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 cast_no_change : forall v from to m,
tc_val from v ->
is_true (cast_no_val_change from to) ->
Cop.sem_cast v from to m = Some v.