anchor.diff:  
           static member private entityStateFinder entity world =
               let entityStateOpt = entity.EntityStateOpt
  -            match entityStateOpt :> obj with
  -            | null ->
  +            if isNull ^ box entityStateOpt then
                   let entityStateOpt =
                       KeyedCache.getValue
                           World.entityStateKeyEquality
  
positive.code: 
          static member private getEntityStateOpt entity world =
              let entityStateOpt = World.entityStateFinder entity world
              match entityStateOpt :> obj with
              | null -> None
              | _ -> Some entityStateOpt
  
          static member private getEntityState entity world =
  #if DEBUG
  
negative.code:                             | Some entityState -> entityState
                      entityState
                  | None -> Unchecked.defaultof<EntityState>
              else entityStateOpt
  
          static member private entityStateAdder entityState entity world =
              let screenDirectory =
  