proposition: Lemma subst_exp_spec_rec_mutual : (forall e1 e2 x1 n1, subst_exp e2 x1 e1 = open_exp_wrt_exp_rec n1 e2 (close_exp_wrt_exp_rec n1 x1 e1)).
proof: Proof. apply_mutual_ind exp_mutind; default_simp. Qed.
imports: Coq.Logic.FunctionalExtensionality Coq.Program.Equality Metalib.Metatheory Metalib.LibLNgen Stlc