proposition: Lemma steps_msgid_inv: forall s1 s2 h, step_star s1 h s2 -> msgid_inv s1 -> msgid_inv s2.
proof: Proof. induction 1; eauto using step_msgid_inv. Qed.
imports: Coq(FunctionalExtensionality Arith Lia) Coq(Arith.Peano_dec Arith.Compare_dec) Coq(Relations.Relation_Operators) Coq(List) Chapar(Predefs)