anchor.diff:  
       type System<'w when 'w :> Freezable> with
           member this.RegisterPipedValue (ecs : 'w Ecs) = ecs.RegisterPipedValue<obj> this.PipedKey this.PipedInit
  -        member this.UnregisterPipedValue (ecs : 'w Ecs) = ecs.UnregisterPipedValue this.PipedKey
           member this.IndexPipedValue<'a> (ecs : 'w Ecs) = ecs.IndexPipedValue<'a> this.PipedKey
   
   [<Extension>]
  
positive.code:         pipedValues.[key] <- value :> obj
  
      /// Thread-safe.
      member this.UnregisterPipedValue key =
          pipedValues.TryRemove (key, ref (obj ()))
  
      /// Thread-safe.
      member this.TryIndexPipedValue<'a> key =
          match pipedValues.TryGetValue key with
          | (true, value) -> Some (value :?> 'a)
  
negative.code:     member this.RegisterSystemGeneralized (system : 'w System) =
          systemsUnordered.Add (system.Name, system)
          systemsOrdered.Add (system.Name, system)
          this.RegisterPipedValue<obj> system.PipedKey system.PipedInit
  
      member this.TryIndexSystem<'s when 's :> 'w System> systemName =
          match systemsUnordered.TryGetValue systemName with
  