Module R := R.
Hint Resolve (@subp_sepcon _ Join_rmap Perm_rmap Sep_rmap): contractive.
unfold identity_rmap; intros.
rewrite R.unsquash_squash.
simpl.
apply extensionality; intro l.
unfold compose; simpl; auto.
Qed.

Lemma age1_resource_at_identity:
forall phi phi' loc, age1 phi = Some phi' ->
identity (phi@loc) ->
identity (phi'@loc).