module Empty : sig end
type u = A
type v = B
module type S = sig end
val m : (module S) = <module>
module M : sig type 'a t = X of 'a end
val x : (u * v * (module S)) M.t = M.X (A, B, <module>)
module type S = sig end
val m : (module S) = <module>
type u = A
type v = B
module M : sig type 'a t = X of 'a end
val y : (u * v * (module S)) M.t = M.X (A, B, <module>)
Line 2, characters 4-5:
2 | x = y;;
        ^
Error: This expression has type (u/1 * v/1 * (module S/1)) M/1.t
       but an expression was expected of type
         (u/2 * v/2 * (module S/2)) M/2.t
       Hint: The types v and u have been defined multiple times in this
         toplevel session. Some toplevel values still refer to old versions
         of those types. Did you try to redefine them?
       Hint: The module M has been defined multiple times in this toplevel
         session. Some toplevel values still refer to old versions of this
         module. Did you try to redefine them?
       Hint: The module type S has been defined multiple times in this
         toplevel session. Some toplevel values still refer to old versions
         of this module type. Did you try to redefine them?
type a = A
val a : a = A
type a = A
val b : a = A
Line 2, characters 4-5:
2 | a = b;;
        ^
Error: This expression has type a/1 but an expression was expected of type
         a/2
       Hint: The type a has been defined multiple times in this toplevel
         session. Some toplevel values still refer to old versions of this
         type. Did you try to redefine them?