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:     let result = 
          match message with
          | NestedError(position, userState, errors)          ->
              false, sprintf "Nested errors: %s"   <| produceErrorMessageList (indent + 1) errors
          | CompoundError(label, position, userState, errors) ->
              false, sprintf "Compound errors: %s" <| produceErrorMessageList (indent + 1) errors
          | Expected           label -> true, expected + String.Format(CompilerMessages.LexemExpected, label)
          | ExpectedString     str
          | ExpectedStringCI   str   -> true, expected + String.Format(CompilerMessages.StringExpected, str)
  
negative.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
      result
  
  and private produceErrorMessageList (messages : ErrorMessageList) : string =
      // TODO: Filter only not nested errors.
      // TODO: Dispatch message by token from Expected or ExpectedString.
      let filter = function
                   | Expected _
                   | ExpectedString _
                   | ExpectedStringCI _ -> true
  
      let msgSeq = messageSeq messages
      let converter (expected, msg) error = let expected', msg' = produceMessage expected error
                                            (expected || expected', msg + "\n" + msg')
      let state = (false, String.Empty)
      snd <| Seq.fold converter state msgSeq
  