// In header: <boost/utility/base_from_member.hpp>

template<typename MemberType, int UniqueID = 0> 
class base_from_member {
public:
  // construct/copy/destruct
  template<typename ... T, 
           typename EnableIf = typename ::boost::detail::enable_if_unrelated<base_from_member, T...>::type> 
    explicit base_from_member(T &&...) noexcept(noexcept((::new((void *) 0) MemberType(static_cast< T && >(x)...)))));
};