anchor.diff:          override this.Correlation = correlation
   
           override this.Filter entityId =
  -            let system = ecs.IndexSystem<'c, SystemCorrelated<'c, 'w>> ()
  -            let system2 = ecs.IndexSystem<'c2, SystemCorrelated<'c2, 'w>> ()
  -            let system3 = ecs.IndexSystem<'c3, SystemCorrelated<'c3, 'w>> ()
  -            let system4 = ecs.IndexSystem<'c4, SystemCorrelated<'c4, 'w>> ()
               let indexOpt = system.TryIndexCorrelatedToI entityId
               let indexOpt2 = system2.TryIndexCorrelatedToI entityId
               let indexOpt3 = system3.TryIndexCorrelatedToI entityId
  
positive.code: 
      let cache = OrderedDictionary<Guid, struct (int * int * int * int * int)> HashIdentity.Structural
      let correlation = hashSetPlus<string> StringComparer.Ordinal [typeof<'c>.Name; typeof<'c2>.Name; typeof<'c3>.Name; typeof<'c4>.Name; typeof<'c5>.Name]
      
      member this.Ecs = ecs
      member this.Cache = cache
  
negative.code: 
  namespace Nu
  open System
  open System.Collections.Generic
  open System.Runtime.CompilerServices
  open System.Threading.Tasks
  