protected function parseFilter($buf)
 {
     if (!$buf->match('/:(.*)/A', $match)) {
         return null;
     }
     $node = new Filter($match['pos'][0], $match[1]);
     while (null !== ($next = $buf->peekLine())) {
         $indent = '';
         if ('' !== trim($next)) {
             $indent = $this->getIndentString(1, $next);
             if ('' === $indent) {
                 break;
             }
             if (strpos($next, $indent) !== 0) {
                 break;
             }
         }
         $buf->nextLine();
         $buf->eatChars(strlen($indent));
         $str = $this->parseInterpolatedString($buf, false);
         $node->addChild(new Statement($str->getPosition(), $str));
     }
     return $node;
 }