Goal:
    G : t  z : Z  H : is_true (z <=? 0)
  ============================
   (exists z0 : Z, Some z = Some z0 /\ z0 <= 0)


DEBUG:Going to execute:
<Coq.Init.Tauto.is_disj> flags X1; (solve
            [ Ltac.left; t_tauto_intuit | Ltac.right; t_tauto_intuit ])