module type T = sig
    type t
    val x : t
    val show : t -> string
  end

  module Int = struct
    type t = int
    let x = 0
    let show x = string_of_int x
  end

  module String = struct
    type t = string
    let x = "Hello"
    let show x = x
  end

  let switch = ref true

  module Choose () = struct
    module Choice =
      (val if !switch then (module Int : T)
           else (module String : T))
    let r = ref (ref [])
  end

  module type S = sig
    module Choice : T
    val r : Choice.t list ref ref
  end

  module Force (X : functor () -> S) = struct end

  module M = Choose ()

  let () = switch := false

  module N = Choose ()

  let () = N.r := !M.r

  module Ignore = Force(Choose)

  module M' = (M : S)

  let () = (!M'.r) := [M'.Choice.x]

  module N' = (N : S)

  let () = List.iter (fun x -> print_string (N'.Choice.show x)) !(!N'.r)