anchor.diff:          let el = DU.CreateElement "input"
           el.AddEventListener("click", (fun (x : DomEvent) -> Var.Set var value), false)
           let predView = View.Map (fun x -> x = value) var.View
  -        let valAttr = Attr.DynamicPred "checked" predView (View.Const "checked")
  +        let valAttr = Attr.DynamicProp "checked" predView
           let (==>) k v = Attr.Create k v
           let attr =
               [
  
positive.code:                 Seq.distinct obs
                  |> Seq.toList)
          let checkedView = View.Map (List.exists (fun x -> x = item)) rvi
          let checkedAttr =
              Attr.DynamicPred "checked" checkedView (View.Const "checked")
          let attrs =
              [
                  Attr.Create "type" "checkbox"
                  Attr.Create "name" (Var.GetId chk |> string)
                  Attr.Create "value" (Fresh.Id ())
                  checkedAttr
              ] @ (List.ofSeq attrs) |> Attr.Concat
          let el = DU.CreateElement "input"
          let onClick (x: DomEvent) =
  
negative.code:         let attrs =
              Attr.Concat [
                  yield! attrs
                  yield Attr.DynamicProp "checked" chk.View
              ]
          Doc.Elem el attrs Doc.Empty
  
  