let stuff x =
  x + 1

type foo =
  | Bar
  | Biz of ('ex, 'en) list

let do_stuff x =
  match x with
  | `Foo -> 1
  | _ -> 3

let stuffs y =
  y + 1

type thing =
  | X [@visitor.opaque]
  | Y
[@@visitor.opaque]