type error

type_error.ml

module type S1 = sig
  type t
end

module X = struct
  type t = int
  let f x = x
end

module type S2 = sig
  module S: S1
end

module Y = struct
  module S = (X:S1 with type t = int)
end

module Z: S2 with module S = X = Y

   In module S:
   Modules do not match:
     sig type t = int end
   is not included in
     sig type t = int val f : 'a -> 'a end
   In module S:
   The field `f' is required but not provided