WP_REST_Menus_Controller::handle_locations( int $menu_id, WP_REST_Request $request ): true|WP_Error

491	protected function handle_locations( $menu_id, $request ) {492		if ( ! isset( $request['locations'] ) ) {493			return true;494		}495 496		$menu_locations = get_registered_nav_menus();497		$menu_locations = array_keys( $menu_locations );498		$new_locations  = array();499		foreach ( $request['locations'] as $location ) {500			if ( ! in_array( $location, $menu_locations, true ) ) {501				return new WP_Error(502					'rest_invalid_menu_location',503					__( 'Invalid menu location.' ),504					array(505						'status'   => 400,506						'location' => $location,507					)508				);509			}510			$new_locations[ $location ] = $menu_id;511		}512		$assigned_menu = get_nav_menu_locations();513		foreach ( $assigned_menu as $location => $term_id ) {514			if ( $term_id === $menu_id ) {515				unset( $assigned_menu[ $location ] );516			}517		}518		$new_assignments = array_merge( $assigned_menu, $new_locations );519		set_theme_mod( 'nav_menu_locations', $new_assignments );520 521		return true;522	}