I'm curious about that clang built-in you made for nth-element on packs. Did that ever get merged in? Would it be feasible to make something like that for the construction of detail::hash_table? Even if it wasn't canonical clang it would be cool to have a "distro" with built-ins added specifically for optimizing hana internals.
Actually, I just checked and I’m not sure where we would be using it in the current scheme. Indeed, what we need more is a builtin to get the nth element of a parameter pack, not just a type parameter pack.