Improving Type Error Messages in OCaml, by Arthur Charguéraud (INRIA & Université Paris Sud)

Cryptic type error messages are a major obstacle to learning OCaml. In many cases, error messages cannot be interpreted with- out a sufficiently-precise model of the type inference algorithm. However, improving type error messages in ML is a hard problem. This problem has received quite a bit of attention over the past two decades, and many different strategies have been considered. Un- fortunately, none of these strategies has so far proved its ability to scale up to a full-blown ML implementation.