private void Consume(HaystackToken expected)
        {
            if (expected != null)
            {
                Verify(expected);
            }

            _currentToken      = _peekToken;
            _currentValue      = _peekValue;
            _currentLineNumber = _peekLineNumber;

            _peekToken      = _tokenizer.Next();
            _peekValue      = _tokenizer.Val;
            _peekLineNumber = _tokenizer.LineNumber;
        }