Proposed resolution:

This wording is relative to N4659.

1. Change [deque.modifiers] as indicated:

   iterator erase(const_iterator position);
   iterator erase(const_iterator first, const_iterator last);
   void pop_front();
   void pop_back();
   

   -4- Effects: […]

   -5- Complexity: The number of calls to the destructor of T is the same as the number of elements erased, but the number of calls to the assignment operator of T is no more than the lesser of the number of elements before the erased elements and the number of elements after the erased elements.

   -6- Throws: Nothing unless an exception is thrown by the copy constructor, move constructor, assignment operator, or move assignment operator of T.