Bad ocaml

bad.ml

let gen_const_list ~is_done:(is_done : 'n -> bool) ~pred:(pred : 'n -> 'n)
    (size : 'n) (v : 'a) : 'a list =
  let rec helper size v =
    if is_done size then [] else v::(helper (pred size) v)
  in helper size v

let const_list : int -> 'a -> 'a list =
  gen_const_list ~is_done:(fun size -> size <= 0) ~pred:(fun n -> n - 1)

module Stupid = struct
  type t = X | Y
  let x (sz : int) : t list = const_list sz X
end;;

(** Error: This expression has type t but an expression was expected of type 'a
       The type constructor t would escape its scope *)