Support for refutation cases in pattern matching

[hcarty]

http://caml.inria.fr/pub/docs/manual-ocaml/extn.html#sec238 -- see the subsection titled "Refutation cases and redundancy"

Something along the lines of:

switch x {
| A -> /* Handle this case */
| B -> /* Handle this case */
| _ -> . /* States (with a check by the type system) that this case isn't possible */
}

[glennsl]

Surprised to see that this still isn't supported. Are there any workarounds for this? I've tried various forms of type annotations, but that doesn't seem to be sufficient. I guess I could either disable warning 8 or just convert the whole module implementation to OCaml.

[rdavison]

@glennsl Been hitting this issue as well. You could also disable warning 56.

type t(_) =
  | A : t(int);

[@warning "-56"];

let foo = (x: t(float)) =>
  switch(x) {
  | _ => assert(false)
  };

[@warning "+56"];