template <class T, class D> struct hash<unique_ptr<T, D>>;
Letting UP be unique_ptr<T,D>, the specialization hash<UP> is enabled ([unord.hash]) if and only if hash<typename UP::pointer> is enabled. When enabled, for an object p of type UP, hash<UP>()(p) shall evaluate to the same value as hash<typename UP::pointer>()(p.get()). The member functions are not guaranteed to be noexcept.
template <class T> struct hash<shared_ptr<T>>;