[ErrorHandler] Fix parsing messages that contain anonymous classes on PHP >= 8.3.3

Author: nicolas-grekas

DebugClassLoader.php

@@ -1097,7 +1097,7 @@ private function fixReturnStatements(\ReflectionMethod $method, string $returnTy
         $braces = 0;
         for (; $i < $end; ++$i) {
             if (!$inClosure) {
-                $inClosure = str_contains($code[$i], 'function (');
+                $inClosure = false !== strpos($code[$i], 'function (');
             }
 
             if ($inClosure) {

ErrorHandler.php

@@ -457,23 +457,27 @@ public function handleError(int $type, string $message, string $file, int $line)
                 return true;
             }
         } else {
-            if (false !== strpos($message, '@anonymous')) {
+            if (PHP_VERSION_ID < 80303 && false !== strpos($message, '@anonymous')) {
                 $backtrace = debug_backtrace(false, 5);
 
                 for ($i = 1; isset($backtrace[$i]); ++$i) {
                     if (isset($backtrace[$i]['function'], $backtrace[$i]['args'][0])
                         && ('trigger_error' === $backtrace[$i]['function'] || 'user_error' === $backtrace[$i]['function'])
                     ) {
                         if ($backtrace[$i]['args'][0] !== $message) {
-                            $message = $this->parseAnonymousClass($backtrace[$i]['args'][0]);
-                            $logMessage = $this->levels[$type].': '.$message;
+                            $message = $backtrace[$i]['args'][0];
                         }
 
                         break;
                     }
                 }
             }
 
+            if (false !== strpos($message, "@anonymous\0")) {
+                $message = $this->parseAnonymousClass($message);
+                $logMessage = $this->levels[$type].': '.$message;
+            }
+
             $errorAsException = new \ErrorException($logMessage, 0, $type, $file, $line);
 
             if ($throw || $this->tracedErrors & $type) {