/**
 * @template TChild of object
 *
 * @extends ArrayAccess<int, ?TChild>
 */
interface ParentNode extends ArrayAccess {
    // empty
}

class HelloWorld
{
	public function sayHelloBug(object $node): void
	{
		if ($node instanceof ParentNode) {
		     assertType('object|null', $node[0]);
		}
	}
}