anchor.diff:      let mutable components = ArrayRef<'c>.make reserve
       let mutable freeIndex = 0
       let freeList = HashSet<int> ()
  -    let preDeque = Deque<int> ()
  +    let preDeque = HashSet<int> ()
       let correlations = dictPlus [] : Dictionary<Guid, int>
   
       new (reserve) = SystemCorrelated (reserve, typeof<'c>.Name)
  
positive.code:                     if i = 0 then
                          comp.RefCount <- inc comp.RefCount
                          this.Correlations.Add (entityId, index)
                      else
                          this.PreDeque.AddToBack index
                      this.Components.Array.[index] <- comp
  
                  // fin
  
negative.code: 
              // new component; use a pre-allocated component
              if preDeque.Count > 0 then
                  let index = Seq.head preDeque
                  let _ : bool = preDeque.Remove index
                  correlations.Add (entityId, index)
                  components.Array.[index] <- comp
                  let comp = &components.Array.[index]
  