wp-admin/includes/widgets.php:162$id_basestringintfunction next_widget_id_number( $id_base ) { global $wp_registered_widgets; $number = 1; foreach ( $wp_registered_widgets as $widget_id => $widget ) { if ( preg_match( '/' . preg_quote( $id_base, '/' ) . '-([0-9]+)$/', $widget_id, $matches ) ) { $number = max( $number, $matches[1] ); } } ++$number; return $number;}Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-admin/includes/widgets.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.