fact: Axiom dom_cons : dom ((x, b) :: E) [=] union (singleton x) (dom E).
imports: Coq.FSets.FSets Coq.Lists.List Coq.Logic.Decidable Metalib.CoqFSetDecide Metalib.CoqListFacts Metalib.AssocList Metalib.MetatheoryAtom Metalib.LibTactics