Arguments resource_at_empty [phi] _ _.
Ltac inj_pair_tac :=
match goal with H: (@existT ?U ?P ?p ?x = @existT _ _ _ ?y) |- _ =>
generalize (@inj_pair2 U P p x y H); clear H; intro; try (subst x || subst y)
end.

Lemma age1_resource_at:
forall phi phi',
age1 phi = Some phi' ->
forall loc r,
phi @ loc = resource_fmap (approx (level phi)) (approx (level phi)) r ->
phi' @ loc = resource_fmap (approx (level phi')) (approx (level phi')) r.