Proposed resolution:

This wording is relative to n4944.

1. Modify [range.enumerate.iterator] as indicated:

   
   namespace std::ranges {
     template<view V>
       requires range-with-movable-references<V>
     template<bool Const>
     class enumerate_view<V>::iterator {
       […]
       public:
       […]
       friend constexpr difference_type operator-(const iterator& x, const iterator& y) noexcept;
       […]
     }
     […]
   }
   

   […]

   
   friend constexpr difference_type operator-(const iterator& x, const iterator& y) noexcept;
   

   -19- Effects: Equivalent to: return x.pos_ - y.pos_;