proposition: Lemma degree_exp_wrt_exp_close_exp_wrt_exp : forall e1 x1, degree_exp_wrt_exp 0 e1 -> degree_exp_wrt_exp 1 (close_exp_wrt_exp x1 e1).
proof: Proof. unfold close_exp_wrt_exp; default_simp. Qed.
imports: Coq.Logic.FunctionalExtensionality Coq.Program.Equality Metalib.Metatheory Metalib.LibLNgen Stlc