I'm not sure i get what you mean by "hav[ing] to be compiled separately", but as far as i understand, the flambda intermediate representation of the ocaml backe

I'm not sure i get what you mean by "hav[ing] to be compiled separately", but as far as i understand, the flambda intermediate representation of the ocaml backend has no (notable) distinction between a functor and a function (or a module and a record). Everything is untyped so it works. That's also how the runtime values are (which need to exist since there are first-class modules now). I believe that thanks to this ocaml does (could?) inline modules and functors. I'm not so sure about cross-file or cross-package inlining tho.