proposition: Lemma subst_exp_degree_exp_wrt_exp : 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. pose proof subst_exp_degree_exp_wrt_exp_mutual as H; intuition eauto. Qed.
imports: Coq.Logic.FunctionalExtensionality Coq.Program.Equality Metalib.Metatheory Metalib.LibLNgen Stlc