Goal:
    _z_ : VSet.t  x0 : V.t  a : V.t
  ============================
   ((VSet.In a (VSet.add x0 _z_) -> VSet.In a (VSet.add x0 _z_)) /\
    (VSet.In a (VSet.add x0 _z_) -> VSet.In a (VSet.add x0 _z_)))


DEBUG:Going to execute:
autorewrite with set_eq_simpl in *;
            VSetDecide.MSetDecideAuxiliary.inst_MSet_hypotheses; autorewrite
            with set_simpl set_eq_simpl in *; push not in * using
            MSet_decidability; VSetDecide.MSetDecideAuxiliary.substMSet;
            VSetDecide.MSetDecideAuxiliary.assert_decidability; auto;
            intuition VSetDecide.MSetDecideAuxiliary.fsetdec_rec ||
              fail 1 "because the goal is beyond the scope of this tactic"