--->.<--- THIS CLOSE TO JUST USING VARIANTS INSTEAD OF OBJE

class virtual foo (x: int) =
  object (s:'s)
    method get = x
    method virtual foo : int -> foo
    (* method virtual foo : int -> #foo *)
  end

class bar = object
  inherit foo 0
  method foo x = (mkfoo 0 :> foo)
end

class baz = object
  inherit foo 1
  method foo x = (mkfoo 1 :> foo)
end

let mkfoo (x: int) =
  if x = 0
    then (new baz :> foo)
    else (new bar :> foo)