Ltac do_map_arg :=
match goal with |- ?a = ?b =>
match a with context [map ?x _] =>
match b with context [map ?y _] => replace y with x; auto end end end.

Lemma necR_resource_at:
forall phi phi' loc r,
necR phi phi' ->
phi @ loc = resource_fmap (approx (level phi)) r ->
phi' @ loc = resource_fmap (approx (level phi')) r.