destruct rho.
unfold finite_idfun, finMap in *.
generalize f; intros [l ?].
exists l; simpl in *.
intros; unfold compose in *.
apply e; auto.
Qed.

Lemma env_funct: forall rho1 rho2,
rho1 = rho2 -> forall id sh1 sh2 v1 v2, env_get rho1 id = Some(sh1, v1)
-> env_get rho2 id = Some(sh2, v2)
-> v1 = v2.