anchor.diff:                          let entityState = World.getEntityState entity world
                           (entityState, world)
                       | None -> (entityState, world)
  -                let facetNames = Set.remove facetName entityState.FacetNames
  -                let facetsNp = List.remove ((=) facet) entityState.FacetsNp
  -                let entityState = { entityState with FacetNames = facetNames }
  -                let entityState = { entityState with FacetsNp = facetsNp }
                   let propertyNames = World.getEntityPropertyDefinitionNamesToDetach entityState facet
                   let entityState = Reflection.detachPropertiesViaNames EntityState.copy propertyNames entityState
  +                let entityState = { entityState with FacetNames = Set.remove facetName entityState.FacetNames }
  +                let entityState = { entityState with FacetsNp = List.remove ((=) facet) entityState.FacetsNp }
                   match optEntity with
                   | Some entity ->
                       let oldWorld = world
  
positive.code:                 List.notExists
                      (fun definition ->
                          match Xtension.tryGetProperty definition.PropertyName entityState.Xtension with
                          | Some property -> property.GetType () <> definition.PropertyType
                          | None -> false)
                      facetPropertyDefinitions
              else false
  
negative.code:             | Right facet ->
                  let entityDispatchers = World.getEntityDispatchers world
                  if World.isFacetCompatibleWithEntity entityDispatchers facet entityState then
                      let entityState = { entityState with FacetNames = Set.add facetName entityState.FacetNames }
                      let entityState = { entityState with FacetsNp = facet :: entityState.FacetsNp }
                      let entityState = Reflection.attachProperties EntityState.copy facet entityState
                      match optEntity with
                      | Some entity ->
  