diff --git a/.github/patch-types.php b/.github/patch-types.php
index 7302921df0..31bb7050ee 100644
--- a/.github/patch-types.php
+++ b/.github/patch-types.php
@@ -32,4 +32,4 @@ foreach ($loader->getClassMap() as $class => $file) {
     class_exists($class);
 }
 
-Symfony\Component\ErrorHandler\DebugClassLoader::disable();
+Symfony\Component\ErrorHandler\DebugClassLoader::checkClasses();
diff --git a/src/Symfony/Bridge/PhpUnit/DeprecationErrorHandler.php b/src/Symfony/Bridge/PhpUnit/DeprecationErrorHandler.php
index 732866dc52..a81c95eea6 100644
--- a/src/Symfony/Bridge/PhpUnit/DeprecationErrorHandler.php
+++ b/src/Symfony/Bridge/PhpUnit/DeprecationErrorHandler.php
@@ -15,6 +15,7 @@ use PHPUnit\Framework\TestResult;
 use PHPUnit\Util\ErrorHandler;
 use Symfony\Bridge\PhpUnit\DeprecationErrorHandler\Configuration;
 use Symfony\Bridge\PhpUnit\DeprecationErrorHandler\Deprecation;
+use Symfony\Component\ErrorHandler\DebugClassLoader;
 
 /**
  * Catch deprecation notices and print a summary report at the end of the test suite.
@@ -173,6 +174,9 @@ class DeprecationErrorHandler
             return;
         }
 
+        if (method_exists(DebugClassLoader::class, 'checkClasses')) {
+            DebugClassLoader::checkClasses();
+        }
         $currErrorHandler = set_error_handler('var_dump');
         restore_error_handler();
 
diff --git a/src/Symfony/Bridge/PhpUnit/Legacy/CommandForV5.php b/src/Symfony/Bridge/PhpUnit/Legacy/CommandForV5.php
index 95dcb1e554..ed4128482f 100644
--- a/src/Symfony/Bridge/PhpUnit/Legacy/CommandForV5.php
+++ b/src/Symfony/Bridge/PhpUnit/Legacy/CommandForV5.php
@@ -23,8 +23,6 @@ class CommandForV5 extends \PHPUnit_TextUI_Command
      */
     protected function createRunner()
     {
-        $listener = new SymfonyTestsListenerForV5();
-
         $this->arguments['listeners'] = isset($this->arguments['listeners']) ? $this->arguments['listeners'] : array();
 
         $registeredLocally = false;
@@ -37,8 +35,21 @@ class CommandForV5 extends \PHPUnit_TextUI_Command
             }
         }
 
+        if (isset($this->arguments['configuration'])) {
+            $configuration = $this->arguments['configuration'];
+            if (!$configuration instanceof \PHPUnit_Util_Configuration) {
+                $configuration = \PHPUnit_Util_Configuration::getInstance($this->arguments['configuration']);
+            }
+            foreach ($configuration->getListenerConfiguration() as $registeredListener) {
+                if ('Symfony\Bridge\PhpUnit\SymfonyTestsListener' === ltrim($registeredListener['class'], '\\')) {
+                    $registeredLocally = true;
+                    break;
+                }
+            }
+        }
+
         if (!$registeredLocally) {
-            $this->arguments['listeners'][] = $listener;
+            $this->arguments['listeners'][] = new SymfonyTestsListenerForV5();
         }
 
         return parent::createRunner();
diff --git a/src/Symfony/Bridge/PhpUnit/Legacy/CommandForV6.php b/src/Symfony/Bridge/PhpUnit/Legacy/CommandForV6.php
index f8f75bb09a..93e1ad975b 100644
--- a/src/Symfony/Bridge/PhpUnit/Legacy/CommandForV6.php
+++ b/src/Symfony/Bridge/PhpUnit/Legacy/CommandForV6.php
@@ -13,6 +13,7 @@ namespace Symfony\Bridge\PhpUnit\Legacy;
 
 use PHPUnit\TextUI\Command as BaseCommand;
 use PHPUnit\TextUI\TestRunner as BaseRunner;
+use PHPUnit\Util\Configuration;
 use Symfony\Bridge\PhpUnit\SymfonyTestsListener;
 
 /**
@@ -27,8 +28,6 @@ class CommandForV6 extends BaseCommand
      */
     protected function createRunner(): BaseRunner
     {
-        $listener = new SymfonyTestsListener();
-
         $this->arguments['listeners'] = isset($this->arguments['listeners']) ? $this->arguments['listeners'] : [];
 
         $registeredLocally = false;
@@ -41,8 +40,21 @@ class CommandForV6 extends BaseCommand
             }
         }
 
+        if (isset($this->arguments['configuration'])) {
+            $configuration = $this->arguments['configuration'];
+            if (!$configuration instanceof Configuration) {
+                $configuration = Configuration::getInstance($this->arguments['configuration']);
+            }
+            foreach ($configuration->getListenerConfiguration() as $registeredListener) {
+                if ('Symfony\Bridge\PhpUnit\SymfonyTestsListener' === ltrim($registeredListener['class'], '\\')) {
+                    $registeredLocally = true;
+                    break;
+                }
+            }
+        }
+
         if (!$registeredLocally) {
-            $this->arguments['listeners'][] = $listener;
+            $this->arguments['listeners'][] = new SymfonyTestsListener();
         }
 
         return parent::createRunner();
diff --git a/src/Symfony/Bridge/PhpUnit/bin/simple-phpunit.php b/src/Symfony/Bridge/PhpUnit/bin/simple-phpunit.php
index 92e5caded6..cdcc423031 100644
--- a/src/Symfony/Bridge/PhpUnit/bin/simple-phpunit.php
+++ b/src/Symfony/Bridge/PhpUnit/bin/simple-phpunit.php
@@ -10,7 +10,7 @@
  */
 
 // Please update when phpunit needs to be reinstalled with fresh deps:
-// Cache-Id: 2019-08-09 13:00 UTC
+// Cache-Id: 2019-09-02 16:00 UTC
 
 error_reporting(-1);
 
diff --git a/src/Symfony/Bridge/Twig/CHANGELOG.md b/src/Symfony/Bridge/Twig/CHANGELOG.md
index d692bf4431..38f3ed5043 100644
--- a/src/Symfony/Bridge/Twig/CHANGELOG.md
+++ b/src/Symfony/Bridge/Twig/CHANGELOG.md
@@ -14,6 +14,7 @@ CHANGELOG
  * marked all classes extending twig as `@final`
  * deprecated to pass `$rootDir` and `$fileLinkFormatter` as 5th and 6th argument respectively to the 
    `DebugCommand::__construct()` method, swap the variables position.
+ * the `LintCommand` lints all the templates stored in all configured Twig paths if none argument is provided
 
 4.3.0
 -----
diff --git a/src/Symfony/Bridge/Twig/Command/LintCommand.php b/src/Symfony/Bridge/Twig/Command/LintCommand.php
index 1e482337f5..036362fcc7 100644
--- a/src/Symfony/Bridge/Twig/Command/LintCommand.php
+++ b/src/Symfony/Bridge/Twig/Command/LintCommand.php
@@ -23,6 +23,7 @@ use Symfony\Component\Finder\Finder;
 use Twig\Environment;
 use Twig\Error\Error;
 use Twig\Loader\ArrayLoader;
+use Twig\Loader\FilesystemLoader;
 use Twig\Source;
 
 /**
@@ -78,16 +79,27 @@ EOF
         $filenames = $input->getArgument('filename');
 
         if (0 === \count($filenames)) {
-            if (0 !== ftell(STDIN)) {
+            if (0 === ftell(STDIN)) {
+                $template = '';
+                while (!feof(STDIN)) {
+                    $template .= fread(STDIN, 1024);
+                }
+
+                return $this->display($input, $output, $io, [$this->validate($template, uniqid('sf_', true))]);
+            }
+
+            $loader = $this->twig->getLoader();
+            if ($loader instanceof FilesystemLoader) {
+                $paths = [];
+                foreach ($loader->getNamespaces() as $namespace) {
+                    $paths[] = $loader->getPaths($namespace);
+                }
+                $filenames = array_merge(...$paths);
+            }
+
+            if (0 === \count($filenames)) {
                 throw new RuntimeException('Please provide a filename or pipe template content to STDIN.');
             }
-
-            $template = '';
-            while (!feof(STDIN)) {
-                $template .= fread(STDIN, 1024);
-            }
-
-            return $this->display($input, $output, $io, [$this->validate($template, uniqid('sf_', true))]);
         }
 
         $filesInfo = $this->getFilesInfo($filenames);
diff --git a/src/Symfony/Bridge/Twig/Resources/views/Form/bootstrap_4_layout.html.twig b/src/Symfony/Bridge/Twig/Resources/views/Form/bootstrap_4_layout.html.twig
index 97710c79b5..ef45624c4e 100644
--- a/src/Symfony/Bridge/Twig/Resources/views/Form/bootstrap_4_layout.html.twig
+++ b/src/Symfony/Bridge/Twig/Resources/views/Form/bootstrap_4_layout.html.twig
@@ -124,7 +124,7 @@
         {{- block('form_widget_simple') -}}
         {%- set label_attr = label_attr|merge({ class: (label_attr.class|default('') ~ ' custom-file-label')|trim }) -%}
         <label for="{{ form.vars.id }}" {% with { attr: label_attr } %}{{ block('attributes') }}{% endwith %}>
-            {%- if attr.placeholder is defined -%}
+            {%- if attr.placeholder is defined and attr.placeholder is not none -%}
                 {{- translation_domain is same as(false) ? attr.placeholder : attr.placeholder|trans({}, translation_domain) -}}
             {%- endif -%}
         </label>
diff --git a/src/Symfony/Bridge/Twig/Tests/Command/LintCommandTest.php b/src/Symfony/Bridge/Twig/Tests/Command/LintCommandTest.php
index 22f048e6bc..fe3a7231b4 100644
--- a/src/Symfony/Bridge/Twig/Tests/Command/LintCommandTest.php
+++ b/src/Symfony/Bridge/Twig/Tests/Command/LintCommandTest.php
@@ -66,9 +66,18 @@ class LintCommandTest extends TestCase
         $this->assertRegExp('/ERROR  in \S+ \(line /', trim($tester->getDisplay()));
     }
 
+    public function testLintDefaultPaths()
+    {
+        $tester = $this->createCommandTester();
+        $ret = $tester->execute([], ['verbosity' => OutputInterface::VERBOSITY_VERBOSE, 'decorated' => false]);
+
+        $this->assertEquals(0, $ret, 'Returns 0 in case of success');
+        self::assertStringContainsString('OK in', trim($tester->getDisplay()));
+    }
+
     private function createCommandTester(): CommandTester
     {
-        $command = new LintCommand(new Environment(new FilesystemLoader()));
+        $command = new LintCommand(new Environment(new FilesystemLoader(\dirname(__DIR__).'/Fixtures/templates/')));
 
         $application = new Application();
         $application->add($command);
diff --git a/src/Symfony/Component/DependencyInjection/Loader/Configurator/ContainerConfigurator.php b/src/Symfony/Component/DependencyInjection/Loader/Configurator/ContainerConfigurator.php
index 2aa9b0eafa..643b252049 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/Configurator/ContainerConfigurator.php
+++ b/src/Symfony/Component/DependencyInjection/Loader/Configurator/ContainerConfigurator.php
@@ -124,7 +124,7 @@ function tagged_iterator(string $tag, string $indexAttribute = null, string $def
 /**
  * Creates a service locator by tag name.
  */
-function tagged_locator(string $tag, string $indexAttribute, string $defaultIndexMethod = null): ServiceLocatorArgument
+function tagged_locator(string $tag, string $indexAttribute = null, string $defaultIndexMethod = null): ServiceLocatorArgument
 {
     return new ServiceLocatorArgument(new TaggedIteratorArgument($tag, $indexAttribute, $defaultIndexMethod, true));
 }
diff --git a/src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php b/src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php
index 8d4b550c93..d68098b3c9 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php
+++ b/src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php
@@ -707,25 +707,23 @@ class YamlFileLoader extends FileLoader
             if (\in_array($value->getTag(), ['tagged_iterator', 'tagged_locator'], true)) {
                 $forLocator = 'tagged_locator' === $value->getTag();
 
-                if (\is_string($argument) && $argument) {
-                    return new TaggedIteratorArgument($argument, null, null, $forLocator);
-                }
-
                 if (\is_array($argument) && isset($argument['tag']) && $argument['tag']) {
                     if ($diff = array_diff(array_keys($argument), ['tag', 'index_by', 'default_index_method'])) {
                         throw new InvalidArgumentException(sprintf('"!%s" tag contains unsupported key "%s"; supported ones are "tag", "index_by" and "default_index_method".', $value->getTag(), implode('"", "', $diff)));
                     }
 
                     $argument = new TaggedIteratorArgument($argument['tag'], $argument['index_by'] ?? null, $argument['default_index_method'] ?? null, $forLocator);
-
-                    if ($forLocator) {
-                        $argument = new ServiceLocatorArgument($argument);
-                    }
-
-                    return $argument;
+                } elseif (\is_string($argument) && $argument) {
+                    $argument = new TaggedIteratorArgument($argument, null, null, $forLocator);
+                } else {
+                    throw new InvalidArgumentException(sprintf('"!%s" tags only accept a non empty string or an array with a key "tag" in "%s".', $value->getTag(), $file));
                 }
 
-                throw new InvalidArgumentException(sprintf('"!%s" tags only accept a non empty string or an array with a key "tag" in "%s".', $value->getTag(), $file));
+                if ($forLocator) {
+                    $argument = new ServiceLocatorArgument($argument);
+                }
+
+                return $argument;
             }
             if ('service' === $value->getTag()) {
                 if ($isParameter) {
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Dumper/YamlDumperTest.php b/src/Symfony/Component/DependencyInjection/Tests/Dumper/YamlDumperTest.php
index ca41a5b339..56512e89c1 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Dumper/YamlDumperTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Dumper/YamlDumperTest.php
@@ -104,6 +104,7 @@ class YamlDumperTest extends TestCase
         $container->register('foo_service', 'Foo')->addTag('foo');
         $container->register('foo_service_tagged_iterator', 'Bar')->addArgument($taggedIterator);
         $container->register('foo_service_tagged_locator', 'Bar')->addArgument(new ServiceLocatorArgument($taggedIterator));
+        $container->register('bar_service_tagged_locator', 'Bar')->addArgument(new ServiceLocatorArgument(new TaggedIteratorArgument('foo')));
 
         $dumper = new YamlDumper($container);
         $this->assertStringEqualsFile(self::$fixturesPath.'/yaml/services_with_tagged_argument.yml', $dumper->dump());
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/services_with_tagged_argument.yml b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/services_with_tagged_argument.yml
index b30aeb7bff..8c2cd59aaf 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/services_with_tagged_argument.yml
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/services_with_tagged_argument.yml
@@ -14,6 +14,9 @@ services:
     foo_service_tagged_locator:
         class: Bar
         arguments: [!tagged_locator { tag: foo, index_by: barfoo, default_index_method: foobar }]
+    bar_service_tagged_locator:
+        class: Bar
+        arguments: [!tagged_locator foo]
     Psr\Container\ContainerInterface:
         alias: service_container
         public: false
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Loader/YamlFileLoaderTest.php b/src/Symfony/Component/DependencyInjection/Tests/Loader/YamlFileLoaderTest.php
index 9518d1a512..2758d4de83 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Loader/YamlFileLoaderTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Loader/YamlFileLoaderTest.php
@@ -282,6 +282,9 @@ class YamlFileLoaderTest extends TestCase
 
         $taggedIterator = new TaggedIteratorArgument('foo', 'barfoo', 'foobar', true);
         $this->assertEquals(new ServiceLocatorArgument($taggedIterator), $container->getDefinition('foo_service_tagged_locator')->getArgument(0));
+
+        $taggedIterator = new TaggedIteratorArgument('foo', null, null, true);
+        $this->assertEquals(new ServiceLocatorArgument($taggedIterator), $container->getDefinition('bar_service_tagged_locator')->getArgument(0));
     }
 
     public function testNameOnlyTagsAreAllowedAsString()
diff --git a/src/Symfony/Component/ErrorHandler/DebugClassLoader.php b/src/Symfony/Component/ErrorHandler/DebugClassLoader.php
index 1f30cfa9f5..67a6c1500b 100644
--- a/src/Symfony/Component/ErrorHandler/DebugClassLoader.php
+++ b/src/Symfony/Component/ErrorHandler/DebugClassLoader.php
@@ -11,7 +11,11 @@
 
 namespace Symfony\Component\ErrorHandler;
 
+use Doctrine\Common\Persistence\Proxy;
 use PHPUnit\Framework\MockObject\Matcher\StatelessInvocation;
+use PHPUnit\Framework\MockObject\MockObject;
+use Prophecy\Prophecy\ProphecySubjectInterface;
+use ProxyManager\Proxy\ProxyInterface;
 
 /**
  * Autoloader checking if the class is really defined in the file found.
@@ -230,22 +234,57 @@ class DebugClassLoader
             spl_autoload_unregister($function);
         }
 
-        $loader = null;
-
         foreach ($functions as $function) {
             if (\is_array($function) && $function[0] instanceof self) {
-                $loader = $function[0];
                 $function = $function[0]->getClassLoader();
             }
 
             spl_autoload_register($function);
         }
+    }
 
-        if (null !== $loader) {
-            foreach (array_merge(get_declared_interfaces(), get_declared_traits(), get_declared_classes()) as $class) {
-                $loader->checkClass($class);
+    public static function checkClasses(): bool
+    {
+        if (!\is_array($functions = spl_autoload_functions())) {
+            return false;
+        }
+
+        $loader = null;
+
+        foreach ($functions as $function) {
+            if (\is_array($function) && $function[0] instanceof self) {
+                $loader = $function[0];
+                break;
             }
         }
+
+        if (null === $loader) {
+            return false;
+        }
+
+        static $offsets = [
+            'get_declared_interfaces' => 0,
+            'get_declared_traits' => 0,
+            'get_declared_classes' => 0,
+        ];
+
+        foreach ($offsets as $getSymbols => $i) {
+            $symbols = $getSymbols();
+
+            for (; $i < \count($symbols); ++$i) {
+                if (!is_subclass_of($symbols[$i], MockObject::class)
+                    && !is_subclass_of($symbols[$i], ProphecySubjectInterface::class)
+                    && !is_subclass_of($symbols[$i], Proxy::class)
+                    && !is_subclass_of($symbols[$i], ProxyInterface::class)
+                ) {
+                    $loader->checkClass($symbols[$i]);
+                }
+            }
+
+            $offsets[$getSymbols] = $i;
+        }
+
+        return true;
     }
 
     public function findFile(string $class): ?string
diff --git a/src/Symfony/Component/ErrorHandler/ErrorHandler.php b/src/Symfony/Component/ErrorHandler/ErrorHandler.php
index 5493e61a63..2064427f0a 100644
--- a/src/Symfony/Component/ErrorHandler/ErrorHandler.php
+++ b/src/Symfony/Component/ErrorHandler/ErrorHandler.php
@@ -592,7 +592,11 @@ class ErrorHandler
             }
         }
         $exceptionHandler = $this->exceptionHandler;
-        $this->exceptionHandler = null;
+        if ((!\is_array($exceptionHandler) || !$exceptionHandler[0] instanceof self || 'sendPhpResponse' !== $exceptionHandler[1]) && !\in_array(\PHP_SAPI, ['cli', 'phpdbg'], true)) {
+            $this->exceptionHandler = [$this, 'sendPhpResponse'];
+        } else {
+            $this->exceptionHandler = null;
+        }
         try {
             if (null !== $exceptionHandler) {
                 return $exceptionHandler($exception);
@@ -696,18 +700,28 @@ class ErrorHandler
     private function sendPhpResponse(\Throwable $exception)
     {
         $charset = ini_get('default_charset') ?: 'UTF-8';
-
-        if (!headers_sent()) {
-            header('HTTP/1.0 500');
-            header(sprintf('Content-Type: text/html; charset=%s', $charset));
-        }
+        $statusCode = 500;
+        $headers = [];
 
         if (class_exists(HtmlErrorRenderer::class)) {
-            echo (new HtmlErrorRenderer(true))->render(FlattenException::createFromThrowable($exception));
+            $exception = FlattenException::createFromThrowable($exception);
+            $statusCode = $exception->getStatusCode();
+            $headers = $exception->getHeaders();
+            $response = (new HtmlErrorRenderer(true))->render($exception);
         } else {
             $message = htmlspecialchars($exception->getMessage(), ENT_COMPAT | ENT_SUBSTITUTE, $charset);
-            echo sprintf('<!DOCTYPE html><html><head><meta charset="%s" /><meta name="robots" content="noindex,nofollow" /></head><body>%s</body></html>', $charset, $message);
+            $response = sprintf('<!DOCTYPE html><html><head><meta charset="%s" /><meta name="robots" content="noindex,nofollow" /></head><body>%s</body></html>', $charset, $message);
         }
+
+        if (!headers_sent()) {
+            header(sprintf('HTTP/1.0 %s', $statusCode));
+            foreach ($headers as $name => $value) {
+                header($name.': '.$value, false);
+            }
+            header('Content-Type: text/html; charset='.$charset);
+        }
+
+        echo $response;
     }
 
     /**
diff --git a/src/Symfony/Component/ErrorHandler/Tests/ErrorHandlerTest.php b/src/Symfony/Component/ErrorHandler/Tests/ErrorHandlerTest.php
index 6f8f56ef69..b536627a02 100644
--- a/src/Symfony/Component/ErrorHandler/Tests/ErrorHandlerTest.php
+++ b/src/Symfony/Component/ErrorHandler/Tests/ErrorHandlerTest.php
@@ -557,6 +557,18 @@ class ErrorHandlerTest extends TestCase
         $handler->handleException(new \Exception());
     }
 
+    public function testSendPhpResponse()
+    {
+        $handler = new ErrorHandler();
+        $handler->setExceptionHandler([$handler, 'sendPhpResponse']);
+
+        ob_start();
+        $handler->handleException(new \RuntimeException('Class Foo not found'));
+        $response = ob_get_clean();
+
+        self::assertStringContainsString('Class Foo not found', $response);
+    }
+
     /**
      * @dataProvider errorHandlerWhenLoggingProvider
      */
diff --git a/src/Symfony/Component/HttpClient/Chunk/DataChunk.php b/src/Symfony/Component/HttpClient/Chunk/DataChunk.php
index 618112834d..37ca848541 100644
--- a/src/Symfony/Component/HttpClient/Chunk/DataChunk.php
+++ b/src/Symfony/Component/HttpClient/Chunk/DataChunk.php
@@ -20,8 +20,8 @@ use Symfony\Contracts\HttpClient\ChunkInterface;
  */
 class DataChunk implements ChunkInterface
 {
-    private $offset;
-    private $content;
+    private $offset = 0;
+    private $content = '';
 
     public function __construct(int $offset = 0, string $content = '')
     {
@@ -53,6 +53,14 @@ class DataChunk implements ChunkInterface
         return false;
     }
 
+    /**
+     * {@inheritdoc}
+     */
+    public function getInformationalStatus(): ?array
+    {
+        return null;
+    }
+
     /**
      * {@inheritdoc}
      */
diff --git a/src/Symfony/Component/HttpClient/Chunk/ErrorChunk.php b/src/Symfony/Component/HttpClient/Chunk/ErrorChunk.php
index d2a69bc38a..3792dccf6d 100644
--- a/src/Symfony/Component/HttpClient/Chunk/ErrorChunk.php
+++ b/src/Symfony/Component/HttpClient/Chunk/ErrorChunk.php
@@ -65,6 +65,15 @@ class ErrorChunk implements ChunkInterface
         throw new TransportException($this->errorMessage, 0, $this->error);
     }
 
+    /**
+     * {@inheritdoc}
+     */
+    public function getInformationalStatus(): ?array
+    {
+        $this->didThrow = true;
+        throw new TransportException($this->errorMessage, 0, $this->error);
+    }
+
     /**
      * {@inheritdoc}
      */
diff --git a/src/Symfony/Component/HttpClient/Chunk/InformationalChunk.php b/src/Symfony/Component/HttpClient/Chunk/InformationalChunk.php
new file mode 100644
index 0000000000..c4452f15a0
--- /dev/null
+++ b/src/Symfony/Component/HttpClient/Chunk/InformationalChunk.php
@@ -0,0 +1,35 @@
+<?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\HttpClient\Chunk;
+
+/**
+ * @author Nicolas Grekas <p@tchwork.com>
+ *
+ * @internal
+ */
+class InformationalChunk extends DataChunk
+{
+    private $status;
+
+    public function __construct(int $statusCode, array $headers)
+    {
+        $this->status = [$statusCode, $headers];
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getInformationalStatus(): ?array
+    {
+        return $this->status;
+    }
+}
diff --git a/src/Symfony/Component/HttpClient/CurlHttpClient.php b/src/Symfony/Component/HttpClient/CurlHttpClient.php
index 9ecd62b086..c034d869d8 100644
--- a/src/Symfony/Component/HttpClient/CurlHttpClient.php
+++ b/src/Symfony/Component/HttpClient/CurlHttpClient.php
@@ -56,7 +56,7 @@ final class CurlHttpClient implements HttpClientInterface, LoggerAwareInterface
      *
      * @see HttpClientInterface::OPTIONS_DEFAULTS for available options
      */
-    public function __construct(array $defaultOptions = [], int $maxHostConnections = 6, int $maxPendingPushes = 50)
+    public function __construct(array $defaultOptions = [], int $maxHostConnections = 6, int $maxPendingPushes = 0)
     {
         if (!\extension_loaded('curl')) {
             throw new \LogicException('You cannot use the "Symfony\Component\HttpClient\CurlHttpClient" as the "curl" extension is not installed.');
@@ -106,20 +106,15 @@ final class CurlHttpClient implements HttpClientInterface, LoggerAwareInterface
         $host = parse_url($authority, PHP_URL_HOST);
         $url = implode('', $url);
 
+        if (!isset($options['normalized_headers']['user-agent'])) {
+            $options['normalized_headers']['user-agent'][] = $options['headers'][] = 'User-Agent: Symfony HttpClient/Curl';
+        }
+
         if ($pushedResponse = $this->multi->pushedResponses[$url] ?? null) {
             unset($this->multi->pushedResponses[$url]);
-            // Accept pushed responses only if their headers related to authentication match the request
-            $expectedHeaders = ['authorization', 'cookie', 'x-requested-with', 'range'];
-            foreach ($expectedHeaders as $k => $v) {
-                $expectedHeaders[$k] = null;
 
-                foreach ($options['normalized_headers'][$v] ?? [] as $h) {
-                    $expectedHeaders[$k][] = substr($h, 2 + \strlen($v));
-                }
-            }
-
-            if ('GET' === $method && $expectedHeaders === $pushedResponse->headers && !$options['body']) {
-                $this->logger && $this->logger->debug(sprintf('Connecting request to pushed response: "%s %s"', $method, $url));
+            if (self::acceptPushForRequest($method, $options, $pushedResponse)) {
+                $this->logger && $this->logger->debug(sprintf('Accepting pushed response: "%s %s"', $method, $url));
 
                 // Reinitialize the pushed response with request's options
                 $pushedResponse->response->__construct($this->multi, $url, $options, $this->logger);
@@ -127,14 +122,13 @@ final class CurlHttpClient implements HttpClientInterface, LoggerAwareInterface
                 return $pushedResponse->response;
             }
 
-            $this->logger && $this->logger->debug(sprintf('Rejecting pushed response for "%s": authorization headers don\'t match the request', $url));
+            $this->logger && $this->logger->debug(sprintf('Rejecting pushed response: "%s".', $url));
         }
 
         $this->logger && $this->logger->info(sprintf('Request: "%s %s"', $method, $url));
 
         $curlopts = [
             CURLOPT_URL => $url,
-            CURLOPT_USERAGENT => 'Symfony HttpClient/Curl',
             CURLOPT_TCP_NODELAY => true,
             CURLOPT_PROTOCOLS => CURLPROTO_HTTP | CURLPROTO_HTTPS,
             CURLOPT_REDIR_PROTOCOLS => CURLPROTO_HTTP | CURLPROTO_HTTPS,
@@ -330,7 +324,7 @@ final class CurlHttpClient implements HttpClientInterface, LoggerAwareInterface
         $active = 0;
         while (CURLM_CALL_MULTI_PERFORM === curl_multi_exec($this->multi->handle, $active));
 
-        foreach ($this->multi->openHandles as $ch) {
+        foreach ($this->multi->openHandles as [$ch]) {
             curl_setopt($ch, CURLOPT_VERBOSE, false);
         }
     }
@@ -342,17 +336,17 @@ final class CurlHttpClient implements HttpClientInterface, LoggerAwareInterface
 
         foreach ($requestHeaders as $h) {
             if (false !== $i = strpos($h, ':', 1)) {
-                $headers[substr($h, 0, $i)] = substr($h, 1 + $i);
+                $headers[substr($h, 0, $i)][] = substr($h, 1 + $i);
             }
         }
 
-        if (!isset($headers[':method']) || !isset($headers[':scheme']) || !isset($headers[':authority']) || !isset($headers[':path']) || 'GET' !== $headers[':method'] || isset($headers['range'])) {
+        if (!isset($headers[':method']) || !isset($headers[':scheme']) || !isset($headers[':authority']) || !isset($headers[':path'])) {
             $logger && $logger->debug(sprintf('Rejecting pushed response from "%s": pushed headers are invalid', $origin));
 
             return CURL_PUSH_DENY;
         }
 
-        $url = $headers[':scheme'].'://'.$headers[':authority'];
+        $url = $headers[':scheme'][0].'://'.$headers[':authority'][0];
 
         if ($maxPendingPushes <= \count($multi->pushedResponses)) {
             $logger && $logger->debug(sprintf('Rejecting pushed response from "%s" for "%s": the queue is full', $origin, $url));
@@ -369,22 +363,43 @@ final class CurlHttpClient implements HttpClientInterface, LoggerAwareInterface
             return CURL_PUSH_DENY;
         }
 
-        $url .= $headers[':path'];
+        $url .= $headers[':path'][0];
         $logger && $logger->debug(sprintf('Queueing pushed response: "%s"', $url));
 
-        $multi->pushedResponses[$url] = new PushedResponse(
-            new CurlResponse($multi, $pushed),
-            [
-                $headers['authorization'] ?? null,
-                $headers['cookie'] ?? null,
-                $headers['x-requested-with'] ?? null,
-                null,
-            ]
-        );
+        $multi->pushedResponses[$url] = new PushedResponse(new CurlResponse($multi, $pushed), $headers, $multi->openHandles[(int) $parent][1] ?? []);
 
         return CURL_PUSH_OK;
     }
 
+    /**
+     * Accepts pushed responses only if their headers related to authentication match the request.
+     */
+    private static function acceptPushForRequest(string $method, array $options, PushedResponse $pushedResponse): bool
+    {
+        if ($options['body'] || $method !== $pushedResponse->requestHeaders[':method'][0]) {
+            return false;
+        }
+
+        foreach (['proxy', 'no_proxy', 'bindto'] as $k) {
+            if ($options[$k] !== $pushedResponse->parentOptions[$k]) {
+                return false;
+            }
+        }
+
+        foreach (['authorization', 'cookie', 'range', 'proxy-authorization'] as $k) {
+            $normalizedHeaders = $options['normalized_headers'][$k] ?? [];
+            foreach ($normalizedHeaders as $i => $v) {
+                $normalizedHeaders[$i] = substr($v, \strlen($k) + 2);
+            }
+
+            if (($pushedResponse->requestHeaders[$k] ?? []) !== $normalizedHeaders) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
     /**
      * Wraps the request's body callback to allow it to return strings longer than curl requested.
      */
diff --git a/src/Symfony/Component/HttpClient/Internal/PushedResponse.php b/src/Symfony/Component/HttpClient/Internal/PushedResponse.php
index 632f0c41d0..6f8e8fda3a 100644
--- a/src/Symfony/Component/HttpClient/Internal/PushedResponse.php
+++ b/src/Symfony/Component/HttpClient/Internal/PushedResponse.php
@@ -14,7 +14,7 @@ namespace Symfony\Component\HttpClient\Internal;
 use Symfony\Component\HttpClient\Response\CurlResponse;
 
 /**
- * A pushed response with headers.
+ * A pushed response with its request headers.
  *
  * @author Alexander M. Turek <me@derrabus.de>
  *
@@ -22,15 +22,17 @@ use Symfony\Component\HttpClient\Response\CurlResponse;
  */
 final class PushedResponse
 {
-    /** @var CurlResponse */
     public $response;
 
     /** @var string[] */
-    public $headers;
+    public $requestHeaders;
 
-    public function __construct(CurlResponse $response, array $headers)
+    public $parentOptions = [];
+
+    public function __construct(CurlResponse $response, array $requestHeaders, array $parentOptions)
     {
         $this->response = $response;
-        $this->headers = $headers;
+        $this->requestHeaders = $requestHeaders;
+        $this->parentOptions = $parentOptions;
     }
 }
diff --git a/src/Symfony/Component/HttpClient/Response/CurlResponse.php b/src/Symfony/Component/HttpClient/Response/CurlResponse.php
index a064361763..0b044630f6 100644
--- a/src/Symfony/Component/HttpClient/Response/CurlResponse.php
+++ b/src/Symfony/Component/HttpClient/Response/CurlResponse.php
@@ -13,6 +13,7 @@ namespace Symfony\Component\HttpClient\Response;
 
 use Psr\Log\LoggerInterface;
 use Symfony\Component\HttpClient\Chunk\FirstChunk;
+use Symfony\Component\HttpClient\Chunk\InformationalChunk;
 use Symfony\Component\HttpClient\Exception\TransportException;
 use Symfony\Component\HttpClient\Internal\CurlClientState;
 use Symfony\Contracts\HttpClient\ResponseInterface;
@@ -120,9 +121,6 @@ final class CurlResponse implements ResponseInterface
 
             if (\in_array($waitFor, ['headers', 'destruct'], true)) {
                 try {
-                    if (\defined('CURLOPT_STREAM_WEIGHT')) {
-                        curl_setopt($ch, CURLOPT_STREAM_WEIGHT, 32);
-                    }
                     self::stream([$response])->current();
                 } catch (\Throwable $e) {
                     // Persist timeouts thrown during initialization
@@ -140,7 +138,7 @@ final class CurlResponse implements ResponseInterface
         };
 
         // Schedule the request in a non-blocking way
-        $multi->openHandles[$id] = $ch;
+        $multi->openHandles[$id] = [$ch, $options];
         curl_multi_add_handle($multi->handle, $ch);
         self::perform($multi);
     }
@@ -314,8 +312,11 @@ final class CurlResponse implements ResponseInterface
             return \strlen($data);
         }
 
-        // End of headers: handle redirects and add to the activity list
+        // End of headers: handle informational responses, redirects, etc.
+
         if (200 > $statusCode = curl_getinfo($ch, CURLINFO_RESPONSE_CODE)) {
+            $multi->handlesActivity[$id][] = new InformationalChunk($statusCode, $headers);
+
             return \strlen($data);
         }
 
@@ -342,7 +343,7 @@ final class CurlResponse implements ResponseInterface
 
         if ($statusCode < 300 || 400 <= $statusCode || curl_getinfo($ch, CURLINFO_REDIRECT_COUNT) === $options['max_redirects']) {
             // Headers and redirects completed, time to get the response's body
-            $multi->handlesActivity[$id] = [new FirstChunk()];
+            $multi->handlesActivity[$id][] = new FirstChunk();
 
             if ('destruct' === $waitFor) {
                 return 0;
diff --git a/src/Symfony/Component/HttpClient/Response/MockResponse.php b/src/Symfony/Component/HttpClient/Response/MockResponse.php
index fe94bc3436..fa8abebea4 100644
--- a/src/Symfony/Component/HttpClient/Response/MockResponse.php
+++ b/src/Symfony/Component/HttpClient/Response/MockResponse.php
@@ -45,7 +45,7 @@ class MockResponse implements ResponseInterface
     public function __construct($body = '', array $info = [])
     {
         $this->body = is_iterable($body) ? $body : (string) $body;
-        $this->info = $info + $this->info;
+        $this->info = $info + ['http_code' => 200] + $this->info;
 
         if (!isset($info['response_headers'])) {
             return;
@@ -59,7 +59,8 @@ class MockResponse implements ResponseInterface
             }
         }
 
-        $this->info['response_headers'] = $responseHeaders;
+        $this->info['response_headers'] = [];
+        self::addResponseHeaders($responseHeaders, $this->info, $this->headers);
     }
 
     /**
diff --git a/src/Symfony/Component/HttpClient/Response/ResponseStream.php b/src/Symfony/Component/HttpClient/Response/ResponseStream.php
index cf53abcded..f86d2d4077 100644
--- a/src/Symfony/Component/HttpClient/Response/ResponseStream.php
+++ b/src/Symfony/Component/HttpClient/Response/ResponseStream.php
@@ -17,8 +17,6 @@ use Symfony\Contracts\HttpClient\ResponseStreamInterface;
 
 /**
  * @author Nicolas Grekas <p@tchwork.com>
- *
- * @internal
  */
 final class ResponseStream implements ResponseStreamInterface
 {
diff --git a/src/Symfony/Component/HttpClient/Tests/CurlHttpClientTest.php b/src/Symfony/Component/HttpClient/Tests/CurlHttpClientTest.php
index 1d1d7c10a5..4fd367fd9d 100644
--- a/src/Symfony/Component/HttpClient/Tests/CurlHttpClientTest.php
+++ b/src/Symfony/Component/HttpClient/Tests/CurlHttpClientTest.php
@@ -47,27 +47,22 @@ class CurlHttpClientTest extends HttpClientTestCase
             }
         };
 
-        $client = new CurlHttpClient();
+        $client = new CurlHttpClient([], 6, 2);
         $client->setLogger($logger);
 
-        $index = $client->request('GET', 'https://http2-push.io');
+        $index = $client->request('GET', 'https://http2.akamai.com/');
         $index->getContent();
 
-        $css = $client->request('GET', 'https://http2-push.io/css/style.css');
-        $js = $client->request('GET', 'https://http2-push.io/js/http2-push.js');
+        $css = $client->request('GET', 'https://http2.akamai.com/resources/push.css');
 
         $css->getHeaders();
-        $js->getHeaders();
 
         $expected = [
-            'Request: "GET https://http2-push.io/"',
-            'Queueing pushed response: "https://http2-push.io/css/style.css"',
-            'Queueing pushed response: "https://http2-push.io/js/http2-push.js"',
-            'Response: "200 https://http2-push.io/"',
-            'Connecting request to pushed response: "GET https://http2-push.io/css/style.css"',
-            'Connecting request to pushed response: "GET https://http2-push.io/js/http2-push.js"',
-            'Response: "200 https://http2-push.io/css/style.css"',
-            'Response: "200 https://http2-push.io/js/http2-push.js"',
+            'Request: "GET https://http2.akamai.com/"',
+            'Queueing pushed response: "https://http2.akamai.com/resources/push.css"',
+            'Response: "200 https://http2.akamai.com/"',
+            'Accepting pushed response: "GET https://http2.akamai.com/resources/push.css"',
+            'Response: "200 https://http2.akamai.com/resources/push.css"',
         ];
         $this->assertSame($expected, $logger->logs);
     }
diff --git a/src/Symfony/Component/HttpClient/Tests/MockHttpClientTest.php b/src/Symfony/Component/HttpClient/Tests/MockHttpClientTest.php
index 91fc21873a..542d19333b 100644
--- a/src/Symfony/Component/HttpClient/Tests/MockHttpClientTest.php
+++ b/src/Symfony/Component/HttpClient/Tests/MockHttpClientTest.php
@@ -15,6 +15,8 @@ use Symfony\Component\HttpClient\Exception\TransportException;
 use Symfony\Component\HttpClient\MockHttpClient;
 use Symfony\Component\HttpClient\NativeHttpClient;
 use Symfony\Component\HttpClient\Response\MockResponse;
+use Symfony\Component\HttpClient\Response\ResponseStream;
+use Symfony\Contracts\HttpClient\ChunkInterface;
 use Symfony\Contracts\HttpClient\HttpClientInterface;
 use Symfony\Contracts\HttpClient\ResponseInterface;
 
@@ -124,6 +126,41 @@ class MockHttpClientTest extends HttpClientTestCase
                 $responses[] = new MockResponse($body, ['response_headers' => $headers]);
                 break;
 
+            case 'testInformationalResponseStream':
+                $client = $this->createMock(HttpClientInterface::class);
+                $response = new MockResponse('Here the body', ['response_headers' => [
+                    'HTTP/1.1 103 ',
+                    'Link: </style.css>; rel=preload; as=style',
+                    'HTTP/1.1 200 ',
+                    'Date: foo',
+                    'Content-Length: 13',
+                ]]);
+                $client->method('request')->willReturn($response);
+                $client->method('stream')->willReturn(new ResponseStream((function () use ($response) {
+                    $chunk = $this->createMock(ChunkInterface::class);
+                    $chunk->method('getInformationalStatus')
+                        ->willReturn([103, ['link' => ['</style.css>; rel=preload; as=style', '</script.js>; rel=preload; as=script']]]);
+
+                    yield $response => $chunk;
+
+                    $chunk = $this->createMock(ChunkInterface::class);
+                    $chunk->method('isFirst')->willReturn(true);
+
+                    yield $response => $chunk;
+
+                    $chunk = $this->createMock(ChunkInterface::class);
+                    $chunk->method('getContent')->willReturn('Here the body');
+
+                    yield $response => $chunk;
+
+                    $chunk = $this->createMock(ChunkInterface::class);
+                    $chunk->method('isLast')->willReturn(true);
+
+                    yield $response => $chunk;
+                })()));
+
+                return $client;
+
             case 'testMaxDuration':
                 $mock = $this->getMockBuilder(ResponseInterface::class)->getMock();
                 $mock->expects($this->any())
diff --git a/src/Symfony/Component/HttpClient/Tests/NativeHttpClientTest.php b/src/Symfony/Component/HttpClient/Tests/NativeHttpClientTest.php
index 2d8b7b8fad..bcfab64bdc 100644
--- a/src/Symfony/Component/HttpClient/Tests/NativeHttpClientTest.php
+++ b/src/Symfony/Component/HttpClient/Tests/NativeHttpClientTest.php
@@ -20,4 +20,9 @@ class NativeHttpClientTest extends HttpClientTestCase
     {
         return new NativeHttpClient();
     }
+
+    public function testInformationalResponseStream()
+    {
+        $this->markTestSkipped('NativeHttpClient doesn\'t support informational status codes.');
+    }
 }
diff --git a/src/Symfony/Component/HttpClient/composer.json b/src/Symfony/Component/HttpClient/composer.json
index 9cb320049d..66d80bfb51 100644
--- a/src/Symfony/Component/HttpClient/composer.json
+++ b/src/Symfony/Component/HttpClient/composer.json
@@ -22,7 +22,7 @@
     "require": {
         "php": "^7.2.9",
         "psr/log": "^1.0",
-        "symfony/http-client-contracts": "^1.1.6",
+        "symfony/http-client-contracts": "^1.1.7",
         "symfony/polyfill-php73": "^1.11"
     },
     "require-dev": {
diff --git a/src/Symfony/Component/Mailer/Tests/Transport/TransportsTest.php b/src/Symfony/Component/Mailer/Tests/Transport/TransportsTest.php
index 93f6dee9f5..10d46ca846 100644
--- a/src/Symfony/Component/Mailer/Tests/Transport/TransportsTest.php
+++ b/src/Symfony/Component/Mailer/Tests/Transport/TransportsTest.php
@@ -12,6 +12,7 @@
 namespace Symfony\Component\Mailer\Tests\Transport;
 
 use PHPUnit\Framework\TestCase;
+use Symfony\Component\Mailer\Exception\InvalidArgumentException;
 use Symfony\Component\Mailer\Transport\TransportInterface;
 use Symfony\Component\Mailer\Transport\Transports;
 use Symfony\Component\Mime\Header\Headers;
@@ -48,4 +49,19 @@ class TransportsTest extends TestCase
         $email = new Message($headers, new TextPart('...'));
         $transport->send($email);
     }
+
+    public function testTransportDoesNotExist()
+    {
+        $transport = new Transports([
+            'foo' => $this->createMock(TransportInterface::class),
+            'bar' => $this->createMock(TransportInterface::class),
+        ]);
+
+        $headers = (new Headers())->addTextHeader('X-Transport', 'foobar');
+        $email = new Message($headers, new TextPart('...'));
+
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('The "foobar" transport does not exist (available transports: "foo", "bar").');
+        $transport->send($email);
+    }
 }
diff --git a/src/Symfony/Component/Mailer/Transport/Transports.php b/src/Symfony/Component/Mailer/Transport/Transports.php
index 0158d2a1f8..983ad15018 100644
--- a/src/Symfony/Component/Mailer/Transport/Transports.php
+++ b/src/Symfony/Component/Mailer/Transport/Transports.php
@@ -56,7 +56,7 @@ class Transports implements TransportInterface
         $headers->remove('X-Transport');
 
         if (!isset($this->transports[$transport])) {
-            throw new InvalidArgumentException(sprintf('The "%s" transport does not exist.', $transport));
+            throw new InvalidArgumentException(sprintf('The "%s" transport does not exist (available transports: "%s").', $transport, implode('", "', array_keys($this->transports))));
         }
 
         return $this->transports[$transport]->send($message, $envelope);
diff --git a/src/Symfony/Component/Translation/DataCollectorTranslator.php b/src/Symfony/Component/Translation/DataCollectorTranslator.php
index c46e058c9e..9c51b5ad97 100644
--- a/src/Symfony/Component/Translation/DataCollectorTranslator.php
+++ b/src/Symfony/Component/Translation/DataCollectorTranslator.php
@@ -119,7 +119,7 @@ class DataCollectorTranslator implements TranslatorInterface, TranslatorBagInter
         return $this->messages;
     }
 
-    private function collectMessage(?string $locale, ?string $domain, string $id, string $translation, ?array $parameters = [])
+    private function collectMessage(?string $locale, ?string $domain, ?string $id, string $translation, ?array $parameters = [])
     {
         if (null === $domain) {
             $domain = 'messages';
diff --git a/src/Symfony/Component/Translation/Formatter/IntlFormatter.php b/src/Symfony/Component/Translation/Formatter/IntlFormatter.php
index 1d5f468d46..ad4a45b95b 100644
--- a/src/Symfony/Component/Translation/Formatter/IntlFormatter.php
+++ b/src/Symfony/Component/Translation/Formatter/IntlFormatter.php
@@ -28,6 +28,11 @@ class IntlFormatter implements IntlFormatterInterface
      */
     public function formatIntl(string $message, string $locale, array $parameters = []): string
     {
+        // MessageFormatter constructor throws an exception if the message is empty
+        if ('' === $message) {
+            return '';
+        }
+
         if (!$formatter = $this->cache[$locale][$message] ?? null) {
             if (!($this->hasMessageFormatter ?? $this->hasMessageFormatter = class_exists(\MessageFormatter::class))) {
                 throw new LogicException('Cannot parse message translation: please install the "intl" PHP extension or the "symfony/polyfill-intl-messageformatter" package.');
diff --git a/src/Symfony/Component/Translation/LoggingTranslator.php b/src/Symfony/Component/Translation/LoggingTranslator.php
index 2c9e97c1e9..cac8141cc5 100644
--- a/src/Symfony/Component/Translation/LoggingTranslator.php
+++ b/src/Symfony/Component/Translation/LoggingTranslator.php
@@ -107,7 +107,7 @@ class LoggingTranslator implements TranslatorInterface, TranslatorBagInterface,
     /**
      * Logs for missing translations.
      */
-    private function log(string $id, ?string $domain, ?string $locale)
+    private function log(?string $id, ?string $domain, ?string $locale)
     {
         if (null === $domain) {
             $domain = 'messages';
diff --git a/src/Symfony/Component/Translation/Tests/Formatter/IntlFormatterTest.php b/src/Symfony/Component/Translation/Tests/Formatter/IntlFormatterTest.php
index 45ce6d4f6e..37d982cf29 100644
--- a/src/Symfony/Component/Translation/Tests/Formatter/IntlFormatterTest.php
+++ b/src/Symfony/Component/Translation/Tests/Formatter/IntlFormatterTest.php
@@ -82,6 +82,11 @@ _MSG_;
                 '{0,number,integer} monkeys on {1,number,integer} trees make {2,number} monkeys per tree',
                 [4560, 123, 4560 / 123],
             ],
+            [
+                '',
+                '',
+                [],
+            ],
         ];
     }
 
diff --git a/src/Symfony/Component/Translation/Tests/TranslatorTest.php b/src/Symfony/Component/Translation/Tests/TranslatorTest.php
index 20c83686fa..9666ac97ea 100644
--- a/src/Symfony/Component/Translation/Tests/TranslatorTest.php
+++ b/src/Symfony/Component/Translation/Tests/TranslatorTest.php
@@ -382,6 +382,19 @@ class TranslatorTest extends TestCase
         $this->assertEquals($expected, $translator->trans($id, [], '', 'fr'));
     }
 
+    public function testTransNullId()
+    {
+        $translator = new Translator('en');
+        $translator->addLoader('array', new ArrayLoader());
+        $translator->addResource('array', ['foo' => 'foofoo'], 'en');
+
+        $this->assertSame('', $translator->trans(null));
+
+        (\Closure::bind(function () use ($translator) {
+            $this->assertSame([], $translator->catalogues);
+        }, $this, Translator::class))();
+    }
+
     public function getTransFileTests()
     {
         return [
@@ -403,6 +416,7 @@ class TranslatorTest extends TestCase
             ['Symfony est super !', 'Symfony is great!', 'Symfony est super !', [], 'fr', ''],
             ['Symfony est awesome !', 'Symfony is %what%!', 'Symfony est %what% !', ['%what%' => 'awesome'], 'fr', ''],
             ['Symfony est super !', new StringClass('Symfony is great!'), 'Symfony est super !', [], 'fr', ''],
+            ['', null, '', [], 'fr', ''],
         ];
     }
 
diff --git a/src/Symfony/Component/Translation/Translator.php b/src/Symfony/Component/Translation/Translator.php
index 0ecfee378b..3e6047d672 100644
--- a/src/Symfony/Component/Translation/Translator.php
+++ b/src/Symfony/Component/Translation/Translator.php
@@ -189,11 +189,14 @@ class Translator implements TranslatorInterface, TranslatorBagInterface, LocaleA
      */
     public function trans($id, array $parameters = [], $domain = null, $locale = null)
     {
+        if ('' === $id = (string) $id) {
+            return '';
+        }
+
         if (null === $domain) {
             $domain = 'messages';
         }
 
-        $id = (string) $id;
         $catalogue = $this->getCatalogue($locale);
         $locale = $catalogue->getLocale();
         while (!$catalogue->defines($id, $domain)) {
diff --git a/src/Symfony/Component/Validator/ConstraintValidator.php b/src/Symfony/Component/Validator/ConstraintValidator.php
index 704252f402..5bcebb7181 100644
--- a/src/Symfony/Component/Validator/ConstraintValidator.php
+++ b/src/Symfony/Component/Validator/ConstraintValidator.php
@@ -85,12 +85,10 @@ abstract class ConstraintValidator implements ConstraintValidatorInterface
      */
     protected function formatValue($value, int $format = 0)
     {
-        $isDateTime = $value instanceof \DateTimeInterface;
-
-        if (($format & self::PRETTY_DATE) && $isDateTime) {
+        if (($format & self::PRETTY_DATE) && $value instanceof \DateTimeInterface) {
             if (class_exists('IntlDateFormatter')) {
                 $locale = \Locale::getDefault();
-                $formatter = new \IntlDateFormatter($locale, \IntlDateFormatter::MEDIUM, \IntlDateFormatter::SHORT);
+                $formatter = new \IntlDateFormatter($locale, \IntlDateFormatter::MEDIUM, \IntlDateFormatter::SHORT, $value->getTimezone());
 
                 // neither the native nor the stub IntlDateFormatter support
                 // DateTimeImmutable as of yet
diff --git a/src/Symfony/Component/Validator/Constraints/AbstractComparisonValidator.php b/src/Symfony/Component/Validator/Constraints/AbstractComparisonValidator.php
index a6ade9c542..6c538fddc9 100644
--- a/src/Symfony/Component/Validator/Constraints/AbstractComparisonValidator.php
+++ b/src/Symfony/Component/Validator/Constraints/AbstractComparisonValidator.php
@@ -65,14 +65,14 @@ abstract class AbstractComparisonValidator extends ConstraintValidator
         // This allows to compare with any date/time value supported by
         // the DateTime constructor:
         // https://php.net/datetime.formats
-        if (\is_string($comparedValue)) {
-            if ($value instanceof \DateTimeImmutable) {
-                // If $value is immutable, convert the compared value to a
-                // DateTimeImmutable too
-                $comparedValue = new \DateTimeImmutable($comparedValue);
-            } elseif ($value instanceof \DateTimeInterface) {
-                // Otherwise use DateTime
-                $comparedValue = new \DateTime($comparedValue);
+        if (\is_string($comparedValue) && $value instanceof \DateTimeInterface) {
+            // If $value is immutable, convert the compared value to a DateTimeImmutable too, otherwise use DateTime
+            $dateTimeClass = $value instanceof \DateTimeImmutable ? \DateTimeImmutable::class : \DateTime::class;
+
+            try {
+                $comparedValue = new $dateTimeClass($comparedValue);
+            } catch (\Exception $e) {
+                throw new ConstraintDefinitionException(sprintf('The compared value "%s" could not be converted to a "%s" instance in the "%s" constraint.', $comparedValue, $dateTimeClass, \get_class($constraint)));
             }
         }
 
diff --git a/src/Symfony/Component/Validator/Constraints/DivisibleByValidator.php b/src/Symfony/Component/Validator/Constraints/DivisibleByValidator.php
index a2def7f50c..53b8d38930 100644
--- a/src/Symfony/Component/Validator/Constraints/DivisibleByValidator.php
+++ b/src/Symfony/Component/Validator/Constraints/DivisibleByValidator.php
@@ -11,6 +11,8 @@
 
 namespace Symfony\Component\Validator\Constraints;
 
+use Symfony\Component\Validator\Exception\UnexpectedValueException;
+
 /**
  * Validates that values are a multiple of the given number.
  *
@@ -23,6 +25,14 @@ class DivisibleByValidator extends AbstractComparisonValidator
      */
     protected function compareValues($value1, $value2)
     {
+        if (!is_numeric($value1)) {
+            throw new UnexpectedValueException($value1, 'numeric');
+        }
+
+        if (!is_numeric($value2)) {
+            throw new UnexpectedValueException($value2, 'numeric');
+        }
+
         if (!$value2 = abs($value2)) {
             return false;
         }
diff --git a/src/Symfony/Component/Validator/Constraints/RangeValidator.php b/src/Symfony/Component/Validator/Constraints/RangeValidator.php
index 46c5ea8e68..44f54a63c0 100644
--- a/src/Symfony/Component/Validator/Constraints/RangeValidator.php
+++ b/src/Symfony/Component/Validator/Constraints/RangeValidator.php
@@ -61,12 +61,26 @@ class RangeValidator extends ConstraintValidator
         // the DateTime constructor:
         // https://php.net/datetime.formats
         if ($value instanceof \DateTimeInterface) {
+            $dateTimeClass = null;
+
             if (\is_string($min)) {
-                $min = new \DateTime($min);
+                $dateTimeClass = $value instanceof \DateTimeImmutable ? \DateTimeImmutable::class : \DateTime::class;
+
+                try {
+                    $min = new $dateTimeClass($min);
+                } catch (\Exception $e) {
+                    throw new ConstraintDefinitionException(sprintf('The min value "%s" could not be converted to a "%s" instance in the "%s" constraint.', $min, $dateTimeClass, \get_class($constraint)));
+                }
             }
 
             if (\is_string($max)) {
-                $max = new \DateTime($max);
+                $dateTimeClass = $dateTimeClass ?: ($value instanceof \DateTimeImmutable ? \DateTimeImmutable::class : \DateTime::class);
+
+                try {
+                    $max = new $dateTimeClass($max);
+                } catch (\Exception $e) {
+                    throw new ConstraintDefinitionException(sprintf('The max value "%s" could not be converted to a "%s" instance in the "%s" constraint.', $max, $dateTimeClass, \get_class($constraint)));
+                }
             }
         }
 
diff --git a/src/Symfony/Component/Validator/Tests/ConstraintValidatorTest.php b/src/Symfony/Component/Validator/Tests/ConstraintValidatorTest.php
new file mode 100644
index 0000000000..96af6f13eb
--- /dev/null
+++ b/src/Symfony/Component/Validator/Tests/ConstraintValidatorTest.php
@@ -0,0 +1,65 @@
+<?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\Validator\Tests;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\ConstraintValidator;
+
+final class ConstraintValidatorTest extends TestCase
+{
+    /**
+     * @dataProvider formatValueProvider
+     */
+    public function testFormatValue($expected, $value, $format = 0)
+    {
+        $this->assertSame($expected, (new TestFormatValueConstraintValidator())->formatValueProxy($value, $format));
+    }
+
+    public function formatValueProvider()
+    {
+        $data = [
+            ['true', true],
+            ['false', false],
+            ['null', null],
+            ['resource', fopen('php://memory', 'r')],
+            ['"foo"', 'foo'],
+            ['array', []],
+            ['object', $toString = new TestToStringObject()],
+            ['ccc', $toString, ConstraintValidator::OBJECT_TO_STRING],
+            ['object', $dateTime = (new \DateTimeImmutable('@0'))->setTimezone(new \DateTimeZone('UTC'))],
+            [class_exists(\IntlDateFormatter::class) ? 'Jan 1, 1970, 12:00 AM' : '1970-01-01 00:00:00', $dateTime, ConstraintValidator::PRETTY_DATE],
+        ];
+
+        return $data;
+    }
+}
+
+final class TestFormatValueConstraintValidator extends ConstraintValidator
+{
+    public function validate($value, Constraint $constraint)
+    {
+    }
+
+    public function formatValueProxy($value, $format)
+    {
+        return $this->formatValue($value, $format);
+    }
+}
+
+final class TestToStringObject
+{
+    public function __toString()
+    {
+        return 'ccc';
+    }
+}
diff --git a/src/Symfony/Component/Validator/Tests/Constraints/AbstractComparisonValidatorTestCase.php b/src/Symfony/Component/Validator/Tests/Constraints/AbstractComparisonValidatorTestCase.php
index 944195f0f3..51ea8aecd5 100644
--- a/src/Symfony/Component/Validator/Tests/Constraints/AbstractComparisonValidatorTestCase.php
+++ b/src/Symfony/Component/Validator/Tests/Constraints/AbstractComparisonValidatorTestCase.php
@@ -13,6 +13,7 @@ namespace Symfony\Component\Validator\Tests\Constraints;
 
 use Symfony\Component\Intl\Util\IntlTestHelper;
 use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\Constraints\AbstractComparison;
 use Symfony\Component\Validator\Exception\ConstraintDefinitionException;
 use Symfony\Component\Validator\Test\ConstraintValidatorTestCase;
 
@@ -224,6 +225,31 @@ abstract class AbstractComparisonValidatorTestCase extends ConstraintValidatorTe
             ->assertRaised();
     }
 
+    /**
+     * @dataProvider throwsOnInvalidStringDatesProvider
+     */
+    public function testThrowsOnInvalidStringDates(AbstractComparison $constraint, $expectedMessage, $value)
+    {
+        $this->expectException(ConstraintDefinitionException::class);
+        $this->expectExceptionMessage($expectedMessage);
+
+        $this->validator->validate($value, $constraint);
+    }
+
+    public function throwsOnInvalidStringDatesProvider(): array
+    {
+        $constraint = $this->createConstraint([
+            'value' => 'foo',
+        ]);
+
+        $constraintClass = \get_class($constraint);
+
+        return [
+            [$constraint, sprintf('The compared value "foo" could not be converted to a "DateTimeImmutable" instance in the "%s" constraint.', $constraintClass), new \DateTimeImmutable()],
+            [$constraint, sprintf('The compared value "foo" could not be converted to a "DateTime" instance in the "%s" constraint.', $constraintClass), new \DateTime()],
+        ];
+    }
+
     public function provideAllInvalidComparisons(): array
     {
         // The provider runs before setUp(), so we need to manually fix
diff --git a/src/Symfony/Component/Validator/Tests/Constraints/DivisibleByValidatorTest.php b/src/Symfony/Component/Validator/Tests/Constraints/DivisibleByValidatorTest.php
index f11fdce97b..25187bafc8 100644
--- a/src/Symfony/Component/Validator/Tests/Constraints/DivisibleByValidatorTest.php
+++ b/src/Symfony/Component/Validator/Tests/Constraints/DivisibleByValidatorTest.php
@@ -14,6 +14,7 @@ namespace Symfony\Component\Validator\Tests\Constraints;
 use Symfony\Component\Validator\Constraint;
 use Symfony\Component\Validator\Constraints\DivisibleBy;
 use Symfony\Component\Validator\Constraints\DivisibleByValidator;
+use Symfony\Component\Validator\Exception\UnexpectedValueException;
 
 /**
  * @author Colin O'Dell <colinodell@gmail.com>
@@ -76,4 +77,25 @@ class DivisibleByValidatorTest extends AbstractComparisonValidatorTestCase
             ['22', '"22"', '10', '"10"', 'string'],
         ];
     }
+
+    /**
+     * @dataProvider throwsOnNonNumericValuesProvider
+     */
+    public function testThrowsOnNonNumericValues(string $expectedGivenType, $value, $comparedValue)
+    {
+        $this->expectException(UnexpectedValueException::class);
+        $this->expectExceptionMessage(sprintf('Expected argument of type "numeric", "%s" given', $expectedGivenType));
+
+        $this->validator->validate($value, $this->createConstraint([
+            'value' => $comparedValue,
+        ]));
+    }
+
+    public function throwsOnNonNumericValuesProvider()
+    {
+        return [
+            [\stdClass::class, 2, new \stdClass()],
+            [\ArrayIterator::class, new \ArrayIterator(), 12],
+        ];
+    }
 }
diff --git a/src/Symfony/Component/Validator/Tests/Constraints/GreaterThanOrEqualValidatorWithPositiveOrZeroConstraintTest.php b/src/Symfony/Component/Validator/Tests/Constraints/GreaterThanOrEqualValidatorWithPositiveOrZeroConstraintTest.php
index 6eab44d1a0..8db8eddf7c 100644
--- a/src/Symfony/Component/Validator/Tests/Constraints/GreaterThanOrEqualValidatorWithPositiveOrZeroConstraintTest.php
+++ b/src/Symfony/Component/Validator/Tests/Constraints/GreaterThanOrEqualValidatorWithPositiveOrZeroConstraintTest.php
@@ -12,6 +12,7 @@
 namespace Symfony\Component\Validator\Tests\Constraints;
 
 use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\Constraints\AbstractComparison;
 use Symfony\Component\Validator\Constraints\PositiveOrZero;
 
 /**
@@ -99,11 +100,11 @@ class GreaterThanOrEqualValidatorWithPositiveOrZeroConstraintTest extends Greate
     }
 
     /**
-     * @dataProvider provideValidComparisonsToPropertyPath
+     * @dataProvider throwsOnInvalidStringDatesProvider
      */
-    public function testValidComparisonToPropertyPathOnArray($comparedValue)
+    public function testThrowsOnInvalidStringDates(AbstractComparison $constraint, $expectedMessage, $value)
     {
-        $this->markTestSkipped('PropertyPath option is not used in Positive constraint');
+        $this->markTestSkipped('The compared value cannot be an invalid string date because it is hardcoded to 0.');
     }
 
     public function testInvalidComparisonToPropertyPathAddsPathAsParameter()
diff --git a/src/Symfony/Component/Validator/Tests/Constraints/GreaterThanValidatorWithPositiveConstraintTest.php b/src/Symfony/Component/Validator/Tests/Constraints/GreaterThanValidatorWithPositiveConstraintTest.php
index 4ea65a5fc5..ef10787bcc 100644
--- a/src/Symfony/Component/Validator/Tests/Constraints/GreaterThanValidatorWithPositiveConstraintTest.php
+++ b/src/Symfony/Component/Validator/Tests/Constraints/GreaterThanValidatorWithPositiveConstraintTest.php
@@ -12,6 +12,7 @@
 namespace Symfony\Component\Validator\Tests\Constraints;
 
 use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\Constraints\AbstractComparison;
 use Symfony\Component\Validator\Constraints\Positive;
 
 /**
@@ -102,11 +103,11 @@ class GreaterThanValidatorWithPositiveConstraintTest extends GreaterThanValidato
     }
 
     /**
-     * @dataProvider provideValidComparisonsToPropertyPath
+     * @dataProvider throwsOnInvalidStringDatesProvider
      */
-    public function testValidComparisonToPropertyPathOnArray($comparedValue)
+    public function testThrowsOnInvalidStringDates(AbstractComparison $constraint, $expectedMessage, $value)
     {
-        $this->markTestSkipped('PropertyPath option is not used in Positive constraint');
+        $this->markTestSkipped('The compared value cannot be an invalid string date because it is hardcoded to 0.');
     }
 
     public function testInvalidComparisonToPropertyPathAddsPathAsParameter()
diff --git a/src/Symfony/Component/Validator/Tests/Constraints/LessThanOrEqualValidatorWithNegativeOrZeroConstraintTest.php b/src/Symfony/Component/Validator/Tests/Constraints/LessThanOrEqualValidatorWithNegativeOrZeroConstraintTest.php
index 3bb1c6ea24..9e09819120 100644
--- a/src/Symfony/Component/Validator/Tests/Constraints/LessThanOrEqualValidatorWithNegativeOrZeroConstraintTest.php
+++ b/src/Symfony/Component/Validator/Tests/Constraints/LessThanOrEqualValidatorWithNegativeOrZeroConstraintTest.php
@@ -12,6 +12,7 @@
 namespace Symfony\Component\Validator\Tests\Constraints;
 
 use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\Constraints\AbstractComparison;
 use Symfony\Component\Validator\Constraints\NegativeOrZero;
 
 /**
@@ -102,11 +103,11 @@ class LessThanOrEqualValidatorWithNegativeOrZeroConstraintTest extends LessThanO
     }
 
     /**
-     * @dataProvider provideValidComparisonsToPropertyPath
+     * @dataProvider throwsOnInvalidStringDatesProvider
      */
-    public function testValidComparisonToPropertyPathOnArray($comparedValue)
+    public function testThrowsOnInvalidStringDates(AbstractComparison $constraint, $expectedMessage, $value)
     {
-        $this->markTestSkipped('PropertyPath option is not used in NegativeOrZero constraint');
+        $this->markTestSkipped('The compared value cannot be an invalid string date because it is hardcoded to 0.');
     }
 
     public function testInvalidComparisonToPropertyPathAddsPathAsParameter()
diff --git a/src/Symfony/Component/Validator/Tests/Constraints/LessThanValidatorWithNegativeConstraintTest.php b/src/Symfony/Component/Validator/Tests/Constraints/LessThanValidatorWithNegativeConstraintTest.php
index 3203adabb9..9150beb07a 100644
--- a/src/Symfony/Component/Validator/Tests/Constraints/LessThanValidatorWithNegativeConstraintTest.php
+++ b/src/Symfony/Component/Validator/Tests/Constraints/LessThanValidatorWithNegativeConstraintTest.php
@@ -12,6 +12,7 @@
 namespace Symfony\Component\Validator\Tests\Constraints;
 
 use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\Constraints\AbstractComparison;
 use Symfony\Component\Validator\Constraints\Negative;
 
 /**
@@ -102,11 +103,11 @@ class LessThanValidatorWithNegativeConstraintTest extends LessThanValidatorTest
     }
 
     /**
-     * @dataProvider provideValidComparisonsToPropertyPath
+     * @dataProvider throwsOnInvalidStringDatesProvider
      */
-    public function testValidComparisonToPropertyPathOnArray($comparedValue)
+    public function testThrowsOnInvalidStringDates(AbstractComparison $constraint, $expectedMessage, $value)
     {
-        $this->markTestSkipped('PropertyPath option is not used in Positive constraint');
+        $this->markTestSkipped('The compared value cannot be an invalid string date because it is hardcoded to 0.');
     }
 
     public function testInvalidComparisonToPropertyPathAddsPathAsParameter()
diff --git a/src/Symfony/Component/Validator/Tests/Constraints/RangeValidatorTest.php b/src/Symfony/Component/Validator/Tests/Constraints/RangeValidatorTest.php
index 0281bc9074..ef70c16145 100644
--- a/src/Symfony/Component/Validator/Tests/Constraints/RangeValidatorTest.php
+++ b/src/Symfony/Component/Validator/Tests/Constraints/RangeValidatorTest.php
@@ -14,6 +14,7 @@ namespace Symfony\Component\Validator\Tests\Constraints;
 use Symfony\Component\Intl\Util\IntlTestHelper;
 use Symfony\Component\Validator\Constraints\Range;
 use Symfony\Component\Validator\Constraints\RangeValidator;
+use Symfony\Component\Validator\Exception\ConstraintDefinitionException;
 use Symfony\Component\Validator\Test\ConstraintValidatorTestCase;
 
 class RangeValidatorTest extends ConstraintValidatorTestCase
@@ -390,6 +391,31 @@ class RangeValidatorTest extends ConstraintValidatorTestCase
             ->assertRaised();
     }
 
+    /**
+     * @dataProvider throwsOnInvalidStringDatesProvider
+     */
+    public function testThrowsOnInvalidStringDates($expectedMessage, $value, $min, $max)
+    {
+        $this->expectException(ConstraintDefinitionException::class);
+        $this->expectExceptionMessage($expectedMessage);
+
+        $this->validator->validate($value, new Range([
+            'min' => $min,
+            'max' => $max,
+        ]));
+    }
+
+    public function throwsOnInvalidStringDatesProvider(): array
+    {
+        return [
+            ['The min value "foo" could not be converted to a "DateTimeImmutable" instance in the "Symfony\Component\Validator\Constraints\Range" constraint.', new \DateTimeImmutable(), 'foo', null],
+            ['The min value "foo" could not be converted to a "DateTime" instance in the "Symfony\Component\Validator\Constraints\Range" constraint.', new \DateTime(), 'foo', null],
+            ['The max value "foo" could not be converted to a "DateTimeImmutable" instance in the "Symfony\Component\Validator\Constraints\Range" constraint.', new \DateTimeImmutable(), null, 'foo'],
+            ['The max value "foo" could not be converted to a "DateTime" instance in the "Symfony\Component\Validator\Constraints\Range" constraint.', new \DateTime(), null, 'foo'],
+            ['The min value "bar" could not be converted to a "DateTimeImmutable" instance in the "Symfony\Component\Validator\Constraints\Range" constraint.', new \DateTimeImmutable(), 'bar', 'ccc'],
+        ];
+    }
+
     public function testNoViolationOnNullObjectWithPropertyPaths()
     {
         $this->setObject(null);
diff --git a/src/Symfony/Contracts/HttpClient/ChunkInterface.php b/src/Symfony/Contracts/HttpClient/ChunkInterface.php
index d6fd73d894..ad5efca9e9 100644
--- a/src/Symfony/Contracts/HttpClient/ChunkInterface.php
+++ b/src/Symfony/Contracts/HttpClient/ChunkInterface.php
@@ -47,6 +47,13 @@ interface ChunkInterface
      */
     public function isLast(): bool;
 
+    /**
+     * Returns a [status code, headers] tuple when a 1xx status code was just received.
+     *
+     * @throws TransportExceptionInterface on a network error or when the idle timeout is reached
+     */
+    public function getInformationalStatus(): ?array;
+
     /**
      * Returns the content of the response chunk.
      *
diff --git a/src/Symfony/Contracts/HttpClient/Test/HttpClientTestCase.php b/src/Symfony/Contracts/HttpClient/Test/HttpClientTestCase.php
index b5364ecab5..bd2e35d3dc 100644
--- a/src/Symfony/Contracts/HttpClient/Test/HttpClientTestCase.php
+++ b/src/Symfony/Contracts/HttpClient/Test/HttpClientTestCase.php
@@ -754,6 +754,27 @@ abstract class HttpClientTestCase extends TestCase
         $this->assertSame(200, $response->getStatusCode());
     }
 
+    public function testInformationalResponseStream()
+    {
+        $client = $this->getHttpClient(__FUNCTION__);
+        $response = $client->request('GET', 'http://localhost:8057/103');
+
+        $chunks = [];
+        foreach ($client->stream($response) as $chunk) {
+            $chunks[] = $chunk;
+        }
+
+        $this->assertSame(103, $chunks[0]->getInformationalStatus()[0]);
+        $this->assertSame(['</style.css>; rel=preload; as=style', '</script.js>; rel=preload; as=script'], $chunks[0]->getInformationalStatus()[1]['link']);
+        $this->assertTrue($chunks[1]->isFirst());
+        $this->assertSame('Here the body', $chunks[2]->getContent());
+        $this->assertTrue($chunks[3]->isLast());
+        $this->assertNull($chunks[3]->getInformationalStatus());
+
+        $this->assertSame(['date', 'content-length'], array_keys($response->getHeaders()));
+        $this->assertContains('Link: </style.css>; rel=preload; as=style', $response->getInfo('response_headers'));
+    }
+
     /**
      * @requires extension zlib
      */
diff --git a/src/Symfony/Contracts/Translation/TranslatorTrait.php b/src/Symfony/Contracts/Translation/TranslatorTrait.php
index 488b4f4f23..a8267342a0 100644
--- a/src/Symfony/Contracts/Translation/TranslatorTrait.php
+++ b/src/Symfony/Contracts/Translation/TranslatorTrait.php
@@ -43,7 +43,9 @@ trait TranslatorTrait
      */
     public function trans($id, array $parameters = [], $domain = null, $locale = null)
     {
-        $id = (string) $id;
+        if ('' === $id = (string) $id) {
+            return '';
+        }
 
         if (!isset($parameters['%count%']) || !is_numeric($parameters['%count%'])) {
             return strtr($id, $parameters);