proposition: Lemma subst_exp_degree_exp_wrt_exp_mutual : (forall e1 e2 x1 n1, degree_exp_wrt_exp n1 e1 -> degree_exp_wrt_exp n1 e2 -> degree_exp_wrt_exp n1 (subst_exp e2 x1 e1)).
proof: Proof. apply_mutual_ind exp_mutind; default_simp. Qed.
imports: Coq.Logic.FunctionalExtensionality Coq.Program.Equality Metalib.Metatheory Metalib.LibLNgen Stlc