code: func lexPathLiteral(l *Lexer) lexFunc {
  	for {
  		r := l.next()
  		if r == eof || r == '\n' {
  			return l.errorf("Unterminated path literal")
  		}
  
  		if r == ']' {
  			break
  		}
  	}
  
  	l.emit(TokenID)
  
  	return lexExpression
  }
docs: // lexPathLiteral scans an [ID]