syntax error, unexpected 'class' (T_CLASS)

// +----------------------------------------------------------------------
// | Licensed ( http://www.apache.org/licenses/LICENSE-2.0 )
// +----------------------------------------------------------------------
// | Author: 流年 <liu21st@gmail.com>
// +----------------------------------------------------------------------
use think\facade\Request;
use think\facade\Env;
// 自定义 404
\think\Container::get('app')->bind('think\exception\Handle', function() {
    return new class extends \think\exception\Handle {
        public function render(\Exception $e)
        {
            // 如果是 404 错误
            if ($e instanceof HttpException && $e->getStatusCode() == 404) {
                header("HTTP/1.1 404 Not Found");
                include $_SERVER['DOCUMENT_ROOT'] . '/404.php';
                exit;
            }
            return parent::render($e); // 其它错误照常处理