split; intros; induction v. simpl in *.
rewrite PTree.gempty in *. congruence.
simpl in *. destruct a. inv H. rewrite PTree.gsspec in *. if_tac in H0.
inv H0. auto. intuition.
inv H0.
simpl in *. destruct a. simpl in *. rewrite PTree.gsspec. destruct H0.
inv H0. if_tac. auto. intuition. inv H. if_tac. subst.
clear - H0 H3. rewrite in_map_iff in *. destruct H3. exists (i,ty). auto.
apply IHv; auto.
Qed.

Lemma tc_exprlist_length : forall {CS: compspecs} Delta tl el rho phi,
denote_tc_assert (typecheck_exprlist Delta tl el) rho phi ->
length tl = length el.