OCaml models "interface" polymorphism using an extension to parametric polymorphism called row polymorphism (https://realworldocaml.org/v1/en/html/objects.html

OCaml models "interface" polymorphism using an extension to parametric polymorphism called row polymorphism (https://realworldocaml.org/v1/en/html/objects.html https://realworldocaml.org/v1/en/html/objects.html), which lets you avoid subtyping even for interface types.