proposition: Lemma subst_exp_spec_rec : 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. pose proof subst_exp_spec_rec_mutual as H; intuition eauto. Qed.
imports: Coq.Logic.FunctionalExtensionality Coq.Program.Equality Metalib.Metatheory Metalib.LibLNgen Stlc