proposition: Lemma dom_consAlt : dom (AltAsn A a :: E) [=] dom E.
proof: Proof. clear. simpl. fsetdec. Qed.
imports: Coq.FSets.FSets Coq.Lists.List Coq.Logic.Decidable Metalib.CoqFSetDecide Metalib.CoqListFacts Metalib.LibTactics Metalib.MetatheoryAtom Metalib.LibTactics