module type Foo = functor(S : sig type s val foo : s -> s end) ->
  sig
    type 'a t
  end

module Bar =
  functor(F: Foo) ->
  struct
    module rec S :
                 sig
                   type s = int
                   type foo = Foo of S.s F(S).t
                   val foo : s -> s
                 end =
      struct
        type s = int
        type foo = Foo of S.s F(S).t
        let foo x = x
      end
  end