anchor.diff:              let indexOpt3 = system3.TryIndexCorrelatedToI entityId
               if indexOpt > -1 && indexOpt2 > -1 && indexOpt3 > -1 then
                   let systemIds = ecs.IndexSystemIds entityId
  -                if not (systemIds.IsSupersetOf excluding)
  +                if excluding.Count = 0 || not (systemIds.IsSupersetOf excluding)
                   then cache.[entityId] <- struct (indexOpt, indexOpt2, indexOpt3)
                   else cache.Remove entityId |> ignore<bool>
               elif indexOpt > -1 || indexOpt2 > -1 || indexOpt3 > -1 then // OPTIMIZATION: make sure it exists and needs removing
  
positive.code:         world
  
      member this.TryClear world =
          if Seq.isEmpty allocated then
              let mutable world = world
              for entityIdInv in unallocated do
                  let entityId = UInt64.MaxValue - entityIdInv
  
negative.code:         override this.Correlation = correlation
  
          override this.Filter entityId =
              if excluding.Count = 0 then
                  () // just pulls from lone associated system
              else
                  let indexOpt = system.TryIndexCorrelatedToI entityId
  