IMO automatic differentiation shouldn’t be baked into the compiler, because that forces a bit of a monoculture around one AD system and forces you to accept the

IMO automatic differentiation shouldn’t be baked into the compiler, because that forces a bit of a monoculture around one AD system and forces you to accept the trade offs of that particular AD system. The Julia approach has been instead to expose an interface for compiler plugins that any AD (or other ‘nonstandard interpretation / code transformation) library can access. There’s negative trade offs to to this as well, but I really like the way it’s turned out and I think it’s given us some fantastic tools for non-AD purposes as well.