proposition: Lemma close_exp_wrt_exp_lc_exp : forall e1 x1, lc_exp e1 -> x1 `notin` fv_exp e1 -> close_exp_wrt_exp x1 e1 = e1.
proof: Proof. unfold close_exp_wrt_exp; default_simp. Qed.
imports: Coq.Logic.FunctionalExtensionality Coq.Program.Equality Metalib.Metatheory Metalib.LibLNgen Stlc