code: func (p *parser) next() item {
  	if p.peekCount > 0 {
  		p.peekCount--
  	} else {
  		t := p.lex.nextItem()
  		// Skip comments.
  		for t.typ == ItemComment {
  			t = p.lex.nextItem()
  		}
  		p.token[0] = t
  	}
  	if p.token[p.peekCount].typ == ItemError {
  		p.errorf("%s", p.token[p.peekCount].val)
  	}
  	return p.token[p.peekCount]
  }
docs: // next returns the next token.