Improve displaying anonymous classes

Author: nicolas-grekas

Application.php

@@ -776,7 +776,7 @@ protected function doRenderThrowable(\Throwable $e, OutputInterface $output): vo
             $message = trim($e->getMessage());
             if ('' === $message || OutputInterface::VERBOSITY_VERBOSE <= $output->getVerbosity()) {
                 $class = \get_class($e);
-                $class = 'c' === $class[0] && 0 === strpos($class, "class@anonymous\0") ? get_parent_class($class).'@anonymous' : $class;
+                $class = 'c' === $class[0] && 0 === strpos($class, "class@anonymous\0") ? (get_parent_class($class) ?: key(class_implements($class))).'@anonymous' : $class;
                 $title = sprintf('  [%s%s]  ', $class, 0 !== ($code = $e->getCode()) ? ' ('.$code.')' : '');
                 $len = Helper::strlen($title);
             } else {
@@ -785,7 +785,7 @@ protected function doRenderThrowable(\Throwable $e, OutputInterface $output): vo
 
             if (false !== strpos($message, "class@anonymous\0")) {
                 $message = preg_replace_callback('/class@anonymous\x00.*?\.php(?:0x?|:[0-9]++\$)[0-9a-fA-F]++/', function ($m) {
-                    return class_exists($m[0], false) ? get_parent_class($m[0]).'@anonymous' : $m[0];
+                    return class_exists($m[0], false) ? (get_parent_class($m[0]) ?: key(class_implements($m[0]))).'@anonymous' : $m[0];
                 }, $message);
             }