Ltac rewrite_closed := repeat   match goal with
| [ |- context [subst ?s _ _] ] => rewrite_cls s
end.
(** ** Tactics to solve equivalences and reductions *)

Lemma rho_correct s t : proc s -> proc t -> rho s t ≻* s (rho s) t.
Hint Resolve rho_lam rho_closed : cbv.