Hint Immediate open_exp_wrt_exp_inj : lngen.
(* *********************************************************************** *)
(** * Theorems about [lc] *)
Ltac default_auto ::= auto with lngen brute_force; tauto.
Ltac default_autorewrite ::= autorewrite with lngen.
(* begin hide *)

Lemma degree_exp_wrt_exp_of_lc_exp_mutual :
(forall e1,
lc_exp e1 ->
degree_exp_wrt_exp 0 e1).