open Sexplib
open Sexplib.Std

module type Tish = sig
        type a
end

module MakeAst (T : Tish) = struct
        type a = T.a

        type t =
                | Int of (a * int)
                | Add of (a * t * t)
end


module Pass = struct
        type t

        type a =
                | Unknown
                | Variable of t
end

module AstPass = MakeAst(Pass)

let x = AstPass.Int (Unknown, 20)

let y = AstPass.Int (Variable (Pass.Int (Unknown, 24)), 24)
(* 29 | let y = AstPass.Int (Variable (AstPass.Int (Unknown, 24)), 24)
 *                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 * Error: This expression has type AstPass.t
 *      but an expression was expected of type Pass.t
 *)