With source_type: boost::fusion::cons < type_id < 0u
, boost::fusion::cons < type_id < 1u > , boost::fusion::cons < type_id < 2u > , boost::fusion::nil >
the result type of fusion::result_of::as_list<source_type>::type is: boost::fusion::cons < type_id < 0u > , boost::fusion::cons < type_id < 1u > , boost::fusion::cons < type_id < 2u > , boost::fusion::nil > >
However, I expected something more like was happens with: fusion::result_of::as_vector<source_type>::type which gives the result type: boost::fusion::vector < type_id < 0u > , type_id < 1u > , type_id < 2u > , boost::fusion::void_ , boost::fusion::void_ , boost::fusion::void_ , boost::fusion::void_ , boost::fusion::void_ , boost::fusion::void_ , boost::fusion::void_
IOW, instead of: boost::fusion::vector<...> there should be: boost::fusion::list<...> as the 1st line of the above result type for as_list<source_type>::type.