[yawaramin]

You don't need a third-party library to derive a pretty-printer for your types, it just makes it simpler. OCaml takes the approach that the core compiler doesn't do any codegen, that is left to PPXs (basically, middlewares which transform code) which run before the compiler.

You can write a pretty-printer yourself using the conventions of the `Format` module. Is it manual and annoying? Yeah. That's why the PPX exists. It's a tradeoff.