There are certainly some design choices here. I want to emphasize that in the few projects where I've used macros (e.g. https://github.com/OlivierNicole/macros-examples), I found that these translating functions were scarcely needed and I never had to pass a non-standard type between phases.

You may want to read this comment which I find relevant: https://www.reddit.com/r/ocaml/comments/5e8slg/bringing_type...