Hint Rewrite @closed_env_set using safe_auto_with_closed : norm2.

(* Specifications: *)
Lemma subst_eval_id_eq:
forall id v, subst id v (eval_id id) = v.
Lemma subst_eval_id_neq:
forall id v j, id<>j -> subst id v (eval_id j) = eval_id j.