anchor.diff:  let private getMessage (message : string) (error : ParserError) (userState : ParserState) : string =
       if enabled then
           let position = error.Position
  -        sprintf "At line %d, column %d: %s" position.Line position.Column <| produceErrorMessageList 0 error.Messages
  +        sprintf "At line %d, column %d: %s" position.Line position.Column <| produceErrorMessageList error.Messages
       else message
   
   let getException message (error : ParserError) userState =
  
positive.code:         | Message            str   -> false, sprintf "Exceptional message: %s" str
          | OtherErrorMessage  o     -> false, sprintf "Exceptional case: %A" o
          | other                    -> false, sprintf "Unknown parse error: %A" other
      let indentString = List.replicate indent "    " |> String.concat String.Empty
      (fst result, indentString + snd result)
  
  and private produceErrorMessageList (indent: int) (messages : ErrorMessageList) : string =
      let msgSeq = messageSeq messages
      let converter (expected, msg) error = let expected', msg' = produceMessage indent expected error
                                            (expected || expected', msg + "\n" + msg')
      let state = (false, String.Empty)
      snd <| Seq.fold converter state msgSeq
  
negative.code:     | _    -> Seq.concat [Seq.singleton list.Head
                            messageSeq list.Tail]
  
  let rec private produceMessage (expectedWordWritten: bool) (message : ErrorMessage) : bool * string =
      let expected = if not expectedWordWritten
                     then "Expected "
                     else "      or "
  