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