anchor.diff:          Attrs.Sync el.El el.Attr
           if hasDirtyChildren el then
               DoSyncElement el
  -        match el.Render with
  -        | None -> ()
  -        | Some f -> f el.El; el.Render <- None
   
       /// Links an element to children by inserting them.
       [<MethodImpl(MethodImplOptions.NoInlining)>]
  
positive.code:     let SyncElemNode el =
          SyncElement el
          Sync el.Children
  
      /// A set of node element nodes.
      type NodeSet =
  
negative.code:     [<MethodImpl(MethodImplOptions.NoInlining)>]
      let LinkPrevElement (el: Node) children =
          InsertDoc (el.ParentNode :?> _) children (DU.BeforeNode el) |> ignore
  
      /// Invokes and clears an element's afterRender callback(s).
      let AfterRender (el: DocElemNode) =
          match el.Render with
          | None -> ()
          | Some f -> f el.El; el.Render <- None
  
      /// Synchronizes the document (deep).
      let Sync doc =
          let rec sync doc =
              match doc with
              | AppendDoc (a, b) -> sync a; sync b
              | ElemDoc el -> SyncElement el; sync el.Children; AfterRender el
              | EmbedDoc n -> sync n.Current
              | EmptyDoc
              | TextNodeDoc _ -> ()
  