anchor.diff:          | TextContent of string
           | VerbatimContent of string
           | CommentContent of string
  +        | INodeContent of INode
   
           interface INode with
   
  -            member this.IsAttribute = false
  +            member this.IsAttribute =
  +                match this with
  +                | INodeContent n -> n.IsAttribute
  +                | _ -> false
   
               member this.Requires =
                   match this with
  
positive.code:         | TagContent e ->
              { e with Annotation = Some x }
              |> TagContent
          | VerbatimContent _
          | TextContent _
          | CommentContent _ -> e
  
negative.code:                         t.Contents |> Seq.collect (fun x -> x.Requires)
                          t.Attributes |> Seq.collect (fun x -> x.Requires)
                      |]
                  | INodeContent n -> n.Requires
                  | _ -> Seq.empty
  
              member this.Write(meta, w) =
  