I'm learning OCaml...

The following code snippet fails due to an "unbound type constructor"
error. How could I achieve the intended result in OCaml?

type combination = T1 of int | T2 of test | T3 of test * test

class test =
      object
            method virtual get : combination
      end


PS: Naive question, why aren't there type members in OCaml classes?

Stephan Tolksdof