wp-includes/class-wp-matchesmapregex.php:75do the actual mapping
string private function _map() { $callback = array( $this, 'callback' ); return preg_replace_callback( $this->_pattern, $callback, $this->_subject ); }Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wp-matchesmapregex.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.