D>& x);
template<class T, class D>
bool operator<=(const unique_ptr<T, D>& x, nullptr_t);
template<class T, class D>
bool operator<=(nullptr_t, const unique_ptr<T, D>& x);
template<class T, class D>
bool operator>=(const unique_ptr<T, D>& x, nullptr_t);
template<class T, class D>
bool operator>=(nullptr_t, const unique_ptr<T, D>& x);
template<class T, class D>
requires three_way_comparable_with<typename unique_ptr<T, D>::pointer, nullptr_t>
compare_three_way_result_t<typename unique_ptr<T, D>::pointer, nullptr_t>
operator<=>(const unique_ptr<T, D>& x, nullptr_t);