(type T (primitive T))
(type U (primitive U))
(type V (primitive V))

(convert T U t_to_u)

(type Result (enum (T (u U) (v V))))

;; Use the implicit converter before the underlying constructor is
;; declared (below). Also use one of the conversions before it is
;; declared (below).
(decl entry (T) Result)
(rule (entry t)
      (Result.T t t))

(convert T V t_to_v)

(decl t_to_u (T) U)
(extern constructor t_to_u t_to_u)

(decl t_to_v (T) V)
(rule (t_to_v _) 0)