wp-includes/class-wp-navigation-fallback.php:181Determines the most appropriate classic navigation menu to use as a fallback.
WP_Term|null private static function get_fallback_classic_menu() { $classic_nav_menus = wp_get_nav_menus(); if ( ! $classic_nav_menus || is_wp_error( $classic_nav_menus ) ) { return null; } $nav_menu = static::get_nav_menu_at_primary_location(); if ( $nav_menu ) { return $nav_menu; } $nav_menu = static::get_nav_menu_with_primary_slug( $classic_nav_menus ); if ( $nav_menu ) { return $nav_menu; } return static::get_most_recently_created_nav_menu( $classic_nav_menus ); }Introduced in 6.3.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wp-navigation-fallback.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.