anchor.diff:  
   namespace Nu
   open System
  -open System.Collections.Concurrent
   open System.Collections.Generic
   open System.Runtime.CompilerServices
   open System.Threading.Tasks
  
positive.code:         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 indexOpt = system.TryIndexCorrelatedToI entityId
              let indexOpt2 = system2.TryIndexCorrelatedToI entityId
              let indexOpt3 = system3.TryIndexCorrelatedToI entityId
  
negative.code:         override this.Correlation = correlation
  
          override this.Filter entityId =
              let indexOpt = system.TryIndexCorrelatedToI entityId
              let indexOpt2 = system2.TryIndexCorrelatedToI entityId
              let indexOpt3 = system3.TryIndexCorrelatedToI entityId
  