This is a follow-up to [[P2484R0] (Extending class types as non-type template parameters)](https://wg21.link/p2484r0) and [[P3380R1] (Extending support for class types as non-type template parameters)](https://wg21.link/p3380r1) (the latter of which starts with a useful reading list), and is a new solution to that problem building upon three insights: