Comment by ogogmad

ML languages have a "types, modules, types-of-modules, and functors" approach to ad-hoc poly. It's a bit strange compared to what other languages do. I am wondering whether it's ever been seen outside of SML and OCaml.

For JSON deserialisation, you would declare a module-type called "JSON-deserialiser", and you would define a bunch of modules of that module-type.

The unusual thing is that a JSON-deserialiser would no longer be tied to a type (read: type, not module-type). Types in ML-like languages don't have any structure at all. I suppose you can now define many different JSON-serialisers for the same type?