# module F (_ : sig end) = struct module type S end;;
  module F : functor (_ : sig  end) -> sig module type S end

  # module M = struct end;;
  module M : sig  end

  # module N = M;;
  module N = M

  # module G (X : F(N).S) : F(M).S = X;;
  Characters 33-34:
    module G (X : F(N).S) : F(M).S = X;;
                                     ^
  Error: Signature mismatch:
         Modules do not match: F(N).S is not included in F(M).S
         Unbound module type F(M).S
``