Definition dest_below (dst: destination) (g: generator) : Prop :=
  match dst with
  | For_set sd => Plt (sd_temp sd) g.(gen_next)
  | _ => True
  end.Remark dest_for_val_below: forall g, dest_below For_val g.Remark dest_for_effect_below: forall g, dest_below For_effects g.

Lemma sd_temp_notin: forall sd g1 g2 l, dest_below (For_set sd) g1 -> contained l g1 g2 -> ~In (sd_temp sd) l.