I find Rust is really effective in this regard. From my understanding of the capabilities of mli files, Rust's visibility modifiers are even more powerful in te

I find Rust is really effective in this regard. From my understanding of the capabilities of mli files, Rust's visibility modifiers are even more powerful in terms of effectively hiding implementation details and maintaining invariants, but they're all written inline in the source code (with the `pub` keyword). I agree that the encapsulation capabilities of mli files are great, but I don't see why they need to be written in a separate file (apart from the obvious reason: that's how OCaml does it, and you can't just change a language's design just because you don't like one bit of it!)