anchor.diff:                      let world = World.choose { world with EntityHierarchy = UMap.add newParent children world.EntityHierarchy }
                       let world = if World.getEntityExists newParent world then World.setEntityIsParent true newParent world |> snd' else world
                       world
  -            | _ -> world
  +            | None -> world
   
           static member internal removeEntityFromHierarchy parentOpt entity world =
               match Option.map (resolve entity) parentOpt with
  -            | Some oldParent when World.getEntityExists oldParent world ->
  +            | Some oldParent ->
                   match world.EntityHierarchy.TryGetValue oldParent with
                   | (true, children) ->
                       let children = USet.remove entity children
  
positive.code:         static member internal getEntityXtensionProperties entity world =
              let entityState = World.getEntityState entity world
              entityState.Xtension |> Xtension.toSeq |> Seq.toList
  
          static member inline private setEntityState entityState entity world =
              World.entityStateSetter entityState entity world
  
negative.code:                 let transform = Math.snapTransform positionSnap rotationSnap transform
                  let entityState = EntityState.setTransformByRef (&transform, entityState)
                  let entity = Entity (group.GroupAddress <-- rtoa<Entity> names)
                  World.synchronizeEntityState entityState entity world
                  let world = World.addEntity false entityState entity world
                  (Some entity, world)
              | None -> (None, world)
  