[boost] [multi_index] Taking advantage of C++17 auto template params to simplify key specification

Consider the following:   struct element   {     int x;     int f()const{return x;}   };   int gf(const element& e){return e.x;}   using container=multi_index_container<     element,     indexed_by< ordered_unique>, ordered_unique>,       ordered_unique>     >   >; With the advent in C++17 of auto non-type template parameters, it is very easy to provide a boost::multi_index::key class template so that we can write:   using container=multi_index_container<     element,     indexed_by<       ordered_unique>,       ordered_unique>,       ordered_unique>     >   >; (Example at http://coliru.stacked-crooked.com/a/5742c768cc093c03 ). Is there interest in adding this to Boost.MultiIndex? Comments on this or alternative syntaxes? Thank you, Joaquín M López Muñoz