Proposed resolution:

This wording is relative to N4659.

1. Change [memory.syn], header <memory> synopsis, as indicated:

   namespace std {
     […]
     
     // [unique.ptr], class template unique_ptr
     […]
     template <class T, class D>
     bool operator>=(nullptr_t, const unique_ptr<T, D>& y);
     
     template<class E, class T, class Y, class D>
     basic_ostream<E, T>& operator<< (basic_ostream<E, T>& os, const unique_ptr<Y, D>& p);
     […]
   }
   

2. Change [unique.ptr], class template unique_ptr synopsis, as indicated:

   namespace std {
     […]
     template <class T, class D>
     bool operator>=(nullptr_t, const unique_ptr<T, D>& y);
     
     template<class E, class T, class Y, class D>
     basic_ostream<E, T>& operator<< (basic_ostream<E, T>& os, const unique_ptr<Y, D>& p);
   }
   

3. Add a new subclause following subclause [unique.ptr.special] as indicated:

   23.11.1.?? unique_ptr I/O [unique.ptr.io]

   template<class E, class T, class Y, class D>
     basic_ostream<E, T>& operator<< (basic_ostream<E, T>& os, const unique_ptr<Y, D>& p);
   

   -?- Effects: Equivalent to os << p.get();

   -?- Returns: os.

   -?- Remarks: This function shall not participate in overload resolution unless os << p.get() is a valid expression.

[ 2017-07 Toronto Wed Issue Prioritization ]

Priority 0; move to Ready

shared_ptr does define operator<<, and unique_ptr should too, for consistency and usability reasons.