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 resource_at_approx:
forall phi l,
resource_fmap (approx (level phi)) (approx (level phi)) (phi @ l) = phi @ l.