wp-includes/class-wp-comment.php:450Adds a child to the comment.
$childWP_Comment public function add_child( WP_Comment $child ): void { $this->children[ (int) $child->comment_ID ] = $child; }Introduced in 4.4.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wp-comment.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.