lolcathost% ocaml
        OCaml version 4.02.3

# class foo = object (_ : 'a) method test (_ : 'a) = () end;;
class foo : object ('a) method test : 'a -> unit end
# class bar = object inherit foo method other = () end;;
class bar : object ('a) method other : unit method test : 'a -> unit end
# let f = new foo;;
val f : foo = <obj>
# let b = new bar;;
val b : bar = <obj>
# f#test f;;
- : unit = ()
# b#test b;;
- : unit = ()
# f#test b;;
Characters 7-8:
  f#test b;;
         ^
Error: This expression has type bar but an expression was expected of type
         foo
       The second object type has no method other
# b#test f;;
Characters 7-8:
  b#test f;;
         ^
Error: This expression has type foo but an expression was expected of type
         bar
       The first object type has no method other
#