nukifw

  ```ocaml
  type _ treated_as = 
   | Int : int -> int treated_as
   | Float : float -> float treated_as

  let f (Int x) = x + 1 (* val f : int treated_as -> int *)
  ```

  ```ocaml
  let f = function 
  | `Foo x -> string_of_int (x + 1) 
  | `Bar x -> x ^ "Hello"
  (* val f : [< `Foo of int | `Bar of string] -> string` *)

  let g = function
  | `Foo _ -> ()
  | _ -> () 
  (* val g : [> `Foo of 'a ] -> unit *)
  ```