anchor.diff:          
           // grab the type descriptor and assign the value
           let entityTds = source :?> EntityTypeDescriptorSource
  +        let entity = entityTds.DescribedEntity
           let changer = (fun world ->
   
               // pull string quotes out of string
  
positive.code: 
              // make property change undo-able
              Globals.pushPastWorld world
              let entity = entityTds.DescribedEntity
              let world = if entity.GetImperative world then World.divergeEntity entity world else world
  
              // change property
  
negative.code:                         let alwaysPublish = Reflection.isPropertyAlwaysPublishByName propertyName
                          let nonPersistent = not (Reflection.isPropertyPersistentByName propertyName)
                          EntityPropertyValue.trySetValue alwaysPublish nonPersistent property value entity world |> snd
                  let world = entity.PropagatePhysics world
                  Globals.World <- world // must be set for property grid
                  entityTds.Form.entityPropertyGrid.Refresh ()
                  world)
  