proposition: Lemma open_exp_wrt_exp_close_exp_wrt_exp : forall e1 x1, open_exp_wrt_exp (close_exp_wrt_exp x1 e1) (var_f x1) = e1.
proof: Proof. unfold close_exp_wrt_exp; unfold open_exp_wrt_exp; default_simp. Qed.
imports: Coq.Logic.FunctionalExtensionality Coq.Program.Equality Metalib.Metatheory Metalib.LibLNgen Stlc