Definition nolabel (s: statement) : Prop :=
  forall k, find_label lbl s k = None.Fixpoint nolabel_list (sl: list statement) : Prop :=
  match sl with
  | nil => True
  | s1 :: sl' => nolabel s1 /\ nolabel_list sl'
  end.

Lemma nolabel_do_set: forall sd a, nolabel_list (do_set sd a).