protected function selectors(&$out)
{
$s = $this->seek();
$selectors = [];
while ($this->selector($sel)) {
$selectors[] = $sel;
if (!$this->literal(',')) {
break;
}
while ($this->literal(',')) {
// ignore extra
}
}
if (count($selectors) === 0) {
$this->seek($s);
return false;
}
$out = $selectors;
return true;
}