protected function addFosterTag(Tag $tag, Tag $fosterTag)
	{
		list($childPos, $childPrio) = $this->getMagicStartCoords($tag->getPos() + $tag->getLen());

		// Add a 0-width copy of the parent tag after this tag and make it depend on this tag
		$childTag = $this->addCopyTag($fosterTag, $childPos, 0, $childPrio);
		$tag->cascadeInvalidationTo($childTag);
	}