diff --git a/src/Symfony/Bundle/FrameworkBundle/Console/Application.php b/src/Symfony/Bundle/FrameworkBundle/Console/Application.php
index 0535d26998..319b9be9dd 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Console/Application.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Console/Application.php
@@ -19,8 +19,8 @@ use Symfony\Component\Console\Input\InputOption;
 use Symfony\Component\Console\Output\ConsoleOutputInterface;
 use Symfony\Component\Console\Output\OutputInterface;
 use Symfony\Component\Console\Style\SymfonyStyle;
+use Symfony\Component\Debug\Exception\FatalThrowableError;
 use Symfony\Component\DependencyInjection\ContainerAwareInterface;
-use Symfony\Component\ErrorCatcher\Exception\FatalThrowableError;
 use Symfony\Component\HttpKernel\Bundle\Bundle;
 use Symfony\Component\HttpKernel\Kernel;
 use Symfony\Component\HttpKernel\KernelInterface;
diff --git a/src/Symfony/Bundle/FrameworkBundle/FrameworkBundle.php b/src/Symfony/Bundle/FrameworkBundle/FrameworkBundle.php
index 6ee99382ea..0ef349ddb5 100644
--- a/src/Symfony/Bundle/FrameworkBundle/FrameworkBundle.php
+++ b/src/Symfony/Bundle/FrameworkBundle/FrameworkBundle.php
@@ -29,11 +29,11 @@ use Symfony\Component\Cache\DependencyInjection\CachePoolPass;
 use Symfony\Component\Cache\DependencyInjection\CachePoolPrunerPass;
 use Symfony\Component\Config\Resource\ClassExistenceResource;
 use Symfony\Component\Console\DependencyInjection\AddConsoleCommandPass;
+use Symfony\Component\Debug\ErrorHandler;
 use Symfony\Component\DependencyInjection\Compiler\PassConfig;
 use Symfony\Component\DependencyInjection\Compiler\RegisterReverseContainerPass;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\ErrorCatcher\DependencyInjection\ErrorCatcherPass;
-use Symfony\Component\ErrorCatcher\ErrorHandler;
 use Symfony\Component\EventDispatcher\DependencyInjection\RegisterListenersPass;
 use Symfony\Component\Form\DependencyInjection\FormPass;
 use Symfony\Component\HttpFoundation\Request;
diff --git a/src/Symfony/Component/Console/Application.php b/src/Symfony/Component/Console/Application.php
index 571ab7cb2f..10ae964d8c 100644
--- a/src/Symfony/Component/Console/Application.php
+++ b/src/Symfony/Component/Console/Application.php
@@ -41,8 +41,8 @@ use Symfony\Component\Console\Output\ConsoleOutput;
 use Symfony\Component\Console\Output\ConsoleOutputInterface;
 use Symfony\Component\Console\Output\OutputInterface;
 use Symfony\Component\Console\Style\SymfonyStyle;
-use Symfony\Component\ErrorCatcher\ErrorHandler;
-use Symfony\Component\ErrorCatcher\Exception\FatalThrowableError;
+use Symfony\Component\Debug\ErrorHandler;
+use Symfony\Component\Debug\Exception\FatalThrowableError;
 use Symfony\Component\EventDispatcher\EventDispatcherInterface;
 use Symfony\Component\EventDispatcher\LegacyEventDispatcherProxy;
 use Symfony\Contracts\Service\ResetInterface;
diff --git a/src/Symfony/Component/Debug/BufferingLogger.php b/src/Symfony/Component/Debug/BufferingLogger.php
index 6f801c0ab3..e7db3a4ce4 100644
--- a/src/Symfony/Component/Debug/BufferingLogger.php
+++ b/src/Symfony/Component/Debug/BufferingLogger.php
@@ -11,16 +11,12 @@
 
 namespace Symfony\Component\Debug;
 
-@trigger_error(sprintf('The "%s" class is deprecated since Symfony 4.4 and will be removed in 5.0.', BufferingLogger::class), E_USER_DEPRECATED);
-
 use Psr\Log\AbstractLogger;
 
 /**
  * A buffering logger that stacks logs for later.
  *
  * @author Nicolas Grekas <p@tchwork.com>
- *
- * @deprecated since Symfony 4.4 and will be removed in 5.0.
  */
 class BufferingLogger extends AbstractLogger
 {
diff --git a/src/Symfony/Component/Debug/CHANGELOG.md b/src/Symfony/Component/Debug/CHANGELOG.md
index 71da439940..e84aa18552 100644
--- a/src/Symfony/Component/Debug/CHANGELOG.md
+++ b/src/Symfony/Component/Debug/CHANGELOG.md
@@ -4,14 +4,7 @@ CHANGELOG
 4.4.0
 -----
 
-* deprecated the `BufferingLogger`, `ErrorHandler` and `ExceptionHandler` classes, 
-  they have been moved to the `ErrorCatcher` component
-* deprecated the `FatalErrorHandlerInterface`, `ClassNotFoundFatalErrorHandler`,  
-  `UndefinedFunctionFatalErrorHandler` and `UndefinedMethodFatalErrorHandler` classes,
-  they have been moved to the `ErrorCatcher` component
-* deprecated the `ClassNotFoundException`, `FatalErrorException`, `FatalThrowableError`,
-  `FlattenException`, `OutOfMemoryException`, `SilencedErrorContext`, `UndefinedFunctionException`,
-  and `UndefinedMethodException`, they have been moved to the `ErrorCatcher` component
+ * deprecated `FlattenException`, use the `FlattenException` of the `ErrorCatcher` component
 
 4.3.0
 -----
diff --git a/src/Symfony/Component/Debug/Debug.php b/src/Symfony/Component/Debug/Debug.php
index 8757476085..5d2d55cf9f 100644
--- a/src/Symfony/Component/Debug/Debug.php
+++ b/src/Symfony/Component/Debug/Debug.php
@@ -11,10 +11,6 @@
 
 namespace Symfony\Component\Debug;
 
-use Symfony\Component\ErrorCatcher\BufferingLogger;
-use Symfony\Component\ErrorCatcher\ErrorHandler;
-use Symfony\Component\ErrorCatcher\ExceptionHandler;
-
 /**
  * Registers all the debug tools.
  *
diff --git a/src/Symfony/Component/Debug/DebugClassLoader.php b/src/Symfony/Component/Debug/DebugClassLoader.php
index 94179f25a5..ff9a8d72f9 100644
--- a/src/Symfony/Component/Debug/DebugClassLoader.php
+++ b/src/Symfony/Component/Debug/DebugClassLoader.php
@@ -86,7 +86,7 @@ class DebugClassLoader
     public static function enable()
     {
         // Ensures we don't hit https://bugs.php.net/42098
-        class_exists('Symfony\Component\ErrorCatcher\ErrorHandler');
+        class_exists('Symfony\Component\Debug\ErrorHandler');
         class_exists('Psr\Log\LogLevel');
 
         if (!\is_array($functions = spl_autoload_functions())) {
diff --git a/src/Symfony/Component/Debug/ErrorHandler.php b/src/Symfony/Component/Debug/ErrorHandler.php
index 68c90c253d..a99a000b07 100644
--- a/src/Symfony/Component/Debug/ErrorHandler.php
+++ b/src/Symfony/Component/Debug/ErrorHandler.php
@@ -11,13 +11,705 @@
 
 namespace Symfony\Component\Debug;
 
-use Symfony\Component\ErrorCatcher\ErrorHandler as BaseErrorHandler;
-
-@trigger_error(sprintf('The "%s" class is deprecated since Symfony 4.4, use "%s" instead.', ErrorHandler::class, BaseErrorHandler::class), E_USER_DEPRECATED);
+use Psr\Log\LoggerInterface;
+use Psr\Log\LogLevel;
+use Symfony\Component\Debug\Exception\FatalErrorException;
+use Symfony\Component\Debug\Exception\FatalThrowableError;
+use Symfony\Component\Debug\Exception\FlattenException;
+use Symfony\Component\Debug\Exception\OutOfMemoryException;
+use Symfony\Component\Debug\Exception\SilencedErrorContext;
+use Symfony\Component\Debug\FatalErrorHandler\ClassNotFoundFatalErrorHandler;
+use Symfony\Component\Debug\FatalErrorHandler\FatalErrorHandlerInterface;
+use Symfony\Component\Debug\FatalErrorHandler\UndefinedFunctionFatalErrorHandler;
+use Symfony\Component\Debug\FatalErrorHandler\UndefinedMethodFatalErrorHandler;
 
 /**
- * @deprecated since Symfony 4.4, use Symfony\Component\ErrorCatcher\ErrorHandler instead.
+ * A generic ErrorHandler for the PHP engine.
+ *
+ * Provides five bit fields that control how errors are handled:
+ * - thrownErrors: errors thrown as \ErrorException
+ * - loggedErrors: logged errors, when not @-silenced
+ * - scopedErrors: errors thrown or logged with their local context
+ * - tracedErrors: errors logged with their stack trace
+ * - screamedErrors: never @-silenced errors
+ *
+ * Each error level can be logged by a dedicated PSR-3 logger object.
+ * Screaming only applies to logging.
+ * Throwing takes precedence over logging.
+ * Uncaught exceptions are logged as E_ERROR.
+ * E_DEPRECATED and E_USER_DEPRECATED levels never throw.
+ * E_RECOVERABLE_ERROR and E_USER_ERROR levels always throw.
+ * Non catchable errors that can be detected at shutdown time are logged when the scream bit field allows so.
+ * As errors have a performance cost, repeated errors are all logged, so that the developer
+ * can see them and weight them as more important to fix than others of the same level.
+ *
+ * @author Nicolas Grekas <p@tchwork.com>
+ * @author Grégoire Pineau <lyrixx@lyrixx.info>
+ *
+ * @final since Symfony 4.3
  */
-class ErrorHandler extends BaseErrorHandler
+class ErrorHandler
 {
+    private $levels = [
+        E_DEPRECATED => 'Deprecated',
+        E_USER_DEPRECATED => 'User Deprecated',
+        E_NOTICE => 'Notice',
+        E_USER_NOTICE => 'User Notice',
+        E_STRICT => 'Runtime Notice',
+        E_WARNING => 'Warning',
+        E_USER_WARNING => 'User Warning',
+        E_COMPILE_WARNING => 'Compile Warning',
+        E_CORE_WARNING => 'Core Warning',
+        E_USER_ERROR => 'User Error',
+        E_RECOVERABLE_ERROR => 'Catchable Fatal Error',
+        E_COMPILE_ERROR => 'Compile Error',
+        E_PARSE => 'Parse Error',
+        E_ERROR => 'Error',
+        E_CORE_ERROR => 'Core Error',
+    ];
+
+    private $loggers = [
+        E_DEPRECATED => [null, LogLevel::INFO],
+        E_USER_DEPRECATED => [null, LogLevel::INFO],
+        E_NOTICE => [null, LogLevel::WARNING],
+        E_USER_NOTICE => [null, LogLevel::WARNING],
+        E_STRICT => [null, LogLevel::WARNING],
+        E_WARNING => [null, LogLevel::WARNING],
+        E_USER_WARNING => [null, LogLevel::WARNING],
+        E_COMPILE_WARNING => [null, LogLevel::WARNING],
+        E_CORE_WARNING => [null, LogLevel::WARNING],
+        E_USER_ERROR => [null, LogLevel::CRITICAL],
+        E_RECOVERABLE_ERROR => [null, LogLevel::CRITICAL],
+        E_COMPILE_ERROR => [null, LogLevel::CRITICAL],
+        E_PARSE => [null, LogLevel::CRITICAL],
+        E_ERROR => [null, LogLevel::CRITICAL],
+        E_CORE_ERROR => [null, LogLevel::CRITICAL],
+    ];
+
+    private $thrownErrors = 0x1FFF; // E_ALL - E_DEPRECATED - E_USER_DEPRECATED
+    private $scopedErrors = 0x1FFF; // E_ALL - E_DEPRECATED - E_USER_DEPRECATED
+    private $tracedErrors = 0x77FB; // E_ALL - E_STRICT - E_PARSE
+    private $screamedErrors = 0x55; // E_ERROR + E_CORE_ERROR + E_COMPILE_ERROR + E_PARSE
+    private $loggedErrors = 0;
+    private $traceReflector;
+
+    private $isRecursive = 0;
+    private $isRoot = false;
+    private $exceptionHandler;
+    private $bootstrappingLogger;
+
+    private static $reservedMemory;
+    private static $toStringException = null;
+    private static $silencedErrorCache = [];
+    private static $silencedErrorCount = 0;
+    private static $exitCode = 0;
+
+    /**
+     * Registers the error handler.
+     *
+     * @param self|null $handler The handler to register
+     * @param bool      $replace Whether to replace or not any existing handler
+     *
+     * @return self The registered error handler
+     */
+    public static function register(self $handler = null, $replace = true)
+    {
+        if (null === self::$reservedMemory) {
+            self::$reservedMemory = str_repeat('x', 10240);
+            register_shutdown_function(__CLASS__.'::handleFatalError');
+        }
+
+        if ($handlerIsNew = null === $handler) {
+            $handler = new static();
+        }
+
+        if (null === $prev = set_error_handler([$handler, 'handleError'])) {
+            restore_error_handler();
+            // Specifying the error types earlier would expose us to https://bugs.php.net/63206
+            set_error_handler([$handler, 'handleError'], $handler->thrownErrors | $handler->loggedErrors);
+            $handler->isRoot = true;
+        }
+
+        if ($handlerIsNew && \is_array($prev) && $prev[0] instanceof self) {
+            $handler = $prev[0];
+            $replace = false;
+        }
+        if (!$replace && $prev) {
+            restore_error_handler();
+            $handlerIsRegistered = \is_array($prev) && $handler === $prev[0];
+        } else {
+            $handlerIsRegistered = true;
+        }
+        if (\is_array($prev = set_exception_handler([$handler, 'handleException'])) && $prev[0] instanceof self) {
+            restore_exception_handler();
+            if (!$handlerIsRegistered) {
+                $handler = $prev[0];
+            } elseif ($handler !== $prev[0] && $replace) {
+                set_exception_handler([$handler, 'handleException']);
+                $p = $prev[0]->setExceptionHandler(null);
+                $handler->setExceptionHandler($p);
+                $prev[0]->setExceptionHandler($p);
+            }
+        } else {
+            $handler->setExceptionHandler($prev);
+        }
+
+        $handler->throwAt(E_ALL & $handler->thrownErrors, true);
+
+        return $handler;
+    }
+
+    public function __construct(BufferingLogger $bootstrappingLogger = null)
+    {
+        if ($bootstrappingLogger) {
+            $this->bootstrappingLogger = $bootstrappingLogger;
+            $this->setDefaultLogger($bootstrappingLogger);
+        }
+        $this->traceReflector = new \ReflectionProperty('Exception', 'trace');
+        $this->traceReflector->setAccessible(true);
+    }
+
+    /**
+     * Sets a logger to non assigned errors levels.
+     *
+     * @param LoggerInterface $logger  A PSR-3 logger to put as default for the given levels
+     * @param array|int       $levels  An array map of E_* to LogLevel::* or an integer bit field of E_* constants
+     * @param bool            $replace Whether to replace or not any existing logger
+     */
+    public function setDefaultLogger(LoggerInterface $logger, $levels = E_ALL, $replace = false)
+    {
+        $loggers = [];
+
+        if (\is_array($levels)) {
+            foreach ($levels as $type => $logLevel) {
+                if (empty($this->loggers[$type][0]) || $replace || $this->loggers[$type][0] === $this->bootstrappingLogger) {
+                    $loggers[$type] = [$logger, $logLevel];
+                }
+            }
+        } else {
+            if (null === $levels) {
+                $levels = E_ALL;
+            }
+            foreach ($this->loggers as $type => $log) {
+                if (($type & $levels) && (empty($log[0]) || $replace || $log[0] === $this->bootstrappingLogger)) {
+                    $log[0] = $logger;
+                    $loggers[$type] = $log;
+                }
+            }
+        }
+
+        $this->setLoggers($loggers);
+    }
+
+    /**
+     * Sets a logger for each error level.
+     *
+     * @param array $loggers Error levels to [LoggerInterface|null, LogLevel::*] map
+     *
+     * @return array The previous map
+     *
+     * @throws \InvalidArgumentException
+     */
+    public function setLoggers(array $loggers)
+    {
+        $prevLogged = $this->loggedErrors;
+        $prev = $this->loggers;
+        $flush = [];
+
+        foreach ($loggers as $type => $log) {
+            if (!isset($prev[$type])) {
+                throw new \InvalidArgumentException('Unknown error type: '.$type);
+            }
+            if (!\is_array($log)) {
+                $log = [$log];
+            } elseif (!\array_key_exists(0, $log)) {
+                throw new \InvalidArgumentException('No logger provided');
+            }
+            if (null === $log[0]) {
+                $this->loggedErrors &= ~$type;
+            } elseif ($log[0] instanceof LoggerInterface) {
+                $this->loggedErrors |= $type;
+            } else {
+                throw new \InvalidArgumentException('Invalid logger provided');
+            }
+            $this->loggers[$type] = $log + $prev[$type];
+
+            if ($this->bootstrappingLogger && $prev[$type][0] === $this->bootstrappingLogger) {
+                $flush[$type] = $type;
+            }
+        }
+        $this->reRegister($prevLogged | $this->thrownErrors);
+
+        if ($flush) {
+            foreach ($this->bootstrappingLogger->cleanLogs() as $log) {
+                $type = $log[2]['exception'] instanceof \ErrorException ? $log[2]['exception']->getSeverity() : E_ERROR;
+                if (!isset($flush[$type])) {
+                    $this->bootstrappingLogger->log($log[0], $log[1], $log[2]);
+                } elseif ($this->loggers[$type][0]) {
+                    $this->loggers[$type][0]->log($this->loggers[$type][1], $log[1], $log[2]);
+                }
+            }
+        }
+
+        return $prev;
+    }
+
+    /**
+     * Sets a user exception handler.
+     *
+     * @param callable $handler A handler that will be called on Exception
+     *
+     * @return callable|null The previous exception handler
+     */
+    public function setExceptionHandler(callable $handler = null)
+    {
+        $prev = $this->exceptionHandler;
+        $this->exceptionHandler = $handler;
+
+        return $prev;
+    }
+
+    /**
+     * Sets the PHP error levels that throw an exception when a PHP error occurs.
+     *
+     * @param int  $levels  A bit field of E_* constants for thrown errors
+     * @param bool $replace Replace or amend the previous value
+     *
+     * @return int The previous value
+     */
+    public function throwAt($levels, $replace = false)
+    {
+        $prev = $this->thrownErrors;
+        $this->thrownErrors = ($levels | E_RECOVERABLE_ERROR | E_USER_ERROR) & ~E_USER_DEPRECATED & ~E_DEPRECATED;
+        if (!$replace) {
+            $this->thrownErrors |= $prev;
+        }
+        $this->reRegister($prev | $this->loggedErrors);
+
+        return $prev;
+    }
+
+    /**
+     * Sets the PHP error levels for which local variables are preserved.
+     *
+     * @param int  $levels  A bit field of E_* constants for scoped errors
+     * @param bool $replace Replace or amend the previous value
+     *
+     * @return int The previous value
+     */
+    public function scopeAt($levels, $replace = false)
+    {
+        $prev = $this->scopedErrors;
+        $this->scopedErrors = (int) $levels;
+        if (!$replace) {
+            $this->scopedErrors |= $prev;
+        }
+
+        return $prev;
+    }
+
+    /**
+     * Sets the PHP error levels for which the stack trace is preserved.
+     *
+     * @param int  $levels  A bit field of E_* constants for traced errors
+     * @param bool $replace Replace or amend the previous value
+     *
+     * @return int The previous value
+     */
+    public function traceAt($levels, $replace = false)
+    {
+        $prev = $this->tracedErrors;
+        $this->tracedErrors = (int) $levels;
+        if (!$replace) {
+            $this->tracedErrors |= $prev;
+        }
+
+        return $prev;
+    }
+
+    /**
+     * Sets the error levels where the @-operator is ignored.
+     *
+     * @param int  $levels  A bit field of E_* constants for screamed errors
+     * @param bool $replace Replace or amend the previous value
+     *
+     * @return int The previous value
+     */
+    public function screamAt($levels, $replace = false)
+    {
+        $prev = $this->screamedErrors;
+        $this->screamedErrors = (int) $levels;
+        if (!$replace) {
+            $this->screamedErrors |= $prev;
+        }
+
+        return $prev;
+    }
+
+    /**
+     * Re-registers as a PHP error handler if levels changed.
+     */
+    private function reRegister($prev)
+    {
+        if ($prev !== $this->thrownErrors | $this->loggedErrors) {
+            $handler = set_error_handler('var_dump');
+            $handler = \is_array($handler) ? $handler[0] : null;
+            restore_error_handler();
+            if ($handler === $this) {
+                restore_error_handler();
+                if ($this->isRoot) {
+                    set_error_handler([$this, 'handleError'], $this->thrownErrors | $this->loggedErrors);
+                } else {
+                    set_error_handler([$this, 'handleError']);
+                }
+            }
+        }
+    }
+
+    /**
+     * Handles errors by filtering then logging them according to the configured bit fields.
+     *
+     * @param int    $type    One of the E_* constants
+     * @param string $message
+     * @param string $file
+     * @param int    $line
+     *
+     * @return bool Returns false when no handling happens so that the PHP engine can handle the error itself
+     *
+     * @throws \ErrorException When $this->thrownErrors requests so
+     *
+     * @internal
+     */
+    public function handleError($type, $message, $file, $line)
+    {
+        // @deprecated to be removed in Symfony 5.0
+        if (\PHP_VERSION_ID >= 70300 && $message && '"' === $message[0] && 0 === strpos($message, '"continue') && preg_match('/^"continue(?: \d++)?" targeting switch is equivalent to "break(?: \d++)?"\. Did you mean to use "continue(?: \d++)?"\?$/', $message)) {
+            $type = E_DEPRECATED;
+        }
+
+        // Level is the current error reporting level to manage silent error.
+        $level = error_reporting();
+        $silenced = 0 === ($level & $type);
+        // Strong errors are not authorized to be silenced.
+        $level |= E_RECOVERABLE_ERROR | E_USER_ERROR | E_DEPRECATED | E_USER_DEPRECATED;
+        $log = $this->loggedErrors & $type;
+        $throw = $this->thrownErrors & $type & $level;
+        $type &= $level | $this->screamedErrors;
+
+        if (!$type || (!$log && !$throw)) {
+            return !$silenced && $type && $log;
+        }
+        $scope = $this->scopedErrors & $type;
+
+        if (4 < $numArgs = \func_num_args()) {
+            $context = $scope ? (func_get_arg(4) ?: []) : [];
+        } else {
+            $context = [];
+        }
+
+        if (isset($context['GLOBALS']) && $scope) {
+            $e = $context;                  // Whatever the signature of the method,
+            unset($e['GLOBALS'], $context); // $context is always a reference in 5.3
+            $context = $e;
+        }
+
+        if (false !== strpos($message, "class@anonymous\0")) {
+            $logMessage = $this->levels[$type].': '.(new FlattenException())->setMessage($message)->getMessage();
+        } else {
+            $logMessage = $this->levels[$type].': '.$message;
+        }
+
+        if (null !== self::$toStringException) {
+            $errorAsException = self::$toStringException;
+            self::$toStringException = null;
+        } elseif (!$throw && !($type & $level)) {
+            if (!isset(self::$silencedErrorCache[$id = $file.':'.$line])) {
+                $lightTrace = $this->tracedErrors & $type ? $this->cleanTrace(debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS, 5), $type, $file, $line, false) : [];
+                $errorAsException = new SilencedErrorContext($type, $file, $line, isset($lightTrace[1]) ? [$lightTrace[0]] : $lightTrace);
+            } elseif (isset(self::$silencedErrorCache[$id][$message])) {
+                $lightTrace = null;
+                $errorAsException = self::$silencedErrorCache[$id][$message];
+                ++$errorAsException->count;
+            } else {
+                $lightTrace = [];
+                $errorAsException = null;
+            }
+
+            if (100 < ++self::$silencedErrorCount) {
+                self::$silencedErrorCache = $lightTrace = [];
+                self::$silencedErrorCount = 1;
+            }
+            if ($errorAsException) {
+                self::$silencedErrorCache[$id][$message] = $errorAsException;
+            }
+            if (null === $lightTrace) {
+                return;
+            }
+        } else {
+            $errorAsException = new \ErrorException($logMessage, 0, $type, $file, $line);
+
+            if ($throw || $this->tracedErrors & $type) {
+                $backtrace = $errorAsException->getTrace();
+                $lightTrace = $this->cleanTrace($backtrace, $type, $file, $line, $throw);
+                $this->traceReflector->setValue($errorAsException, $lightTrace);
+            } else {
+                $this->traceReflector->setValue($errorAsException, []);
+                $backtrace = [];
+            }
+        }
+
+        if ($throw) {
+            if (E_USER_ERROR & $type) {
+                for ($i = 1; isset($backtrace[$i]); ++$i) {
+                    if (isset($backtrace[$i]['function'], $backtrace[$i]['type'], $backtrace[$i - 1]['function'])
+                        && '__toString' === $backtrace[$i]['function']
+                        && '->' === $backtrace[$i]['type']
+                        && !isset($backtrace[$i - 1]['class'])
+                        && ('trigger_error' === $backtrace[$i - 1]['function'] || 'user_error' === $backtrace[$i - 1]['function'])
+                    ) {
+                        // Here, we know trigger_error() has been called from __toString().
+                        // PHP triggers a fatal error when throwing from __toString().
+                        // A small convention allows working around the limitation:
+                        // given a caught $e exception in __toString(), quitting the method with
+                        // `return trigger_error($e, E_USER_ERROR);` allows this error handler
+                        // to make $e get through the __toString() barrier.
+
+                        foreach ($context as $e) {
+                            if ($e instanceof \Throwable && $e->__toString() === $message) {
+                                self::$toStringException = $e;
+
+                                return true;
+                            }
+                        }
+
+                        // Display the original error message instead of the default one.
+                        $this->handleException($errorAsException);
+
+                        // Stop the process by giving back the error to the native handler.
+                        return false;
+                    }
+                }
+            }
+
+            throw $errorAsException;
+        }
+
+        if ($this->isRecursive) {
+            $log = 0;
+        } else {
+            if (!\defined('HHVM_VERSION')) {
+                $currentErrorHandler = set_error_handler('var_dump');
+                restore_error_handler();
+            }
+
+            try {
+                $this->isRecursive = true;
+                $level = ($type & $level) ? $this->loggers[$type][1] : LogLevel::DEBUG;
+                $this->loggers[$type][0]->log($level, $logMessage, $errorAsException ? ['exception' => $errorAsException] : []);
+            } finally {
+                $this->isRecursive = false;
+
+                if (!\defined('HHVM_VERSION')) {
+                    set_error_handler($currentErrorHandler);
+                }
+            }
+        }
+
+        return !$silenced && $type && $log;
+    }
+
+    /**
+     * Handles an exception by logging then forwarding it to another handler.
+     *
+     * @param \Exception|\Throwable $exception An exception to handle
+     * @param array                 $error     An array as returned by error_get_last()
+     *
+     * @internal
+     */
+    public function handleException($exception, array $error = null)
+    {
+        if (null === $error) {
+            self::$exitCode = 255;
+        }
+        if (!$exception instanceof \Exception) {
+            $exception = new FatalThrowableError($exception);
+        }
+        $type = $exception instanceof FatalErrorException ? $exception->getSeverity() : E_ERROR;
+        $handlerException = null;
+
+        if (($this->loggedErrors & $type) || $exception instanceof FatalThrowableError) {
+            if (false !== strpos($message = $exception->getMessage(), "class@anonymous\0")) {
+                $message = (new FlattenException())->setMessage($message)->getMessage();
+            }
+            if ($exception instanceof FatalErrorException) {
+                if ($exception instanceof FatalThrowableError) {
+                    $error = [
+                        'type' => $type,
+                        'message' => $message,
+                        'file' => $exception->getFile(),
+                        'line' => $exception->getLine(),
+                    ];
+                } else {
+                    $message = 'Fatal '.$message;
+                }
+            } elseif ($exception instanceof \ErrorException) {
+                $message = 'Uncaught '.$message;
+            } else {
+                $message = 'Uncaught Exception: '.$message;
+            }
+        }
+        if ($this->loggedErrors & $type) {
+            try {
+                $this->loggers[$type][0]->log($this->loggers[$type][1], $message, ['exception' => $exception]);
+            } catch (\Throwable $handlerException) {
+            }
+        }
+        if ($exception instanceof FatalErrorException && !$exception instanceof OutOfMemoryException && $error) {
+            foreach ($this->getFatalErrorHandlers() as $handler) {
+                if ($e = $handler->handleError($error, $exception)) {
+                    $exception = $e;
+                    break;
+                }
+            }
+        }
+        $exceptionHandler = $this->exceptionHandler;
+        $this->exceptionHandler = null;
+        try {
+            if (null !== $exceptionHandler) {
+                return $exceptionHandler($exception);
+            }
+            $handlerException = $handlerException ?: $exception;
+        } catch (\Throwable $handlerException) {
+        }
+        if ($exception === $handlerException) {
+            self::$reservedMemory = null; // Disable the fatal error handler
+            throw $exception; // Give back $exception to the native handler
+        }
+        $this->handleException($handlerException);
+    }
+
+    /**
+     * Shutdown registered function for handling PHP fatal errors.
+     *
+     * @param array $error An array as returned by error_get_last()
+     *
+     * @internal
+     */
+    public static function handleFatalError(array $error = null)
+    {
+        if (null === self::$reservedMemory) {
+            return;
+        }
+
+        $handler = self::$reservedMemory = null;
+        $handlers = [];
+        $previousHandler = null;
+        $sameHandlerLimit = 10;
+
+        while (!\is_array($handler) || !$handler[0] instanceof self) {
+            $handler = set_exception_handler('var_dump');
+            restore_exception_handler();
+
+            if (!$handler) {
+                break;
+            }
+            restore_exception_handler();
+
+            if ($handler !== $previousHandler) {
+                array_unshift($handlers, $handler);
+                $previousHandler = $handler;
+            } elseif (0 === --$sameHandlerLimit) {
+                $handler = null;
+                break;
+            }
+        }
+        foreach ($handlers as $h) {
+            set_exception_handler($h);
+        }
+        if (!$handler) {
+            return;
+        }
+        if ($handler !== $h) {
+            $handler[0]->setExceptionHandler($h);
+        }
+        $handler = $handler[0];
+        $handlers = [];
+
+        if ($exit = null === $error) {
+            $error = error_get_last();
+        }
+
+        if ($error && $error['type'] &= E_PARSE | E_ERROR | E_CORE_ERROR | E_COMPILE_ERROR) {
+            // Let's not throw anymore but keep logging
+            $handler->throwAt(0, true);
+            $trace = isset($error['backtrace']) ? $error['backtrace'] : null;
+
+            if (0 === strpos($error['message'], 'Allowed memory') || 0 === strpos($error['message'], 'Out of memory')) {
+                $exception = new OutOfMemoryException($handler->levels[$error['type']].': '.$error['message'], 0, $error['type'], $error['file'], $error['line'], 2, false, $trace);
+            } else {
+                $exception = new FatalErrorException($handler->levels[$error['type']].': '.$error['message'], 0, $error['type'], $error['file'], $error['line'], 2, true, $trace);
+            }
+        } else {
+            $exception = null;
+        }
+
+        try {
+            if (null !== $exception) {
+                self::$exitCode = 255;
+                $handler->handleException($exception, $error);
+            }
+        } catch (FatalErrorException $e) {
+            // Ignore this re-throw
+        }
+
+        if ($exit && self::$exitCode) {
+            $exitCode = self::$exitCode;
+            register_shutdown_function('register_shutdown_function', function () use ($exitCode) { exit($exitCode); });
+        }
+    }
+
+    /**
+     * Gets the fatal error handlers.
+     *
+     * Override this method if you want to define more fatal error handlers.
+     *
+     * @return FatalErrorHandlerInterface[] An array of FatalErrorHandlerInterface
+     */
+    protected function getFatalErrorHandlers()
+    {
+        return [
+            new UndefinedFunctionFatalErrorHandler(),
+            new UndefinedMethodFatalErrorHandler(),
+            new ClassNotFoundFatalErrorHandler(),
+        ];
+    }
+
+    /**
+     * Cleans the trace by removing function arguments and the frames added by the error handler and DebugClassLoader.
+     */
+    private function cleanTrace($backtrace, $type, $file, $line, $throw)
+    {
+        $lightTrace = $backtrace;
+
+        for ($i = 0; isset($backtrace[$i]); ++$i) {
+            if (isset($backtrace[$i]['file'], $backtrace[$i]['line']) && $backtrace[$i]['line'] === $line && $backtrace[$i]['file'] === $file) {
+                $lightTrace = \array_slice($lightTrace, 1 + $i);
+                break;
+            }
+        }
+        if (class_exists(DebugClassLoader::class, false)) {
+            for ($i = \count($lightTrace) - 2; 0 < $i; --$i) {
+                if (DebugClassLoader::class === ($lightTrace[$i]['class'] ?? null)) {
+                    array_splice($lightTrace, --$i, 2);
+                }
+            }
+        }
+        if (!($throw || $this->scopedErrors & $type)) {
+            for ($i = 0; isset($lightTrace[$i]); ++$i) {
+                unset($lightTrace[$i]['args'], $lightTrace[$i]['object']);
+            }
+        }
+
+        return $lightTrace;
+    }
 }
diff --git a/src/Symfony/Component/Debug/Exception/ClassNotFoundException.php b/src/Symfony/Component/Debug/Exception/ClassNotFoundException.php
index 4b42cc61e4..fa98c4975d 100644
--- a/src/Symfony/Component/Debug/Exception/ClassNotFoundException.php
+++ b/src/Symfony/Component/Debug/Exception/ClassNotFoundException.php
@@ -11,13 +11,26 @@
 
 namespace Symfony\Component\Debug\Exception;
 
-use Symfony\Component\ErrorCatcher\Exception\ClassNotFoundException as BaseClassNotFoundException;
-
-@trigger_error(sprintf('The "%s" class is deprecated since Symfony 4.4, use "%s" instead.', ClassNotFoundException::class, BaseClassNotFoundException::class), E_USER_DEPRECATED);
-
 /**
- * @deprecated since Symfony 4.4, use Symfony\Component\ErrorCatcher\Exception\ClassNotFoundException instead.
+ * Class (or Trait or Interface) Not Found Exception.
+ *
+ * @author Konstanton Myakshin <koc-dp@yandex.ru>
  */
-class ClassNotFoundException extends BaseClassNotFoundException
+class ClassNotFoundException extends FatalErrorException
 {
+    public function __construct(string $message, \ErrorException $previous)
+    {
+        parent::__construct(
+            $message,
+            $previous->getCode(),
+            $previous->getSeverity(),
+            $previous->getFile(),
+            $previous->getLine(),
+            null,
+            true,
+            null,
+            $previous->getPrevious()
+        );
+        $this->setTrace($previous->getTrace());
+    }
 }
diff --git a/src/Symfony/Component/Debug/Exception/FatalErrorException.php b/src/Symfony/Component/Debug/Exception/FatalErrorException.php
index 09a156ad7a..93880fbc32 100644
--- a/src/Symfony/Component/Debug/Exception/FatalErrorException.php
+++ b/src/Symfony/Component/Debug/Exception/FatalErrorException.php
@@ -11,13 +11,67 @@
 
 namespace Symfony\Component\Debug\Exception;
 
-use Symfony\Component\ErrorCatcher\Exception\FatalErrorException as BaseFatalErrorException;
-
-@trigger_error(sprintf('The "%s" class is deprecated since Symfony 4.4, use "%s" instead.', FatalErrorException::class, BaseFatalErrorException::class), E_USER_DEPRECATED);
-
 /**
- * @deprecated since Symfony 4.4, use Symfony\Component\ErrorCatcher\Exception\FatalErrorException instead.
+ * Fatal Error Exception.
+ *
+ * @author Konstanton Myakshin <koc-dp@yandex.ru>
  */
-class FatalErrorException extends BaseFatalErrorException
+class FatalErrorException extends \ErrorException
 {
+    public function __construct(string $message, int $code, int $severity, string $filename, int $lineno, int $traceOffset = null, bool $traceArgs = true, array $trace = null, \Throwable $previous = null)
+    {
+        parent::__construct($message, $code, $severity, $filename, $lineno, $previous);
+
+        if (null !== $trace) {
+            if (!$traceArgs) {
+                foreach ($trace as &$frame) {
+                    unset($frame['args'], $frame['this'], $frame);
+                }
+            }
+
+            $this->setTrace($trace);
+        } elseif (null !== $traceOffset) {
+            if (\function_exists('xdebug_get_function_stack')) {
+                $trace = xdebug_get_function_stack();
+                if (0 < $traceOffset) {
+                    array_splice($trace, -$traceOffset);
+                }
+
+                foreach ($trace as &$frame) {
+                    if (!isset($frame['type'])) {
+                        // XDebug pre 2.1.1 doesn't currently set the call type key http://bugs.xdebug.org/view.php?id=695
+                        if (isset($frame['class'])) {
+                            $frame['type'] = '::';
+                        }
+                    } elseif ('dynamic' === $frame['type']) {
+                        $frame['type'] = '->';
+                    } elseif ('static' === $frame['type']) {
+                        $frame['type'] = '::';
+                    }
+
+                    // XDebug also has a different name for the parameters array
+                    if (!$traceArgs) {
+                        unset($frame['params'], $frame['args']);
+                    } elseif (isset($frame['params']) && !isset($frame['args'])) {
+                        $frame['args'] = $frame['params'];
+                        unset($frame['params']);
+                    }
+                }
+
+                unset($frame);
+                $trace = array_reverse($trace);
+            } else {
+                $trace = [];
+            }
+
+            $this->setTrace($trace);
+        }
+    }
+
+    protected function setTrace($trace)
+    {
+        $traceReflector = new \ReflectionProperty('Exception', 'trace');
+        $traceReflector->setAccessible(true);
+        $traceReflector->setValue($this, $trace);
+    }
 }
diff --git a/src/Symfony/Component/Debug/Exception/FatalThrowableError.php b/src/Symfony/Component/Debug/Exception/FatalThrowableError.php
index 6046f1c7cb..cdafb2a568 100644
--- a/src/Symfony/Component/Debug/Exception/FatalThrowableError.php
+++ b/src/Symfony/Component/Debug/Exception/FatalThrowableError.php
@@ -11,13 +11,41 @@
 
 namespace Symfony\Component\Debug\Exception;
 
-use Symfony\Component\ErrorCatcher\Exception\FatalThrowableError as BaseFatalThrowableError;
-
-@trigger_error(sprintf('The "%s" class is deprecated since Symfony 4.4, use "%s" instead.', FatalThrowableError::class, BaseFatalThrowableError::class), E_USER_DEPRECATED);
-
 /**
- * @deprecated since Symfony 4.4, use Symfony\Component\ErrorCatcher\Exception\FatalThrowableError instead.
+ * Fatal Throwable Error.
+ *
+ * @author Nicolas Grekas <p@tchwork.com>
  */
-class FatalThrowableError extends BaseFatalThrowableError
+class FatalThrowableError extends FatalErrorException
 {
+    private $originalClassName;
+
+    public function __construct(\Throwable $e)
+    {
+        $this->originalClassName = \get_class($e);
+
+        if ($e instanceof \ParseError) {
+            $severity = E_PARSE;
+        } elseif ($e instanceof \TypeError) {
+            $severity = E_RECOVERABLE_ERROR;
+        } else {
+            $severity = E_ERROR;
+        }
+
+        \ErrorException::__construct(
+            $e->getMessage(),
+            $e->getCode(),
+            $severity,
+            $e->getFile(),
+            $e->getLine(),
+            $e->getPrevious()
+        );
+
+        $this->setTrace($e->getTrace());
+    }
+
+    public function getOriginalClassName(): string
+    {
+        return $this->originalClassName;
+    }
 }
diff --git a/src/Symfony/Component/Debug/Exception/FlattenException.php b/src/Symfony/Component/Debug/Exception/FlattenException.php
index 748e2c6011..8dda8f7223 100644
--- a/src/Symfony/Component/Debug/Exception/FlattenException.php
+++ b/src/Symfony/Component/Debug/Exception/FlattenException.php
@@ -11,22 +11,358 @@
 
 namespace Symfony\Component\Debug\Exception;
 
-use Symfony\Component\ErrorCatcher\Exception\FlattenException as BaseFlattenException;
+use Symfony\Component\HttpFoundation\Exception\RequestExceptionInterface;
+use Symfony\Component\HttpKernel\Exception\HttpExceptionInterface;
 
-@trigger_error(sprintf('The "%s" class is deprecated since Symfony 4.4, use "%s" instead.', FlattenException::class, BaseFlattenException::class), E_USER_DEPRECATED);
+@trigger_error(sprintf('The "%s" class is deprecated since Symfony 4.4, use "Symfony\Component\ErrorCatcher\Exception\FlattenException" instead.', FlattenException::class), E_USER_DEPRECATED);
 
 /**
+ * FlattenException wraps a PHP Error or Exception to be able to serialize it.
+ *
+ * Basically, this class removes all objects from the trace.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ *
  * @deprecated since Symfony 4.4, use Symfony\Component\ErrorCatcher\Exception\FlattenException instead.
  */
-class FlattenException extends BaseFlattenException
+class FlattenException
 {
-    /**
-     * @deprecated since Symfony 4.4, use Symfony\Component\ErrorHandler\Exception::createFromThrowable() instead.
-     */
-    public static function create(\Exception $exception, $statusCode = null, array $headers = []): self
-    {
-        @trigger_error(sprintf('The "%s()" method is deprecated since Symfony 4.4, use Symfony\Component\ErrorHandler\Exception::createFromThrowable() instead.', __METHOD__), E_USER_DEPRECATED);
+    private $message;
+    private $code;
+    private $previous;
+    private $trace;
+    private $traceAsString;
+    private $class;
+    private $statusCode;
+    private $headers;
+    private $file;
+    private $line;
 
-        return parent::createFromThrowable($exception, $statusCode, $headers);
+    /**
+     * @deprecated since Symfony 4.4, use Symfony\Component\ErrorCatcher\Exception::createFromThrowable() instead.
+     */
+    public static function create(\Exception $exception, $statusCode = null, array $headers = [])
+    {
+        @trigger_error(sprintf('The "%s()" method is deprecated since Symfony 4.4, use Symfony\Component\ErrorCatcher\Exception::createFromThrowable() instead.', __METHOD__), E_USER_DEPRECATED);
+
+        return static::createFromThrowable($exception, $statusCode, $headers);
+    }
+
+    public static function createFromThrowable(\Throwable $exception, int $statusCode = null, array $headers = []): self
+    {
+        $e = new static();
+        $e->setMessage($exception->getMessage());
+        $e->setCode($exception->getCode());
+
+        if ($exception instanceof HttpExceptionInterface) {
+            $statusCode = $exception->getStatusCode();
+            $headers = array_merge($headers, $exception->getHeaders());
+        } elseif ($exception instanceof RequestExceptionInterface) {
+            $statusCode = 400;
+        }
+
+        if (null === $statusCode) {
+            $statusCode = 500;
+        }
+
+        $e->setStatusCode($statusCode);
+        $e->setHeaders($headers);
+        $e->setTraceFromThrowable($exception);
+        $e->setClass($exception instanceof FatalThrowableError ? $exception->getOriginalClassName() : \get_class($exception));
+        $e->setFile($exception->getFile());
+        $e->setLine($exception->getLine());
+
+        $previous = $exception->getPrevious();
+
+        if ($previous instanceof \Throwable) {
+            $e->setPrevious(static::createFromThrowable($previous));
+        }
+
+        return $e;
+    }
+
+    public function toArray()
+    {
+        $exceptions = [];
+        foreach (array_merge([$this], $this->getAllPrevious()) as $exception) {
+            $exceptions[] = [
+                'message' => $exception->getMessage(),
+                'class' => $exception->getClass(),
+                'trace' => $exception->getTrace(),
+            ];
+        }
+
+        return $exceptions;
+    }
+
+    public function getStatusCode()
+    {
+        return $this->statusCode;
+    }
+
+    /**
+     * @return $this
+     */
+    public function setStatusCode($code)
+    {
+        $this->statusCode = $code;
+
+        return $this;
+    }
+
+    public function getHeaders()
+    {
+        return $this->headers;
+    }
+
+    /**
+     * @return $this
+     */
+    public function setHeaders(array $headers)
+    {
+        $this->headers = $headers;
+
+        return $this;
+    }
+
+    public function getClass()
+    {
+        return $this->class;
+    }
+
+    /**
+     * @return $this
+     */
+    public function setClass($class)
+    {
+        $this->class = 'c' === $class[0] && 0 === strpos($class, "class@anonymous\0") ? get_parent_class($class).'@anonymous' : $class;
+
+        return $this;
+    }
+
+    public function getFile()
+    {
+        return $this->file;
+    }
+
+    /**
+     * @return $this
+     */
+    public function setFile($file)
+    {
+        $this->file = $file;
+
+        return $this;
+    }
+
+    public function getLine()
+    {
+        return $this->line;
+    }
+
+    /**
+     * @return $this
+     */
+    public function setLine($line)
+    {
+        $this->line = $line;
+
+        return $this;
+    }
+
+    public function getMessage()
+    {
+        return $this->message;
+    }
+
+    /**
+     * @return $this
+     */
+    public function setMessage($message)
+    {
+        if (false !== strpos($message, "class@anonymous\0")) {
+            $message = preg_replace_callback('/class@anonymous\x00.*?\.php0x?[0-9a-fA-F]++/', function ($m) {
+                return class_exists($m[0], false) ? get_parent_class($m[0]).'@anonymous' : $m[0];
+            }, $message);
+        }
+
+        $this->message = $message;
+
+        return $this;
+    }
+
+    public function getCode()
+    {
+        return $this->code;
+    }
+
+    /**
+     * @return $this
+     */
+    public function setCode($code)
+    {
+        $this->code = $code;
+
+        return $this;
+    }
+
+    public function getPrevious()
+    {
+        return $this->previous;
+    }
+
+    /**
+     * @return $this
+     */
+    public function setPrevious(self $previous)
+    {
+        $this->previous = $previous;
+
+        return $this;
+    }
+
+    public function getAllPrevious()
+    {
+        $exceptions = [];
+        $e = $this;
+        while ($e = $e->getPrevious()) {
+            $exceptions[] = $e;
+        }
+
+        return $exceptions;
+    }
+
+    public function getTrace()
+    {
+        return $this->trace;
+    }
+
+    /**
+     * @deprecated since 4.1, use {@see setTraceFromThrowable()} instead.
+     */
+    public function setTraceFromException(\Exception $exception)
+    {
+        @trigger_error(sprintf('The "%s()" method is deprecated since Symfony 4.1, use "setTraceFromThrowable()" instead.', __METHOD__), E_USER_DEPRECATED);
+
+        $this->setTraceFromThrowable($exception);
+    }
+
+    public function setTraceFromThrowable(\Throwable $throwable)
+    {
+        $this->traceAsString = $throwable->getTraceAsString();
+
+        return $this->setTrace($throwable->getTrace(), $throwable->getFile(), $throwable->getLine());
+    }
+
+    /**
+     * @return $this
+     */
+    public function setTrace($trace, $file, $line)
+    {
+        $this->trace = [];
+        $this->trace[] = [
+            'namespace' => '',
+            'short_class' => '',
+            'class' => '',
+            'type' => '',
+            'function' => '',
+            'file' => $file,
+            'line' => $line,
+            'args' => [],
+        ];
+        foreach ($trace as $entry) {
+            $class = '';
+            $namespace = '';
+            if (isset($entry['class'])) {
+                $parts = explode('\\', $entry['class']);
+                $class = array_pop($parts);
+                $namespace = implode('\\', $parts);
+            }
+
+            $this->trace[] = [
+                'namespace' => $namespace,
+                'short_class' => $class,
+                'class' => isset($entry['class']) ? $entry['class'] : '',
+                'type' => isset($entry['type']) ? $entry['type'] : '',
+                'function' => isset($entry['function']) ? $entry['function'] : null,
+                'file' => isset($entry['file']) ? $entry['file'] : null,
+                'line' => isset($entry['line']) ? $entry['line'] : null,
+                'args' => isset($entry['args']) ? $this->flattenArgs($entry['args']) : [],
+            ];
+        }
+
+        return $this;
+    }
+
+    private function flattenArgs($args, $level = 0, &$count = 0)
+    {
+        $result = [];
+        foreach ($args as $key => $value) {
+            if (++$count > 1e4) {
+                return ['array', '*SKIPPED over 10000 entries*'];
+            }
+            if ($value instanceof \__PHP_Incomplete_Class) {
+                // is_object() returns false on PHP<=7.1
+                $result[$key] = ['incomplete-object', $this->getClassNameFromIncomplete($value)];
+            } elseif (\is_object($value)) {
+                $result[$key] = ['object', \get_class($value)];
+            } elseif (\is_array($value)) {
+                if ($level > 10) {
+                    $result[$key] = ['array', '*DEEP NESTED ARRAY*'];
+                } else {
+                    $result[$key] = ['array', $this->flattenArgs($value, $level + 1, $count)];
+                }
+            } elseif (null === $value) {
+                $result[$key] = ['null', null];
+            } elseif (\is_bool($value)) {
+                $result[$key] = ['boolean', $value];
+            } elseif (\is_int($value)) {
+                $result[$key] = ['integer', $value];
+            } elseif (\is_float($value)) {
+                $result[$key] = ['float', $value];
+            } elseif (\is_resource($value)) {
+                $result[$key] = ['resource', get_resource_type($value)];
+            } else {
+                $result[$key] = ['string', (string) $value];
+            }
+        }
+
+        return $result;
+    }
+
+    private function getClassNameFromIncomplete(\__PHP_Incomplete_Class $value)
+    {
+        $array = new \ArrayObject($value);
+
+        return $array['__PHP_Incomplete_Class_Name'];
+    }
+
+    public function getTraceAsString()
+    {
+        return $this->traceAsString;
+    }
+
+    public function getAsString()
+    {
+        $message = '';
+        $next = false;
+
+        foreach (array_reverse(array_merge([$this], $this->getAllPrevious())) as $exception) {
+            if ($next) {
+                $message .= 'Next ';
+            } else {
+                $next = true;
+            }
+            $message .= $exception->getClass();
+
+            if ('' != $exception->getMessage()) {
+                $message .= ': '.$exception->getMessage();
+            }
+
+            $message .= ' in '.$exception->getFile().':'.$exception->getLine().
+                "\nStack trace:\n".$exception->getTraceAsString()."\n\n";
+        }
+
+        return rtrim($message);
     }
 }
diff --git a/src/Symfony/Component/Debug/Exception/OutOfMemoryException.php b/src/Symfony/Component/Debug/Exception/OutOfMemoryException.php
index 20eb185242..fec1979836 100644
--- a/src/Symfony/Component/Debug/Exception/OutOfMemoryException.php
+++ b/src/Symfony/Component/Debug/Exception/OutOfMemoryException.php
@@ -11,13 +11,11 @@
 
 namespace Symfony\Component\Debug\Exception;
 
-use Symfony\Component\ErrorCatcher\Exception\OutOfMemoryException as BaseOutOfMemoryException;
-
-@trigger_error(sprintf('The "%s" class is deprecated since Symfony 4.4, use "%s" instead.', OutOfMemoryException::class, BaseOutOfMemoryException::class), E_USER_DEPRECATED);
-
 /**
- * @deprecated since Symfony 4.4, use Symfony\Component\ErrorCatcher\Exception\OutOfMemoryException instead.
+ * Out of memory exception.
+ *
+ * @author Nicolas Grekas <p@tchwork.com>
  */
-class OutOfMemoryException extends BaseOutOfMemoryException
+class OutOfMemoryException extends FatalErrorException
 {
 }
diff --git a/src/Symfony/Component/Debug/Exception/SilencedErrorContext.php b/src/Symfony/Component/Debug/Exception/SilencedErrorContext.php
index 2b8ddc2bcb..236c56ed0e 100644
--- a/src/Symfony/Component/Debug/Exception/SilencedErrorContext.php
+++ b/src/Symfony/Component/Debug/Exception/SilencedErrorContext.php
@@ -11,13 +11,57 @@
 
 namespace Symfony\Component\Debug\Exception;
 
-use Symfony\Component\ErrorCatcher\Exception\SilencedErrorContext as BaseSilencedErrorContext;
-
-@trigger_error(sprintf('The "%s" class is deprecated since Symfony 4.4, use "%s" instead.', SilencedErrorContext::class, BaseSilencedErrorContext::class), E_USER_DEPRECATED);
-
 /**
- * @deprecated since Symfony 4.4, use Symfony\Component\ErrorCatcher\Exception\SilencedErrorContext instead.
+ * Data Object that represents a Silenced Error.
+ *
+ * @author Grégoire Pineau <lyrixx@lyrixx.info>
  */
-class SilencedErrorContext extends BaseSilencedErrorContext
+class SilencedErrorContext implements \JsonSerializable
 {
+    public $count = 1;
+
+    private $severity;
+    private $file;
+    private $line;
+    private $trace;
+
+    public function __construct(int $severity, string $file, int $line, array $trace = [], int $count = 1)
+    {
+        $this->severity = $severity;
+        $this->file = $file;
+        $this->line = $line;
+        $this->trace = $trace;
+        $this->count = $count;
+    }
+
+    public function getSeverity()
+    {
+        return $this->severity;
+    }
+
+    public function getFile()
+    {
+        return $this->file;
+    }
+
+    public function getLine()
+    {
+        return $this->line;
+    }
+
+    public function getTrace()
+    {
+        return $this->trace;
+    }
+
+    public function JsonSerialize()
+    {
+        return [
+            'severity' => $this->severity,
+            'file' => $this->file,
+            'line' => $this->line,
+            'trace' => $this->trace,
+            'count' => $this->count,
+        ];
+    }
 }
diff --git a/src/Symfony/Component/Debug/Exception/UndefinedFunctionException.php b/src/Symfony/Component/Debug/Exception/UndefinedFunctionException.php
index 9d50933862..d936c8759e 100644
--- a/src/Symfony/Component/Debug/Exception/UndefinedFunctionException.php
+++ b/src/Symfony/Component/Debug/Exception/UndefinedFunctionException.php
@@ -11,13 +11,26 @@
 
 namespace Symfony\Component\Debug\Exception;
 
-use Symfony\Component\ErrorCatcher\Exception\UndefinedFunctionException as BaseUndefinedFunctionException;
-
-@trigger_error(sprintf('The "%s" class is deprecated since Symfony 4.4, use "%s" instead.', UndefinedFunctionException::class, BaseUndefinedFunctionException::class), E_USER_DEPRECATED);
-
 /**
- * @deprecated since Symfony 4.4, use Symfony\Component\ErrorCatcher\Exception\UndefinedFunctionException instead.
+ * Undefined Function Exception.
+ *
+ * @author Konstanton Myakshin <koc-dp@yandex.ru>
  */
-class UndefinedFunctionException extends BaseUndefinedFunctionException
+class UndefinedFunctionException extends FatalErrorException
 {
+    public function __construct(string $message, \ErrorException $previous)
+    {
+        parent::__construct(
+            $message,
+            $previous->getCode(),
+            $previous->getSeverity(),
+            $previous->getFile(),
+            $previous->getLine(),
+            null,
+            true,
+            null,
+            $previous->getPrevious()
+        );
+        $this->setTrace($previous->getTrace());
+    }
 }
diff --git a/src/Symfony/Component/Debug/Exception/UndefinedMethodException.php b/src/Symfony/Component/Debug/Exception/UndefinedMethodException.php
index 0edba83249..f627561fe1 100644
--- a/src/Symfony/Component/Debug/Exception/UndefinedMethodException.php
+++ b/src/Symfony/Component/Debug/Exception/UndefinedMethodException.php
@@ -11,13 +11,26 @@
 
 namespace Symfony\Component\Debug\Exception;
 
-use Symfony\Component\ErrorCatcher\Exception\UndefinedMethodException as BaseUndefinedMethodException;
-
-@trigger_error(sprintf('The "%s" class is deprecated since Symfony 4.4, use "%s" instead.', UndefinedMethodException::class, BaseUndefinedMethodException::class), E_USER_DEPRECATED);
-
 /**
- * @deprecated since Symfony 4.4, use Symfony\Component\ErrorCatcher\Exception\UndefinedMethodException instead.
+ * Undefined Method Exception.
+ *
+ * @author Grégoire Pineau <lyrixx@lyrixx.info>
  */
-class UndefinedMethodException extends BaseUndefinedMethodException
+class UndefinedMethodException extends FatalErrorException
 {
+    public function __construct(string $message, \ErrorException $previous)
+    {
+        parent::__construct(
+            $message,
+            $previous->getCode(),
+            $previous->getSeverity(),
+            $previous->getFile(),
+            $previous->getLine(),
+            null,
+            true,
+            null,
+            $previous->getPrevious()
+        );
+        $this->setTrace($previous->getTrace());
+    }
 }
diff --git a/src/Symfony/Component/Debug/ExceptionHandler.php b/src/Symfony/Component/Debug/ExceptionHandler.php
index d195319ddf..e36610c82e 100644
--- a/src/Symfony/Component/Debug/ExceptionHandler.php
+++ b/src/Symfony/Component/Debug/ExceptionHandler.php
@@ -11,13 +11,456 @@
 
 namespace Symfony\Component\Debug;
 
-use Symfony\Component\ErrorCatcher\ExceptionHandler as BaseExceptionHandler;
-
-@trigger_error(sprintf('The "%s" class is deprecated since Symfony 4.4, use "%s" instead.', ExceptionHandler::class, BaseExceptionHandler::class), E_USER_DEPRECATED);
+use Symfony\Component\Debug\Exception\FlattenException;
+use Symfony\Component\Debug\Exception\OutOfMemoryException;
+use Symfony\Component\HttpKernel\Debug\FileLinkFormatter;
 
 /**
- * @deprecated since Symfony 4.4, use Symfony\Component\ErrorCatcher\ExceptionHandler instead.
+ * ExceptionHandler converts an exception to a Response object.
+ *
+ * It is mostly useful in debug mode to replace the default PHP/XDebug
+ * output with something prettier and more useful.
+ *
+ * As this class is mainly used during Kernel boot, where nothing is yet
+ * available, the Response content is always HTML.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ * @author Nicolas Grekas <p@tchwork.com>
+ *
+ * @final since Symfony 4.3
  */
-class ExceptionHandler extends BaseExceptionHandler
+class ExceptionHandler
 {
+    private const GHOST_ADDONS = [
+        '02-14' => self::GHOST_HEART,
+        '02-29' => self::GHOST_PLUS,
+        '10-18' => self::GHOST_GIFT,
+    ];
+
+    private const GHOST_GIFT = 'M124.005 5.36c.396-.715 1.119-1.648-.124-1.873-.346-.177-.692-.492-1.038-.141-.769.303-1.435.728-.627 1.523.36.514.685 1.634 1.092 1.758.242-.417.47-.842.697-1.266zm-1.699 1.977c-.706-1.26-1.274-2.612-2.138-3.774-1.051-1.123-3.122-.622-3.593.825-.625 1.431.724 3.14 2.251 2.96 1.159.02 2.324.072 3.48-.011zm5.867.043c1.502-.202 2.365-2.092 1.51-3.347-.757-1.34-2.937-1.387-3.698-.025-.659 1.1-1.23 2.25-1.835 3.38 1.336.077 2.686.06 4.023-.008zm2.487 1.611c.512-.45 2.494-.981.993-1.409-.372-.105-.805-.59-1.14-.457-.726.902-1.842 1.432-3.007 1.376-.228.075-1.391-.114-1.077.1.822.47 1.623.979 2.474 1.395.595-.317 1.173-.667 1.757-1.005zm-11.696.255l1.314-.765c-1.338-.066-2.87.127-3.881-.95-.285-.319-.559-.684-.954-.282-.473.326-1.929.66-.808 1.058.976.576 1.945 1.167 2.946 1.701.476-.223.926-.503 1.383-.762zm6.416 2.846c.567-.456 1.942-.89 1.987-1.38-1.282-.737-2.527-1.56-3.87-2.183-.461-.175-.835.094-1.207.328-1.1.654-2.225 1.267-3.288 1.978 1.39.86 2.798 1.695 4.219 2.504.725-.407 1.44-.83 2.16-1.247zm5.692 1.423l1.765-1.114c-.005-1.244.015-2.488-.019-3.732a77.306 77.306 0 0 0-3.51 2.084c-.126 1.282-.062 2.586-.034 3.876.607-.358 1.2-.741 1.798-1.114zm-13.804-.784c.06-1.06.19-2.269-1.09-2.583-.807-.376-1.926-1.341-2.548-1.332-.02 1.195-.01 2.39-.011 3.585 1.192.744 2.364 1.524 3.582 2.226.119-.616.041-1.269.067-1.896zm8.541 4.105l2.117-1.336c-.003-1.284.05-2.57-.008-3.853-.776.223-1.662.91-2.48 1.337l-1.834 1.075c.012 1.37-.033 2.744.044 4.113.732-.427 1.443-.887 2.161-1.336zm-2.957-.72v-2.057c-1.416-.828-2.828-1.664-4.25-2.482-.078 1.311-.033 2.627-.045 3.94 1.416.887 2.817 1.798 4.25 2.655.057-.683.036-1.372.045-2.057zm8.255 2.755l1.731-1.153c-.024-1.218.06-2.453-.062-3.658-1.2.685-2.358 1.464-3.537 2.195.028 1.261-.058 2.536.072 3.786.609-.373 1.2-.777 1.796-1.17zm-13.851-.683l-.014-1.916c-1.193-.746-2.37-1.517-3.58-2.234-.076 1.224-.033 2.453-.044 3.679 1.203.796 2.392 1.614 3.61 2.385.048-.636.024-1.276.028-1.914zm8.584 4.199l2.102-1.396c-.002-1.298.024-2.596-.01-3.893-1.427.88-2.843 1.775-4.25 2.686-.158 1.253-.055 2.545-.056 3.811.437.266 1.553-.912 2.214-1.208zm-2.988-.556c-.085-.894.365-2.154-.773-2.5-1.146-.727-2.288-1.46-3.45-2.163-.17 1.228.008 2.508-.122 3.751a79.399 79.399 0 0 0 4.278 2.885c.117-.641.044-1.32.067-1.973zm-4.872-.236l-5.087-3.396c.002-3.493-.047-6.988.015-10.48.85-.524 1.753-.954 2.627-1.434-.564-1.616.25-3.58 1.887-4.184 1.372-.563 3.025-.055 3.9 1.13l1.906-.978 1.916.987c.915-1.086 2.483-1.706 3.842-1.097 1.631.573 2.52 2.532 1.936 4.145.88.497 1.837.886 2.644 1.492.036 3.473 0 6.946-.003 10.419-3.374 2.233-6.693 4.55-10.122 6.699-.997 0-1.858-1.083-2.783-1.522a735.316 735.316 0 0 1-2.678-1.781z';
+    private const GHOST_HEART = 'M125.914 8.305c3.036-8.71 14.933 0 0 11.2-14.932-11.2-3.036-19.91 0-11.2z';
+    private const GHOST_PLUS = 'M111.368 8.97h7.324V1.645h7.512v7.323h7.324v7.513h-7.324v7.323h-7.512v-7.323h-7.324z';
+
+    private $debug;
+    private $charset;
+    private $handler;
+    private $caughtBuffer;
+    private $caughtLength;
+    private $fileLinkFormat;
+
+    public function __construct(bool $debug = true, string $charset = null, $fileLinkFormat = null)
+    {
+        $this->debug = $debug;
+        $this->charset = $charset ?: ini_get('default_charset') ?: 'UTF-8';
+        $this->fileLinkFormat = $fileLinkFormat;
+    }
+
+    /**
+     * Registers the exception handler.
+     *
+     * @param bool        $debug          Enable/disable debug mode, where the stack trace is displayed
+     * @param string|null $charset        The charset used by exception messages
+     * @param string|null $fileLinkFormat The IDE link template
+     *
+     * @return static
+     */
+    public static function register($debug = true, $charset = null, $fileLinkFormat = null)
+    {
+        $handler = new static($debug, $charset, $fileLinkFormat);
+
+        $prev = set_exception_handler([$handler, 'handle']);
+        if (\is_array($prev) && $prev[0] instanceof ErrorHandler) {
+            restore_exception_handler();
+            $prev[0]->setExceptionHandler([$handler, 'handle']);
+        }
+
+        return $handler;
+    }
+
+    /**
+     * Sets a user exception handler.
+     *
+     * @param callable $handler An handler that will be called on Exception
+     *
+     * @return callable|null The previous exception handler if any
+     */
+    public function setHandler(callable $handler = null)
+    {
+        $old = $this->handler;
+        $this->handler = $handler;
+
+        return $old;
+    }
+
+    /**
+     * Sets the format for links to source files.
+     *
+     * @param string|FileLinkFormatter $fileLinkFormat The format for links to source files
+     *
+     * @return string The previous file link format
+     */
+    public function setFileLinkFormat($fileLinkFormat)
+    {
+        $old = $this->fileLinkFormat;
+        $this->fileLinkFormat = $fileLinkFormat;
+
+        return $old;
+    }
+
+    /**
+     * Sends a response for the given Exception.
+     *
+     * To be as fail-safe as possible, the exception is first handled
+     * by our simple exception handler, then by the user exception handler.
+     * The latter takes precedence and any output from the former is cancelled,
+     * if and only if nothing bad happens in this handling path.
+     */
+    public function handle(\Exception $exception)
+    {
+        if (null === $this->handler || $exception instanceof OutOfMemoryException) {
+            $this->sendPhpResponse($exception);
+
+            return;
+        }
+
+        $caughtLength = $this->caughtLength = 0;
+
+        ob_start(function ($buffer) {
+            $this->caughtBuffer = $buffer;
+
+            return '';
+        });
+
+        $this->sendPhpResponse($exception);
+        while (null === $this->caughtBuffer && ob_end_flush()) {
+            // Empty loop, everything is in the condition
+        }
+        if (isset($this->caughtBuffer[0])) {
+            ob_start(function ($buffer) {
+                if ($this->caughtLength) {
+                    // use substr_replace() instead of substr() for mbstring overloading resistance
+                    $cleanBuffer = substr_replace($buffer, '', 0, $this->caughtLength);
+                    if (isset($cleanBuffer[0])) {
+                        $buffer = $cleanBuffer;
+                    }
+                }
+
+                return $buffer;
+            });
+
+            echo $this->caughtBuffer;
+            $caughtLength = ob_get_length();
+        }
+        $this->caughtBuffer = null;
+
+        try {
+            ($this->handler)($exception);
+            $this->caughtLength = $caughtLength;
+        } catch (\Exception $e) {
+            if (!$caughtLength) {
+                // All handlers failed. Let PHP handle that now.
+                throw $exception;
+            }
+        }
+    }
+
+    /**
+     * Sends the error associated with the given Exception as a plain PHP response.
+     *
+     * This method uses plain PHP functions like header() and echo to output
+     * the response.
+     *
+     * @param \Throwable|FlattenException $exception A \Throwable or FlattenException instance
+     */
+    public function sendPhpResponse($exception)
+    {
+        if ($exception instanceof \Throwable) {
+            $exception = FlattenException::createFromThrowable($exception);
+        }
+
+        if (!headers_sent()) {
+            header(sprintf('HTTP/1.0 %s', $exception->getStatusCode()));
+            foreach ($exception->getHeaders() as $name => $value) {
+                header($name.': '.$value, false);
+            }
+            header('Content-Type: text/html; charset='.$this->charset);
+        }
+
+        echo $this->decorate($this->getContent($exception), $this->getStylesheet($exception));
+    }
+
+    /**
+     * Gets the full HTML content associated with the given exception.
+     *
+     * @param \Exception|FlattenException $exception An \Exception or FlattenException instance
+     *
+     * @return string The HTML content as a string
+     */
+    public function getHtml($exception)
+    {
+        if (!$exception instanceof FlattenException) {
+            $exception = FlattenException::create($exception);
+        }
+
+        return $this->decorate($this->getContent($exception), $this->getStylesheet($exception));
+    }
+
+    /**
+     * Gets the HTML content associated with the given exception.
+     *
+     * @return string The content as a string
+     */
+    public function getContent(FlattenException $exception)
+    {
+        switch ($exception->getStatusCode()) {
+            case 404:
+                $title = 'Sorry, the page you are looking for could not be found.';
+                break;
+            default:
+                $title = $this->debug ? $this->escapeHtml($exception->getMessage()) : 'Whoops, looks like something went wrong.';
+        }
+
+        if (!$this->debug) {
+            return <<<EOF
+                <div class="container">
+                    <h1>$title</h1>
+                </div>
+EOF;
+        }
+
+        $content = '';
+        try {
+            $count = \count($exception->getAllPrevious());
+            $total = $count + 1;
+            foreach ($exception->toArray() as $position => $e) {
+                $ind = $count - $position + 1;
+                $class = $this->formatClass($e['class']);
+                $message = nl2br($this->escapeHtml($e['message']));
+                $content .= sprintf(<<<'EOF'
+                    <div class="trace trace-as-html">
+                        <table class="trace-details">
+                            <thead class="trace-head"><tr><th>
+                                <h3 class="trace-class">
+                                    <span class="text-muted">(%d/%d)</span>
+                                    <span class="exception_title">%s</span>
+                                </h3>
+                                <p class="break-long-words trace-message">%s</p>
+                            </th></tr></thead>
+                            <tbody>
+EOF
+                    , $ind, $total, $class, $message);
+                foreach ($e['trace'] as $trace) {
+                    $content .= '<tr><td>';
+                    if ($trace['function']) {
+                        $content .= sprintf('at <span class="trace-class">%s</span><span class="trace-type">%s</span><span class="trace-method">%s</span>(<span class="trace-arguments">%s</span>)', $this->formatClass($trace['class']), $trace['type'], $trace['function'], $this->formatArgs($trace['args']));
+                    }
+                    if (isset($trace['file']) && isset($trace['line'])) {
+                        $content .= $this->formatPath($trace['file'], $trace['line']);
+                    }
+                    $content .= "</td></tr>\n";
+                }
+
+                $content .= "</tbody>\n</table>\n</div>\n";
+            }
+        } catch (\Exception $e) {
+            // something nasty happened and we cannot throw an exception anymore
+            if ($this->debug) {
+                $e = FlattenException::create($e);
+                $title = sprintf('Exception thrown when handling an exception (%s: %s)', $e->getClass(), $this->escapeHtml($e->getMessage()));
+            } else {
+                $title = 'Whoops, looks like something went wrong.';
+            }
+        }
+
+        $symfonyGhostImageContents = $this->getSymfonyGhostAsSvg();
+
+        return <<<EOF
+            <div class="exception-summary">
+                <div class="container">
+                    <div class="exception-message-wrapper">
+                        <h1 class="break-long-words exception-message">$title</h1>
+                        <div class="exception-illustration hidden-xs-down">$symfonyGhostImageContents</div>
+                    </div>
+                </div>
+            </div>
+
+            <div class="container">
+                $content
+            </div>
+EOF;
+    }
+
+    /**
+     * Gets the stylesheet associated with the given exception.
+     *
+     * @return string The stylesheet as a string
+     */
+    public function getStylesheet(FlattenException $exception)
+    {
+        if (!$this->debug) {
+            return <<<'EOF'
+                body { background-color: #fff; color: #222; font: 16px/1.5 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif; margin: 0; }
+                .container { margin: 30px; max-width: 600px; }
+                h1 { color: #dc3545; font-size: 24px; }
+EOF;
+        }
+
+        return <<<'EOF'
+            body { background-color: #F9F9F9; color: #222; font: 14px/1.4 Helvetica, Arial, sans-serif; margin: 0; padding-bottom: 45px; }
+
+            a { cursor: pointer; text-decoration: none; }
+            a:hover { text-decoration: underline; }
+            abbr[title] { border-bottom: none; cursor: help; text-decoration: none; }
+
+            code, pre { font: 13px/1.5 Consolas, Monaco, Menlo, "Ubuntu Mono", "Liberation Mono", monospace; }
+
+            table, tr, th, td { background: #FFF; border-collapse: collapse; vertical-align: top; }
+            table { background: #FFF; border: 1px solid #E0E0E0; box-shadow: 0px 0px 1px rgba(128, 128, 128, .2); margin: 1em 0; width: 100%; }
+            table th, table td { border: solid #E0E0E0; border-width: 1px 0; padding: 8px 10px; }
+            table th { background-color: #E0E0E0; font-weight: bold; text-align: left; }
+
+            .hidden-xs-down { display: none; }
+            .block { display: block; }
+            .break-long-words { -ms-word-break: break-all; word-break: break-all; word-break: break-word; -webkit-hyphens: auto; -moz-hyphens: auto; hyphens: auto; }
+            .text-muted { color: #999; }
+
+            .container { max-width: 1024px; margin: 0 auto; padding: 0 15px; }
+            .container::after { content: ""; display: table; clear: both; }
+
+            .exception-summary { background: #B0413E; border-bottom: 2px solid rgba(0, 0, 0, 0.1); border-top: 1px solid rgba(0, 0, 0, .3); flex: 0 0 auto; margin-bottom: 30px; }
+
+            .exception-message-wrapper { display: flex; align-items: center; min-height: 70px; }
+            .exception-message { flex-grow: 1; padding: 30px 0; }
+            .exception-message, .exception-message a { color: #FFF; font-size: 21px; font-weight: 400; margin: 0; }
+            .exception-message.long { font-size: 18px; }
+            .exception-message a { border-bottom: 1px solid rgba(255, 255, 255, 0.5); font-size: inherit; text-decoration: none; }
+            .exception-message a:hover { border-bottom-color: #ffffff; }
+
+            .exception-illustration { flex-basis: 111px; flex-shrink: 0; height: 66px; margin-left: 15px; opacity: .7; }
+
+            .trace + .trace { margin-top: 30px; }
+            .trace-head .trace-class { color: #222; font-size: 18px; font-weight: bold; line-height: 1.3; margin: 0; position: relative; }
+
+            .trace-message { font-size: 14px; font-weight: normal; margin: .5em 0 0; }
+
+            .trace-file-path, .trace-file-path a { color: #222; margin-top: 3px; font-size: 13px; }
+            .trace-class { color: #B0413E; }
+            .trace-type { padding: 0 2px; }
+            .trace-method { color: #B0413E; font-weight: bold; }
+            .trace-arguments { color: #777; font-weight: normal; padding-left: 2px; }
+
+            @media (min-width: 575px) {
+                .hidden-xs-down { display: initial; }
+            }
+EOF;
+    }
+
+    private function decorate($content, $css)
+    {
+        return <<<EOF
+<!DOCTYPE html>
+<html>
+    <head>
+        <meta charset="{$this->charset}" />
+        <meta name="robots" content="noindex,nofollow" />
+        <style>$css</style>
+    </head>
+    <body>
+        $content
+    </body>
+</html>
+EOF;
+    }
+
+    private function formatClass($class)
+    {
+        $parts = explode('\\', $class);
+
+        return sprintf('<abbr title="%s">%s</abbr>', $class, array_pop($parts));
+    }
+
+    private function formatPath($path, $line)
+    {
+        $file = $this->escapeHtml(preg_match('#[^/\\\\]*+$#', $path, $file) ? $file[0] : $path);
+        $fmt = $this->fileLinkFormat ?: ini_get('xdebug.file_link_format') ?: get_cfg_var('xdebug.file_link_format');
+
+        if (!$fmt) {
+            return sprintf('<span class="block trace-file-path">in <span title="%s%3$s"><strong>%s</strong>%s</span></span>', $this->escapeHtml($path), $file, 0 < $line ? ' line '.$line : '');
+        }
+
+        if (\is_string($fmt)) {
+            $i = strpos($f = $fmt, '&', max(strrpos($f, '%f'), strrpos($f, '%l'))) ?: \strlen($f);
+            $fmt = [substr($f, 0, $i)] + preg_split('/&([^>]++)>/', substr($f, $i), -1, PREG_SPLIT_DELIM_CAPTURE);
+
+            for ($i = 1; isset($fmt[$i]); ++$i) {
+                if (0 === strpos($path, $k = $fmt[$i++])) {
+                    $path = substr_replace($path, $fmt[$i], 0, \strlen($k));
+                    break;
+                }
+            }
+
+            $link = strtr($fmt[0], ['%f' => $path, '%l' => $line]);
+        } else {
+            try {
+                $link = $fmt->format($path, $line);
+            } catch (\Exception $e) {
+                return sprintf('<span class="block trace-file-path">in <span title="%s%3$s"><strong>%s</strong>%s</span></span>', $this->escapeHtml($path), $file, 0 < $line ? ' line '.$line : '');
+            }
+        }
+
+        return sprintf('<span class="block trace-file-path">in <a href="%s" title="Go to source"><strong>%s</string>%s</a></span>', $this->escapeHtml($link), $file, 0 < $line ? ' line '.$line : '');
+    }
+
+    /**
+     * Formats an array as a string.
+     *
+     * @param array $args The argument array
+     *
+     * @return string
+     */
+    private function formatArgs(array $args)
+    {
+        $result = [];
+        foreach ($args as $key => $item) {
+            if ('object' === $item[0]) {
+                $formattedValue = sprintf('<em>object</em>(%s)', $this->formatClass($item[1]));
+            } elseif ('array' === $item[0]) {
+                $formattedValue = sprintf('<em>array</em>(%s)', \is_array($item[1]) ? $this->formatArgs($item[1]) : $item[1]);
+            } elseif ('null' === $item[0]) {
+                $formattedValue = '<em>null</em>';
+            } elseif ('boolean' === $item[0]) {
+                $formattedValue = '<em>'.strtolower(var_export($item[1], true)).'</em>';
+            } elseif ('resource' === $item[0]) {
+                $formattedValue = '<em>resource</em>';
+            } else {
+                $formattedValue = str_replace("\n", '', $this->escapeHtml(var_export($item[1], true)));
+            }
+
+            $result[] = \is_int($key) ? $formattedValue : sprintf("'%s' => %s", $this->escapeHtml($key), $formattedValue);
+        }
+
+        return implode(', ', $result);
+    }
+
+    /**
+     * HTML-encodes a string.
+     */
+    private function escapeHtml($str)
+    {
+        return htmlspecialchars($str, ENT_COMPAT | ENT_SUBSTITUTE, $this->charset);
+    }
+
+    private function getSymfonyGhostAsSvg()
+    {
+        return '<svg viewBox="0 0 136 81" xmlns="http://www.w3.org/2000/svg" fill-rule="evenodd" clip-rule="evenodd" stroke-linejoin="round" stroke-miterlimit="1.4"><path d="M92.4 20.4a23.2 23.2 0 0 1 9 1.9 23.7 23.7 0 0 1 5.2 3 24.3 24.3 0 0 1 3.4 3.4 24.8 24.8 0 0 1 5 9.4c.5 1.7.8 3.4 1 5.2v14.5h.4l.5.2a7.4 7.4 0 0 0 2.5.2l.2-.2.6-.8.8-1.3-.2-.1a5.5 5.5 0 0 1-.8-.3 5.6 5.6 0 0 1-2.3-1.8 5.7 5.7 0 0 1-.9-1.6 6.5 6.5 0 0 1-.2-2.8 7.3 7.3 0 0 1 .5-2l.3-.3.8-.9.3-.3c.2-.2.5-.3.8-.3H120.7c.2 0 .3-.1.4 0h.4l.2.1.3.2.2-.4.3-.4.1-.1 1.2-1 .3-.2.4-.1.4-.1h.3l1.5.1.4.1.8.5.1.2 1 1.1v.2H129.4l.4-.2 1.4-.5h1.1c.3 0 .7.2 1 .4.2 0 .3.2.5.3l.2.2.5.3.4.6.1.3.4 1.4.1.4v.6a7.8 7.8 0 0 1-.1.6 9.9 9.9 0 0 1-.8 2.4 7.8 7.8 0 0 1-3 3.3 6.4 6.4 0 0 1-1 .5 6.1 6.1 0 0 1-.6.2l-.7.1h-.1a23.4 23.4 0 0 1-.2 1.7 14.3 14.3 0 0 1-.6 2.1l-.8 2a9.2 9.2 0 0 1-.4.6l-.7 1a9.1 9.1 0 0 1-2.3 2.2c-.9.5-2 .6-3 .7l-1.4.1h-.5l-.4.1a15.8 15.8 0 0 1-2.8-.1v4.2a9.7 9.7 0 0 1-.7 3.5 9.6 9.6 0 0 1-1.7 2.8 9.3 9.3 0 0 1-3 2.3 9 9 0 0 1-5.4.7 9 9 0 0 1-3-1 9.4 9.4 0 0 1-2.7-2.5 10 10 0 0 1-1 1.2 9.3 9.3 0 0 1-2 1.3 9 9 0 0 1-2.4 1 9 9 0 0 1-6.5-1.1A9.4 9.4 0 0 1 85 77V77a10.9 10.9 0 0 1-.6.6 9.3 9.3 0 0 1-2.7 2 9 9 0 0 1-6 .8 9 9 0 0 1-2.4-1 9.3 9.3 0 0 1-2.3-1.7 9.6 9.6 0 0 1-1.8-2.8 9.7 9.7 0 0 1-.8-3.7v-4a18.5 18.5 0 0 1-2.9.2l-1.2-.1c-1.9-.3-3.7-1-5.1-2.1A8.2 8.2 0 0 1 58 64a10.2 10.2 0 0 1-.9-1.2 15.3 15.3 0 0 1-.7-1.3 20.8 20.8 0 0 1-1.9-6.2v-.2a6.5 6.5 0 0 1-1-.3 6.1 6.1 0 0 1-.6-.3 6.6 6.6 0 0 1-.9-.5 8.2 8.2 0 0 1-2.7-3.8 10 10 0 0 1-.3-1 10.3 10.3 0 0 1-.3-1.9V47v-.4l.1-.4.6-1.4.1-.2a2 2 0 0 1 .8-.8l.3-.2.3-.2a3.2 3.2 0 0 1 1.8-.5h.4l.3.2 1.4.6.2.2.4.3.3.4.7-.7.2-.2.4-.2.6-.2h2.1l.4.2.4.2.3.2.8 1 .2-.1h.1v-.1H63l1.1.1h.3l.8.5.3.4.7 1 .2.3.1.5a11 11 0 0 1 .2 1.5c0 .8 0 1.6-.3 2.3a6 6 0 0 1-.5 1.2 5.5 5.5 0 0 1-3.3 2.5 12.3 12.3 0 0 0 1.4 3h.1l.2.1 1 .2h1.5l.5-.2H67.8l.5-.2h.1V44v-.4a26.7 26.7 0 0 1 .3-2.3 24.7 24.7 0 0 1 5.7-12.5 24.2 24.2 0 0 1 3.5-3.3 23.7 23.7 0 0 1 4.9-3 23.2 23.2 0 0 1 5.6-1.7 23.7 23.7 0 0 1 4-.3zm-.3 2a21.2 21.2 0 0 0-8 1.7 21.6 21.6 0 0 0-4.8 2.7 22.2 22.2 0 0 0-3.2 3 22.7 22.7 0 0 0-5 9.2 23.4 23.4 0 0 0-.7 4.9v15.7l-.5.1a34.3 34.3 0 0 1-1.5.3h-.2l-.4.1h-.4l-.9.2a10 10 0 0 1-1.9 0c-.5 0-1-.2-1.5-.4a1.8 1.8 0 0 1-.3-.2 2 2 0 0 1-.3-.3 5.2 5.2 0 0 1-.1-.2 9 9 0 0 1-.6-.9 13.8 13.8 0 0 1-1-2 14.3 14.3 0 0 1-.6-2 14 14 0 0 1-.1-.8v-.2h.3a12.8 12.8 0 0 0 1.4-.2 4.4 4.4 0 0 0 .3 0 3.6 3.6 0 0 0 1.1-.7 3.4 3.4 0 0 0 1.2-1.7l.2-1.2a5.1 5.1 0 0 0 0-.8 7.2 7.2 0 0 0-.1-.8l-.7-1-1.2-.2-1 .7-.1 1.3a5 5 0 0 1 .1.4v.6a1 1 0 0 1 0 .3c-.1.3-.4.4-.7.5l-1.2.4v-.7A9.9 9.9 0 0 1 60 49l.3-.6v-.2l.1-.1v-1.6l-1-1.2h-1.5l-1 1.1v.4a5.3 5.3 0 0 0-.2.6 5.5 5.5 0 0 0 0 .5c0 .7 0 1.4.3 2 0 .4.2.8.4 1.2L57 51a9.5 9.5 0 0 1-1.1-.5h-.2a2 2 0 0 1-.4-.3c-.4-.4-.5-1-.6-1.6a5.6 5.6 0 0 1 0-.5v-.5-.5l-.6-1.5-1.4-.6-.9.3s-.2 0-.3.2a2 2 0 0 1-.1 0l-.6 1.4v.7a8.5 8.5 0 0 0 .5 2c.4 1.1 1 2.1 2 2.8a4.7 4.7 0 0 0 2.1.9h1a22.8 22.8 0 0 0 .1 1 18.1 18.1 0 0 0 .8 3.8 18.2 18.2 0 0 0 1.6 3.7l1 1.3c1 1 2.3 1.6 3.7 2a11.7 11.7 0 0 0 4.8 0h.4l.5-.2.5-.1.6-.2v6.6a8 8 0 0 0 .1 1.3 7.5 7.5 0 0 0 2.4 4.3 7.2 7.2 0 0 0 2.3 1.3 7 7 0 0 0 7-1.1 7.5 7.5 0 0 0 2-2.6A7.7 7.7 0 0 0 85 72V71a8.2 8.2 0 0 0 .2 1.3c0 .7.3 1.4.6 2a7.5 7.5 0 0 0 1.7 2.3 7.3 7.3 0 0 0 2.2 1.4 7.1 7.1 0 0 0 4.6.2 7.2 7.2 0 0 0 2.4-1.2 7.5 7.5 0 0 0 2.1-2.7 7.8 7.8 0 0 0 .7-2.4V71a9.3 9.3 0 0 0 .1.6 7.6 7.6 0 0 0 .6 2.5 7.5 7.5 0 0 0 2.4 3 7.1 7.1 0 0 0 7 .8 7.3 7.3 0 0 0 2.3-1.5 7.5 7.5 0 0 0 1.6-2.3 7.6 7.6 0 0 0 .5-2l.1-1.1v-6.7l.4.1a12.2 12.2 0 0 0 2 .5 11.1 11.1 0 0 0 2.5 0h.8l1.2-.1a9.5 9.5 0 0 0 1.4-.2l.9-.3a3.5 3.5 0 0 0 .6-.4l1.2-1.4a12.2 12.2 0 0 0 .8-1.2c0-.3.2-.5.3-.7a15.9 15.9 0 0 0 .7-2l.3-1.6v-1.3l.2-.9V54.6a15.5 15.5 0 0 0 1.8 0 4.5 4.5 0 0 0 1.4-.5 5.7 5.7 0 0 0 2.5-3.2 7.6 7.6 0 0 0 .4-1.5v-.3l-.4-1.4a5.2 5.2 0 0 1-.2-.1l-.4-.4a3.8 3.8 0 0 0-.2 0 1.4 1.4 0 0 0-.5-.2l-1.4.4-.7 1.3v.7a5.7 5.7 0 0 1-.1.8l-.7 1.4a1.9 1.9 0 0 1-.5.3h-.3a9.6 9.6 0 0 1-.8.3 8.8 8.8 0 0 1-.6 0l.2-.4.2-.5.2-.3v-.4l.1-.2V50l.1-1 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0 1.2-1.2 7 7 0 0 0 1-1.7 6.5 6.5 0 0 0 .4-2.5 1 1 0 0 1 .7-1h.4zM30.7 43.7c-15.5 1-28.5-6-30.1-16.4C-1.2 15.7 11.6 4 29 1.3 46.6-1.7 62.3 5.5 64 17.1c1.6 10.4-8.7 21-23.7 25a31.2 31.2 0 0 0 0 .9v.3a19 19 0 0 0 .1 1l.1.4.1.9a4.7 4.7 0 0 0 .5 1l.7 1a9.2 9.2 0 0 0 1.2 1l1.5.8.6.8-.7.6-1.1.3a11.2 11.2 0 0 1-2.6.4 8.6 8.6 0 0 1-3-.5 8.5 8.5 0 0 1-1-.4 11.2 11.2 0 0 1-1.8-1.2 13.3 13.3 0 0 1-1-1 18 18 0 0 1-.7-.6l-.4-.4a23.4 23.4 0 0 1-1.3-1.8l-.1-.1-.3-.5V45l-.3-.6v-.7zM83.1 36c3.6 0 6.5 3.2 6.5 7.1 0 4-3 7.2-6.5 7.2S76.7 47 76.7 43 79.6 36 83 36zm18 0c3.6 0 6.5 3.2 6.5 7.1 0 4-2.9 7.2-6.4 7.2S94.7 47 94.7 43s3-7.1 6.5-7.1zm-18 6.1c2 0 3.5 1.6 3.5 3.6S85 49.2 83 49.2s-3.4-1.6-3.4-3.6S81.2 42 83 42zm17.9 0c1.9 0 3.4 1.6 3.4 3.6s-1.5 3.6-3.4 3.6c-2 0-3.5-1.6-3.5-3.6S99.1 42 101 42zM17 28c-.3 1.6-1.8 5-5.2 5.8-2.5.6-4.1-.8-4.5-2.6-.4-1.9.7-3.5 2.1-4.5A3.5 3.5 0 0 1 8 24.6c-.4-2 .8-3.7 3.2-4.2 1.9-.5 3.1.2 3.4 1.5.3 1.1-.5 2.2-1.8 2.5-.9.3-1.6 0-1.7-.6a1.4 1.4 0 0 1 0-.7s.3.2 1 0c.7-.1 1-.7.9-1.2-.2-.6-1-.8-1.8-.6-1 .2-2 1-1.7 2.6.3 1 .9 1.6 1.5 1.8l.7-.2c1-.2 1.5 0 1.6.5 0 .4-.2 1-1.2 1.2a3.3 3.3 0 0 1-1.5 0c-.9.7-1.6 1.9-1.3 3.2.3 1.3 1.3 2.2 3 1.8 2.5-.7 3.8-3.7 4.2-5-.3-.5-.6-1-.7-1.6-.1-.5.1-1 .9-1.2.4 0 .7.2.8.8a2.8 2.8 0 0 1 0 1l.7 1c.6-2 1.4-4 1.7-4 .6-.2 1.5.6 1.5.6-.8.7-1.7 2.4-2.3 4.2.8.6 1.6 1 2.1 1 .5-.1.8-.6 1-1.2-.3-2.2 1-4.3 2.3-4.6.7-.2 1.3.2 1.4.8.1.5 0 1.3-.9 1.7-.2-1-.6-1.3-1-1.3-.4.1-.7 1.4-.4 2.8.2 1 .7 1.5 1.3 1.4.8-.2 1.3-1.2 1.7-2.1-.3-2.1.9-4.2 2.2-4.5.7-.2 1.2.1 1.4 1 .4 1.4-1 2.8-2.2 3.4.3.7.7 1 1.3.9 1-.3 1.6-1.5 2-2.5l-.5-3v-.3s1.6-.3 1.8.6v.1c.2-.6.7-1.2 1.3-1.4.8-.1 1.5.6 1.7 1.6.5 2.2-.5 4.4-1.8 4.7H33a31.9 31.9 0 0 0 1 5.2c-.4.1-1.8.4-2-.4l-.5-5.6c-.5 1-1.3 2.2-2.5 2.4-1 .3-1.6-.3-2-1.1-.5 1-1.3 2.1-2.4 2.4-.8.2-1.5-.1-2-1-.3.8-.9 1.5-1.5 1.7-.7.1-1.5-.3-2.4-1-.3.8-.4 1.6-.4 2.2 0 0-.7 0-.8-.4-.1-.5 0-1.5.3-2.7a10.3 10.3 0 0 1-.7-.8zm38.2-17.8l.2.9c.5 1.9.4 4.4.8 6.4 0 .6-.4 3-1.4 3.3-.2 0-.3 0-.4-.4-.1-.7 0-1.6-.3-2.6-.2-1.1-.8-1.6-1.5-1.5-.8.2-1.3 1-1.6 2l-.1-.5c-.2-1-1.8-.6-1.8-.6a6.2 6.2 0 0 1 .4 1.3l.2 1c-.2.5-.6 1-1.2 1l-.2.1a7 7 0 0 0-.1-.8c-.3-1.1-1-2-1.6-1.8a.7.7 0 0 0-.4.3c-1.3.3-2.4 2-2.1 3.9-.2.9-.6 1.7-1 1.9-.5 0-.8-.5-1.1-1.8l-.1-1.2a4 4 0 0 0 0-1.7c0-.4-.4-.7-.8-.6-.7.2-.9 1.7-.5 3.8-.2 1-.6 2-1.3 2-.4.2-.8-.2-1-1l-.2-3c1.2-.5 2-1 1.8-1.7-.1-.5-.8-.7-.8-.7s0 .7-1 1.2l-.2-1.4c-.1-.6-.4-1-1.7-.6l.4 1 .2 1.5h-1v.8c0 .3.4.3 1 .2 0 1.3 0 2.7.2 3.6.3 1.4 1.2 2 2 1.7 1-.2 1.6-1.3 2-2.3.3 1.2 1 2 1.9 1.7.7-.2 1.2-1.1 1.6-2.2.4.8 1.1 1.1 2 1 1.2-.4 1.7-1.6 1.8-2.8h.2c.6-.2 1-.6 1.3-1 0 .8 0 1.5.2 2.1.1.5.3.7.6.6.5-.1 1-.9 1-.9a4 4 0 0 1-.3-1c-.3-1.3.3-3.6 1-3.7.2 0 .3.2.5.7v.8l.2 1.5v.7c.2.7.7 1.3 1.5 1 1.3-.2 2-2.6 2.1-3.9.3.2.6.2 1 .1-.6-2.2 0-6.1-.3-7.9-.1-.4-1-.5-1.7-.5h-.4zm-21.5 12c.4 0 .7.3 1 1.1.2 1.3-.3 2.6-.9 2.8-.2 0-.7 0-1-1.2v-.4c0-1.3.4-2 1-2.2zm-5.2 1c.3 0 .6.2.6.5.2.6-.3 1.3-1.2 2-.3-1.4.1-2.3.6-2.5zm18-.4c-.5.2-1-.4-1.2-1.2-.2-1 0-2.1.7-2.5v.5c.2.7.6 1.5 1.3 1.9 0 .7-.2 1.2-.7 1.3zm10-1.6c0 .5.4.7 1 .6.8-.2 1-1 .8-1.6 0-.5-.4-1-1-.8-.5.1-1 .9-.8 1.8zm-14.3-5.5c0-.4-.5-.7-1-.5-.8.2-1 1-.9 1.5.2.6.5 1 1 .8.5 0 1.1-1 1-1.8z" fill="#fff" fill-opacity=".6"/>'.$this->addElementToGhost().'</svg>';
+    }
+
+    private function addElementToGhost()
+    {
+        if (!isset(self::GHOST_ADDONS[date('m-d')])) {
+            return '';
+        }
+
+        return '<path d="'.self::GHOST_ADDONS[date('m-d')].'" fill="#fff" fill-opacity="0.6"></path>';
+    }
 }
diff --git a/src/Symfony/Component/Debug/FatalErrorHandler/ClassNotFoundFatalErrorHandler.php b/src/Symfony/Component/Debug/FatalErrorHandler/ClassNotFoundFatalErrorHandler.php
index e7f1285f98..a0e2f770f0 100644
--- a/src/Symfony/Component/Debug/FatalErrorHandler/ClassNotFoundFatalErrorHandler.php
+++ b/src/Symfony/Component/Debug/FatalErrorHandler/ClassNotFoundFatalErrorHandler.php
@@ -11,13 +11,183 @@
 
 namespace Symfony\Component\Debug\FatalErrorHandler;
 
-use Symfony\Component\ErrorCatcher\FatalErrorHandler\ClassNotFoundFatalErrorHandler as BaseClassNotFoundFatalErrorHandler;
-
-@trigger_error(sprintf('The "%s" class is deprecated since Symfony 4.4, use "%s" instead.', ClassNotFoundFatalErrorHandler::class, BaseClassNotFoundFatalErrorHandler::class), E_USER_DEPRECATED);
+use Composer\Autoload\ClassLoader as ComposerClassLoader;
+use Symfony\Component\ClassLoader\ClassLoader as SymfonyClassLoader;
+use Symfony\Component\Debug\DebugClassLoader;
+use Symfony\Component\Debug\Exception\ClassNotFoundException;
+use Symfony\Component\Debug\Exception\FatalErrorException;
 
 /**
- * @deprecated since Symfony 4.4, use Symfony\Component\ErrorCatcher\FatalErrorHandler\ClassNotFoundFatalErrorHandler instead.
+ * ErrorHandler for classes that do not exist.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
  */
-class ClassNotFoundFatalErrorHandler extends BaseClassNotFoundFatalErrorHandler
+class ClassNotFoundFatalErrorHandler implements FatalErrorHandlerInterface
 {
+    /**
+     * {@inheritdoc}
+     */
+    public function handleError(array $error, FatalErrorException $exception)
+    {
+        $messageLen = \strlen($error['message']);
+        $notFoundSuffix = '\' not found';
+        $notFoundSuffixLen = \strlen($notFoundSuffix);
+        if ($notFoundSuffixLen > $messageLen) {
+            return;
+        }
+
+        if (0 !== substr_compare($error['message'], $notFoundSuffix, -$notFoundSuffixLen)) {
+            return;
+        }
+
+        foreach (['class', 'interface', 'trait'] as $typeName) {
+            $prefix = ucfirst($typeName).' \'';
+            $prefixLen = \strlen($prefix);
+            if (0 !== strpos($error['message'], $prefix)) {
+                continue;
+            }
+
+            $fullyQualifiedClassName = substr($error['message'], $prefixLen, -$notFoundSuffixLen);
+            if (false !== $namespaceSeparatorIndex = strrpos($fullyQualifiedClassName, '\\')) {
+                $className = substr($fullyQualifiedClassName, $namespaceSeparatorIndex + 1);
+                $namespacePrefix = substr($fullyQualifiedClassName, 0, $namespaceSeparatorIndex);
+                $message = sprintf('Attempted to load %s "%s" from namespace "%s".', $typeName, $className, $namespacePrefix);
+                $tail = ' for another namespace?';
+            } else {
+                $className = $fullyQualifiedClassName;
+                $message = sprintf('Attempted to load %s "%s" from the global namespace.', $typeName, $className);
+                $tail = '?';
+            }
+
+            if ($candidates = $this->getClassCandidates($className)) {
+                $tail = array_pop($candidates).'"?';
+                if ($candidates) {
+                    $tail = ' for e.g. "'.implode('", "', $candidates).'" or "'.$tail;
+                } else {
+                    $tail = ' for "'.$tail;
+                }
+            }
+            $message .= "\nDid you forget a \"use\" statement".$tail;
+
+            return new ClassNotFoundException($message, $exception);
+        }
+    }
+
+    /**
+     * Tries to guess the full namespace for a given class name.
+     *
+     * By default, it looks for PSR-0 and PSR-4 classes registered via a Symfony or a Composer
+     * autoloader (that should cover all common cases).
+     *
+     * @param string $class A class name (without its namespace)
+     *
+     * @return array An array of possible fully qualified class names
+     */
+    private function getClassCandidates(string $class): array
+    {
+        if (!\is_array($functions = spl_autoload_functions())) {
+            return [];
+        }
+
+        // find Symfony and Composer autoloaders
+        $classes = [];
+
+        foreach ($functions as $function) {
+            if (!\is_array($function)) {
+                continue;
+            }
+            // get class loaders wrapped by DebugClassLoader
+            if ($function[0] instanceof DebugClassLoader) {
+                $function = $function[0]->getClassLoader();
+
+                if (!\is_array($function)) {
+                    continue;
+                }
+            }
+
+            if ($function[0] instanceof ComposerClassLoader || $function[0] instanceof SymfonyClassLoader) {
+                foreach ($function[0]->getPrefixes() as $prefix => $paths) {
+                    foreach ($paths as $path) {
+                        $classes = array_merge($classes, $this->findClassInPath($path, $class, $prefix));
+                    }
+                }
+            }
+            if ($function[0] instanceof ComposerClassLoader) {
+                foreach ($function[0]->getPrefixesPsr4() as $prefix => $paths) {
+                    foreach ($paths as $path) {
+                        $classes = array_merge($classes, $this->findClassInPath($path, $class, $prefix));
+                    }
+                }
+            }
+        }
+
+        return array_unique($classes);
+    }
+
+    private function findClassInPath(string $path, string $class, string $prefix): array
+    {
+        if (!$path = realpath($path.'/'.strtr($prefix, '\\_', '//')) ?: realpath($path.'/'.\dirname(strtr($prefix, '\\_', '//'))) ?: realpath($path)) {
+            return [];
+        }
+
+        $classes = [];
+        $filename = $class.'.php';
+        foreach (new \RecursiveIteratorIterator(new \RecursiveDirectoryIterator($path, \RecursiveDirectoryIterator::SKIP_DOTS), \RecursiveIteratorIterator::LEAVES_ONLY) as $file) {
+            if ($filename == $file->getFileName() && $class = $this->convertFileToClass($path, $file->getPathName(), $prefix)) {
+                $classes[] = $class;
+            }
+        }
+
+        return $classes;
+    }
+
+    private function convertFileToClass(string $path, string $file, string $prefix): ?string
+    {
+        $candidates = [
+            // namespaced class
+            $namespacedClass = str_replace([$path.\DIRECTORY_SEPARATOR, '.php', '/'], ['', '', '\\'], $file),
+            // namespaced class (with target dir)
+            $prefix.$namespacedClass,
+            // namespaced class (with target dir and separator)
+            $prefix.'\\'.$namespacedClass,
+            // PEAR class
+            str_replace('\\', '_', $namespacedClass),
+            // PEAR class (with target dir)
+            str_replace('\\', '_', $prefix.$namespacedClass),
+            // PEAR class (with target dir and separator)
+            str_replace('\\', '_', $prefix.'\\'.$namespacedClass),
+        ];
+
+        if ($prefix) {
+            $candidates = array_filter($candidates, function ($candidate) use ($prefix) { return 0 === strpos($candidate, $prefix); });
+        }
+
+        // We cannot use the autoloader here as most of them use require; but if the class
+        // is not found, the new autoloader call will require the file again leading to a
+        // "cannot redeclare class" error.
+        foreach ($candidates as $candidate) {
+            if ($this->classExists($candidate)) {
+                return $candidate;
+            }
+        }
+
+        try {
+            require_once $file;
+        } catch (\Throwable $e) {
+            return null;
+        }
+
+        foreach ($candidates as $candidate) {
+            if ($this->classExists($candidate)) {
+                return $candidate;
+            }
+        }
+
+        return null;
+    }
+
+    private function classExists(string $class): bool
+    {
+        return class_exists($class, false) || interface_exists($class, false) || trait_exists($class, false);
+    }
 }
diff --git a/src/Symfony/Component/Debug/FatalErrorHandler/FatalErrorHandlerInterface.php b/src/Symfony/Component/Debug/FatalErrorHandler/FatalErrorHandlerInterface.php
index 701ebe7640..6b87eb30a1 100644
--- a/src/Symfony/Component/Debug/FatalErrorHandler/FatalErrorHandlerInterface.php
+++ b/src/Symfony/Component/Debug/FatalErrorHandler/FatalErrorHandlerInterface.php
@@ -11,13 +11,22 @@
 
 namespace Symfony\Component\Debug\FatalErrorHandler;
 
-use Symfony\Component\ErrorCatcher\FatalErrorHandler\FatalErrorHandlerInterface as BaseFatalErrorHandlerInterface;
-
-@trigger_error(sprintf('The "%s" interface is deprecated since Symfony 4.4, use "%s" instead.', FatalErrorHandlerInterface::class, BaseFatalErrorHandlerInterface::class), E_USER_DEPRECATED);
+use Symfony\Component\Debug\Exception\FatalErrorException;
 
 /**
- * @deprecated since Symfony 4.4, use Symfony\Component\ErrorCatcher\FatalErrorHandler\FatalErrorHandlerInterface instead.
+ * Attempts to convert fatal errors to exceptions.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
  */
-interface FatalErrorHandlerInterface extends BaseFatalErrorHandlerInterface
+interface FatalErrorHandlerInterface
 {
+    /**
+     * Attempts to convert an error into an exception.
+     *
+     * @param array               $error     An array as returned by error_get_last()
+     * @param FatalErrorException $exception A FatalErrorException instance
+     *
+     * @return FatalErrorException|null A FatalErrorException instance if the class is able to convert the error, null otherwise
+     */
+    public function handleError(array $error, FatalErrorException $exception);
 }
diff --git a/src/Symfony/Component/Debug/FatalErrorHandler/UndefinedFunctionFatalErrorHandler.php b/src/Symfony/Component/Debug/FatalErrorHandler/UndefinedFunctionFatalErrorHandler.php
index 51015368e0..9eddeba5a6 100644
--- a/src/Symfony/Component/Debug/FatalErrorHandler/UndefinedFunctionFatalErrorHandler.php
+++ b/src/Symfony/Component/Debug/FatalErrorHandler/UndefinedFunctionFatalErrorHandler.php
@@ -11,13 +11,74 @@
 
 namespace Symfony\Component\Debug\FatalErrorHandler;
 
-use Symfony\Component\ErrorCatcher\FatalErrorHandler\UndefinedFunctionFatalErrorHandler as BaseUndefinedFunctionFatalErrorHandler;
-
-@trigger_error(sprintf('The "%s" class is deprecated since Symfony 4.4, use "%s" instead.', UndefinedFunctionFatalErrorHandler::class, BaseUndefinedFunctionFatalErrorHandler::class), E_USER_DEPRECATED);
+use Symfony\Component\Debug\Exception\FatalErrorException;
+use Symfony\Component\Debug\Exception\UndefinedFunctionException;
 
 /**
- * @deprecated since Symfony 4.4, use Symfony\Component\ErrorCatcher\FatalErrorHandler\UndefinedFunctionFatalErrorHandler instead.
+ * ErrorHandler for undefined functions.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
  */
-class UndefinedFunctionFatalErrorHandler extends BaseUndefinedFunctionFatalErrorHandler
+class UndefinedFunctionFatalErrorHandler implements FatalErrorHandlerInterface
 {
+    /**
+     * {@inheritdoc}
+     */
+    public function handleError(array $error, FatalErrorException $exception)
+    {
+        $messageLen = \strlen($error['message']);
+        $notFoundSuffix = '()';
+        $notFoundSuffixLen = \strlen($notFoundSuffix);
+        if ($notFoundSuffixLen > $messageLen) {
+            return;
+        }
+
+        if (0 !== substr_compare($error['message'], $notFoundSuffix, -$notFoundSuffixLen)) {
+            return;
+        }
+
+        $prefix = 'Call to undefined function ';
+        $prefixLen = \strlen($prefix);
+        if (0 !== strpos($error['message'], $prefix)) {
+            return;
+        }
+
+        $fullyQualifiedFunctionName = substr($error['message'], $prefixLen, -$notFoundSuffixLen);
+        if (false !== $namespaceSeparatorIndex = strrpos($fullyQualifiedFunctionName, '\\')) {
+            $functionName = substr($fullyQualifiedFunctionName, $namespaceSeparatorIndex + 1);
+            $namespacePrefix = substr($fullyQualifiedFunctionName, 0, $namespaceSeparatorIndex);
+            $message = sprintf('Attempted to call function "%s" from namespace "%s".', $functionName, $namespacePrefix);
+        } else {
+            $functionName = $fullyQualifiedFunctionName;
+            $message = sprintf('Attempted to call function "%s" from the global namespace.', $functionName);
+        }
+
+        $candidates = [];
+        foreach (get_defined_functions() as $type => $definedFunctionNames) {
+            foreach ($definedFunctionNames as $definedFunctionName) {
+                if (false !== $namespaceSeparatorIndex = strrpos($definedFunctionName, '\\')) {
+                    $definedFunctionNameBasename = substr($definedFunctionName, $namespaceSeparatorIndex + 1);
+                } else {
+                    $definedFunctionNameBasename = $definedFunctionName;
+                }
+
+                if ($definedFunctionNameBasename === $functionName) {
+                    $candidates[] = '\\'.$definedFunctionName;
+                }
+            }
+        }
+
+        if ($candidates) {
+            sort($candidates);
+            $last = array_pop($candidates).'"?';
+            if ($candidates) {
+                $candidates = 'e.g. "'.implode('", "', $candidates).'" or "'.$last;
+            } else {
+                $candidates = '"'.$last;
+            }
+            $message .= "\nDid you mean to call ".$candidates;
+        }
+
+        return new UndefinedFunctionException($message, $exception);
+    }
 }
diff --git a/src/Symfony/Component/Debug/FatalErrorHandler/UndefinedMethodFatalErrorHandler.php b/src/Symfony/Component/Debug/FatalErrorHandler/UndefinedMethodFatalErrorHandler.php
index 9e9164e07f..1318cb13ba 100644
--- a/src/Symfony/Component/Debug/FatalErrorHandler/UndefinedMethodFatalErrorHandler.php
+++ b/src/Symfony/Component/Debug/FatalErrorHandler/UndefinedMethodFatalErrorHandler.php
@@ -11,13 +11,56 @@
 
 namespace Symfony\Component\Debug\FatalErrorHandler;
 
-use Symfony\Component\ErrorCatcher\FatalErrorHandler\UndefinedMethodFatalErrorHandler as BaseUndefinedMethodFatalErrorHandler;
-
-@trigger_error(sprintf('The "%s" class is deprecated since Symfony 4.4, use "%s" instead.', UndefinedMethodFatalErrorHandler::class, BaseUndefinedMethodFatalErrorHandler::class), E_USER_DEPRECATED);
+use Symfony\Component\Debug\Exception\FatalErrorException;
+use Symfony\Component\Debug\Exception\UndefinedMethodException;
 
 /**
- * @deprecated since Symfony 4.4, use Symfony\Component\ErrorCatcher\FatalErrorHandler\UndefinedMethodFatalErrorHandler instead.
+ * ErrorHandler for undefined methods.
+ *
+ * @author Grégoire Pineau <lyrixx@lyrixx.info>
  */
-class UndefinedMethodFatalErrorHandler extends BaseUndefinedMethodFatalErrorHandler
+class UndefinedMethodFatalErrorHandler implements FatalErrorHandlerInterface
 {
+    /**
+     * {@inheritdoc}
+     */
+    public function handleError(array $error, FatalErrorException $exception)
+    {
+        preg_match('/^Call to undefined method (.*)::(.*)\(\)$/', $error['message'], $matches);
+        if (!$matches) {
+            return;
+        }
+
+        $className = $matches[1];
+        $methodName = $matches[2];
+
+        $message = sprintf('Attempted to call an undefined method named "%s" of class "%s".', $methodName, $className);
+
+        if (!class_exists($className) || null === $methods = get_class_methods($className)) {
+            // failed to get the class or its methods on which an unknown method was called (for example on an anonymous class)
+            return new UndefinedMethodException($message, $exception);
+        }
+
+        $candidates = [];
+        foreach ($methods as $definedMethodName) {
+            $lev = levenshtein($methodName, $definedMethodName);
+            if ($lev <= \strlen($methodName) / 3 || false !== strpos($definedMethodName, $methodName)) {
+                $candidates[] = $definedMethodName;
+            }
+        }
+
+        if ($candidates) {
+            sort($candidates);
+            $last = array_pop($candidates).'"?';
+            if ($candidates) {
+                $candidates = 'e.g. "'.implode('", "', $candidates).'" or "'.$last;
+            } else {
+                $candidates = '"'.$last;
+            }
+
+            $message .= "\nDid you mean to call ".$candidates;
+        }
+
+        return new UndefinedMethodException($message, $exception);
+    }
 }
diff --git a/src/Symfony/Component/ErrorCatcher/Tests/ErrorHandlerTest.php b/src/Symfony/Component/Debug/Tests/ErrorHandlerTest.php
similarity index 97%
rename from src/Symfony/Component/ErrorCatcher/Tests/ErrorHandlerTest.php
rename to src/Symfony/Component/Debug/Tests/ErrorHandlerTest.php
index d1d845a866..f758d21e0e 100644
--- a/src/Symfony/Component/ErrorCatcher/Tests/ErrorHandlerTest.php
+++ b/src/Symfony/Component/Debug/Tests/ErrorHandlerTest.php
@@ -9,16 +9,16 @@
  * file that was distributed with this source code.
  */
 
-namespace Symfony\Component\ErrorCatcher\Tests;
+namespace Symfony\Component\Debug\Tests;
 
 use PHPUnit\Framework\TestCase;
 use Psr\Log\LogLevel;
 use Psr\Log\NullLogger;
-use Symfony\Component\ErrorCatcher\BufferingLogger;
-use Symfony\Component\ErrorCatcher\ErrorHandler;
-use Symfony\Component\ErrorCatcher\Exception\SilencedErrorContext;
-use Symfony\Component\ErrorCatcher\Tests\Fixtures\ErrorHandlerThatUsesThePreviousOne;
-use Symfony\Component\ErrorCatcher\Tests\Fixtures\LoggerThatSetAnErrorHandler;
+use Symfony\Component\Debug\BufferingLogger;
+use Symfony\Component\Debug\ErrorHandler;
+use Symfony\Component\Debug\Exception\SilencedErrorContext;
+use Symfony\Component\Debug\Tests\Fixtures\ErrorHandlerThatUsesThePreviousOne;
+use Symfony\Component\Debug\Tests\Fixtures\LoggerThatSetAnErrorHandler;
 
 /**
  * ErrorHandlerTest.
@@ -33,7 +33,7 @@ class ErrorHandlerTest extends TestCase
         $handler = ErrorHandler::register();
 
         try {
-            $this->assertInstanceOf('Symfony\Component\ErrorCatcher\ErrorHandler', $handler);
+            $this->assertInstanceOf('Symfony\Component\Debug\ErrorHandler', $handler);
             $this->assertSame($handler, ErrorHandler::register());
 
             $newHandler = new ErrorHandler();
@@ -151,21 +151,21 @@ class ErrorHandlerTest extends TestCase
             $handler->setDefaultLogger($logger, [E_USER_NOTICE => LogLevel::CRITICAL]);
 
             $loggers = [
-                E_COMPILE_ERROR => [null, LogLevel::CRITICAL],
-                E_COMPILE_WARNING => [null, LogLevel::WARNING],
-                E_CORE_ERROR => [null, LogLevel::CRITICAL],
-                E_CORE_WARNING => [null, LogLevel::WARNING],
                 E_DEPRECATED => [null, LogLevel::INFO],
-                E_ERROR => [null, LogLevel::CRITICAL],
-                E_NOTICE => [$logger, LogLevel::WARNING],
-                E_PARSE => [null, LogLevel::CRITICAL],
-                E_RECOVERABLE_ERROR => [null, LogLevel::CRITICAL],
-                E_STRICT => [null, LogLevel::WARNING],
                 E_USER_DEPRECATED => [null, LogLevel::INFO],
-                E_USER_ERROR => [null, LogLevel::CRITICAL],
+                E_NOTICE => [$logger, LogLevel::WARNING],
                 E_USER_NOTICE => [$logger, LogLevel::CRITICAL],
-                E_USER_WARNING => [null, LogLevel::WARNING],
+                E_STRICT => [null, LogLevel::WARNING],
                 E_WARNING => [null, LogLevel::WARNING],
+                E_USER_WARNING => [null, LogLevel::WARNING],
+                E_COMPILE_WARNING => [null, LogLevel::WARNING],
+                E_CORE_WARNING => [null, LogLevel::WARNING],
+                E_USER_ERROR => [null, LogLevel::CRITICAL],
+                E_RECOVERABLE_ERROR => [null, LogLevel::CRITICAL],
+                E_COMPILE_ERROR => [null, LogLevel::CRITICAL],
+                E_PARSE => [null, LogLevel::CRITICAL],
+                E_ERROR => [null, LogLevel::CRITICAL],
+                E_CORE_ERROR => [null, LogLevel::CRITICAL],
             ];
             $this->assertSame($loggers, $handler->setLoggers([]));
         } finally {
@@ -375,21 +375,21 @@ class ErrorHandlerTest extends TestCase
         $handler = new ErrorHandler($bootLogger);
 
         $loggers = [
-            E_COMPILE_ERROR => [$bootLogger, LogLevel::CRITICAL],
-            E_COMPILE_WARNING => [$bootLogger, LogLevel::WARNING],
-            E_CORE_ERROR => [$bootLogger, LogLevel::CRITICAL],
-            E_CORE_WARNING => [$bootLogger, LogLevel::WARNING],
             E_DEPRECATED => [$bootLogger, LogLevel::INFO],
-            E_ERROR => [$bootLogger, LogLevel::CRITICAL],
-            E_NOTICE => [$bootLogger, LogLevel::WARNING],
-            E_PARSE => [$bootLogger, LogLevel::CRITICAL],
-            E_RECOVERABLE_ERROR => [$bootLogger, LogLevel::CRITICAL],
-            E_STRICT => [$bootLogger, LogLevel::WARNING],
             E_USER_DEPRECATED => [$bootLogger, LogLevel::INFO],
-            E_USER_ERROR => [$bootLogger, LogLevel::CRITICAL],
+            E_NOTICE => [$bootLogger, LogLevel::WARNING],
             E_USER_NOTICE => [$bootLogger, LogLevel::WARNING],
-            E_USER_WARNING => [$bootLogger, LogLevel::WARNING],
+            E_STRICT => [$bootLogger, LogLevel::WARNING],
             E_WARNING => [$bootLogger, LogLevel::WARNING],
+            E_USER_WARNING => [$bootLogger, LogLevel::WARNING],
+            E_COMPILE_WARNING => [$bootLogger, LogLevel::WARNING],
+            E_CORE_WARNING => [$bootLogger, LogLevel::WARNING],
+            E_USER_ERROR => [$bootLogger, LogLevel::CRITICAL],
+            E_RECOVERABLE_ERROR => [$bootLogger, LogLevel::CRITICAL],
+            E_COMPILE_ERROR => [$bootLogger, LogLevel::CRITICAL],
+            E_PARSE => [$bootLogger, LogLevel::CRITICAL],
+            E_ERROR => [$bootLogger, LogLevel::CRITICAL],
+            E_CORE_ERROR => [$bootLogger, LogLevel::CRITICAL],
         ];
 
         $this->assertSame($loggers, $handler->setLoggers([]));
@@ -490,7 +490,7 @@ class ErrorHandlerTest extends TestCase
 
         $handler->handleException($exception);
 
-        $this->assertInstanceOf('Symfony\Component\ErrorCatcher\Exception\ClassNotFoundException', $args[0]);
+        $this->assertInstanceOf('Symfony\Component\Debug\Exception\ClassNotFoundException', $args[0]);
         $this->assertStringStartsWith("Attempted to load class \"IReallyReallyDoNotExistAnywhereInTheRepositoryISwear\" from the global namespace.\nDid you forget a \"use\" statement", $args[0]->getMessage());
     }
 
diff --git a/src/Symfony/Component/Debug/Tests/Exception/FlattenExceptionTest.php b/src/Symfony/Component/Debug/Tests/Exception/FlattenExceptionTest.php
new file mode 100644
index 0000000000..f18809a5a2
--- /dev/null
+++ b/src/Symfony/Component/Debug/Tests/Exception/FlattenExceptionTest.php
@@ -0,0 +1,391 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Debug\Tests\Exception;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Debug\Exception\FatalThrowableError;
+use Symfony\Component\Debug\Exception\FlattenException;
+use Symfony\Component\HttpFoundation\Exception\SuspiciousOperationException;
+use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
+use Symfony\Component\HttpKernel\Exception\BadRequestHttpException;
+use Symfony\Component\HttpKernel\Exception\ConflictHttpException;
+use Symfony\Component\HttpKernel\Exception\GoneHttpException;
+use Symfony\Component\HttpKernel\Exception\LengthRequiredHttpException;
+use Symfony\Component\HttpKernel\Exception\MethodNotAllowedHttpException;
+use Symfony\Component\HttpKernel\Exception\NotAcceptableHttpException;
+use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
+use Symfony\Component\HttpKernel\Exception\PreconditionFailedHttpException;
+use Symfony\Component\HttpKernel\Exception\PreconditionRequiredHttpException;
+use Symfony\Component\HttpKernel\Exception\ServiceUnavailableHttpException;
+use Symfony\Component\HttpKernel\Exception\TooManyRequestsHttpException;
+use Symfony\Component\HttpKernel\Exception\UnauthorizedHttpException;
+use Symfony\Component\HttpKernel\Exception\UnsupportedMediaTypeHttpException;
+
+/**
+ * @group legacy
+ */
+class FlattenExceptionTest extends TestCase
+{
+    public function testStatusCode()
+    {
+        $flattened = FlattenException::create(new \RuntimeException(), 403);
+        $this->assertEquals('403', $flattened->getStatusCode());
+
+        $flattened = FlattenException::create(new \RuntimeException());
+        $this->assertEquals('500', $flattened->getStatusCode());
+
+        $flattened = FlattenException::createFromThrowable(new \DivisionByZeroError(), 403);
+        $this->assertEquals('403', $flattened->getStatusCode());
+
+        $flattened = FlattenException::createFromThrowable(new \DivisionByZeroError());
+        $this->assertEquals('500', $flattened->getStatusCode());
+
+        $flattened = FlattenException::create(new NotFoundHttpException());
+        $this->assertEquals('404', $flattened->getStatusCode());
+
+        $flattened = FlattenException::create(new UnauthorizedHttpException('Basic realm="My Realm"'));
+        $this->assertEquals('401', $flattened->getStatusCode());
+
+        $flattened = FlattenException::create(new BadRequestHttpException());
+        $this->assertEquals('400', $flattened->getStatusCode());
+
+        $flattened = FlattenException::create(new NotAcceptableHttpException());
+        $this->assertEquals('406', $flattened->getStatusCode());
+
+        $flattened = FlattenException::create(new ConflictHttpException());
+        $this->assertEquals('409', $flattened->getStatusCode());
+
+        $flattened = FlattenException::create(new MethodNotAllowedHttpException(['POST']));
+        $this->assertEquals('405', $flattened->getStatusCode());
+
+        $flattened = FlattenException::create(new AccessDeniedHttpException());
+        $this->assertEquals('403', $flattened->getStatusCode());
+
+        $flattened = FlattenException::create(new GoneHttpException());
+        $this->assertEquals('410', $flattened->getStatusCode());
+
+        $flattened = FlattenException::create(new LengthRequiredHttpException());
+        $this->assertEquals('411', $flattened->getStatusCode());
+
+        $flattened = FlattenException::create(new PreconditionFailedHttpException());
+        $this->assertEquals('412', $flattened->getStatusCode());
+
+        $flattened = FlattenException::create(new PreconditionRequiredHttpException());
+        $this->assertEquals('428', $flattened->getStatusCode());
+
+        $flattened = FlattenException::create(new ServiceUnavailableHttpException());
+        $this->assertEquals('503', $flattened->getStatusCode());
+
+        $flattened = FlattenException::create(new TooManyRequestsHttpException());
+        $this->assertEquals('429', $flattened->getStatusCode());
+
+        $flattened = FlattenException::create(new UnsupportedMediaTypeHttpException());
+        $this->assertEquals('415', $flattened->getStatusCode());
+
+        if (class_exists(SuspiciousOperationException::class)) {
+            $flattened = FlattenException::create(new SuspiciousOperationException());
+            $this->assertEquals('400', $flattened->getStatusCode());
+        }
+    }
+
+    public function testHeadersForHttpException()
+    {
+        $flattened = FlattenException::create(new MethodNotAllowedHttpException(['POST']));
+        $this->assertEquals(['Allow' => 'POST'], $flattened->getHeaders());
+
+        $flattened = FlattenException::create(new UnauthorizedHttpException('Basic realm="My Realm"'));
+        $this->assertEquals(['WWW-Authenticate' => 'Basic realm="My Realm"'], $flattened->getHeaders());
+
+        $flattened = FlattenException::create(new ServiceUnavailableHttpException('Fri, 31 Dec 1999 23:59:59 GMT'));
+        $this->assertEquals(['Retry-After' => 'Fri, 31 Dec 1999 23:59:59 GMT'], $flattened->getHeaders());
+
+        $flattened = FlattenException::create(new ServiceUnavailableHttpException(120));
+        $this->assertEquals(['Retry-After' => 120], $flattened->getHeaders());
+
+        $flattened = FlattenException::create(new TooManyRequestsHttpException('Fri, 31 Dec 1999 23:59:59 GMT'));
+        $this->assertEquals(['Retry-After' => 'Fri, 31 Dec 1999 23:59:59 GMT'], $flattened->getHeaders());
+
+        $flattened = FlattenException::create(new TooManyRequestsHttpException(120));
+        $this->assertEquals(['Retry-After' => 120], $flattened->getHeaders());
+    }
+
+    /**
+     * @dataProvider flattenDataProvider
+     */
+    public function testFlattenHttpException(\Throwable $exception)
+    {
+        $flattened = FlattenException::createFromThrowable($exception);
+        $flattened2 = FlattenException::createFromThrowable($exception);
+
+        $flattened->setPrevious($flattened2);
+
+        $this->assertEquals($exception->getMessage(), $flattened->getMessage(), 'The message is copied from the original exception.');
+        $this->assertEquals($exception->getCode(), $flattened->getCode(), 'The code is copied from the original exception.');
+        $this->assertInstanceOf($flattened->getClass(), $exception, 'The class is set to the class of the original exception');
+    }
+
+    public function testWrappedThrowable()
+    {
+        $exception = new FatalThrowableError(new \DivisionByZeroError('Ouch', 42));
+        $flattened = FlattenException::create($exception);
+
+        $this->assertSame('Ouch', $flattened->getMessage(), 'The message is copied from the original error.');
+        $this->assertSame(42, $flattened->getCode(), 'The code is copied from the original error.');
+        $this->assertSame('DivisionByZeroError', $flattened->getClass(), 'The class is set to the class of the original error');
+    }
+
+    public function testThrowable()
+    {
+        $error = new \DivisionByZeroError('Ouch', 42);
+        $flattened = FlattenException::createFromThrowable($error);
+
+        $this->assertSame('Ouch', $flattened->getMessage(), 'The message is copied from the original error.');
+        $this->assertSame(42, $flattened->getCode(), 'The code is copied from the original error.');
+        $this->assertSame('DivisionByZeroError', $flattened->getClass(), 'The class is set to the class of the original error');
+    }
+
+    /**
+     * @dataProvider flattenDataProvider
+     */
+    public function testPrevious(\Throwable $exception)
+    {
+        $flattened = FlattenException::createFromThrowable($exception);
+        $flattened2 = FlattenException::createFromThrowable($exception);
+
+        $flattened->setPrevious($flattened2);
+
+        $this->assertSame($flattened2, $flattened->getPrevious());
+
+        $this->assertSame([$flattened2], $flattened->getAllPrevious());
+    }
+
+    public function testPreviousError()
+    {
+        $exception = new \Exception('test', 123, new \ParseError('Oh noes!', 42));
+
+        $flattened = FlattenException::create($exception)->getPrevious();
+
+        $this->assertEquals($flattened->getMessage(), 'Oh noes!', 'The message is copied from the original exception.');
+        $this->assertEquals($flattened->getCode(), 42, 'The code is copied from the original exception.');
+        $this->assertEquals($flattened->getClass(), 'ParseError', 'The class is set to the class of the original exception');
+    }
+
+    /**
+     * @dataProvider flattenDataProvider
+     */
+    public function testLine(\Throwable $exception)
+    {
+        $flattened = FlattenException::createFromThrowable($exception);
+        $this->assertSame($exception->getLine(), $flattened->getLine());
+    }
+
+    /**
+     * @dataProvider flattenDataProvider
+     */
+    public function testFile(\Throwable $exception)
+    {
+        $flattened = FlattenException::createFromThrowable($exception);
+        $this->assertSame($exception->getFile(), $flattened->getFile());
+    }
+
+    /**
+     * @dataProvider flattenDataProvider
+     */
+    public function testToArray(\Throwable $exception, string $expectedClass)
+    {
+        $flattened = FlattenException::createFromThrowable($exception);
+        $flattened->setTrace([], 'foo.php', 123);
+
+        $this->assertEquals([
+            [
+                'message' => 'test',
+                'class' => $expectedClass,
+                'trace' => [[
+                    'namespace' => '', 'short_class' => '', 'class' => '', 'type' => '', 'function' => '', 'file' => 'foo.php', 'line' => 123,
+                    'args' => [],
+                ]],
+            ],
+        ], $flattened->toArray());
+    }
+
+    public function testCreate()
+    {
+        $exception = new NotFoundHttpException(
+            'test',
+            new \RuntimeException('previous', 123)
+        );
+
+        $this->assertSame(
+            FlattenException::createFromThrowable($exception)->toArray(),
+            FlattenException::create($exception)->toArray()
+        );
+    }
+
+    public function flattenDataProvider()
+    {
+        return [
+            [new \Exception('test', 123), 'Exception'],
+            [new \Error('test', 123), 'Error'],
+        ];
+    }
+
+    public function testArguments()
+    {
+        $dh = opendir(__DIR__);
+        $fh = tmpfile();
+
+        $incomplete = unserialize('O:14:"BogusTestClass":0:{}');
+
+        $exception = $this->createException([
+            (object) ['foo' => 1],
+            new NotFoundHttpException(),
+            $incomplete,
+            $dh,
+            $fh,
+            function () {},
+            [1, 2],
+            ['foo' => 123],
+            null,
+            true,
+            false,
+            0,
+            0.0,
+            '0',
+            '',
+            INF,
+            NAN,
+        ]);
+
+        $flattened = FlattenException::create($exception);
+        $trace = $flattened->getTrace();
+        $args = $trace[1]['args'];
+        $array = $args[0][1];
+
+        closedir($dh);
+        fclose($fh);
+
+        $i = 0;
+        $this->assertSame(['object', 'stdClass'], $array[$i++]);
+        $this->assertSame(['object', 'Symfony\Component\HttpKernel\Exception\NotFoundHttpException'], $array[$i++]);
+        $this->assertSame(['incomplete-object', 'BogusTestClass'], $array[$i++]);
+        $this->assertSame(['resource', 'stream'], $array[$i++]);
+        $this->assertSame(['resource', 'stream'], $array[$i++]);
+
+        $args = $array[$i++];
+        $this->assertSame($args[0], 'object');
+        $this->assertTrue('Closure' === $args[1] || is_subclass_of($args[1], '\Closure'), 'Expect object class name to be Closure or a subclass of Closure.');
+
+        $this->assertSame(['array', [['integer', 1], ['integer', 2]]], $array[$i++]);
+        $this->assertSame(['array', ['foo' => ['integer', 123]]], $array[$i++]);
+        $this->assertSame(['null', null], $array[$i++]);
+        $this->assertSame(['boolean', true], $array[$i++]);
+        $this->assertSame(['boolean', false], $array[$i++]);
+        $this->assertSame(['integer', 0], $array[$i++]);
+        $this->assertSame(['float', 0.0], $array[$i++]);
+        $this->assertSame(['string', '0'], $array[$i++]);
+        $this->assertSame(['string', ''], $array[$i++]);
+        $this->assertSame(['float', INF], $array[$i++]);
+
+        // assertEquals() does not like NAN values.
+        $this->assertEquals($array[$i][0], 'float');
+        $this->assertTrue(is_nan($array[$i++][1]));
+    }
+
+    public function testRecursionInArguments()
+    {
+        $a = null;
+        $a = ['foo', [2, &$a]];
+        $exception = $this->createException($a);
+
+        $flattened = FlattenException::create($exception);
+        $trace = $flattened->getTrace();
+        $this->assertContains('*DEEP NESTED ARRAY*', serialize($trace));
+    }
+
+    public function testTooBigArray()
+    {
+        $a = [];
+        for ($i = 0; $i < 20; ++$i) {
+            for ($j = 0; $j < 50; ++$j) {
+                for ($k = 0; $k < 10; ++$k) {
+                    $a[$i][$j][$k] = 'value';
+                }
+            }
+        }
+        $a[20] = 'value';
+        $a[21] = 'value1';
+        $exception = $this->createException($a);
+
+        $flattened = FlattenException::create($exception);
+        $trace = $flattened->getTrace();
+
+        $this->assertSame($trace[1]['args'][0], ['array', ['array', '*SKIPPED over 10000 entries*']]);
+
+        $serializeTrace = serialize($trace);
+
+        $this->assertContains('*SKIPPED over 10000 entries*', $serializeTrace);
+        $this->assertNotContains('*value1*', $serializeTrace);
+    }
+
+    public function testAnonymousClass()
+    {
+        $flattened = FlattenException::create(new class() extends \RuntimeException {
+        });
+
+        $this->assertSame('RuntimeException@anonymous', $flattened->getClass());
+
+        $flattened = FlattenException::create(new \Exception(sprintf('Class "%s" blah.', \get_class(new class() extends \RuntimeException {
+        }))));
+
+        $this->assertSame('Class "RuntimeException@anonymous" blah.', $flattened->getMessage());
+    }
+
+    public function testToStringEmptyMessage()
+    {
+        $exception = new \RuntimeException();
+
+        $flattened = FlattenException::create($exception);
+
+        $this->assertSame($exception->getTraceAsString(), $flattened->getTraceAsString());
+        $this->assertSame($exception->__toString(), $flattened->getAsString());
+    }
+
+    public function testToString()
+    {
+        $test = function ($a, $b, $c, $d) {
+            return new \RuntimeException('This is a test message');
+        };
+
+        $exception = $test('foo123', 1, null, 1.5);
+
+        $flattened = FlattenException::create($exception);
+
+        $this->assertSame($exception->getTraceAsString(), $flattened->getTraceAsString());
+        $this->assertSame($exception->__toString(), $flattened->getAsString());
+    }
+
+    public function testToStringParent()
+    {
+        $exception = new \LogicException('This is message 1');
+        $exception = new \RuntimeException('This is messsage 2', 500, $exception);
+
+        $flattened = FlattenException::create($exception);
+
+        $this->assertSame($exception->getTraceAsString(), $flattened->getTraceAsString());
+        $this->assertSame($exception->__toString(), $flattened->getAsString());
+    }
+
+    private function createException($foo)
+    {
+        return new \Exception();
+    }
+}
diff --git a/src/Symfony/Component/ErrorCatcher/Tests/ExceptionHandlerTest.php b/src/Symfony/Component/Debug/Tests/ExceptionHandlerTest.php
similarity index 86%
rename from src/Symfony/Component/ErrorCatcher/Tests/ExceptionHandlerTest.php
rename to src/Symfony/Component/Debug/Tests/ExceptionHandlerTest.php
index d3b8deec80..31f9a90bc4 100644
--- a/src/Symfony/Component/ErrorCatcher/Tests/ExceptionHandlerTest.php
+++ b/src/Symfony/Component/Debug/Tests/ExceptionHandlerTest.php
@@ -9,11 +9,11 @@
  * file that was distributed with this source code.
  */
 
-namespace Symfony\Component\ErrorCatcher\Tests;
+namespace Symfony\Component\Debug\Tests;
 
 use PHPUnit\Framework\TestCase;
-use Symfony\Component\ErrorCatcher\Exception\OutOfMemoryException;
-use Symfony\Component\ErrorCatcher\ExceptionHandler;
+use Symfony\Component\Debug\Exception\OutOfMemoryException;
+use Symfony\Component\Debug\ExceptionHandler;
 use Symfony\Component\HttpKernel\Exception\MethodNotAllowedHttpException;
 use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
 
@@ -31,6 +31,9 @@ class ExceptionHandlerTest extends TestCase
         testHeader();
     }
 
+    /**
+     * @group legacy
+     */
     public function testDebug()
     {
         $handler = new ExceptionHandler(false);
@@ -39,7 +42,7 @@ class ExceptionHandlerTest extends TestCase
         $handler->sendPhpResponse(new \RuntimeException('Foo'));
         $response = ob_get_clean();
 
-        $this->assertContains('The server returned a "500 Internal Server Error".', $response);
+        $this->assertContains('Whoops, looks like something went wrong.', $response);
         $this->assertNotContains('<div class="trace trace-as-html">', $response);
 
         $handler = new ExceptionHandler(true);
@@ -69,7 +72,7 @@ content="0;url=data:text/html;base64,PHNjcmlwdD5hbGVydCgndGVzdDMnKTwvc2NyaXB0Pg"
         $handler->sendPhpResponse(new NotFoundHttpException('Foo'));
         $response = ob_get_clean();
 
-        $this->assertContains('The server returned a "404 Not Found".', $response);
+        $this->assertContains('Sorry, the page you are looking for could not be found.', $response);
 
         $expectedHeaders = [
             ['HTTP/1.0 404', true, null],
@@ -110,7 +113,7 @@ content="0;url=data:text/html;base64,PHNjcmlwdD5hbGVydCgndGVzdDMnKTwvc2NyaXB0Pg"
     {
         $exception = new \Exception('foo');
 
-        $handler = $this->getMockBuilder('Symfony\Component\ErrorCatcher\ExceptionHandler')->setMethods(['sendPhpResponse'])->getMock();
+        $handler = $this->getMockBuilder('Symfony\Component\Debug\ExceptionHandler')->setMethods(['sendPhpResponse'])->getMock();
         $handler
             ->expects($this->exactly(2))
             ->method('sendPhpResponse');
@@ -128,7 +131,7 @@ content="0;url=data:text/html;base64,PHNjcmlwdD5hbGVydCgndGVzdDMnKTwvc2NyaXB0Pg"
     {
         $exception = new OutOfMemoryException('foo', 0, E_ERROR, __FILE__, __LINE__);
 
-        $handler = $this->getMockBuilder('Symfony\Component\ErrorCatcher\ExceptionHandler')->setMethods(['sendPhpResponse'])->getMock();
+        $handler = $this->getMockBuilder('Symfony\Component\Debug\ExceptionHandler')->setMethods(['sendPhpResponse'])->getMock();
         $handler
             ->expects($this->once())
             ->method('sendPhpResponse');
diff --git a/src/Symfony/Component/ErrorCatcher/Tests/FatalErrorHandler/ClassNotFoundFatalErrorHandlerTest.php b/src/Symfony/Component/Debug/Tests/FatalErrorHandler/ClassNotFoundFatalErrorHandlerTest.php
similarity index 80%
rename from src/Symfony/Component/ErrorCatcher/Tests/FatalErrorHandler/ClassNotFoundFatalErrorHandlerTest.php
rename to src/Symfony/Component/Debug/Tests/FatalErrorHandler/ClassNotFoundFatalErrorHandlerTest.php
index 0d02f6ca93..8e615ac640 100644
--- a/src/Symfony/Component/ErrorCatcher/Tests/FatalErrorHandler/ClassNotFoundFatalErrorHandlerTest.php
+++ b/src/Symfony/Component/Debug/Tests/FatalErrorHandler/ClassNotFoundFatalErrorHandlerTest.php
@@ -9,13 +9,13 @@
  * file that was distributed with this source code.
  */
 
-namespace Symfony\Component\ErrorCatcher\Tests\FatalErrorHandler;
+namespace Symfony\Component\Debug\Tests\FatalErrorHandler;
 
 use Composer\Autoload\ClassLoader as ComposerClassLoader;
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\Debug\DebugClassLoader;
-use Symfony\Component\ErrorCatcher\Exception\FatalErrorException;
-use Symfony\Component\ErrorCatcher\FatalErrorHandler\ClassNotFoundFatalErrorHandler;
+use Symfony\Component\Debug\Exception\FatalErrorException;
+use Symfony\Component\Debug\FatalErrorHandler\ClassNotFoundFatalErrorHandler;
 
 class ClassNotFoundFatalErrorHandlerTest extends TestCase
 {
@@ -32,7 +32,7 @@ class ClassNotFoundFatalErrorHandlerTest extends TestCase
             }
 
             if ($function[0] instanceof ComposerClassLoader) {
-                $function[0]->add('Symfony_Component_ErrorCatcher_Tests_Fixtures', \dirname(\dirname(\dirname(\dirname(\dirname(__DIR__))))));
+                $function[0]->add('Symfony_Component_Debug_Tests_Fixtures', \dirname(\dirname(\dirname(\dirname(\dirname(__DIR__))))));
                 break;
             }
         }
@@ -60,7 +60,7 @@ class ClassNotFoundFatalErrorHandlerTest extends TestCase
             array_map('spl_autoload_register', $autoloaders);
         }
 
-        $this->assertInstanceOf('Symfony\Component\ErrorCatcher\Exception\ClassNotFoundException', $exception);
+        $this->assertInstanceOf('Symfony\Component\Debug\Exception\ClassNotFoundException', $exception);
         $this->assertSame($translatedMessage, $exception->getMessage());
         $this->assertSame($error['type'], $exception->getSeverity());
         $this->assertSame($error['file'], $exception->getFile());
@@ -70,7 +70,7 @@ class ClassNotFoundFatalErrorHandlerTest extends TestCase
     public function provideClassNotFoundData()
     {
         $autoloader = new ComposerClassLoader();
-        $autoloader->add('Symfony\Component\ErrorCatcher\Exception\\', realpath(__DIR__.'/../../Exception'));
+        $autoloader->add('Symfony\Component\Debug\Exception\\', realpath(__DIR__.'/../../Exception'));
 
         $debugClassLoader = new DebugClassLoader([$autoloader, 'loadClass']);
 
@@ -98,9 +98,9 @@ class ClassNotFoundFatalErrorHandlerTest extends TestCase
                     'type' => 1,
                     'line' => 12,
                     'file' => 'foo.php',
-                    'message' => 'Class \'UndefinedFuncException\' not found',
+                    'message' => 'Class \'UndefinedFunctionException\' not found',
                 ],
-                "Attempted to load class \"UndefinedFuncException\" from the global namespace.\nDid you forget a \"use\" statement for \"Symfony\Component\ErrorCatcher\Tests\Fixtures\UndefinedFuncException\"?",
+                "Attempted to load class \"UndefinedFunctionException\" from the global namespace.\nDid you forget a \"use\" statement for \"Symfony\Component\Debug\Exception\UndefinedFunctionException\"?",
             ],
             [
                 [
@@ -109,16 +109,7 @@ class ClassNotFoundFatalErrorHandlerTest extends TestCase
                     'file' => 'foo.php',
                     'message' => 'Class \'PEARClass\' not found',
                 ],
-                "Attempted to load class \"PEARClass\" from the global namespace.\nDid you forget a \"use\" statement for \"Symfony_Component_ErrorCatcher_Tests_Fixtures_PEARClass\"?",
-            ],
-            [
-                [
-                    'type' => 1,
-                    'line' => 12,
-                    'file' => 'foo.php',
-                    'message' => 'Class \'Foo\\Bar\\UndefinedFuncException\' not found',
-                ],
-                "Attempted to load class \"UndefinedFuncException\" from namespace \"Foo\Bar\".\nDid you forget a \"use\" statement for \"Symfony\Component\ErrorCatcher\Tests\Fixtures\UndefinedFuncException\"?",
+                "Attempted to load class \"PEARClass\" from the global namespace.\nDid you forget a \"use\" statement for \"Symfony_Component_Debug_Tests_Fixtures_PEARClass\"?",
             ],
             [
                 [
@@ -127,7 +118,16 @@ class ClassNotFoundFatalErrorHandlerTest extends TestCase
                     'file' => 'foo.php',
                     'message' => 'Class \'Foo\\Bar\\UndefinedFunctionException\' not found',
                 ],
-                "Attempted to load class \"UndefinedFunctionException\" from namespace \"Foo\Bar\".\nDid you forget a \"use\" statement for \"Symfony\Component\ErrorCatcher\Exception\UndefinedFunctionException\"?",
+                "Attempted to load class \"UndefinedFunctionException\" from namespace \"Foo\Bar\".\nDid you forget a \"use\" statement for \"Symfony\Component\Debug\Exception\UndefinedFunctionException\"?",
+            ],
+            [
+                [
+                    'type' => 1,
+                    'line' => 12,
+                    'file' => 'foo.php',
+                    'message' => 'Class \'Foo\\Bar\\UndefinedFunctionException\' not found',
+                ],
+                "Attempted to load class \"UndefinedFunctionException\" from namespace \"Foo\Bar\".\nDid you forget a \"use\" statement for \"Symfony\Component\Debug\Exception\UndefinedFunctionException\"?",
                 [$autoloader, 'loadClass'],
             ],
             [
@@ -137,7 +137,7 @@ class ClassNotFoundFatalErrorHandlerTest extends TestCase
                     'file' => 'foo.php',
                     'message' => 'Class \'Foo\\Bar\\UndefinedFunctionException\' not found',
                 ],
-                "Attempted to load class \"UndefinedFunctionException\" from namespace \"Foo\Bar\".\nDid you forget a \"use\" statement for \"Symfony\Component\ErrorCatcher\Exception\UndefinedFunctionException\"?",
+                "Attempted to load class \"UndefinedFunctionException\" from namespace \"Foo\Bar\".\nDid you forget a \"use\" statement for \"Symfony\Component\Debug\Exception\UndefinedFunctionException\"?",
                 [$debugClassLoader, 'loadClass'],
             ],
             [
@@ -171,6 +171,6 @@ class ClassNotFoundFatalErrorHandlerTest extends TestCase
         $handler = new ClassNotFoundFatalErrorHandler();
         $exception = $handler->handleError($error, new FatalErrorException('', 0, $error['type'], $error['file'], $error['line']));
 
-        $this->assertInstanceOf('Symfony\Component\ErrorCatcher\Exception\ClassNotFoundException', $exception);
+        $this->assertInstanceOf('Symfony\Component\Debug\Exception\ClassNotFoundException', $exception);
     }
 }
diff --git a/src/Symfony/Component/ErrorCatcher/Tests/FatalErrorHandler/UndefinedFunctionFatalErrorHandlerTest.php b/src/Symfony/Component/Debug/Tests/FatalErrorHandler/UndefinedFunctionFatalErrorHandlerTest.php
similarity index 84%
rename from src/Symfony/Component/ErrorCatcher/Tests/FatalErrorHandler/UndefinedFunctionFatalErrorHandlerTest.php
rename to src/Symfony/Component/Debug/Tests/FatalErrorHandler/UndefinedFunctionFatalErrorHandlerTest.php
index cf8a5fc319..de9994e447 100644
--- a/src/Symfony/Component/ErrorCatcher/Tests/FatalErrorHandler/UndefinedFunctionFatalErrorHandlerTest.php
+++ b/src/Symfony/Component/Debug/Tests/FatalErrorHandler/UndefinedFunctionFatalErrorHandlerTest.php
@@ -9,11 +9,11 @@
  * file that was distributed with this source code.
  */
 
-namespace Symfony\Component\ErrorCatcher\Tests\FatalErrorHandler;
+namespace Symfony\Component\Debug\Tests\FatalErrorHandler;
 
 use PHPUnit\Framework\TestCase;
-use Symfony\Component\ErrorCatcher\Exception\FatalErrorException;
-use Symfony\Component\ErrorCatcher\FatalErrorHandler\UndefinedFunctionFatalErrorHandler;
+use Symfony\Component\Debug\Exception\FatalErrorException;
+use Symfony\Component\Debug\FatalErrorHandler\UndefinedFunctionFatalErrorHandler;
 
 class UndefinedFunctionFatalErrorHandlerTest extends TestCase
 {
@@ -25,7 +25,7 @@ class UndefinedFunctionFatalErrorHandlerTest extends TestCase
         $handler = new UndefinedFunctionFatalErrorHandler();
         $exception = $handler->handleError($error, new FatalErrorException('', 0, $error['type'], $error['file'], $error['line']));
 
-        $this->assertInstanceOf('Symfony\Component\ErrorCatcher\Exception\UndefinedFunctionException', $exception);
+        $this->assertInstanceOf('Symfony\Component\Debug\Exception\UndefinedFunctionException', $exception);
         // class names are case insensitive and PHP do not return the same
         $this->assertSame(strtolower($translatedMessage), strtolower($exception->getMessage()));
         $this->assertSame($error['type'], $exception->getSeverity());
@@ -43,7 +43,7 @@ class UndefinedFunctionFatalErrorHandlerTest extends TestCase
                     'file' => 'foo.php',
                     'message' => 'Call to undefined function test_namespaced_function()',
                 ],
-                "Attempted to call function \"test_namespaced_function\" from the global namespace.\nDid you mean to call \"\\symfony\\component\\errorcatcher\\tests\\fatalerrorhandler\\test_namespaced_function\"?",
+                "Attempted to call function \"test_namespaced_function\" from the global namespace.\nDid you mean to call \"\\symfony\\component\\debug\\tests\\fatalerrorhandler\\test_namespaced_function\"?",
             ],
             [
                 [
@@ -52,7 +52,7 @@ class UndefinedFunctionFatalErrorHandlerTest extends TestCase
                     'file' => 'foo.php',
                     'message' => 'Call to undefined function Foo\\Bar\\Baz\\test_namespaced_function()',
                 ],
-                "Attempted to call function \"test_namespaced_function\" from namespace \"Foo\\Bar\\Baz\".\nDid you mean to call \"\\symfony\\component\\errorcatcher\\tests\\fatalerrorhandler\\test_namespaced_function\"?",
+                "Attempted to call function \"test_namespaced_function\" from namespace \"Foo\\Bar\\Baz\".\nDid you mean to call \"\\symfony\\component\\debug\\tests\\fatalerrorhandler\\test_namespaced_function\"?",
             ],
             [
                 [
diff --git a/src/Symfony/Component/ErrorCatcher/Tests/FatalErrorHandler/UndefinedMethodFatalErrorHandlerTest.php b/src/Symfony/Component/Debug/Tests/FatalErrorHandler/UndefinedMethodFatalErrorHandlerTest.php
similarity index 88%
rename from src/Symfony/Component/ErrorCatcher/Tests/FatalErrorHandler/UndefinedMethodFatalErrorHandlerTest.php
rename to src/Symfony/Component/Debug/Tests/FatalErrorHandler/UndefinedMethodFatalErrorHandlerTest.php
index 0f0c9c5f2d..268a841351 100644
--- a/src/Symfony/Component/ErrorCatcher/Tests/FatalErrorHandler/UndefinedMethodFatalErrorHandlerTest.php
+++ b/src/Symfony/Component/Debug/Tests/FatalErrorHandler/UndefinedMethodFatalErrorHandlerTest.php
@@ -9,11 +9,11 @@
  * file that was distributed with this source code.
  */
 
-namespace Symfony\Component\ErrorCatcher\Tests\FatalErrorHandler;
+namespace Symfony\Component\Debug\Tests\FatalErrorHandler;
 
 use PHPUnit\Framework\TestCase;
-use Symfony\Component\ErrorCatcher\Exception\FatalErrorException;
-use Symfony\Component\ErrorCatcher\FatalErrorHandler\UndefinedMethodFatalErrorHandler;
+use Symfony\Component\Debug\Exception\FatalErrorException;
+use Symfony\Component\Debug\FatalErrorHandler\UndefinedMethodFatalErrorHandler;
 
 class UndefinedMethodFatalErrorHandlerTest extends TestCase
 {
@@ -25,7 +25,7 @@ class UndefinedMethodFatalErrorHandlerTest extends TestCase
         $handler = new UndefinedMethodFatalErrorHandler();
         $exception = $handler->handleError($error, new FatalErrorException('', 0, $error['type'], $error['file'], $error['line']));
 
-        $this->assertInstanceOf('Symfony\Component\ErrorCatcher\Exception\UndefinedMethodException', $exception);
+        $this->assertInstanceOf('Symfony\Component\Debug\Exception\UndefinedMethodException', $exception);
         $this->assertSame($translatedMessage, $exception->getMessage());
         $this->assertSame($error['type'], $exception->getSeverity());
         $this->assertSame($error['file'], $exception->getFile());
diff --git a/src/Symfony/Component/ErrorCatcher/Tests/Fixtures/ErrorHandlerThatUsesThePreviousOne.php b/src/Symfony/Component/Debug/Tests/Fixtures/ErrorHandlerThatUsesThePreviousOne.php
similarity index 88%
rename from src/Symfony/Component/ErrorCatcher/Tests/Fixtures/ErrorHandlerThatUsesThePreviousOne.php
rename to src/Symfony/Component/Debug/Tests/Fixtures/ErrorHandlerThatUsesThePreviousOne.php
index c3c477fbf5..d449c40cc7 100644
--- a/src/Symfony/Component/ErrorCatcher/Tests/Fixtures/ErrorHandlerThatUsesThePreviousOne.php
+++ b/src/Symfony/Component/Debug/Tests/Fixtures/ErrorHandlerThatUsesThePreviousOne.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Symfony\Component\ErrorCatcher\Tests\Fixtures;
+namespace Symfony\Component\Debug\Tests\Fixtures;
 
 class ErrorHandlerThatUsesThePreviousOne
 {
diff --git a/src/Symfony/Component/Debug/Tests/Fixtures/LoggerThatSetAnErrorHandler.php b/src/Symfony/Component/Debug/Tests/Fixtures/LoggerThatSetAnErrorHandler.php
new file mode 100644
index 0000000000..dd8563627a
--- /dev/null
+++ b/src/Symfony/Component/Debug/Tests/Fixtures/LoggerThatSetAnErrorHandler.php
@@ -0,0 +1,15 @@
+<?php
+
+namespace Symfony\Component\Debug\Tests\Fixtures;
+
+use Symfony\Component\Debug\BufferingLogger;
+
+class LoggerThatSetAnErrorHandler extends BufferingLogger
+{
+    public function log($level, $message, array $context = [])
+    {
+        set_error_handler('is_string');
+        parent::log($level, $message, $context);
+        restore_error_handler();
+    }
+}
diff --git a/src/Symfony/Component/Debug/Tests/Fixtures/PEARClass.php b/src/Symfony/Component/Debug/Tests/Fixtures/PEARClass.php
new file mode 100644
index 0000000000..39f228182e
--- /dev/null
+++ b/src/Symfony/Component/Debug/Tests/Fixtures/PEARClass.php
@@ -0,0 +1,5 @@
+<?php
+
+class Symfony_Component_Debug_Tests_Fixtures_PEARClass
+{
+}
diff --git a/src/Symfony/Component/ErrorCatcher/Tests/Fixtures/ToStringThrower.php b/src/Symfony/Component/Debug/Tests/Fixtures/ToStringThrower.php
similarity index 89%
rename from src/Symfony/Component/ErrorCatcher/Tests/Fixtures/ToStringThrower.php
rename to src/Symfony/Component/Debug/Tests/Fixtures/ToStringThrower.php
index 22d4b052b5..24ac8926d2 100644
--- a/src/Symfony/Component/ErrorCatcher/Tests/Fixtures/ToStringThrower.php
+++ b/src/Symfony/Component/Debug/Tests/Fixtures/ToStringThrower.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Symfony\Component\ErrorCatcher\Tests\Fixtures;
+namespace Symfony\Component\Debug\Tests\Fixtures;
 
 class ToStringThrower
 {
diff --git a/src/Symfony/Component/Debug/Tests/Fixtures2/RequiredTwice.php b/src/Symfony/Component/Debug/Tests/Fixtures2/RequiredTwice.php
new file mode 100644
index 0000000000..604bc37ff1
--- /dev/null
+++ b/src/Symfony/Component/Debug/Tests/Fixtures2/RequiredTwice.php
@@ -0,0 +1,7 @@
+<?php
+
+namespace Symfony\Component\Debug\Tests\Fixtures2;
+
+class RequiredTwice
+{
+}
diff --git a/src/Symfony/Component/ErrorCatcher/Tests/HeaderMock.php b/src/Symfony/Component/Debug/Tests/HeaderMock.php
similarity index 86%
rename from src/Symfony/Component/ErrorCatcher/Tests/HeaderMock.php
rename to src/Symfony/Component/Debug/Tests/HeaderMock.php
index 1e7b947d5e..d7564db485 100644
--- a/src/Symfony/Component/ErrorCatcher/Tests/HeaderMock.php
+++ b/src/Symfony/Component/Debug/Tests/HeaderMock.php
@@ -9,7 +9,7 @@
  * file that was distributed with this source code.
  */
 
-namespace Symfony\Component\ErrorCatcher;
+namespace Symfony\Component\Debug;
 
 function headers_sent()
 {
@@ -21,7 +21,7 @@ function header($str, $replace = true, $status = null)
     Tests\testHeader($str, $replace, $status);
 }
 
-namespace Symfony\Component\ErrorCatcher\Tests;
+namespace Symfony\Component\Debug\Tests;
 
 function testHeader()
 {
diff --git a/src/Symfony/Component/ErrorCatcher/Tests/MockExceptionHandler.php b/src/Symfony/Component/Debug/Tests/MockExceptionHandler.php
similarity index 79%
rename from src/Symfony/Component/ErrorCatcher/Tests/MockExceptionHandler.php
rename to src/Symfony/Component/Debug/Tests/MockExceptionHandler.php
index b09f9a7497..2d6ce564d2 100644
--- a/src/Symfony/Component/ErrorCatcher/Tests/MockExceptionHandler.php
+++ b/src/Symfony/Component/Debug/Tests/MockExceptionHandler.php
@@ -9,9 +9,9 @@
  * file that was distributed with this source code.
  */
 
-namespace Symfony\Component\ErrorCatcher\Tests;
+namespace Symfony\Component\Debug\Tests;
 
-use Symfony\Component\ErrorCatcher\ExceptionHandler;
+use Symfony\Component\Debug\ExceptionHandler;
 
 class MockExceptionHandler extends ExceptionHandler
 {
diff --git a/src/Symfony/Component/ErrorCatcher/Tests/phpt/decorate_exception_hander.phpt b/src/Symfony/Component/Debug/Tests/phpt/decorate_exception_hander.phpt
similarity index 78%
rename from src/Symfony/Component/ErrorCatcher/Tests/phpt/decorate_exception_hander.phpt
rename to src/Symfony/Component/Debug/Tests/phpt/decorate_exception_hander.phpt
index 754b39990c..9cd44388c3 100644
--- a/src/Symfony/Component/ErrorCatcher/Tests/phpt/decorate_exception_hander.phpt
+++ b/src/Symfony/Component/Debug/Tests/phpt/decorate_exception_hander.phpt
@@ -5,7 +5,7 @@ display_errors=0
 --FILE--
 <?php
 
-namespace Symfony\Component\ErrorCatcher;
+namespace Symfony\Component\Debug;
 
 $vendor = __DIR__;
 while (!file_exists($vendor.'/vendor')) {
@@ -26,9 +26,9 @@ if (true) {
 
 ?>
 --EXPECTF--
-object(Symfony\Component\ErrorCatcher\Exception\ClassNotFoundException)#%d (8) {
+object(Symfony\Component\Debug\Exception\ClassNotFoundException)#%d (8) {
   ["message":protected]=>
-  string(138) "Attempted to load class "missing" from namespace "Symfony\Component\ErrorCatcher".
+  string(131) "Attempted to load class "missing" from namespace "Symfony\Component\Debug".
 Did you forget a "use" statement for another namespace?"
   ["string":"Exception":private]=>
   string(0) ""
diff --git a/src/Symfony/Component/ErrorCatcher/Tests/phpt/exception_rethrown.phpt b/src/Symfony/Component/Debug/Tests/phpt/exception_rethrown.phpt
similarity index 94%
rename from src/Symfony/Component/ErrorCatcher/Tests/phpt/exception_rethrown.phpt
rename to src/Symfony/Component/Debug/Tests/phpt/exception_rethrown.phpt
index df3495c991..b743d93ad7 100644
--- a/src/Symfony/Component/ErrorCatcher/Tests/phpt/exception_rethrown.phpt
+++ b/src/Symfony/Component/Debug/Tests/phpt/exception_rethrown.phpt
@@ -3,7 +3,7 @@ Test rethrowing in custom exception handler
 --FILE--
 <?php
 
-namespace Symfony\Component\ErrorCatcher;
+namespace Symfony\Component\Debug;
 
 $vendor = __DIR__;
 while (!file_exists($vendor.'/vendor')) {
diff --git a/src/Symfony/Component/ErrorCatcher/Tests/phpt/fatal_with_nested_handlers.phpt b/src/Symfony/Component/Debug/Tests/phpt/fatal_with_nested_handlers.phpt
similarity index 67%
rename from src/Symfony/Component/ErrorCatcher/Tests/phpt/fatal_with_nested_handlers.phpt
rename to src/Symfony/Component/Debug/Tests/phpt/fatal_with_nested_handlers.phpt
index e43a6d3b24..1736a3b5f2 100644
--- a/src/Symfony/Component/ErrorCatcher/Tests/phpt/fatal_with_nested_handlers.phpt
+++ b/src/Symfony/Component/Debug/Tests/phpt/fatal_with_nested_handlers.phpt
@@ -3,9 +3,7 @@ Test catching fatal errors when handlers are nested
 --FILE--
 <?php
 
-namespace Symfony\Component\ErrorCatcher;
-
-use Symfony\Component\Debug\Debug;
+namespace Symfony\Component\Debug;
 
 $vendor = __DIR__;
 while (!file_exists($vendor.'/vendor')) {
@@ -37,8 +35,8 @@ array(1) {
   [0]=>
   string(37) "Error and exception handlers do match"
 }
-object(Symfony\Component\ErrorCatcher\Exception\FatalErrorException)#%d (%d) {
+object(Symfony\Component\Debug\Exception\FatalErrorException)#%d (%d) {
   ["message":protected]=>
-  string(186) "Error: Class Symfony\Component\ErrorCatcher\Broken contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (JsonSerializable::jsonSerialize)"
+  string(179) "Error: Class Symfony\Component\Debug\Broken contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (JsonSerializable::jsonSerialize)"
 %a
 }
diff --git a/src/Symfony/Component/Debug/composer.json b/src/Symfony/Component/Debug/composer.json
index 90f0347e6f..96fe201bdd 100644
--- a/src/Symfony/Component/Debug/composer.json
+++ b/src/Symfony/Component/Debug/composer.json
@@ -17,8 +17,7 @@
     ],
     "require": {
         "php": "^7.1.3",
-        "psr/log": "~1.0",
-        "symfony/error-catcher": "^4.4|^5.0"
+        "psr/log": "~1.0"
     },
     "conflict": {
         "symfony/http-kernel": "<3.4"
diff --git a/src/Symfony/Component/ErrorCatcher/BufferingLogger.php b/src/Symfony/Component/ErrorCatcher/BufferingLogger.php
deleted file mode 100644
index c0f1c56302..0000000000
--- a/src/Symfony/Component/ErrorCatcher/BufferingLogger.php
+++ /dev/null
@@ -1,37 +0,0 @@
-<?php
-
-/*
- * This file is part of the Symfony package.
- *
- * (c) Fabien Potencier <fabien@symfony.com>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
-namespace Symfony\Component\ErrorCatcher;
-
-use Psr\Log\AbstractLogger;
-
-/**
- * A buffering logger that stacks logs for later.
- *
- * @author Nicolas Grekas <p@tchwork.com>
- */
-final class BufferingLogger extends AbstractLogger
-{
-    private $logs = [];
-
-    public function log($level, $message, array $context = [])
-    {
-        $this->logs[] = [$level, $message, $context];
-    }
-
-    public function cleanLogs(): array
-    {
-        $logs = $this->logs;
-        $this->logs = [];
-
-        return $logs;
-    }
-}
diff --git a/src/Symfony/Component/ErrorCatcher/ErrorHandler.php b/src/Symfony/Component/ErrorCatcher/ErrorHandler.php
deleted file mode 100644
index 635482d42a..0000000000
--- a/src/Symfony/Component/ErrorCatcher/ErrorHandler.php
+++ /dev/null
@@ -1,711 +0,0 @@
-<?php
-
-/*
- * This file is part of the Symfony package.
- *
- * (c) Fabien Potencier <fabien@symfony.com>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
-namespace Symfony\Component\ErrorCatcher;
-
-use Psr\Log\LoggerInterface;
-use Psr\Log\LogLevel;
-use Symfony\Component\Debug\DebugClassLoader;
-use Symfony\Component\ErrorCatcher\Exception\FatalErrorException;
-use Symfony\Component\ErrorCatcher\Exception\FatalThrowableError;
-use Symfony\Component\ErrorCatcher\Exception\FlattenException;
-use Symfony\Component\ErrorCatcher\Exception\OutOfMemoryException;
-use Symfony\Component\ErrorCatcher\Exception\SilencedErrorContext;
-use Symfony\Component\ErrorCatcher\FatalErrorHandler\ClassNotFoundFatalErrorHandler;
-use Symfony\Component\ErrorCatcher\FatalErrorHandler\FatalErrorHandlerInterface;
-use Symfony\Component\ErrorCatcher\FatalErrorHandler\UndefinedFunctionFatalErrorHandler;
-use Symfony\Component\ErrorCatcher\FatalErrorHandler\UndefinedMethodFatalErrorHandler;
-
-/**
- * A generic ErrorHandler for the PHP engine.
- *
- * Provides five bit fields that control how errors are handled:
- * - thrownErrors: errors thrown as \ErrorException
- * - loggedErrors: logged errors, when not @-silenced
- * - scopedErrors: errors thrown or logged with their local context
- * - tracedErrors: errors logged with their stack trace
- * - screamedErrors: never @-silenced errors
- *
- * Each error level can be logged by a dedicated PSR-3 logger object.
- * Screaming only applies to logging.
- * Throwing takes precedence over logging.
- * Uncaught exceptions are logged as E_ERROR.
- * E_DEPRECATED and E_USER_DEPRECATED levels never throw.
- * E_RECOVERABLE_ERROR and E_USER_ERROR levels always throw.
- * Non catchable errors that can be detected at shutdown time are logged when the scream bit field allows so.
- * As errors have a performance cost, repeated errors are all logged, so that the developer
- * can see them and weight them as more important to fix than others of the same level.
- *
- * @author Nicolas Grekas <p@tchwork.com>
- * @author Grégoire Pineau <lyrixx@lyrixx.info>
- *
- * @final
- */
-class ErrorHandler
-{
-    private $levels = [
-        E_COMPILE_ERROR => 'Compile Error',
-        E_COMPILE_WARNING => 'Compile Warning',
-        E_CORE_ERROR => 'Core Error',
-        E_CORE_WARNING => 'Core Warning',
-        E_DEPRECATED => 'Deprecated',
-        E_ERROR => 'Error',
-        E_NOTICE => 'Notice',
-        E_PARSE => 'Parse Error',
-        E_RECOVERABLE_ERROR => 'Catchable Fatal Error',
-        E_STRICT => 'Runtime Notice',
-        E_USER_DEPRECATED => 'User Deprecated',
-        E_USER_ERROR => 'User Error',
-        E_USER_NOTICE => 'User Notice',
-        E_USER_WARNING => 'User Warning',
-        E_WARNING => 'Warning',
-    ];
-
-    private $loggers = [
-        E_COMPILE_ERROR => [null, LogLevel::CRITICAL],
-        E_COMPILE_WARNING => [null, LogLevel::WARNING],
-        E_CORE_ERROR => [null, LogLevel::CRITICAL],
-        E_CORE_WARNING => [null, LogLevel::WARNING],
-        E_DEPRECATED => [null, LogLevel::INFO],
-        E_ERROR => [null, LogLevel::CRITICAL],
-        E_NOTICE => [null, LogLevel::WARNING],
-        E_PARSE => [null, LogLevel::CRITICAL],
-        E_RECOVERABLE_ERROR => [null, LogLevel::CRITICAL],
-        E_STRICT => [null, LogLevel::WARNING],
-        E_USER_DEPRECATED => [null, LogLevel::INFO],
-        E_USER_ERROR => [null, LogLevel::CRITICAL],
-        E_USER_NOTICE => [null, LogLevel::WARNING],
-        E_USER_WARNING => [null, LogLevel::WARNING],
-        E_WARNING => [null, LogLevel::WARNING],
-    ];
-
-    private $thrownErrors = 0x1FFF; // E_ALL - E_DEPRECATED - E_USER_DEPRECATED
-    private $scopedErrors = 0x1FFF; // E_ALL - E_DEPRECATED - E_USER_DEPRECATED
-    private $tracedErrors = 0x77FB; // E_ALL - E_STRICT - E_PARSE
-    private $screamedErrors = 0x55; // E_ERROR + E_CORE_ERROR + E_COMPILE_ERROR + E_PARSE
-    private $loggedErrors = 0;
-    private $traceReflector;
-
-    private $isRecursive = 0;
-    private $isRoot = false;
-    private $exceptionHandler;
-    private $bootstrappingLogger;
-
-    private static $reservedMemory;
-    private static $toStringException = null;
-    private static $silencedErrorCache = [];
-    private static $silencedErrorCount = 0;
-    private static $exitCode = 0;
-
-    /**
-     * Registers the error handler.
-     *
-     * @param self|null $handler The handler to register
-     * @param bool      $replace Whether to replace or not any existing handler
-     *
-     * @return self The registered error handler
-     */
-    public static function register(self $handler = null, $replace = true)
-    {
-        if (null === self::$reservedMemory) {
-            self::$reservedMemory = str_repeat('x', 10240);
-            register_shutdown_function(__CLASS__.'::handleFatalError');
-        }
-
-        if ($handlerIsNew = null === $handler) {
-            $handler = new static();
-        }
-
-        if (null === $prev = set_error_handler([$handler, 'handleError'])) {
-            restore_error_handler();
-            // Specifying the error types earlier would expose us to https://bugs.php.net/63206
-            set_error_handler([$handler, 'handleError'], $handler->thrownErrors | $handler->loggedErrors);
-            $handler->isRoot = true;
-        }
-
-        if ($handlerIsNew && \is_array($prev) && $prev[0] instanceof self) {
-            $handler = $prev[0];
-            $replace = false;
-        }
-        if (!$replace && $prev) {
-            restore_error_handler();
-            $handlerIsRegistered = \is_array($prev) && $handler === $prev[0];
-        } else {
-            $handlerIsRegistered = true;
-        }
-        if (\is_array($prev = set_exception_handler([$handler, 'handleException'])) && $prev[0] instanceof self) {
-            restore_exception_handler();
-            if (!$handlerIsRegistered) {
-                $handler = $prev[0];
-            } elseif ($handler !== $prev[0] && $replace) {
-                set_exception_handler([$handler, 'handleException']);
-                $p = $prev[0]->setExceptionHandler(null);
-                $handler->setExceptionHandler($p);
-                $prev[0]->setExceptionHandler($p);
-            }
-        } else {
-            $handler->setExceptionHandler($prev);
-        }
-
-        $handler->throwAt(E_ALL & $handler->thrownErrors, true);
-
-        return $handler;
-    }
-
-    public function __construct(BufferingLogger $bootstrappingLogger = null)
-    {
-        if ($bootstrappingLogger) {
-            $this->bootstrappingLogger = $bootstrappingLogger;
-            $this->setDefaultLogger($bootstrappingLogger);
-        }
-        $this->traceReflector = new \ReflectionProperty('Exception', 'trace');
-        $this->traceReflector->setAccessible(true);
-    }
-
-    /**
-     * Sets a logger to non assigned errors levels.
-     *
-     * @param LoggerInterface $logger  A PSR-3 logger to put as default for the given levels
-     * @param array|int       $levels  An array map of E_* to LogLevel::* or an integer bit field of E_* constants
-     * @param bool            $replace Whether to replace or not any existing logger
-     */
-    public function setDefaultLogger(LoggerInterface $logger, $levels = E_ALL, $replace = false)
-    {
-        $loggers = [];
-
-        if (\is_array($levels)) {
-            foreach ($levels as $type => $logLevel) {
-                if (empty($this->loggers[$type][0]) || $replace || $this->loggers[$type][0] === $this->bootstrappingLogger) {
-                    $loggers[$type] = [$logger, $logLevel];
-                }
-            }
-        } else {
-            if (null === $levels) {
-                $levels = E_ALL;
-            }
-            foreach ($this->loggers as $type => $log) {
-                if (($type & $levels) && (empty($log[0]) || $replace || $log[0] === $this->bootstrappingLogger)) {
-                    $log[0] = $logger;
-                    $loggers[$type] = $log;
-                }
-            }
-        }
-
-        $this->setLoggers($loggers);
-    }
-
-    /**
-     * Sets a logger for each error level.
-     *
-     * @param array $loggers Error levels to [LoggerInterface|null, LogLevel::*] map
-     *
-     * @return array The previous map
-     *
-     * @throws \InvalidArgumentException
-     */
-    public function setLoggers(array $loggers)
-    {
-        $prevLogged = $this->loggedErrors;
-        $prev = $this->loggers;
-        $flush = [];
-
-        foreach ($loggers as $type => $log) {
-            if (!isset($prev[$type])) {
-                throw new \InvalidArgumentException('Unknown error type: '.$type);
-            }
-            if (!\is_array($log)) {
-                $log = [$log];
-            } elseif (!\array_key_exists(0, $log)) {
-                throw new \InvalidArgumentException('No logger provided');
-            }
-            if (null === $log[0]) {
-                $this->loggedErrors &= ~$type;
-            } elseif ($log[0] instanceof LoggerInterface) {
-                $this->loggedErrors |= $type;
-            } else {
-                throw new \InvalidArgumentException('Invalid logger provided');
-            }
-            $this->loggers[$type] = $log + $prev[$type];
-
-            if ($this->bootstrappingLogger && $prev[$type][0] === $this->bootstrappingLogger) {
-                $flush[$type] = $type;
-            }
-        }
-        $this->reRegister($prevLogged | $this->thrownErrors);
-
-        if ($flush) {
-            foreach ($this->bootstrappingLogger->cleanLogs() as $log) {
-                $type = $log[2]['exception'] instanceof \ErrorException ? $log[2]['exception']->getSeverity() : E_ERROR;
-                if (!isset($flush[$type])) {
-                    $this->bootstrappingLogger->log($log[0], $log[1], $log[2]);
-                } elseif ($this->loggers[$type][0]) {
-                    $this->loggers[$type][0]->log($this->loggers[$type][1], $log[1], $log[2]);
-                }
-            }
-        }
-
-        return $prev;
-    }
-
-    /**
-     * Sets a user exception handler.
-     *
-     * @param callable $handler A handler that will be called on Exception
-     *
-     * @return callable|null The previous exception handler
-     */
-    public function setExceptionHandler(callable $handler = null)
-    {
-        $prev = $this->exceptionHandler;
-        $this->exceptionHandler = $handler;
-
-        return $prev;
-    }
-
-    /**
-     * Sets the PHP error levels that throw an exception when a PHP error occurs.
-     *
-     * @param int  $levels  A bit field of E_* constants for thrown errors
-     * @param bool $replace Replace or amend the previous value
-     *
-     * @return int The previous value
-     */
-    public function throwAt($levels, $replace = false)
-    {
-        $prev = $this->thrownErrors;
-        $this->thrownErrors = ($levels | E_RECOVERABLE_ERROR | E_USER_ERROR) & ~E_USER_DEPRECATED & ~E_DEPRECATED;
-        if (!$replace) {
-            $this->thrownErrors |= $prev;
-        }
-        $this->reRegister($prev | $this->loggedErrors);
-
-        return $prev;
-    }
-
-    /**
-     * Sets the PHP error levels for which local variables are preserved.
-     *
-     * @param int  $levels  A bit field of E_* constants for scoped errors
-     * @param bool $replace Replace or amend the previous value
-     *
-     * @return int The previous value
-     */
-    public function scopeAt($levels, $replace = false)
-    {
-        $prev = $this->scopedErrors;
-        $this->scopedErrors = (int) $levels;
-        if (!$replace) {
-            $this->scopedErrors |= $prev;
-        }
-
-        return $prev;
-    }
-
-    /**
-     * Sets the PHP error levels for which the stack trace is preserved.
-     *
-     * @param int  $levels  A bit field of E_* constants for traced errors
-     * @param bool $replace Replace or amend the previous value
-     *
-     * @return int The previous value
-     */
-    public function traceAt($levels, $replace = false)
-    {
-        $prev = $this->tracedErrors;
-        $this->tracedErrors = (int) $levels;
-        if (!$replace) {
-            $this->tracedErrors |= $prev;
-        }
-
-        return $prev;
-    }
-
-    /**
-     * Sets the error levels where the @-operator is ignored.
-     *
-     * @param int  $levels  A bit field of E_* constants for screamed errors
-     * @param bool $replace Replace or amend the previous value
-     *
-     * @return int The previous value
-     */
-    public function screamAt($levels, $replace = false)
-    {
-        $prev = $this->screamedErrors;
-        $this->screamedErrors = (int) $levels;
-        if (!$replace) {
-            $this->screamedErrors |= $prev;
-        }
-
-        return $prev;
-    }
-
-    /**
-     * Re-registers as a PHP error handler if levels changed.
-     */
-    private function reRegister($prev)
-    {
-        if ($prev !== $this->thrownErrors | $this->loggedErrors) {
-            $handler = set_error_handler('var_dump');
-            $handler = \is_array($handler) ? $handler[0] : null;
-            restore_error_handler();
-            if ($handler === $this) {
-                restore_error_handler();
-                if ($this->isRoot) {
-                    set_error_handler([$this, 'handleError'], $this->thrownErrors | $this->loggedErrors);
-                } else {
-                    set_error_handler([$this, 'handleError']);
-                }
-            }
-        }
-    }
-
-    /**
-     * Handles errors by filtering then logging them according to the configured bit fields.
-     *
-     * @return bool Returns false when no handling happens so that the PHP engine can handle the error itself
-     *
-     * @throws \ErrorException When $this->thrownErrors requests so
-     *
-     * @internal
-     */
-    public function handleError(int $type, string $message, string $file, int $line): bool
-    {
-        // @deprecated to be removed in Symfony 5.0
-        if (\PHP_VERSION_ID >= 70300 && $message && '"' === $message[0] && 0 === strpos($message, '"continue') && preg_match('/^"continue(?: \d++)?" targeting switch is equivalent to "break(?: \d++)?"\. Did you mean to use "continue(?: \d++)?"\?$/', $message)) {
-            $type = E_DEPRECATED;
-        }
-
-        // Level is the current error reporting level to manage silent error.
-        $level = error_reporting();
-        $silenced = 0 === ($level & $type);
-        // Strong errors are not authorized to be silenced.
-        $level |= E_RECOVERABLE_ERROR | E_USER_ERROR | E_DEPRECATED | E_USER_DEPRECATED;
-        $log = $this->loggedErrors & $type;
-        $throw = $this->thrownErrors & $type & $level;
-        $type &= $level | $this->screamedErrors;
-
-        if (!$type || (!$log && !$throw)) {
-            return !$silenced && $type && $log;
-        }
-        $scope = $this->scopedErrors & $type;
-
-        if (4 < $numArgs = \func_num_args()) {
-            $context = $scope ? (func_get_arg(4) ?: []) : [];
-        } else {
-            $context = [];
-        }
-
-        if (isset($context['GLOBALS']) && $scope) {
-            $e = $context;                  // Whatever the signature of the method,
-            unset($e['GLOBALS'], $context);
-            $context = $e;
-        }
-
-        if (false !== strpos($message, "class@anonymous\0")) {
-            $logMessage = $this->levels[$type].': '.(new FlattenException())->setMessage($message)->getMessage();
-        } else {
-            $logMessage = $this->levels[$type].': '.$message;
-        }
-
-        if (null !== self::$toStringException) {
-            $errorAsException = self::$toStringException;
-            self::$toStringException = null;
-        } elseif (!$throw && !($type & $level)) {
-            if (!isset(self::$silencedErrorCache[$id = $file.':'.$line])) {
-                $lightTrace = $this->tracedErrors & $type ? $this->cleanTrace(debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS, 5), $type, $file, $line, false) : [];
-                $errorAsException = new SilencedErrorContext($type, $file, $line, isset($lightTrace[1]) ? [$lightTrace[0]] : $lightTrace);
-            } elseif (isset(self::$silencedErrorCache[$id][$message])) {
-                $lightTrace = null;
-                $errorAsException = self::$silencedErrorCache[$id][$message];
-                ++$errorAsException->count;
-            } else {
-                $lightTrace = [];
-                $errorAsException = null;
-            }
-
-            if (100 < ++self::$silencedErrorCount) {
-                self::$silencedErrorCache = $lightTrace = [];
-                self::$silencedErrorCount = 1;
-            }
-            if ($errorAsException) {
-                self::$silencedErrorCache[$id][$message] = $errorAsException;
-            }
-            if (null === $lightTrace) {
-                return true;
-            }
-        } else {
-            $errorAsException = new \ErrorException($logMessage, 0, $type, $file, $line);
-
-            if ($throw || $this->tracedErrors & $type) {
-                $backtrace = $errorAsException->getTrace();
-                $lightTrace = $this->cleanTrace($backtrace, $type, $file, $line, $throw);
-                $this->traceReflector->setValue($errorAsException, $lightTrace);
-            } else {
-                $this->traceReflector->setValue($errorAsException, []);
-                $backtrace = [];
-            }
-        }
-
-        if ($throw) {
-            if (E_USER_ERROR & $type) {
-                for ($i = 1; isset($backtrace[$i]); ++$i) {
-                    if (isset($backtrace[$i]['function'], $backtrace[$i]['type'], $backtrace[$i - 1]['function'])
-                        && '__toString' === $backtrace[$i]['function']
-                        && '->' === $backtrace[$i]['type']
-                        && !isset($backtrace[$i - 1]['class'])
-                        && ('trigger_error' === $backtrace[$i - 1]['function'] || 'user_error' === $backtrace[$i - 1]['function'])
-                    ) {
-                        // Here, we know trigger_error() has been called from __toString().
-                        // PHP triggers a fatal error when throwing from __toString().
-                        // A small convention allows working around the limitation:
-                        // given a caught $e exception in __toString(), quitting the method with
-                        // `return trigger_error($e, E_USER_ERROR);` allows this error handler
-                        // to make $e get through the __toString() barrier.
-
-                        foreach ($context as $e) {
-                            if ($e instanceof \Throwable && $e->__toString() === $message) {
-                                self::$toStringException = $e;
-
-                                return true;
-                            }
-                        }
-
-                        // Display the original error message instead of the default one.
-                        $this->handleException($errorAsException);
-
-                        // Stop the process by giving back the error to the native handler.
-                        return false;
-                    }
-                }
-            }
-
-            throw $errorAsException;
-        }
-
-        if ($this->isRecursive) {
-            $log = 0;
-        } else {
-            if (!\defined('HHVM_VERSION')) {
-                $currentErrorHandler = set_error_handler('var_dump');
-                restore_error_handler();
-            }
-
-            try {
-                $this->isRecursive = true;
-                $level = ($type & $level) ? $this->loggers[$type][1] : LogLevel::DEBUG;
-                $this->loggers[$type][0]->log($level, $logMessage, $errorAsException ? ['exception' => $errorAsException] : []);
-            } finally {
-                $this->isRecursive = false;
-
-                if (!\defined('HHVM_VERSION')) {
-                    set_error_handler($currentErrorHandler);
-                }
-            }
-        }
-
-        return !$silenced && $type && $log;
-    }
-
-    /**
-     * Handles an exception by logging then forwarding it to another handler.
-     *
-     * @param \Exception|\Throwable $exception An exception to handle
-     * @param array                 $error     An array as returned by error_get_last()
-     *
-     * @internal
-     */
-    public function handleException($exception, array $error = null)
-    {
-        if (null === $error) {
-            self::$exitCode = 255;
-        }
-        if (!$exception instanceof \Exception) {
-            $exception = new FatalThrowableError($exception);
-        }
-        $type = $exception instanceof FatalErrorException ? $exception->getSeverity() : E_ERROR;
-        $handlerException = null;
-
-        if (($this->loggedErrors & $type) || $exception instanceof FatalThrowableError) {
-            if (false !== strpos($message = $exception->getMessage(), "class@anonymous\0")) {
-                $message = (new FlattenException())->setMessage($message)->getMessage();
-            }
-            if ($exception instanceof FatalErrorException) {
-                if ($exception instanceof FatalThrowableError) {
-                    $error = [
-                        'type' => $type,
-                        'message' => $message,
-                        'file' => $exception->getFile(),
-                        'line' => $exception->getLine(),
-                    ];
-                } else {
-                    $message = 'Fatal '.$message;
-                }
-            } elseif ($exception instanceof \ErrorException) {
-                $message = 'Uncaught '.$message;
-            } else {
-                $message = 'Uncaught Exception: '.$message;
-            }
-        }
-        if ($this->loggedErrors & $type) {
-            try {
-                $this->loggers[$type][0]->log($this->loggers[$type][1], $message, ['exception' => $exception]);
-            } catch (\Throwable $handlerException) {
-            }
-        }
-        if ($exception instanceof FatalErrorException && !$exception instanceof OutOfMemoryException && $error) {
-            foreach ($this->getFatalErrorHandlers() as $handler) {
-                if ($e = $handler->handleError($error, $exception)) {
-                    $exception = $e;
-                    break;
-                }
-            }
-        }
-        $exceptionHandler = $this->exceptionHandler;
-        $this->exceptionHandler = null;
-        try {
-            if (null !== $exceptionHandler) {
-                return $exceptionHandler($exception);
-            }
-            $handlerException = $handlerException ?: $exception;
-        } catch (\Throwable $handlerException) {
-        }
-        if ($exception === $handlerException) {
-            self::$reservedMemory = null; // Disable the fatal error handler
-            throw $exception; // Give back $exception to the native handler
-        }
-        $this->handleException($handlerException);
-    }
-
-    /**
-     * Shutdown registered function for handling PHP fatal errors.
-     *
-     * @param array $error An array as returned by error_get_last()
-     *
-     * @internal
-     */
-    public static function handleFatalError(array $error = null)
-    {
-        if (null === self::$reservedMemory) {
-            return;
-        }
-
-        $handler = self::$reservedMemory = null;
-        $handlers = [];
-        $previousHandler = null;
-        $sameHandlerLimit = 10;
-
-        while (!\is_array($handler) || !$handler[0] instanceof self) {
-            $handler = set_exception_handler('var_dump');
-            restore_exception_handler();
-
-            if (!$handler) {
-                break;
-            }
-            restore_exception_handler();
-
-            if ($handler !== $previousHandler) {
-                array_unshift($handlers, $handler);
-                $previousHandler = $handler;
-            } elseif (0 === --$sameHandlerLimit) {
-                $handler = null;
-                break;
-            }
-        }
-        foreach ($handlers as $h) {
-            set_exception_handler($h);
-        }
-        if (!$handler) {
-            return;
-        }
-        if ($handler !== $h) {
-            $handler[0]->setExceptionHandler($h);
-        }
-        $handler = $handler[0];
-        $handlers = [];
-
-        if ($exit = null === $error) {
-            $error = error_get_last();
-        }
-
-        if ($error && $error['type'] &= E_PARSE | E_ERROR | E_CORE_ERROR | E_COMPILE_ERROR) {
-            // Let's not throw anymore but keep logging
-            $handler->throwAt(0, true);
-            $trace = isset($error['backtrace']) ? $error['backtrace'] : null;
-
-            if (0 === strpos($error['message'], 'Allowed memory') || 0 === strpos($error['message'], 'Out of memory')) {
-                $exception = new OutOfMemoryException($handler->levels[$error['type']].': '.$error['message'], 0, $error['type'], $error['file'], $error['line'], 2, false, $trace);
-            } else {
-                $exception = new FatalErrorException($handler->levels[$error['type']].': '.$error['message'], 0, $error['type'], $error['file'], $error['line'], 2, true, $trace);
-            }
-        } else {
-            $exception = null;
-        }
-
-        try {
-            if (null !== $exception) {
-                self::$exitCode = 255;
-                $handler->handleException($exception, $error);
-            }
-        } catch (FatalErrorException $e) {
-            // Ignore this re-throw
-        }
-
-        if ($exit && self::$exitCode) {
-            $exitCode = self::$exitCode;
-            register_shutdown_function('register_shutdown_function', function () use ($exitCode) { exit($exitCode); });
-        }
-    }
-
-    /**
-     * Gets the fatal error handlers.
-     *
-     * Override this method if you want to define more fatal error handlers.
-     *
-     * @return FatalErrorHandlerInterface[] An array of FatalErrorHandlerInterface
-     */
-    protected function getFatalErrorHandlers()
-    {
-        return [
-            new UndefinedFunctionFatalErrorHandler(),
-            new UndefinedMethodFatalErrorHandler(),
-            new ClassNotFoundFatalErrorHandler(),
-        ];
-    }
-
-    /**
-     * Cleans the trace by removing function arguments and the frames added by the error handler and DebugClassLoader.
-     */
-    private function cleanTrace($backtrace, $type, $file, $line, $throw)
-    {
-        $lightTrace = $backtrace;
-
-        for ($i = 0; isset($backtrace[$i]); ++$i) {
-            if (isset($backtrace[$i]['file'], $backtrace[$i]['line']) && $backtrace[$i]['line'] === $line && $backtrace[$i]['file'] === $file) {
-                $lightTrace = \array_slice($lightTrace, 1 + $i);
-                break;
-            }
-        }
-        if (class_exists(DebugClassLoader::class, false)) {
-            for ($i = \count($lightTrace) - 2; 0 < $i; --$i) {
-                if (DebugClassLoader::class === ($lightTrace[$i]['class'] ?? null)) {
-                    array_splice($lightTrace, --$i, 2);
-                }
-            }
-        }
-        if (!($throw || $this->scopedErrors & $type)) {
-            for ($i = 0; isset($lightTrace[$i]); ++$i) {
-                unset($lightTrace[$i]['args'], $lightTrace[$i]['object']);
-            }
-        }
-
-        return $lightTrace;
-    }
-}
diff --git a/src/Symfony/Component/ErrorCatcher/Exception/ClassNotFoundException.php b/src/Symfony/Component/ErrorCatcher/Exception/ClassNotFoundException.php
deleted file mode 100644
index f793f8d55c..0000000000
--- a/src/Symfony/Component/ErrorCatcher/Exception/ClassNotFoundException.php
+++ /dev/null
@@ -1,36 +0,0 @@
-<?php
-
-/*
- * This file is part of the Symfony package.
- *
- * (c) Fabien Potencier <fabien@symfony.com>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
-namespace Symfony\Component\ErrorCatcher\Exception;
-
-/**
- * Class (or Trait or Interface) Not Found Exception.
- *
- * @author Konstanton Myakshin <koc-dp@yandex.ru>
- */
-class ClassNotFoundException extends FatalErrorException
-{
-    public function __construct(string $message, \ErrorException $previous)
-    {
-        parent::__construct(
-            $message,
-            $previous->getCode(),
-            $previous->getSeverity(),
-            $previous->getFile(),
-            $previous->getLine(),
-            null,
-            true,
-            null,
-            $previous->getPrevious()
-        );
-        $this->setTrace($previous->getTrace());
-    }
-}
diff --git a/src/Symfony/Component/ErrorCatcher/Exception/FatalErrorException.php b/src/Symfony/Component/ErrorCatcher/Exception/FatalErrorException.php
deleted file mode 100644
index c98e46d5aa..0000000000
--- a/src/Symfony/Component/ErrorCatcher/Exception/FatalErrorException.php
+++ /dev/null
@@ -1,77 +0,0 @@
-<?php
-
-/*
- * This file is part of the Symfony package.
- *
- * (c) Fabien Potencier <fabien@symfony.com>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
-namespace Symfony\Component\ErrorCatcher\Exception;
-
-/**
- * Fatal Error Exception.
- *
- * @author Konstanton Myakshin <koc-dp@yandex.ru>
- */
-class FatalErrorException extends \ErrorException
-{
-    public function __construct(string $message, int $code, int $severity, string $filename, int $lineno, int $traceOffset = null, bool $traceArgs = true, array $trace = null, \Throwable $previous = null)
-    {
-        parent::__construct($message, $code, $severity, $filename, $lineno, $previous);
-
-        if (null !== $trace) {
-            if (!$traceArgs) {
-                foreach ($trace as &$frame) {
-                    unset($frame['args'], $frame['this'], $frame);
-                }
-            }
-
-            $this->setTrace($trace);
-        } elseif (null !== $traceOffset) {
-            if (\function_exists('xdebug_get_function_stack')) {
-                $trace = xdebug_get_function_stack();
-                if (0 < $traceOffset) {
-                    array_splice($trace, -$traceOffset);
-                }
-
-                foreach ($trace as &$frame) {
-                    if (!isset($frame['type'])) {
-                        // XDebug pre 2.1.1 doesn't currently set the call type key http://bugs.xdebug.org/view.php?id=695
-                        if (isset($frame['class'])) {
-                            $frame['type'] = '::';
-                        }
-                    } elseif ('dynamic' === $frame['type']) {
-                        $frame['type'] = '->';
-                    } elseif ('static' === $frame['type']) {
-                        $frame['type'] = '::';
-                    }
-
-                    // XDebug also has a different name for the parameters array
-                    if (!$traceArgs) {
-                        unset($frame['params'], $frame['args']);
-                    } elseif (isset($frame['params']) && !isset($frame['args'])) {
-                        $frame['args'] = $frame['params'];
-                        unset($frame['params']);
-                    }
-                }
-
-                unset($frame);
-                $trace = array_reverse($trace);
-            } else {
-                $trace = [];
-            }
-
-            $this->setTrace($trace);
-        }
-    }
-
-    protected function setTrace($trace)
-    {
-        $traceReflector = new \ReflectionProperty('Exception', 'trace');
-        $traceReflector->setAccessible(true);
-        $traceReflector->setValue($this, $trace);
-    }
-}
diff --git a/src/Symfony/Component/ErrorCatcher/Exception/FatalThrowableError.php b/src/Symfony/Component/ErrorCatcher/Exception/FatalThrowableError.php
deleted file mode 100644
index 86aa298db8..0000000000
--- a/src/Symfony/Component/ErrorCatcher/Exception/FatalThrowableError.php
+++ /dev/null
@@ -1,51 +0,0 @@
-<?php
-
-/*
- * This file is part of the Symfony package.
- *
- * (c) Fabien Potencier <fabien@symfony.com>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
-namespace Symfony\Component\ErrorCatcher\Exception;
-
-/**
- * Fatal Throwable Error.
- *
- * @author Nicolas Grekas <p@tchwork.com>
- */
-class FatalThrowableError extends FatalErrorException
-{
-    private $originalClassName;
-
-    public function __construct(\Throwable $e)
-    {
-        $this->originalClassName = \get_class($e);
-
-        if ($e instanceof \ParseError) {
-            $severity = E_PARSE;
-        } elseif ($e instanceof \TypeError) {
-            $severity = E_RECOVERABLE_ERROR;
-        } else {
-            $severity = E_ERROR;
-        }
-
-        \ErrorException::__construct(
-            $e->getMessage(),
-            $e->getCode(),
-            $severity,
-            $e->getFile(),
-            $e->getLine(),
-            $e->getPrevious()
-        );
-
-        $this->setTrace($e->getTrace());
-    }
-
-    public function getOriginalClassName(): string
-    {
-        return $this->originalClassName;
-    }
-}
diff --git a/src/Symfony/Component/ErrorCatcher/Exception/FlattenException.php b/src/Symfony/Component/ErrorCatcher/Exception/FlattenException.php
index 8acff9dbfc..f783b6e620 100644
--- a/src/Symfony/Component/ErrorCatcher/Exception/FlattenException.php
+++ b/src/Symfony/Component/ErrorCatcher/Exception/FlattenException.php
@@ -11,6 +11,7 @@
 
 namespace Symfony\Component\ErrorCatcher\Exception;
 
+use Symfony\Component\Debug\Exception\FatalThrowableError;
 use Symfony\Component\HttpFoundation\Exception\RequestExceptionInterface;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\HttpKernel\Exception\HttpExceptionInterface;
diff --git a/src/Symfony/Component/ErrorCatcher/Exception/OutOfMemoryException.php b/src/Symfony/Component/ErrorCatcher/Exception/OutOfMemoryException.php
deleted file mode 100644
index ed01e6e661..0000000000
--- a/src/Symfony/Component/ErrorCatcher/Exception/OutOfMemoryException.php
+++ /dev/null
@@ -1,21 +0,0 @@
-<?php
-
-/*
- * This file is part of the Symfony package.
- *
- * (c) Fabien Potencier <fabien@symfony.com>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
-namespace Symfony\Component\ErrorCatcher\Exception;
-
-/**
- * Out of memory exception.
- *
- * @author Nicolas Grekas <p@tchwork.com>
- */
-class OutOfMemoryException extends FatalErrorException
-{
-}
diff --git a/src/Symfony/Component/ErrorCatcher/Exception/SilencedErrorContext.php b/src/Symfony/Component/ErrorCatcher/Exception/SilencedErrorContext.php
deleted file mode 100644
index 46e9b55d7c..0000000000
--- a/src/Symfony/Component/ErrorCatcher/Exception/SilencedErrorContext.php
+++ /dev/null
@@ -1,67 +0,0 @@
-<?php
-
-/*
- * This file is part of the Symfony package.
- *
- * (c) Fabien Potencier <fabien@symfony.com>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
-namespace Symfony\Component\ErrorCatcher\Exception;
-
-/**
- * Data Object that represents a Silenced Error.
- *
- * @author Grégoire Pineau <lyrixx@lyrixx.info>
- */
-class SilencedErrorContext implements \JsonSerializable
-{
-    public $count = 1;
-
-    private $severity;
-    private $file;
-    private $line;
-    private $trace;
-
-    public function __construct(int $severity, string $file, int $line, array $trace = [], int $count = 1)
-    {
-        $this->severity = $severity;
-        $this->file = $file;
-        $this->line = $line;
-        $this->trace = $trace;
-        $this->count = $count;
-    }
-
-    public function getSeverity()
-    {
-        return $this->severity;
-    }
-
-    public function getFile()
-    {
-        return $this->file;
-    }
-
-    public function getLine()
-    {
-        return $this->line;
-    }
-
-    public function getTrace()
-    {
-        return $this->trace;
-    }
-
-    public function JsonSerialize()
-    {
-        return [
-            'severity' => $this->severity,
-            'file' => $this->file,
-            'line' => $this->line,
-            'trace' => $this->trace,
-            'count' => $this->count,
-        ];
-    }
-}
diff --git a/src/Symfony/Component/ErrorCatcher/Exception/UndefinedFunctionException.php b/src/Symfony/Component/ErrorCatcher/Exception/UndefinedFunctionException.php
deleted file mode 100644
index aef70895c1..0000000000
--- a/src/Symfony/Component/ErrorCatcher/Exception/UndefinedFunctionException.php
+++ /dev/null
@@ -1,36 +0,0 @@
-<?php
-
-/*
- * This file is part of the Symfony package.
- *
- * (c) Fabien Potencier <fabien@symfony.com>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
-namespace Symfony\Component\ErrorCatcher\Exception;
-
-/**
- * Undefined Function Exception.
- *
- * @author Konstanton Myakshin <koc-dp@yandex.ru>
- */
-class UndefinedFunctionException extends FatalErrorException
-{
-    public function __construct(string $message, \ErrorException $previous)
-    {
-        parent::__construct(
-            $message,
-            $previous->getCode(),
-            $previous->getSeverity(),
-            $previous->getFile(),
-            $previous->getLine(),
-            null,
-            true,
-            null,
-            $previous->getPrevious()
-        );
-        $this->setTrace($previous->getTrace());
-    }
-}
diff --git a/src/Symfony/Component/ErrorCatcher/Exception/UndefinedMethodException.php b/src/Symfony/Component/ErrorCatcher/Exception/UndefinedMethodException.php
deleted file mode 100644
index 50a9d1f391..0000000000
--- a/src/Symfony/Component/ErrorCatcher/Exception/UndefinedMethodException.php
+++ /dev/null
@@ -1,36 +0,0 @@
-<?php
-
-/*
- * This file is part of the Symfony package.
- *
- * (c) Fabien Potencier <fabien@symfony.com>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
-namespace Symfony\Component\ErrorCatcher\Exception;
-
-/**
- * Undefined Method Exception.
- *
- * @author Grégoire Pineau <lyrixx@lyrixx.info>
- */
-class UndefinedMethodException extends FatalErrorException
-{
-    public function __construct(string $message, \ErrorException $previous)
-    {
-        parent::__construct(
-            $message,
-            $previous->getCode(),
-            $previous->getSeverity(),
-            $previous->getFile(),
-            $previous->getLine(),
-            null,
-            true,
-            null,
-            $previous->getPrevious()
-        );
-        $this->setTrace($previous->getTrace());
-    }
-}
diff --git a/src/Symfony/Component/ErrorCatcher/ExceptionHandler.php b/src/Symfony/Component/ErrorCatcher/ExceptionHandler.php
deleted file mode 100644
index 225db00622..0000000000
--- a/src/Symfony/Component/ErrorCatcher/ExceptionHandler.php
+++ /dev/null
@@ -1,177 +0,0 @@
-<?php
-
-/*
- * This file is part of the Symfony package.
- *
- * (c) Fabien Potencier <fabien@symfony.com>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
-namespace Symfony\Component\ErrorCatcher;
-
-use Symfony\Component\ErrorCatcher\ErrorRenderer\HtmlErrorRenderer;
-use Symfony\Component\ErrorCatcher\Exception\FlattenException;
-use Symfony\Component\ErrorCatcher\Exception\OutOfMemoryException;
-use Symfony\Component\HttpKernel\Debug\FileLinkFormatter;
-
-/**
- * ExceptionHandler converts an exception to a Response object.
- *
- * It is mostly useful in debug mode to replace the default PHP/XDebug
- * output with something prettier and more useful.
- *
- * As this class is mainly used during Kernel boot, where nothing is yet
- * available, the Response content is always HTML.
- *
- * @author Fabien Potencier <fabien@symfony.com>
- * @author Nicolas Grekas <p@tchwork.com>
- *
- * @final
- */
-class ExceptionHandler
-{
-    private $charset;
-    private $errorRenderer;
-    private $handler;
-    private $caughtBuffer;
-    private $caughtLength;
-
-    /**
-     * Registers the exception handler.
-     *
-     * @param bool        $debug          Enable/disable debug mode, where the stack trace is displayed
-     * @param string|null $charset        The charset used by exception messages
-     * @param string|null $fileLinkFormat The IDE link template
-     *
-     * @return static
-     */
-    public static function register($debug = true, $charset = null, $fileLinkFormat = null)
-    {
-        $handler = new static($debug, $charset, $fileLinkFormat);
-
-        $prev = set_exception_handler([$handler, 'handle']);
-        if (\is_array($prev) && $prev[0] instanceof ErrorHandler) {
-            restore_exception_handler();
-            $prev[0]->setExceptionHandler([$handler, 'handle']);
-        }
-
-        return $handler;
-    }
-
-    public function __construct(bool $debug = true, string $charset = null, $fileLinkFormat = null, HtmlErrorRenderer $errorRenderer = null)
-    {
-        $this->charset = $charset ?: ini_get('default_charset') ?: 'UTF-8';
-        $this->errorRenderer = $errorRenderer ?? new HtmlErrorRenderer($debug, $this->charset, $fileLinkFormat);
-    }
-
-    /**
-     * Sets the format for links to source files.
-     *
-     * @param string|FileLinkFormatter $fileLinkFormat The format for links to source files
-     *
-     * @return string The previous file link format
-     */
-    public function setFileLinkFormat($fileLinkFormat)
-    {
-        return $this->errorRenderer->setFileLinkFormat($fileLinkFormat);
-    }
-
-    /**
-     * Sets a user exception handler.
-     *
-     * @param callable $handler An handler that will be called on Exception
-     *
-     * @return callable|null The previous exception handler if any
-     */
-    public function setHandler(callable $handler = null)
-    {
-        $old = $this->handler;
-        $this->handler = $handler;
-
-        return $old;
-    }
-
-    /**
-     * Sends a response for the given Exception.
-     *
-     * To be as fail-safe as possible, the exception is first handled
-     * by our simple exception handler, then by the user exception handler.
-     * The latter takes precedence and any output from the former is cancelled,
-     * if and only if nothing bad happens in this handling path.
-     */
-    public function handle(\Exception $exception)
-    {
-        if (null === $this->handler || $exception instanceof OutOfMemoryException) {
-            $this->sendPhpResponse($exception);
-
-            return;
-        }
-
-        $caughtLength = $this->caughtLength = 0;
-
-        ob_start(function ($buffer) {
-            $this->caughtBuffer = $buffer;
-
-            return '';
-        });
-
-        $this->sendPhpResponse($exception);
-        while (null === $this->caughtBuffer && ob_end_flush()) {
-            // Empty loop, everything is in the condition
-        }
-        if (isset($this->caughtBuffer[0])) {
-            ob_start(function ($buffer) {
-                if ($this->caughtLength) {
-                    // use substr_replace() instead of substr() for mbstring overloading resistance
-                    $cleanBuffer = substr_replace($buffer, '', 0, $this->caughtLength);
-                    if (isset($cleanBuffer[0])) {
-                        $buffer = $cleanBuffer;
-                    }
-                }
-
-                return $buffer;
-            });
-
-            echo $this->caughtBuffer;
-            $caughtLength = ob_get_length();
-        }
-        $this->caughtBuffer = null;
-
-        try {
-            ($this->handler)($exception);
-            $this->caughtLength = $caughtLength;
-        } catch (\Exception $e) {
-            if (!$caughtLength) {
-                // All handlers failed. Let PHP handle that now.
-                throw $exception;
-            }
-        }
-    }
-
-    /**
-     * Sends the error associated with the given Exception as a plain PHP response.
-     *
-     * This method uses plain PHP functions like header() and echo to output
-     * the response.
-     *
-     * @param \Throwable|FlattenException $exception A \Throwable or FlattenException instance
-     */
-    public function sendPhpResponse($exception)
-    {
-        if ($exception instanceof \Throwable) {
-            $exception = FlattenException::createFromThrowable($exception);
-        }
-
-        if (!headers_sent()) {
-            header(sprintf('HTTP/1.0 %s', $exception->getStatusCode()));
-            foreach ($exception->getHeaders() as $name => $value) {
-                header($name.': '.$value, false);
-            }
-            header('Content-Type: text/html; charset='.$this->charset);
-        }
-
-        echo $this->errorRenderer->render($exception);
-    }
-}
diff --git a/src/Symfony/Component/ErrorCatcher/FatalErrorHandler/ClassNotFoundFatalErrorHandler.php b/src/Symfony/Component/ErrorCatcher/FatalErrorHandler/ClassNotFoundFatalErrorHandler.php
deleted file mode 100644
index a9f3e39bb7..0000000000
--- a/src/Symfony/Component/ErrorCatcher/FatalErrorHandler/ClassNotFoundFatalErrorHandler.php
+++ /dev/null
@@ -1,193 +0,0 @@
-<?php
-
-/*
- * This file is part of the Symfony package.
- *
- * (c) Fabien Potencier <fabien@symfony.com>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
-namespace Symfony\Component\ErrorCatcher\FatalErrorHandler;
-
-use Composer\Autoload\ClassLoader as ComposerClassLoader;
-use Symfony\Component\ClassLoader\ClassLoader as SymfonyClassLoader;
-use Symfony\Component\Debug\DebugClassLoader;
-use Symfony\Component\ErrorCatcher\Exception\ClassNotFoundException;
-use Symfony\Component\ErrorCatcher\Exception\FatalErrorException;
-
-/**
- * ErrorHandler for classes that do not exist.
- *
- * @author Fabien Potencier <fabien@symfony.com>
- */
-class ClassNotFoundFatalErrorHandler implements FatalErrorHandlerInterface
-{
-    /**
-     * {@inheritdoc}
-     */
-    public function handleError(array $error, FatalErrorException $exception)
-    {
-        $messageLen = \strlen($error['message']);
-        $notFoundSuffix = '\' not found';
-        $notFoundSuffixLen = \strlen($notFoundSuffix);
-        if ($notFoundSuffixLen > $messageLen) {
-            return;
-        }
-
-        if (0 !== substr_compare($error['message'], $notFoundSuffix, -$notFoundSuffixLen)) {
-            return;
-        }
-
-        foreach (['class', 'interface', 'trait'] as $typeName) {
-            $prefix = ucfirst($typeName).' \'';
-            $prefixLen = \strlen($prefix);
-            if (0 !== strpos($error['message'], $prefix)) {
-                continue;
-            }
-
-            $fullyQualifiedClassName = substr($error['message'], $prefixLen, -$notFoundSuffixLen);
-            if (false !== $namespaceSeparatorIndex = strrpos($fullyQualifiedClassName, '\\')) {
-                $className = substr($fullyQualifiedClassName, $namespaceSeparatorIndex + 1);
-                $namespacePrefix = substr($fullyQualifiedClassName, 0, $namespaceSeparatorIndex);
-                $message = sprintf('Attempted to load %s "%s" from namespace "%s".', $typeName, $className, $namespacePrefix);
-                $tail = ' for another namespace?';
-            } else {
-                $className = $fullyQualifiedClassName;
-                $message = sprintf('Attempted to load %s "%s" from the global namespace.', $typeName, $className);
-                $tail = '?';
-            }
-
-            if ($candidates = $this->getClassCandidates($className)) {
-                $tail = array_pop($candidates).'"?';
-                if ($candidates) {
-                    $tail = ' for e.g. "'.implode('", "', $candidates).'" or "'.$tail;
-                } else {
-                    $tail = ' for "'.$tail;
-                }
-            }
-            $message .= "\nDid you forget a \"use\" statement".$tail;
-
-            return new ClassNotFoundException($message, $exception);
-        }
-    }
-
-    /**
-     * Tries to guess the full namespace for a given class name.
-     *
-     * By default, it looks for PSR-0 and PSR-4 classes registered via a Symfony or a Composer
-     * autoloader (that should cover all common cases).
-     *
-     * @param string $class A class name (without its namespace)
-     *
-     * @return array An array of possible fully qualified class names
-     */
-    private function getClassCandidates(string $class): array
-    {
-        if (!\is_array($functions = spl_autoload_functions())) {
-            return [];
-        }
-
-        // find Symfony and Composer autoloaders
-        $classes = [];
-
-        foreach ($functions as $function) {
-            if (!\is_array($function)) {
-                continue;
-            }
-            // get class loaders wrapped by DebugClassLoader
-            if ($function[0] instanceof DebugClassLoader) {
-                $function = $function[0]->getClassLoader();
-
-                if (!\is_array($function)) {
-                    continue;
-                }
-            }
-
-            if ($function[0] instanceof ComposerClassLoader || $function[0] instanceof SymfonyClassLoader) {
-                foreach ($function[0]->getPrefixes() as $prefix => $paths) {
-                    foreach ($paths as $path) {
-                        $classes = array_merge($classes, $this->findClassInPath($path, $class, $prefix));
-                    }
-                }
-            }
-            if ($function[0] instanceof ComposerClassLoader) {
-                foreach ($function[0]->getPrefixesPsr4() as $prefix => $paths) {
-                    foreach ($paths as $path) {
-                        $classes = array_merge($classes, $this->findClassInPath($path, $class, $prefix));
-                    }
-                }
-            }
-        }
-
-        return array_unique($classes);
-    }
-
-    private function findClassInPath(string $path, string $class, string $prefix): array
-    {
-        if (!$path = realpath($path.'/'.strtr($prefix, '\\_', '//')) ?: realpath($path.'/'.\dirname(strtr($prefix, '\\_', '//'))) ?: realpath($path)) {
-            return [];
-        }
-
-        $classes = [];
-        $filename = $class.'.php';
-        foreach (new \RecursiveIteratorIterator(new \RecursiveDirectoryIterator($path, \RecursiveDirectoryIterator::SKIP_DOTS), \RecursiveIteratorIterator::LEAVES_ONLY) as $file) {
-            if ($filename == $file->getFileName() && $class = $this->convertFileToClass($path, $file->getPathName(), $prefix)) {
-                $classes[] = $class;
-            }
-        }
-
-        return $classes;
-    }
-
-    private function convertFileToClass(string $path, string $file, string $prefix): ?string
-    {
-        $candidates = [
-            // namespaced class
-            $namespacedClass = str_replace([$path.\DIRECTORY_SEPARATOR, '.php', '/'], ['', '', '\\'], $file),
-            // namespaced class (with target dir)
-            $prefix.$namespacedClass,
-            // namespaced class (with target dir and separator)
-            $prefix.'\\'.$namespacedClass,
-            // PEAR class
-            str_replace('\\', '_', $namespacedClass),
-            // PEAR class (with target dir)
-            str_replace('\\', '_', $prefix.$namespacedClass),
-            // PEAR class (with target dir and separator)
-            str_replace('\\', '_', $prefix.'\\'.$namespacedClass),
-        ];
-
-        if ($prefix) {
-            $candidates = array_filter($candidates, function ($candidate) use ($prefix) { return 0 === strpos($candidate, $prefix); });
-        }
-
-        // We cannot use the autoloader here as most of them use require; but if the class
-        // is not found, the new autoloader call will require the file again leading to a
-        // "cannot redeclare class" error.
-        foreach ($candidates as $candidate) {
-            if ($this->classExists($candidate)) {
-                return $candidate;
-            }
-        }
-
-        try {
-            require_once $file;
-        } catch (\Throwable $e) {
-            return null;
-        }
-
-        foreach ($candidates as $candidate) {
-            if ($this->classExists($candidate)) {
-                return $candidate;
-            }
-        }
-
-        return null;
-    }
-
-    private function classExists(string $class): bool
-    {
-        return class_exists($class, false) || interface_exists($class, false) || trait_exists($class, false);
-    }
-}
diff --git a/src/Symfony/Component/ErrorCatcher/FatalErrorHandler/FatalErrorHandlerInterface.php b/src/Symfony/Component/ErrorCatcher/FatalErrorHandler/FatalErrorHandlerInterface.php
deleted file mode 100644
index 6fc237c094..0000000000
--- a/src/Symfony/Component/ErrorCatcher/FatalErrorHandler/FatalErrorHandlerInterface.php
+++ /dev/null
@@ -1,32 +0,0 @@
-<?php
-
-/*
- * This file is part of the Symfony package.
- *
- * (c) Fabien Potencier <fabien@symfony.com>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
-namespace Symfony\Component\ErrorCatcher\FatalErrorHandler;
-
-use Symfony\Component\ErrorCatcher\Exception\FatalErrorException;
-
-/**
- * Attempts to convert fatal errors to exceptions.
- *
- * @author Fabien Potencier <fabien@symfony.com>
- */
-interface FatalErrorHandlerInterface
-{
-    /**
-     * Attempts to convert an error into an exception.
-     *
-     * @param array               $error     An array as returned by error_get_last()
-     * @param FatalErrorException $exception A FatalErrorException instance
-     *
-     * @return FatalErrorException|null A FatalErrorException instance if the class is able to convert the error, null otherwise
-     */
-    public function handleError(array $error, FatalErrorException $exception);
-}
diff --git a/src/Symfony/Component/ErrorCatcher/FatalErrorHandler/UndefinedFunctionFatalErrorHandler.php b/src/Symfony/Component/ErrorCatcher/FatalErrorHandler/UndefinedFunctionFatalErrorHandler.php
deleted file mode 100644
index f20cb1185d..0000000000
--- a/src/Symfony/Component/ErrorCatcher/FatalErrorHandler/UndefinedFunctionFatalErrorHandler.php
+++ /dev/null
@@ -1,84 +0,0 @@
-<?php
-
-/*
- * This file is part of the Symfony package.
- *
- * (c) Fabien Potencier <fabien@symfony.com>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
-namespace Symfony\Component\ErrorCatcher\FatalErrorHandler;
-
-use Symfony\Component\ErrorCatcher\Exception\FatalErrorException;
-use Symfony\Component\ErrorCatcher\Exception\UndefinedFunctionException;
-
-/**
- * ErrorHandler for undefined functions.
- *
- * @author Fabien Potencier <fabien@symfony.com>
- */
-class UndefinedFunctionFatalErrorHandler implements FatalErrorHandlerInterface
-{
-    /**
-     * {@inheritdoc}
-     */
-    public function handleError(array $error, FatalErrorException $exception)
-    {
-        $messageLen = \strlen($error['message']);
-        $notFoundSuffix = '()';
-        $notFoundSuffixLen = \strlen($notFoundSuffix);
-        if ($notFoundSuffixLen > $messageLen) {
-            return;
-        }
-
-        if (0 !== substr_compare($error['message'], $notFoundSuffix, -$notFoundSuffixLen)) {
-            return;
-        }
-
-        $prefix = 'Call to undefined function ';
-        $prefixLen = \strlen($prefix);
-        if (0 !== strpos($error['message'], $prefix)) {
-            return;
-        }
-
-        $fullyQualifiedFunctionName = substr($error['message'], $prefixLen, -$notFoundSuffixLen);
-        if (false !== $namespaceSeparatorIndex = strrpos($fullyQualifiedFunctionName, '\\')) {
-            $functionName = substr($fullyQualifiedFunctionName, $namespaceSeparatorIndex + 1);
-            $namespacePrefix = substr($fullyQualifiedFunctionName, 0, $namespaceSeparatorIndex);
-            $message = sprintf('Attempted to call function "%s" from namespace "%s".', $functionName, $namespacePrefix);
-        } else {
-            $functionName = $fullyQualifiedFunctionName;
-            $message = sprintf('Attempted to call function "%s" from the global namespace.', $functionName);
-        }
-
-        $candidates = [];
-        foreach (get_defined_functions() as $type => $definedFunctionNames) {
-            foreach ($definedFunctionNames as $definedFunctionName) {
-                if (false !== $namespaceSeparatorIndex = strrpos($definedFunctionName, '\\')) {
-                    $definedFunctionNameBasename = substr($definedFunctionName, $namespaceSeparatorIndex + 1);
-                } else {
-                    $definedFunctionNameBasename = $definedFunctionName;
-                }
-
-                if ($definedFunctionNameBasename === $functionName) {
-                    $candidates[] = '\\'.$definedFunctionName;
-                }
-            }
-        }
-
-        if ($candidates) {
-            sort($candidates);
-            $last = array_pop($candidates).'"?';
-            if ($candidates) {
-                $candidates = 'e.g. "'.implode('", "', $candidates).'" or "'.$last;
-            } else {
-                $candidates = '"'.$last;
-            }
-            $message .= "\nDid you mean to call ".$candidates;
-        }
-
-        return new UndefinedFunctionException($message, $exception);
-    }
-}
diff --git a/src/Symfony/Component/ErrorCatcher/FatalErrorHandler/UndefinedMethodFatalErrorHandler.php b/src/Symfony/Component/ErrorCatcher/FatalErrorHandler/UndefinedMethodFatalErrorHandler.php
deleted file mode 100644
index 6f9a3eb545..0000000000
--- a/src/Symfony/Component/ErrorCatcher/FatalErrorHandler/UndefinedMethodFatalErrorHandler.php
+++ /dev/null
@@ -1,66 +0,0 @@
-<?php
-
-/*
- * This file is part of the Symfony package.
- *
- * (c) Fabien Potencier <fabien@symfony.com>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
-namespace Symfony\Component\ErrorCatcher\FatalErrorHandler;
-
-use Symfony\Component\ErrorCatcher\Exception\FatalErrorException;
-use Symfony\Component\ErrorCatcher\Exception\UndefinedMethodException;
-
-/**
- * ErrorHandler for undefined methods.
- *
- * @author Grégoire Pineau <lyrixx@lyrixx.info>
- */
-class UndefinedMethodFatalErrorHandler implements FatalErrorHandlerInterface
-{
-    /**
-     * {@inheritdoc}
-     */
-    public function handleError(array $error, FatalErrorException $exception)
-    {
-        preg_match('/^Call to undefined method (.*)::(.*)\(\)$/', $error['message'], $matches);
-        if (!$matches) {
-            return;
-        }
-
-        $className = $matches[1];
-        $methodName = $matches[2];
-
-        $message = sprintf('Attempted to call an undefined method named "%s" of class "%s".', $methodName, $className);
-
-        if (!class_exists($className) || null === $methods = get_class_methods($className)) {
-            // failed to get the class or its methods on which an unknown method was called (for example on an anonymous class)
-            return new UndefinedMethodException($message, $exception);
-        }
-
-        $candidates = [];
-        foreach ($methods as $definedMethodName) {
-            $lev = levenshtein($methodName, $definedMethodName);
-            if ($lev <= \strlen($methodName) / 3 || false !== strpos($definedMethodName, $methodName)) {
-                $candidates[] = $definedMethodName;
-            }
-        }
-
-        if ($candidates) {
-            sort($candidates);
-            $last = array_pop($candidates).'"?';
-            if ($candidates) {
-                $candidates = 'e.g. "'.implode('", "', $candidates).'" or "'.$last;
-            } else {
-                $candidates = '"'.$last;
-            }
-
-            $message .= "\nDid you mean to call ".$candidates;
-        }
-
-        return new UndefinedMethodException($message, $exception);
-    }
-}
diff --git a/src/Symfony/Component/ErrorCatcher/Tests/Exception/FlattenExceptionTest.php b/src/Symfony/Component/ErrorCatcher/Tests/Exception/FlattenExceptionTest.php
index 3f8749578b..6a39025cc1 100644
--- a/src/Symfony/Component/ErrorCatcher/Tests/Exception/FlattenExceptionTest.php
+++ b/src/Symfony/Component/ErrorCatcher/Tests/Exception/FlattenExceptionTest.php
@@ -12,7 +12,7 @@
 namespace Symfony\Component\ErrorCatcher\Tests\Exception;
 
 use PHPUnit\Framework\TestCase;
-use Symfony\Component\ErrorCatcher\Exception\FatalThrowableError;
+use Symfony\Component\Debug\Exception\FatalThrowableError;
 use Symfony\Component\ErrorCatcher\Exception\FlattenException;
 use Symfony\Component\HttpFoundation\Exception\SuspiciousOperationException;
 use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
diff --git a/src/Symfony/Component/ErrorCatcher/Tests/Fixtures/LoggerThatSetAnErrorHandler.php b/src/Symfony/Component/ErrorCatcher/Tests/Fixtures/LoggerThatSetAnErrorHandler.php
deleted file mode 100644
index 380d4b3dd6..0000000000
--- a/src/Symfony/Component/ErrorCatcher/Tests/Fixtures/LoggerThatSetAnErrorHandler.php
+++ /dev/null
@@ -1,25 +0,0 @@
-<?php
-
-namespace Symfony\Component\ErrorCatcher\Tests\Fixtures;
-
-use Psr\Log\AbstractLogger;
-
-class LoggerThatSetAnErrorHandler extends AbstractLogger
-{
-    private $logs = [];
-
-    public function log($level, $message, array $context = [])
-    {
-        set_error_handler('is_string');
-        $this->logs[] = [$level, $message, $context];
-        restore_error_handler();
-    }
-
-    public function cleanLogs(): array
-    {
-        $logs = $this->logs;
-        $this->logs = [];
-
-        return $logs;
-    }
-}
diff --git a/src/Symfony/Component/ErrorCatcher/Tests/Fixtures/PEARClass.php b/src/Symfony/Component/ErrorCatcher/Tests/Fixtures/PEARClass.php
deleted file mode 100644
index 4cc8c825dc..0000000000
--- a/src/Symfony/Component/ErrorCatcher/Tests/Fixtures/PEARClass.php
+++ /dev/null
@@ -1,5 +0,0 @@
-<?php
-
-class Symfony_Component_ErrorCatcher_Tests_Fixtures_PEARClass
-{
-}
diff --git a/src/Symfony/Component/ErrorCatcher/Tests/Fixtures/UndefinedFuncException.php b/src/Symfony/Component/ErrorCatcher/Tests/Fixtures/UndefinedFuncException.php
deleted file mode 100644
index 10507964f1..0000000000
--- a/src/Symfony/Component/ErrorCatcher/Tests/Fixtures/UndefinedFuncException.php
+++ /dev/null
@@ -1,7 +0,0 @@
-<?php
-
-namespace Symfony\Component\ErrorCatcher\Tests\Fixtures;
-
-class UndefinedFuncException
-{
-}
diff --git a/src/Symfony/Component/ErrorCatcher/Tests/Fixtures2/RequiredTwice.php b/src/Symfony/Component/ErrorCatcher/Tests/Fixtures2/RequiredTwice.php
deleted file mode 100644
index 89a0d88295..0000000000
--- a/src/Symfony/Component/ErrorCatcher/Tests/Fixtures2/RequiredTwice.php
+++ /dev/null
@@ -1,7 +0,0 @@
-<?php
-
-namespace Symfony\Component\ErrorCatcher\Tests\Fixtures2;
-
-class RequiredTwice
-{
-}
diff --git a/src/Symfony/Component/ErrorCatcher/composer.json b/src/Symfony/Component/ErrorCatcher/composer.json
index 42579d087b..e8c2e74050 100644
--- a/src/Symfony/Component/ErrorCatcher/composer.json
+++ b/src/Symfony/Component/ErrorCatcher/composer.json
@@ -25,6 +25,7 @@
         "symfony/http-kernel": "^4.4"
     },
     "conflict": {
+        "symfony/debug": "<4.4",
         "symfony/http-kernel": "<4.4"
     },
     "autoload": {
diff --git a/src/Symfony/Component/HttpKernel/DataCollector/LoggerDataCollector.php b/src/Symfony/Component/HttpKernel/DataCollector/LoggerDataCollector.php
index 83a51bbfee..4091b6760f 100644
--- a/src/Symfony/Component/HttpKernel/DataCollector/LoggerDataCollector.php
+++ b/src/Symfony/Component/HttpKernel/DataCollector/LoggerDataCollector.php
@@ -11,7 +11,7 @@
 
 namespace Symfony\Component\HttpKernel\DataCollector;
 
-use Symfony\Component\ErrorCatcher\Exception\SilencedErrorContext;
+use Symfony\Component\Debug\Exception\SilencedErrorContext;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\RequestStack;
 use Symfony\Component\HttpFoundation\Response;
diff --git a/src/Symfony/Component/HttpKernel/EventListener/DebugHandlersListener.php b/src/Symfony/Component/HttpKernel/EventListener/DebugHandlersListener.php
index ebf6c96fcb..9d78440e96 100644
--- a/src/Symfony/Component/HttpKernel/EventListener/DebugHandlersListener.php
+++ b/src/Symfony/Component/HttpKernel/EventListener/DebugHandlersListener.php
@@ -15,11 +15,11 @@ use Psr\Log\LoggerInterface;
 use Symfony\Component\Console\ConsoleEvents;
 use Symfony\Component\Console\Event\ConsoleEvent;
 use Symfony\Component\Console\Output\ConsoleOutputInterface;
-use Symfony\Component\ErrorCatcher\ErrorHandler;
+use Symfony\Component\Debug\ErrorHandler;
+use Symfony\Component\Debug\ExceptionHandler;
 use Symfony\Component\ErrorCatcher\ErrorRenderer\ErrorFormatter;
 use Symfony\Component\ErrorCatcher\ErrorRenderer\HtmlErrorRenderer;
 use Symfony\Component\ErrorCatcher\Exception\ErrorRendererNotFoundException;
-use Symfony\Component\ErrorCatcher\ExceptionHandler;
 use Symfony\Component\EventDispatcher\Event;
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
 use Symfony\Component\HttpFoundation\Request;
diff --git a/src/Symfony/Component/HttpKernel/Tests/DataCollector/LoggerDataCollectorTest.php b/src/Symfony/Component/HttpKernel/Tests/DataCollector/LoggerDataCollectorTest.php
index 7dbd60ef9c..261f098a72 100644
--- a/src/Symfony/Component/HttpKernel/Tests/DataCollector/LoggerDataCollectorTest.php
+++ b/src/Symfony/Component/HttpKernel/Tests/DataCollector/LoggerDataCollectorTest.php
@@ -12,7 +12,7 @@
 namespace Symfony\Component\HttpKernel\Tests\DataCollector;
 
 use PHPUnit\Framework\TestCase;
-use Symfony\Component\ErrorCatcher\Exception\SilencedErrorContext;
+use Symfony\Component\Debug\Exception\SilencedErrorContext;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\RequestStack;
 use Symfony\Component\HttpFoundation\Response;
@@ -106,7 +106,7 @@ class LoggerDataCollectorTest extends TestCase
         $logs = array_map(function ($v) {
             if (isset($v['context']['exception'])) {
                 $e = &$v['context']['exception'];
-                $e = isset($e["\0*\0message"]) ? [$e["\0*\0message"], $e["\0*\0severity"]] : [$e["\0Symfony\Component\ErrorCatcher\Exception\SilencedErrorContext\0severity"]];
+                $e = isset($e["\0*\0message"]) ? [$e["\0*\0message"], $e["\0*\0severity"]] : [$e["\0Symfony\Component\Debug\Exception\SilencedErrorContext\0severity"]];
             }
 
             return $v;
diff --git a/src/Symfony/Component/HttpKernel/Tests/EventListener/DebugHandlersListenerTest.php b/src/Symfony/Component/HttpKernel/Tests/EventListener/DebugHandlersListenerTest.php
index 1f16b5d813..1e52bce7a3 100644
--- a/src/Symfony/Component/HttpKernel/Tests/EventListener/DebugHandlersListenerTest.php
+++ b/src/Symfony/Component/HttpKernel/Tests/EventListener/DebugHandlersListenerTest.php
@@ -19,8 +19,8 @@ use Symfony\Component\Console\Event\ConsoleEvent;
 use Symfony\Component\Console\Helper\HelperSet;
 use Symfony\Component\Console\Input\ArgvInput;
 use Symfony\Component\Console\Output\ConsoleOutput;
-use Symfony\Component\ErrorCatcher\ErrorHandler;
-use Symfony\Component\ErrorCatcher\ExceptionHandler;
+use Symfony\Component\Debug\ErrorHandler;
+use Symfony\Component\Debug\ExceptionHandler;
 use Symfony\Component\EventDispatcher\EventDispatcher;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpKernel\Event\KernelEvent;
diff --git a/src/Symfony/Component/HttpKernel/composer.json b/src/Symfony/Component/HttpKernel/composer.json
index 3ad3c21e24..e2a954a3f6 100644
--- a/src/Symfony/Component/HttpKernel/composer.json
+++ b/src/Symfony/Component/HttpKernel/composer.json
@@ -17,6 +17,7 @@
     ],
     "require": {
         "php": "^7.1.3",
+        "symfony/debug": "^4.4|^5.0",
         "symfony/error-catcher": "^4.4|^5.0",
         "symfony/event-dispatcher": "^4.3",
         "symfony/http-foundation": "^4.4|^5.0",
diff --git a/src/Symfony/Component/VarDumper/Caster/ExceptionCaster.php b/src/Symfony/Component/VarDumper/Caster/ExceptionCaster.php
index d467dda943..ec168c8da9 100644
--- a/src/Symfony/Component/VarDumper/Caster/ExceptionCaster.php
+++ b/src/Symfony/Component/VarDumper/Caster/ExceptionCaster.php
@@ -11,7 +11,7 @@
 
 namespace Symfony\Component\VarDumper\Caster;
 
-use Symfony\Component\ErrorCatcher\Exception\SilencedErrorContext;
+use Symfony\Component\Debug\Exception\SilencedErrorContext;
 use Symfony\Component\VarDumper\Cloner\Stub;
 use Symfony\Component\VarDumper\Exception\ThrowingCasterException;