diff --git a/src/Symfony/Bridge/Doctrine/Logger/DbalLogger.php b/src/Symfony/Bridge/Doctrine/Logger/DbalLogger.php
index 42d68de902dd..27bbd984cb38 100644
--- a/src/Symfony/Bridge/Doctrine/Logger/DbalLogger.php
+++ b/src/Symfony/Bridge/Doctrine/Logger/DbalLogger.php
@@ -71,7 +71,7 @@ protected function log($message, array $params)
         $this->logger->debug($message, $params);
     }
 
-    private function normalizeParams(array $params)
+    private function normalizeParams(array $params): array
     {
         foreach ($params as $index => $param) {
             // normalize recursively
diff --git a/src/Symfony/Bridge/Doctrine/Security/User/EntityUserProvider.php b/src/Symfony/Bridge/Doctrine/Security/User/EntityUserProvider.php
index 9a3ff10b823a..0f396a395832 100644
--- a/src/Symfony/Bridge/Doctrine/Security/User/EntityUserProvider.php
+++ b/src/Symfony/Bridge/Doctrine/Security/User/EntityUserProvider.php
@@ -12,6 +12,9 @@
 namespace Symfony\Bridge\Doctrine\Security\User;
 
 use Doctrine\Common\Persistence\ManagerRegistry;
+use Doctrine\Common\Persistence\Mapping\ClassMetadata;
+use Doctrine\Common\Persistence\ObjectManager;
+use Doctrine\Common\Persistence\ObjectRepository;
 use Symfony\Component\Security\Core\Exception\UnsupportedUserException;
 use Symfony\Component\Security\Core\Exception\UsernameNotFoundException;
 use Symfony\Component\Security\Core\User\PasswordUpgraderInterface;
@@ -124,17 +127,17 @@ public function upgradePassword(UserInterface $user, string $newEncodedPassword)
         }
     }
 
-    private function getObjectManager()
+    private function getObjectManager(): ObjectManager
     {
         return $this->registry->getManager($this->managerName);
     }
 
-    private function getRepository()
+    private function getRepository(): ObjectRepository
     {
         return $this->getObjectManager()->getRepository($this->classOrAlias);
     }
 
-    private function getClass()
+    private function getClass(): string
     {
         if (null === $this->class) {
             $class = $this->classOrAlias;
@@ -149,7 +152,7 @@ private function getClass()
         return $this->class;
     }
 
-    private function getClassMetadata()
+    private function getClassMetadata(): ClassMetadata
     {
         return $this->getObjectManager()->getClassMetadata($this->classOrAlias);
     }
diff --git a/src/Symfony/Bridge/Doctrine/Test/TestRepositoryFactory.php b/src/Symfony/Bridge/Doctrine/Test/TestRepositoryFactory.php
index 5f161358cf9c..0a44dcbf85da 100644
--- a/src/Symfony/Bridge/Doctrine/Test/TestRepositoryFactory.php
+++ b/src/Symfony/Bridge/Doctrine/Test/TestRepositoryFactory.php
@@ -40,7 +40,7 @@ public function getRepository(EntityManagerInterface $entityManager, $entityName
         return $this->repositoryList[$repositoryHash] = $this->createRepository($entityManager, $entityName);
     }
 
-    public function setRepository(EntityManagerInterface $entityManager, $entityName, ObjectRepository $repository)
+    public function setRepository(EntityManagerInterface $entityManager, string $entityName, ObjectRepository $repository)
     {
         $repositoryHash = $this->getRepositoryHash($entityManager, $entityName);
 
@@ -56,7 +56,7 @@ private function createRepository(EntityManagerInterface $entityManager, string
         return new $repositoryClassName($entityManager, $metadata);
     }
 
-    private function getRepositoryHash(EntityManagerInterface $entityManager, string $entityName)
+    private function getRepositoryHash(EntityManagerInterface $entityManager, string $entityName): string
     {
         return $entityManager->getClassMetadata($entityName)->getName().spl_object_hash($entityManager);
     }
diff --git a/src/Symfony/Bridge/Doctrine/Tests/Security/User/EntityUserProviderTest.php b/src/Symfony/Bridge/Doctrine/Tests/Security/User/EntityUserProviderTest.php
index c0b4a56e5070..5988aafefc74 100644
--- a/src/Symfony/Bridge/Doctrine/Tests/Security/User/EntityUserProviderTest.php
+++ b/src/Symfony/Bridge/Doctrine/Tests/Security/User/EntityUserProviderTest.php
@@ -11,9 +11,11 @@
 
 namespace Symfony\Bridge\Doctrine\Tests\Security\User;
 
+use Doctrine\Common\Persistence\ObjectRepository;
 use Doctrine\ORM\Tools\SchemaTool;
 use PHPUnit\Framework\TestCase;
 use Symfony\Bridge\Doctrine\Security\User\EntityUserProvider;
+use Symfony\Bridge\Doctrine\Security\User\UserLoaderInterface;
 use Symfony\Bridge\Doctrine\Test\DoctrineTestHelper;
 use Symfony\Bridge\Doctrine\Tests\Fixtures\User;
 use Symfony\Component\Security\Core\User\PasswordUpgraderInterface;
@@ -59,9 +61,7 @@ public function testLoadUserByUsernameWithUserLoaderRepositoryAndWithoutProperty
     {
         $user = new User(1, 1, 'user1');
 
-        $repository = $this->getMockBuilder('Symfony\Bridge\Doctrine\Security\User\UserLoaderInterface')
-            ->disableOriginalConstructor()
-            ->getMock();
+        $repository = $this->createMock([ObjectRepository::class, UserLoaderInterface::class]);
         $repository
             ->expects($this->once())
             ->method('loadUserByUsername')
@@ -147,7 +147,7 @@ public function testSupportProxy()
 
     public function testLoadUserByUserNameShouldLoadUserWhenProperInterfaceProvided()
     {
-        $repository = $this->getMockBuilder('\Symfony\Bridge\Doctrine\Security\User\UserLoaderInterface')->getMock();
+        $repository = $this->createMock([ObjectRepository::class, UserLoaderInterface::class]);
         $repository->expects($this->once())
             ->method('loadUserByUsername')
             ->with('name')
@@ -166,7 +166,7 @@ public function testLoadUserByUserNameShouldLoadUserWhenProperInterfaceProvided(
     public function testLoadUserByUserNameShouldDeclineInvalidInterface()
     {
         $this->expectException('InvalidArgumentException');
-        $repository = $this->getMockBuilder('\Symfony\Component\Security\Core\User\AdvancedUserInterface')->getMock();
+        $repository = $this->createMock(ObjectRepository::class);
 
         $provider = new EntityUserProvider(
             $this->getManager($this->getObjectManager($repository)),
@@ -180,7 +180,7 @@ public function testPasswordUpgrades()
     {
         $user = new User(1, 1, 'user1');
 
-        $repository = $this->getMockBuilder(PasswordUpgraderInterface::class)->getMock();
+        $repository = $this->createMock([ObjectRepository::class, PasswordUpgraderInterface::class]);
         $repository->expects($this->once())
             ->method('upgradePassword')
             ->with($user, 'foobar');
diff --git a/src/Symfony/Bridge/Monolog/Formatter/ConsoleFormatter.php b/src/Symfony/Bridge/Monolog/Formatter/ConsoleFormatter.php
index 101c61f07882..8285254e1299 100644
--- a/src/Symfony/Bridge/Monolog/Formatter/ConsoleFormatter.php
+++ b/src/Symfony/Bridge/Monolog/Formatter/ConsoleFormatter.php
@@ -133,7 +133,7 @@ public function format(array $record)
     /**
      * @internal
      */
-    public function echoLine($line, $depth, $indentPad)
+    public function echoLine(string $line, int $depth, string $indentPad)
     {
         if (-1 !== $depth) {
             fwrite($this->outputBuffer, $line);
@@ -143,7 +143,7 @@ public function echoLine($line, $depth, $indentPad)
     /**
      * @internal
      */
-    public function castObject($v, array $a, Stub $s, $isNested)
+    public function castObject($v, array $a, Stub $s, bool $isNested): array
     {
         if ($this->options['multiline']) {
             return $a;
@@ -157,7 +157,7 @@ public function castObject($v, array $a, Stub $s, $isNested)
         return $a;
     }
 
-    private function replacePlaceHolder(array $record)
+    private function replacePlaceHolder(array $record): array
     {
         $message = $record['message'];
 
diff --git a/src/Symfony/Bridge/Monolog/Handler/ServerLogHandler.php b/src/Symfony/Bridge/Monolog/Handler/ServerLogHandler.php
index c11fe901ea9a..28582d31725a 100644
--- a/src/Symfony/Bridge/Monolog/Handler/ServerLogHandler.php
+++ b/src/Symfony/Bridge/Monolog/Handler/ServerLogHandler.php
@@ -103,7 +103,7 @@ private function createSocket()
         return $socket;
     }
 
-    private function formatRecord(array $record)
+    private function formatRecord(array $record): string
     {
         if ($this->processors) {
             foreach ($this->processors as $processor) {
diff --git a/src/Symfony/Bridge/Twig/Command/DebugCommand.php b/src/Symfony/Bridge/Twig/Command/DebugCommand.php
index b3a2c44df313..edefbd8bcb45 100644
--- a/src/Symfony/Bridge/Twig/Command/DebugCommand.php
+++ b/src/Symfony/Bridge/Twig/Command/DebugCommand.php
@@ -364,7 +364,7 @@ private function getMetadata(string $type, $entity)
         return null;
     }
 
-    private function getPrettyMetadata(string $type, $entity, bool $decorated)
+    private function getPrettyMetadata(string $type, $entity, bool $decorated): ?string
     {
         if ('tests' === $type) {
             return '';
diff --git a/src/Symfony/Bridge/Twig/Command/LintCommand.php b/src/Symfony/Bridge/Twig/Command/LintCommand.php
index f25574c1e2dc..f3e718c0a4a9 100644
--- a/src/Symfony/Bridge/Twig/Command/LintCommand.php
+++ b/src/Symfony/Bridge/Twig/Command/LintCommand.php
@@ -119,7 +119,7 @@ private function getStdin(): string
         return $template;
     }
 
-    private function getFilesInfo(array $filenames)
+    private function getFilesInfo(array $filenames): array
     {
         $filesInfo = [];
         foreach ($filenames as $filename) {
diff --git a/src/Symfony/Bridge/Twig/Extension/CodeExtension.php b/src/Symfony/Bridge/Twig/Extension/CodeExtension.php
index b5dadfe06822..d91e1c167600 100644
--- a/src/Symfony/Bridge/Twig/Extension/CodeExtension.php
+++ b/src/Symfony/Bridge/Twig/Extension/CodeExtension.php
@@ -236,7 +236,7 @@ public function formatFileFromText($text)
     /**
      * @internal
      */
-    public function formatLogMessage($message, array $context)
+    public function formatLogMessage(string $message, array $context): string
     {
         if ($context && false !== strpos($message, '{')) {
             $replacements = [];
diff --git a/src/Symfony/Bridge/Twig/Extension/FormExtension.php b/src/Symfony/Bridge/Twig/Extension/FormExtension.php
index 842042aac7ac..174a5cc3fe4b 100644
--- a/src/Symfony/Bridge/Twig/Extension/FormExtension.php
+++ b/src/Symfony/Bridge/Twig/Extension/FormExtension.php
@@ -111,7 +111,7 @@ public function getName()
  *
  * @see ChoiceView::isSelected()
  */
-function twig_is_selected_choice(ChoiceView $choice, $selectedValue)
+function twig_is_selected_choice(ChoiceView $choice, $selectedValue): bool
 {
     if (\is_array($selectedValue)) {
         return \in_array($choice->value, $selectedValue, true);
@@ -123,7 +123,7 @@ function twig_is_selected_choice(ChoiceView $choice, $selectedValue)
 /**
  * @internal
  */
-function twig_is_root_form(FormView $formView)
+function twig_is_root_form(FormView $formView): bool
 {
     return null === $formView->parent;
 }
diff --git a/src/Symfony/Bridge/Twig/NodeVisitor/TranslationDefaultDomainNodeVisitor.php b/src/Symfony/Bridge/Twig/NodeVisitor/TranslationDefaultDomainNodeVisitor.php
index a75b7b2cc46c..72badea2d2bd 100644
--- a/src/Symfony/Bridge/Twig/NodeVisitor/TranslationDefaultDomainNodeVisitor.php
+++ b/src/Symfony/Bridge/Twig/NodeVisitor/TranslationDefaultDomainNodeVisitor.php
@@ -132,7 +132,7 @@ private function isNamedArguments(Node $arguments): bool
         return false;
     }
 
-    private function getVarName()
+    private function getVarName(): string
     {
         return sprintf('__internal_%s', hash('sha256', uniqid(mt_rand(), true), false));
     }
diff --git a/src/Symfony/Bridge/Twig/UndefinedCallableHandler.php b/src/Symfony/Bridge/Twig/UndefinedCallableHandler.php
index be5f97eeca5a..fa3049d3dd7c 100644
--- a/src/Symfony/Bridge/Twig/UndefinedCallableHandler.php
+++ b/src/Symfony/Bridge/Twig/UndefinedCallableHandler.php
@@ -65,7 +65,7 @@ class UndefinedCallableHandler
         'workflow' => 'enable "framework.workflows"',
     ];
 
-    public static function onUndefinedFilter($name)
+    public static function onUndefinedFilter(string $name): bool
     {
         if (!isset(self::$filterComponents[$name])) {
             return false;
@@ -76,7 +76,7 @@ public static function onUndefinedFilter($name)
         return true;
     }
 
-    public static function onUndefinedFunction($name)
+    public static function onUndefinedFunction(string $name): bool
     {
         if (!isset(self::$functionComponents[$name])) {
             return false;
@@ -87,7 +87,7 @@ public static function onUndefinedFunction($name)
         return true;
     }
 
-    private static function onUndefined($name, $type, $component)
+    private static function onUndefined(string $name, string $type, string $component)
     {
         if (class_exists(FullStack::class) && isset(self::$fullStackEnable[$component])) {
             throw new SyntaxError(sprintf('Did you forget to %s? Unknown %s "%s".', self::$fullStackEnable[$component], $type, $name));
diff --git a/src/Symfony/Bundle/FrameworkBundle/Command/AssetsInstallCommand.php b/src/Symfony/Bundle/FrameworkBundle/Command/AssetsInstallCommand.php
index d38e89f0e9bd..396dcbaf659c 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Command/AssetsInstallCommand.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Command/AssetsInstallCommand.php
@@ -262,7 +262,7 @@ private function hardCopy(string $originDir, string $targetDir): string
         return self::METHOD_COPY;
     }
 
-    private function getPublicDirectory(ContainerInterface $container)
+    private function getPublicDirectory(ContainerInterface $container): string
     {
         $defaultPublicDir = 'public';
 
diff --git a/src/Symfony/Bundle/FrameworkBundle/Command/ContainerDebugCommand.php b/src/Symfony/Bundle/FrameworkBundle/Command/ContainerDebugCommand.php
index ef3a70d33ef1..4b55579d689d 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Command/ContainerDebugCommand.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Command/ContainerDebugCommand.php
@@ -238,7 +238,7 @@ protected function getContainerBuilder(): ContainerBuilder
         return $this->containerBuilder = $container;
     }
 
-    private function findProperServiceName(InputInterface $input, SymfonyStyle $io, ContainerBuilder $builder, string $name, bool $showHidden)
+    private function findProperServiceName(InputInterface $input, SymfonyStyle $io, ContainerBuilder $builder, string $name, bool $showHidden): string
     {
         $name = ltrim($name, '\\');
 
@@ -258,7 +258,7 @@ private function findProperServiceName(InputInterface $input, SymfonyStyle $io,
         return $io->choice('Select one of the following services to display its information', $matchingServices);
     }
 
-    private function findServiceIdsContaining(ContainerBuilder $builder, string $name, bool $showHidden)
+    private function findServiceIdsContaining(ContainerBuilder $builder, string $name, bool $showHidden): array
     {
         $serviceIds = $builder->getServiceIds();
         $foundServiceIds = $foundServiceIdsIgnoringBackslashes = [];
@@ -280,7 +280,7 @@ private function findServiceIdsContaining(ContainerBuilder $builder, string $nam
     /**
      * @internal
      */
-    public function filterToServiceTypes($serviceId)
+    public function filterToServiceTypes(string $serviceId): bool
     {
         // filter out things that could not be valid class names
         if (!preg_match('/(?(DEFINE)(?<V>[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*+))^(?&V)(?:\\\\(?&V))*+(?: \$(?&V))?$/', $serviceId)) {
diff --git a/src/Symfony/Bundle/FrameworkBundle/Controller/AbstractController.php b/src/Symfony/Bundle/FrameworkBundle/Controller/AbstractController.php
index ac7ab231e01a..bc4c75585d7b 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Controller/AbstractController.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Controller/AbstractController.php
@@ -47,7 +47,7 @@ abstract class AbstractController implements ServiceSubscriberInterface
      * @internal
      * @required
      */
-    public function setContainer(ContainerInterface $container)
+    public function setContainer(ContainerInterface $container): ?ContainerInterface
     {
         $previous = $this->container;
         $this->container = $container;
diff --git a/src/Symfony/Bundle/FrameworkBundle/Templating/Helper/RequestHelper.php b/src/Symfony/Bundle/FrameworkBundle/Templating/Helper/RequestHelper.php
index 351ed712c4a5..fbc054909700 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Templating/Helper/RequestHelper.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Templating/Helper/RequestHelper.php
@@ -13,6 +13,7 @@
 
 @trigger_error('The '.RequestHelper::class.' class is deprecated since version 4.3 and will be removed in 5.0; use Twig instead.', E_USER_DEPRECATED);
 
+use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\RequestStack;
 use Symfony\Component\Templating\Helper\Helper;
 
@@ -57,7 +58,7 @@ public function getLocale()
         return $this->getRequest()->getLocale();
     }
 
-    private function getRequest()
+    private function getRequest(): Request
     {
         if (!$this->requestStack->getCurrentRequest()) {
             throw new \LogicException('A Request must be available.');
diff --git a/src/Symfony/Bundle/FrameworkBundle/Templating/Helper/SessionHelper.php b/src/Symfony/Bundle/FrameworkBundle/Templating/Helper/SessionHelper.php
index 86c0fcda1b93..296387b5c46c 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Templating/Helper/SessionHelper.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Templating/Helper/SessionHelper.php
@@ -14,6 +14,7 @@
 @trigger_error('The '.SessionHelper::class.' class is deprecated since version 4.3 and will be removed in 5.0; use Twig instead.', E_USER_DEPRECATED);
 
 use Symfony\Component\HttpFoundation\RequestStack;
+use Symfony\Component\HttpFoundation\Session\SessionInterface;
 use Symfony\Component\Templating\Helper\Helper;
 
 /**
@@ -61,7 +62,7 @@ public function hasFlash($name)
         return $this->getSession()->getFlashBag()->has($name);
     }
 
-    private function getSession()
+    private function getSession(): SessionInterface
     {
         if (null === $this->session) {
             if (!$this->requestStack->getMasterRequest()) {
diff --git a/src/Symfony/Bundle/FrameworkBundle/Tests/Controller/AbstractControllerTest.php b/src/Symfony/Bundle/FrameworkBundle/Tests/Controller/AbstractControllerTest.php
index 68db3bb99f48..27eed3fbface 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Tests/Controller/AbstractControllerTest.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Tests/Controller/AbstractControllerTest.php
@@ -93,7 +93,7 @@ public function __call(string $method, array $arguments)
         return $this->$method(...$arguments);
     }
 
-    public function setContainer(ContainerInterface $container)
+    public function setContainer(ContainerInterface $container): ?ContainerInterface
     {
         if (!$this->throwOnUnexpectedService) {
             return parent::setContainer($container);
diff --git a/src/Symfony/Bundle/SecurityBundle/Command/UserPasswordEncoderCommand.php b/src/Symfony/Bundle/SecurityBundle/Command/UserPasswordEncoderCommand.php
index c80e3c4bb11d..fa651fd588b3 100644
--- a/src/Symfony/Bundle/SecurityBundle/Command/UserPasswordEncoderCommand.php
+++ b/src/Symfony/Bundle/SecurityBundle/Command/UserPasswordEncoderCommand.php
@@ -182,12 +182,12 @@ private function createPasswordQuestion(): Question
         })->setHidden(true)->setMaxAttempts(20);
     }
 
-    private function generateSalt()
+    private function generateSalt(): string
     {
         return base64_encode(random_bytes(30));
     }
 
-    private function getUserClass(InputInterface $input, SymfonyStyle $io)
+    private function getUserClass(InputInterface $input, SymfonyStyle $io): string
     {
         if (null !== $userClass = $input->getArgument('user-class')) {
             return $userClass;
diff --git a/src/Symfony/Bundle/SecurityBundle/Debug/WrappedListener.php b/src/Symfony/Bundle/SecurityBundle/Debug/WrappedListener.php
index 81d7b8a68f2e..36b01fda12fb 100644
--- a/src/Symfony/Bundle/SecurityBundle/Debug/WrappedListener.php
+++ b/src/Symfony/Bundle/SecurityBundle/Debug/WrappedListener.php
@@ -60,7 +60,7 @@ public function __invoke(RequestEvent $event)
     /**
      * Proxies all method calls to the original listener.
      */
-    public function __call($method, $arguments)
+    public function __call(string $method, array $arguments)
     {
         return $this->listener->{$method}(...$arguments);
     }
diff --git a/src/Symfony/Bundle/SecurityBundle/DependencyInjection/Security/Factory/AbstractFactory.php b/src/Symfony/Bundle/SecurityBundle/DependencyInjection/Security/Factory/AbstractFactory.php
index 5e07c6303f5a..79ef873ec2ad 100644
--- a/src/Symfony/Bundle/SecurityBundle/DependencyInjection/Security/Factory/AbstractFactory.php
+++ b/src/Symfony/Bundle/SecurityBundle/DependencyInjection/Security/Factory/AbstractFactory.php
@@ -89,7 +89,7 @@ public function addConfiguration(NodeDefinition $node)
         }
     }
 
-    final public function addOption($name, $default = null)
+    final public function addOption(string $name, $default = null)
     {
         $this->options[$name] = $default;
     }
diff --git a/src/Symfony/Bundle/SecurityBundle/DependencyInjection/Security/Factory/GuardAuthenticationFactory.php b/src/Symfony/Bundle/SecurityBundle/DependencyInjection/Security/Factory/GuardAuthenticationFactory.php
index 9fe4ea847035..0946cfeaa49d 100644
--- a/src/Symfony/Bundle/SecurityBundle/DependencyInjection/Security/Factory/GuardAuthenticationFactory.php
+++ b/src/Symfony/Bundle/SecurityBundle/DependencyInjection/Security/Factory/GuardAuthenticationFactory.php
@@ -92,7 +92,7 @@ public function create(ContainerBuilder $container, $id, $config, $userProvider,
         return [$providerId, $listenerId, $entryPointId];
     }
 
-    private function determineEntryPoint(?string $defaultEntryPointId, array $config)
+    private function determineEntryPoint(?string $defaultEntryPointId, array $config): string
     {
         if ($defaultEntryPointId) {
             // explode if they've configured the entry_point, but there is already one
diff --git a/src/Symfony/Bundle/SecurityBundle/DependencyInjection/SecurityExtension.php b/src/Symfony/Bundle/SecurityBundle/DependencyInjection/SecurityExtension.php
index 4eca9ecef4b1..a2aa67c95881 100644
--- a/src/Symfony/Bundle/SecurityBundle/DependencyInjection/SecurityExtension.php
+++ b/src/Symfony/Bundle/SecurityBundle/DependencyInjection/SecurityExtension.php
@@ -598,7 +598,7 @@ private function createEncoder(array $config)
     }
 
     // Parses user providers and returns an array of their ids
-    private function createUserProviders(array $config, ContainerBuilder $container)
+    private function createUserProviders(array $config, ContainerBuilder $container): array
     {
         $providerIds = [];
         foreach ($config['providers'] as $name => $provider) {
@@ -610,7 +610,7 @@ private function createUserProviders(array $config, ContainerBuilder $container)
     }
 
     // Parses a <provider> tag and returns the id for the related user provider service
-    private function createUserDaoProvider(string $name, array $provider, ContainerBuilder $container)
+    private function createUserDaoProvider(string $name, array $provider, ContainerBuilder $container): string
     {
         $name = $this->getUserProviderId($name);
 
@@ -649,12 +649,12 @@ private function createUserDaoProvider(string $name, array $provider, ContainerB
         throw new InvalidConfigurationException(sprintf('Unable to create definition for "%s" user provider', $name));
     }
 
-    private function getUserProviderId(string $name)
+    private function getUserProviderId(string $name): string
     {
         return 'security.user.provider.concrete.'.strtolower($name);
     }
 
-    private function createExceptionListener(ContainerBuilder $container, array $config, string $id, ?string $defaultEntryPoint, bool $stateless)
+    private function createExceptionListener(ContainerBuilder $container, array $config, string $id, ?string $defaultEntryPoint, bool $stateless): string
     {
         $exceptionListenerId = 'security.exception_listener.'.$id;
         $listener = $container->setDefinition($exceptionListenerId, new ChildDefinition('security.exception_listener'));
@@ -672,7 +672,7 @@ private function createExceptionListener(ContainerBuilder $container, array $con
         return $exceptionListenerId;
     }
 
-    private function createSwitchUserListener(ContainerBuilder $container, string $id, array $config, string $defaultProvider, bool $stateless)
+    private function createSwitchUserListener(ContainerBuilder $container, string $id, array $config, string $defaultProvider, bool $stateless): string
     {
         $userProvider = isset($config['provider']) ? $this->getUserProviderId($config['provider']) : $defaultProvider;
 
@@ -692,7 +692,7 @@ private function createSwitchUserListener(ContainerBuilder $container, string $i
         return $switchUserListenerId;
     }
 
-    private function createExpression(ContainerBuilder $container, string $expression)
+    private function createExpression(ContainerBuilder $container, string $expression): Reference
     {
         if (isset($this->expressions[$id = '.security.expression.'.ContainerBuilder::hash($expression)])) {
             return $this->expressions[$id];
@@ -711,7 +711,7 @@ private function createExpression(ContainerBuilder $container, string $expressio
         return $this->expressions[$id] = new Reference($id);
     }
 
-    private function createRequestMatcher(ContainerBuilder $container, string $path = null, string $host = null, int $port = null, array $methods = [], array $ips = null, array $attributes = [])
+    private function createRequestMatcher(ContainerBuilder $container, string $path = null, string $host = null, int $port = null, array $methods = [], array $ips = null, array $attributes = []): Reference
     {
         if ($methods) {
             $methods = array_map('strtoupper', (array) $methods);
diff --git a/src/Symfony/Bundle/TwigBundle/Command/LintCommand.php b/src/Symfony/Bundle/TwigBundle/Command/LintCommand.php
index c0b175c3a2ed..386653eb22d9 100644
--- a/src/Symfony/Bundle/TwigBundle/Command/LintCommand.php
+++ b/src/Symfony/Bundle/TwigBundle/Command/LintCommand.php
@@ -42,7 +42,7 @@ protected function configure()
         ;
     }
 
-    protected function findFiles($filename)
+    protected function findFiles($filename): iterable
     {
         if (0 === strpos($filename, '@')) {
             $dir = $this->getApplication()->getKernel()->locateResource($filename);
diff --git a/src/Symfony/Bundle/TwigBundle/DependencyInjection/TwigExtension.php b/src/Symfony/Bundle/TwigBundle/DependencyInjection/TwigExtension.php
index 9aefb8dbb03f..9d2447aed42b 100644
--- a/src/Symfony/Bundle/TwigBundle/DependencyInjection/TwigExtension.php
+++ b/src/Symfony/Bundle/TwigBundle/DependencyInjection/TwigExtension.php
@@ -172,7 +172,7 @@ public function load(array $configs, ContainerBuilder $container)
         }
     }
 
-    private function getBundleTemplatePaths(ContainerBuilder $container, array $config)
+    private function getBundleTemplatePaths(ContainerBuilder $container, array $config): array
     {
         $bundleHierarchy = [];
         foreach ($container->getParameter('kernel.bundles_metadata') as $name => $bundle) {
@@ -199,7 +199,7 @@ private function getBundleTemplatePaths(ContainerBuilder $container, array $conf
         return $bundleHierarchy;
     }
 
-    private function normalizeBundleName(string $name)
+    private function normalizeBundleName(string $name): string
     {
         if ('Bundle' === substr($name, -6)) {
             $name = substr($name, 0, -6);
diff --git a/src/Symfony/Bundle/WebProfilerBundle/Controller/ProfilerController.php b/src/Symfony/Bundle/WebProfilerBundle/Controller/ProfilerController.php
index 6bda0e00acef..28b0e2aa57cf 100644
--- a/src/Symfony/Bundle/WebProfilerBundle/Controller/ProfilerController.php
+++ b/src/Symfony/Bundle/WebProfilerBundle/Controller/ProfilerController.php
@@ -397,7 +397,7 @@ private function denyAccessIfProfilerDisabled()
         $this->profiler->disable();
     }
 
-    private function renderWithCspNonces(Request $request, string $template, array $variables, int $code = 200, array $headers = ['Content-Type' => 'text/html'])
+    private function renderWithCspNonces(Request $request, string $template, array $variables, int $code = 200, array $headers = ['Content-Type' => 'text/html']): Response
     {
         $response = new Response('', $code, $headers);
 
diff --git a/src/Symfony/Bundle/WebProfilerBundle/Csp/NonceGenerator.php b/src/Symfony/Bundle/WebProfilerBundle/Csp/NonceGenerator.php
index 728043551f3e..19af8496908d 100644
--- a/src/Symfony/Bundle/WebProfilerBundle/Csp/NonceGenerator.php
+++ b/src/Symfony/Bundle/WebProfilerBundle/Csp/NonceGenerator.php
@@ -20,7 +20,7 @@
  */
 class NonceGenerator
 {
-    public function generate()
+    public function generate(): string
     {
         return bin2hex(random_bytes(16));
     }
diff --git a/src/Symfony/Bundle/WebServerBundle/Command/ServerLogCommand.php b/src/Symfony/Bundle/WebServerBundle/Command/ServerLogCommand.php
index ff9e32f589b8..40d257c335b2 100644
--- a/src/Symfony/Bundle/WebServerBundle/Command/ServerLogCommand.php
+++ b/src/Symfony/Bundle/WebServerBundle/Command/ServerLogCommand.php
@@ -127,7 +127,7 @@ protected function execute(InputInterface $input, OutputInterface $output)
         return 0;
     }
 
-    private function getLogs($socket)
+    private function getLogs($socket): iterable
     {
         $sockets = [(int) $socket => $socket];
         $write = [];
@@ -150,7 +150,7 @@ private function getLogs($socket)
         }
     }
 
-    private function displayLog(InputInterface $input, OutputInterface $output, $clientId, array $record)
+    private function displayLog(InputInterface $input, OutputInterface $output, int $clientId, array $record)
     {
         if (isset($record['log_id'])) {
             $clientId = unpack('H*', $record['log_id'])[1];
diff --git a/src/Symfony/Bundle/WebServerBundle/DependencyInjection/WebServerExtension.php b/src/Symfony/Bundle/WebServerBundle/DependencyInjection/WebServerExtension.php
index 596b32c5fb14..63a8197d5e4a 100644
--- a/src/Symfony/Bundle/WebServerBundle/DependencyInjection/WebServerExtension.php
+++ b/src/Symfony/Bundle/WebServerBundle/DependencyInjection/WebServerExtension.php
@@ -44,7 +44,7 @@ public function load(array $configs, ContainerBuilder $container)
         }
     }
 
-    private function getPublicDirectory(ContainerBuilder $container)
+    private function getPublicDirectory(ContainerBuilder $container): string
     {
         $kernelProjectDir = $container->getParameter('kernel.project_dir');
         $publicDir = 'public';
diff --git a/src/Symfony/Bundle/WebServerBundle/WebServer.php b/src/Symfony/Bundle/WebServerBundle/WebServer.php
index d0161772404d..ec0bd0321973 100644
--- a/src/Symfony/Bundle/WebServerBundle/WebServer.php
+++ b/src/Symfony/Bundle/WebServerBundle/WebServer.php
@@ -174,7 +174,7 @@ private function createServerProcess(WebServerConfig $config): Process
         return $process;
     }
 
-    private function getDefaultPidFile()
+    private function getDefaultPidFile(): string
     {
         return ($this->pidFileDirectory ?? getcwd()).'/.web-server-pid';
     }
diff --git a/src/Symfony/Component/Validator/Constraints/AbstractComparisonValidator.php b/src/Symfony/Component/Validator/Constraints/AbstractComparisonValidator.php
index 6c538fddc930..dc268ebcb9e7 100644
--- a/src/Symfony/Component/Validator/Constraints/AbstractComparisonValidator.php
+++ b/src/Symfony/Component/Validator/Constraints/AbstractComparisonValidator.php
@@ -91,7 +91,7 @@ public function validate($value, Constraint $constraint)
         }
     }
 
-    private function getPropertyAccessor()
+    private function getPropertyAccessor(): PropertyAccessorInterface
     {
         if (null === $this->propertyAccessor) {
             $this->propertyAccessor = PropertyAccess::createPropertyAccessor();
diff --git a/src/Symfony/Component/Validator/Constraints/ExpressionValidator.php b/src/Symfony/Component/Validator/Constraints/ExpressionValidator.php
index 3d061554d5a7..f9f954b1cbc7 100644
--- a/src/Symfony/Component/Validator/Constraints/ExpressionValidator.php
+++ b/src/Symfony/Component/Validator/Constraints/ExpressionValidator.php
@@ -65,7 +65,7 @@ public function validate($value, Constraint $constraint)
         }
     }
 
-    private function getExpressionLanguage()
+    private function getExpressionLanguage(): ExpressionLanguage
     {
         if (null === $this->expressionLanguage) {
             if (!class_exists('Symfony\Component\ExpressionLanguage\ExpressionLanguage')) {
diff --git a/src/Symfony/Component/Validator/Constraints/FileValidator.php b/src/Symfony/Component/Validator/Constraints/FileValidator.php
index eb06c732ec99..243cf316ab4b 100644
--- a/src/Symfony/Component/Validator/Constraints/FileValidator.php
+++ b/src/Symfony/Component/Validator/Constraints/FileValidator.php
@@ -208,7 +208,7 @@ private static function moreDecimalsThan(string $double, int $numberOfDecimals):
      * Convert the limit to the smallest possible number
      * (i.e. try "MB", then "kB", then "bytes").
      */
-    private function factorizeSizes(int $size, int $limit, bool $binaryFormat)
+    private function factorizeSizes(int $size, int $limit, bool $binaryFormat): array
     {
         if ($binaryFormat) {
             $coef = self::MIB_BYTES;
diff --git a/src/Symfony/Component/Validator/Constraints/IbanValidator.php b/src/Symfony/Component/Validator/Constraints/IbanValidator.php
index e927f013aa05..95fed46a7772 100644
--- a/src/Symfony/Component/Validator/Constraints/IbanValidator.php
+++ b/src/Symfony/Component/Validator/Constraints/IbanValidator.php
@@ -225,7 +225,7 @@ public function validate($value, Constraint $constraint)
         }
     }
 
-    private static function toBigInt($string)
+    private static function toBigInt(string $string): string
     {
         $chars = str_split($string);
         $bigInt = '';
@@ -245,7 +245,7 @@ private static function toBigInt($string)
         return $bigInt;
     }
 
-    private static function bigModulo97($bigInt)
+    private static function bigModulo97(string $bigInt): int
     {
         $parts = str_split($bigInt, 7);
         $rest = 0;
diff --git a/src/Symfony/Component/Validator/Context/ExecutionContext.php b/src/Symfony/Component/Validator/Context/ExecutionContext.php
index 10eff4475b33..d9461fe53a6c 100644
--- a/src/Symfony/Component/Validator/Context/ExecutionContext.php
+++ b/src/Symfony/Component/Validator/Context/ExecutionContext.php
@@ -15,6 +15,7 @@
 use Symfony\Component\Validator\Constraint;
 use Symfony\Component\Validator\ConstraintViolation;
 use Symfony\Component\Validator\ConstraintViolationList;
+use Symfony\Component\Validator\ConstraintViolationListInterface;
 use Symfony\Component\Validator\Mapping\ClassMetadataInterface;
 use Symfony\Component\Validator\Mapping\MemberMetadata;
 use Symfony\Component\Validator\Mapping\MetadataInterface;
@@ -22,6 +23,7 @@
 use Symfony\Component\Validator\Util\PropertyPath;
 use Symfony\Component\Validator\Validator\ValidatorInterface;
 use Symfony\Component\Validator\Violation\ConstraintViolationBuilder;
+use Symfony\Component\Validator\Violation\ConstraintViolationBuilderInterface;
 use Symfony\Contracts\Translation\TranslatorInterface;
 
 /**
@@ -200,7 +202,7 @@ public function addViolation($message, array $parameters = [])
     /**
      * {@inheritdoc}
      */
-    public function buildViolation($message, array $parameters = [])
+    public function buildViolation($message, array $parameters = []): ConstraintViolationBuilderInterface
     {
         return new ConstraintViolationBuilder(
             $this->violations,
@@ -218,7 +220,7 @@ public function buildViolation($message, array $parameters = [])
     /**
      * {@inheritdoc}
      */
-    public function getViolations()
+    public function getViolations(): ConstraintViolationListInterface
     {
         return $this->violations;
     }
@@ -226,7 +228,7 @@ public function getViolations()
     /**
      * {@inheritdoc}
      */
-    public function getValidator()
+    public function getValidator(): ValidatorInterface
     {
         return $this->validator;
     }
@@ -258,7 +260,7 @@ public function getObject()
     /**
      * {@inheritdoc}
      */
-    public function getMetadata()
+    public function getMetadata(): ?MetadataInterface
     {
         return $this->metadata;
     }
@@ -266,12 +268,12 @@ public function getMetadata()
     /**
      * {@inheritdoc}
      */
-    public function getGroup()
+    public function getGroup(): ?string
     {
         return $this->group;
     }
 
-    public function getConstraint()
+    public function getConstraint(): ?Constraint
     {
         return $this->constraint;
     }
@@ -279,7 +281,7 @@ public function getConstraint()
     /**
      * {@inheritdoc}
      */
-    public function getClassName()
+    public function getClassName(): ?string
     {
         return $this->metadata instanceof MemberMetadata || $this->metadata instanceof ClassMetadataInterface ? $this->metadata->getClassName() : null;
     }
@@ -287,7 +289,7 @@ public function getClassName()
     /**
      * {@inheritdoc}
      */
-    public function getPropertyName()
+    public function getPropertyName(): ?string
     {
         return $this->metadata instanceof PropertyMetadataInterface ? $this->metadata->getPropertyName() : null;
     }
@@ -295,7 +297,7 @@ public function getPropertyName()
     /**
      * {@inheritdoc}
      */
-    public function getPropertyPath($subPath = '')
+    public function getPropertyPath($subPath = ''): string
     {
         return PropertyPath::append($this->propertyPath, $subPath);
     }
@@ -315,7 +317,7 @@ public function markGroupAsValidated($cacheKey, $groupHash)
     /**
      * {@inheritdoc}
      */
-    public function isGroupValidated($cacheKey, $groupHash)
+    public function isGroupValidated($cacheKey, $groupHash): bool
     {
         return isset($this->validatedObjects[$cacheKey][$groupHash]);
     }
@@ -331,7 +333,7 @@ public function markConstraintAsValidated($cacheKey, $constraintHash)
     /**
      * {@inheritdoc}
      */
-    public function isConstraintValidated($cacheKey, $constraintHash)
+    public function isConstraintValidated($cacheKey, $constraintHash): bool
     {
         return isset($this->validatedConstraints[$cacheKey.':'.$constraintHash]);
     }
@@ -347,7 +349,7 @@ public function markObjectAsInitialized($cacheKey)
     /**
      * {@inheritdoc}
      */
-    public function isObjectInitialized($cacheKey)
+    public function isObjectInitialized($cacheKey): bool
     {
         return isset($this->initializedObjects[$cacheKey]);
     }
diff --git a/src/Symfony/Component/Validator/Mapping/Cache/DoctrineCache.php b/src/Symfony/Component/Validator/Mapping/Cache/DoctrineCache.php
index bfce37c49d0d..f448b0a6803b 100644
--- a/src/Symfony/Component/Validator/Mapping/Cache/DoctrineCache.php
+++ b/src/Symfony/Component/Validator/Mapping/Cache/DoctrineCache.php
@@ -40,7 +40,7 @@ public function setCache(Cache $cache)
     /**
      * {@inheritdoc}
      */
-    public function has($class)
+    public function has($class): bool
     {
         return $this->cache->contains($class);
     }
diff --git a/src/Symfony/Component/Validator/Test/ConstraintValidatorTestCase.php b/src/Symfony/Component/Validator/Test/ConstraintValidatorTestCase.php
index ac9ace919dc0..1863641c91e5 100644
--- a/src/Symfony/Component/Validator/Test/ConstraintValidatorTestCase.php
+++ b/src/Symfony/Component/Validator/Test/ConstraintValidatorTestCase.php
@@ -236,7 +236,7 @@ class ConstraintViolationAssertion
     private $constraint;
     private $cause;
 
-    public function __construct(ExecutionContextInterface $context, $message, Constraint $constraint = null, array $assertions = [])
+    public function __construct(ExecutionContextInterface $context, string $message, Constraint $constraint = null, array $assertions = [])
     {
         $this->context = $context;
         $this->message = $message;
@@ -244,14 +244,14 @@ public function __construct(ExecutionContextInterface $context, $message, Constr
         $this->assertions = $assertions;
     }
 
-    public function atPath($path)
+    public function atPath(string $path)
     {
         $this->propertyPath = $path;
 
         return $this;
     }
 
-    public function setParameter($key, $value)
+    public function setParameter(string $key, $value)
     {
         $this->parameters[$key] = $value;
 
@@ -279,14 +279,14 @@ public function setInvalidValue($invalidValue)
         return $this;
     }
 
-    public function setPlural($number)
+    public function setPlural(int $number)
     {
         $this->plural = $number;
 
         return $this;
     }
 
-    public function setCode($code)
+    public function setCode(string $code)
     {
         $this->code = $code;
 
@@ -300,7 +300,7 @@ public function setCause($cause)
         return $this;
     }
 
-    public function buildNextViolation($message)
+    public function buildNextViolation(string $message): self
     {
         $assertions = $this->assertions;
         $assertions[] = $this;
@@ -328,7 +328,7 @@ public function assertRaised()
         }
     }
 
-    private function getViolation()
+    private function getViolation(): ConstraintViolation
     {
         return new ConstraintViolation(
             $this->message,
diff --git a/src/Symfony/Component/Validator/Util/LegacyTranslatorProxy.php b/src/Symfony/Component/Validator/Util/LegacyTranslatorProxy.php
index d9deeaa5fd58..908b85400533 100644
--- a/src/Symfony/Component/Validator/Util/LegacyTranslatorProxy.php
+++ b/src/Symfony/Component/Validator/Util/LegacyTranslatorProxy.php
@@ -57,7 +57,7 @@ public function setLocale($locale)
     /**
      * {@inheritdoc}
      */
-    public function getLocale()
+    public function getLocale(): string
     {
         return $this->translator->getLocale();
     }
@@ -65,7 +65,7 @@ public function getLocale()
     /**
      * {@inheritdoc}
      */
-    public function trans($id, array $parameters = [], $domain = null, $locale = null)
+    public function trans($id, array $parameters = [], $domain = null, $locale = null): string
     {
         return $this->translator->trans($id, $parameters, $domain, $locale);
     }
@@ -73,7 +73,7 @@ public function trans($id, array $parameters = [], $domain = null, $locale = nul
     /**
      * {@inheritdoc}
      */
-    public function transChoice($id, $number, array $parameters = [], $domain = null, $locale = null)
+    public function transChoice($id, $number, array $parameters = [], $domain = null, $locale = null): string
     {
         return $this->translator->trans($id, ['%count%' => $number] + $parameters, $domain, $locale);
     }
diff --git a/src/Symfony/Component/Validator/Validation.php b/src/Symfony/Component/Validator/Validation.php
index 71edfedb1839..dbf1dbc0ed7d 100644
--- a/src/Symfony/Component/Validator/Validation.php
+++ b/src/Symfony/Component/Validator/Validation.php
@@ -25,8 +25,6 @@ final class Validation
      *
      * If you want to configure the validator, use
      * {@link createValidatorBuilder()} instead.
-     *
-     * @return ValidatorInterface The new validator
      */
     public static function createValidator(): ValidatorInterface
     {
@@ -35,8 +33,6 @@ public static function createValidator(): ValidatorInterface
 
     /**
      * Creates a configurable builder for validator objects.
-     *
-     * @return ValidatorBuilderInterface The new builder
      */
     public static function createValidatorBuilder(): ValidatorBuilder
     {
diff --git a/src/Symfony/Component/VarDumper/Caster/Caster.php b/src/Symfony/Component/VarDumper/Caster/Caster.php
index 2dc71b66b2da..fd228045fcd3 100644
--- a/src/Symfony/Component/VarDumper/Caster/Caster.php
+++ b/src/Symfony/Component/VarDumper/Caster/Caster.php
@@ -41,12 +41,11 @@ class Caster
      * Casts objects to arrays and adds the dynamic property prefix.
      *
      * @param object $obj          The object to cast
-     * @param string $class        The class of the object
      * @param bool   $hasDebugInfo Whether the __debugInfo method exists on $obj or not
      *
      * @return array The array-cast of the object, with prefixed dynamic properties
      */
-    public static function castObject($obj, $class, $hasDebugInfo = false): array
+    public static function castObject($obj, string $class, bool $hasDebugInfo = false): array
     {
         $a = $obj instanceof \Closure ? [] : (array) $obj;
 
@@ -110,7 +109,7 @@ public static function castObject($obj, $class, $hasDebugInfo = false): array
      *
      * @return array The filtered array
      */
-    public static function filter(array $a, $filter, array $listedProperties = [], &$count = 0): array
+    public static function filter(array $a, int $filter, array $listedProperties = [], ?int &$count = 0): array
     {
         $count = 0;
 
@@ -151,7 +150,7 @@ public static function filter(array $a, $filter, array $listedProperties = [], &
         return $a;
     }
 
-    public static function castPhpIncompleteClass(\__PHP_Incomplete_Class $c, array $a, Stub $stub, $isNested)
+    public static function castPhpIncompleteClass(\__PHP_Incomplete_Class $c, array $a, Stub $stub, bool $isNested): array
     {
         if (isset($a['__PHP_Incomplete_Class_Name'])) {
             $stub->class .= '('.$a['__PHP_Incomplete_Class_Name'].')';
diff --git a/src/Symfony/Component/VarDumper/Caster/DateCaster.php b/src/Symfony/Component/VarDumper/Caster/DateCaster.php
index f2f518266250..26925170acdd 100644
--- a/src/Symfony/Component/VarDumper/Caster/DateCaster.php
+++ b/src/Symfony/Component/VarDumper/Caster/DateCaster.php
@@ -54,7 +54,7 @@ public static function castInterval(\DateInterval $interval, array $a, Stub $stu
         return $filter & Caster::EXCLUDE_VERBOSE ? $i : $i + $a;
     }
 
-    private static function formatInterval(\DateInterval $i)
+    private static function formatInterval(\DateInterval $i): string
     {
         $format = '%R ';
 
diff --git a/src/Symfony/Component/VarDumper/Caster/MemcachedCaster.php b/src/Symfony/Component/VarDumper/Caster/MemcachedCaster.php
index b0177fa4887d..942eecb11fb4 100644
--- a/src/Symfony/Component/VarDumper/Caster/MemcachedCaster.php
+++ b/src/Symfony/Component/VarDumper/Caster/MemcachedCaster.php
@@ -35,7 +35,7 @@ public static function castMemcached(\Memcached $c, array $a, Stub $stub, $isNes
         return $a;
     }
 
-    private static function getNonDefaultOptions(\Memcached $c)
+    private static function getNonDefaultOptions(\Memcached $c): array
     {
         self::$defaultOptions = self::$defaultOptions ?? self::discoverDefaultOptions();
         self::$optionConstants = self::$optionConstants ?? self::getOptionConstants();
@@ -50,7 +50,7 @@ private static function getNonDefaultOptions(\Memcached $c)
         return $nonDefaultOptions;
     }
 
-    private static function discoverDefaultOptions()
+    private static function discoverDefaultOptions(): array
     {
         $defaultMemcached = new \Memcached();
         $defaultMemcached->addServer('127.0.0.1', 11211);
@@ -65,7 +65,7 @@ private static function discoverDefaultOptions()
         return $defaultOptions;
     }
 
-    private static function getOptionConstants()
+    private static function getOptionConstants(): array
     {
         $reflectedMemcached = new \ReflectionClass(\Memcached::class);
 
diff --git a/src/Symfony/Component/VarDumper/Caster/ReflectionCaster.php b/src/Symfony/Component/VarDumper/Caster/ReflectionCaster.php
index a3bbadd53827..7a6e89ad7782 100644
--- a/src/Symfony/Component/VarDumper/Caster/ReflectionCaster.php
+++ b/src/Symfony/Component/VarDumper/Caster/ReflectionCaster.php
@@ -363,7 +363,7 @@ public static function getSignature(array $a)
         return $signature;
     }
 
-    private static function addExtra(&$a, \Reflector $c)
+    private static function addExtra(array &$a, \Reflector $c)
     {
         $x = isset($a[Caster::PREFIX_VIRTUAL.'extra']) ? $a[Caster::PREFIX_VIRTUAL.'extra']->value : [];
 
@@ -379,7 +379,7 @@ private static function addExtra(&$a, \Reflector $c)
         }
     }
 
-    private static function addMap(&$a, \Reflector $c, $map, $prefix = Caster::PREFIX_VIRTUAL)
+    private static function addMap(array &$a, \Reflector $c, array $map, string $prefix = Caster::PREFIX_VIRTUAL)
     {
         foreach ($map as $k => $m) {
             if (method_exists($c, $m) && false !== ($m = $c->$m()) && null !== $m) {
diff --git a/src/Symfony/Component/VarDumper/Caster/SplCaster.php b/src/Symfony/Component/VarDumper/Caster/SplCaster.php
index 4901b3c110bc..b2d4e3c8a9a8 100644
--- a/src/Symfony/Component/VarDumper/Caster/SplCaster.php
+++ b/src/Symfony/Component/VarDumper/Caster/SplCaster.php
@@ -203,7 +203,7 @@ public static function castWeakReference(\WeakReference $c, array $a, Stub $stub
         return $a;
     }
 
-    private static function castSplArray($c, array $a, Stub $stub, $isNested)
+    private static function castSplArray($c, array $a, Stub $stub, bool $isNested): array
     {
         $prefix = Caster::PREFIX_VIRTUAL;
         $class = $stub->class;
diff --git a/src/Symfony/Component/VarDumper/Test/VarDumperTestTrait.php b/src/Symfony/Component/VarDumper/Test/VarDumperTestTrait.php
index afc65350eb2d..3d3d18eeb21e 100644
--- a/src/Symfony/Component/VarDumper/Test/VarDumperTestTrait.php
+++ b/src/Symfony/Component/VarDumper/Test/VarDumperTestTrait.php
@@ -76,7 +76,7 @@ protected function getDump($data, $key = null, $filter = 0)
         return rtrim($dumper->dump($data, true));
     }
 
-    private function prepareExpectation($expected, int $filter)
+    private function prepareExpectation($expected, int $filter): string
     {
         if (!\is_string($expected)) {
             $expected = $this->getDump($expected, null, $filter);
diff --git a/src/Symfony/Component/Workflow/Dumper/GraphvizDumper.php b/src/Symfony/Component/Workflow/Dumper/GraphvizDumper.php
index fbae74dd9182..e3f690b52338 100644
--- a/src/Symfony/Component/Workflow/Dumper/GraphvizDumper.php
+++ b/src/Symfony/Component/Workflow/Dumper/GraphvizDumper.php
@@ -61,7 +61,7 @@ public function dump(Definition $definition, Marking $marking = null, array $opt
     /**
      * @internal
      */
-    protected function findPlaces(Definition $definition, Marking $marking = null)
+    protected function findPlaces(Definition $definition, Marking $marking = null): array
     {
         $workflowMetadata = $definition->getMetadataStore();
 
@@ -96,7 +96,7 @@ protected function findPlaces(Definition $definition, Marking $marking = null)
     /**
      * @internal
      */
-    protected function findTransitions(Definition $definition)
+    protected function findTransitions(Definition $definition): array
     {
         $workflowMetadata = $definition->getMetadataStore();
 
@@ -124,7 +124,7 @@ protected function findTransitions(Definition $definition)
     /**
      * @internal
      */
-    protected function addPlaces(array $places)
+    protected function addPlaces(array $places): string
     {
         $code = '';
 
@@ -145,7 +145,7 @@ protected function addPlaces(array $places)
     /**
      * @internal
      */
-    protected function addTransitions(array $transitions)
+    protected function addTransitions(array $transitions): string
     {
         $code = '';
 
@@ -159,7 +159,7 @@ protected function addTransitions(array $transitions)
     /**
      * @internal
      */
-    protected function findEdges(Definition $definition)
+    protected function findEdges(Definition $definition): array
     {
         $workflowMetadata = $definition->getMetadataStore();
 
@@ -192,7 +192,7 @@ protected function findEdges(Definition $definition)
     /**
      * @internal
      */
-    protected function addEdges(array $edges)
+    protected function addEdges(array $edges): string
     {
         $code = '';
 
@@ -216,7 +216,7 @@ protected function addEdges(array $edges)
     /**
      * @internal
      */
-    protected function startDot(array $options)
+    protected function startDot(array $options): string
     {
         return sprintf("digraph workflow {\n  %s\n  node [%s];\n  edge [%s];\n\n",
             $this->addOptions($options['graph']),
@@ -228,7 +228,7 @@ protected function startDot(array $options)
     /**
      * @internal
      */
-    protected function endDot()
+    protected function endDot(): string
     {
         return "}\n";
     }
@@ -236,7 +236,7 @@ protected function endDot()
     /**
      * @internal
      */
-    protected function dotize($id)
+    protected function dotize(string $id): string
     {
         return hash('sha1', $id);
     }
diff --git a/src/Symfony/Component/Workflow/Dumper/StateMachineGraphvizDumper.php b/src/Symfony/Component/Workflow/Dumper/StateMachineGraphvizDumper.php
index 56ec2697be99..4bd818d5363f 100644
--- a/src/Symfony/Component/Workflow/Dumper/StateMachineGraphvizDumper.php
+++ b/src/Symfony/Component/Workflow/Dumper/StateMachineGraphvizDumper.php
@@ -44,7 +44,7 @@ public function dump(Definition $definition, Marking $marking = null, array $opt
     /**
      * @internal
      */
-    protected function findEdges(Definition $definition)
+    protected function findEdges(Definition $definition): array
     {
         $workflowMetadata = $definition->getMetadataStore();
 
@@ -82,7 +82,7 @@ protected function findEdges(Definition $definition)
     /**
      * @internal
      */
-    protected function addEdges(array $edges)
+    protected function addEdges(array $edges): string
     {
         $code = '';
 
diff --git a/src/Symfony/Component/Workflow/Workflow.php b/src/Symfony/Component/Workflow/Workflow.php
index 2d56bd9ee508..32cabdaae5b1 100644
--- a/src/Symfony/Component/Workflow/Workflow.php
+++ b/src/Symfony/Component/Workflow/Workflow.php
@@ -254,7 +254,7 @@ public function getMetadataStore(): MetadataStoreInterface
         return $this->definition->getMetadataStore();
     }
 
-    private function buildTransitionBlockerListForTransition($subject, Marking $marking, Transition $transition)
+    private function buildTransitionBlockerListForTransition($subject, Marking $marking, Transition $transition): TransitionBlockerList
     {
         foreach ($transition->getFroms() as $place) {
             if (!$marking->has($place)) {
diff --git a/src/Symfony/Component/Yaml/Command/LintCommand.php b/src/Symfony/Component/Yaml/Command/LintCommand.php
index 9fdef61af081..d15ffb38c8aa 100644
--- a/src/Symfony/Component/Yaml/Command/LintCommand.php
+++ b/src/Symfony/Component/Yaml/Command/LintCommand.php
@@ -137,7 +137,7 @@ private function validate(string $content, int $flags, string $file = null)
         return ['file' => $file, 'valid' => true];
     }
 
-    private function display(SymfonyStyle $io, array $files)
+    private function display(SymfonyStyle $io, array $files): int
     {
         switch ($this->format) {
             case 'txt':
@@ -149,7 +149,7 @@ private function display(SymfonyStyle $io, array $files)
         }
     }
 
-    private function displayTxt(SymfonyStyle $io, array $filesInfo)
+    private function displayTxt(SymfonyStyle $io, array $filesInfo): int
     {
         $countFiles = \count($filesInfo);
         $erroredFiles = 0;
@@ -178,7 +178,7 @@ private function displayTxt(SymfonyStyle $io, array $filesInfo)
         return min($erroredFiles, 1);
     }
 
-    private function displayJson(SymfonyStyle $io, array $filesInfo)
+    private function displayJson(SymfonyStyle $io, array $filesInfo): int
     {
         $errors = 0;
 
@@ -198,7 +198,7 @@ private function displayJson(SymfonyStyle $io, array $filesInfo)
         return min($errors, 1);
     }
 
-    private function getFiles(string $fileOrDirectory)
+    private function getFiles(string $fileOrDirectory): iterable
     {
         if (is_file($fileOrDirectory)) {
             yield new \SplFileInfo($fileOrDirectory);
@@ -225,7 +225,7 @@ private function getStdin(): string
         return $yaml;
     }
 
-    private function getParser()
+    private function getParser(): Parser
     {
         if (!$this->parser) {
             $this->parser = new Parser();
@@ -234,7 +234,7 @@ private function getParser()
         return $this->parser;
     }
 
-    private function getDirectoryIterator(string $directory)
+    private function getDirectoryIterator(string $directory): iterable
     {
         $default = function ($directory) {
             return new \RecursiveIteratorIterator(
@@ -250,7 +250,7 @@ private function getDirectoryIterator(string $directory)
         return $default($directory);
     }
 
-    private function isReadable(string $fileOrDirectory)
+    private function isReadable(string $fileOrDirectory): bool
     {
         $default = function ($fileOrDirectory) {
             return is_readable($fileOrDirectory);
diff --git a/src/Symfony/Component/Yaml/Parser.php b/src/Symfony/Component/Yaml/Parser.php
index c34e264b669a..b43ce64bdee5 100644
--- a/src/Symfony/Component/Yaml/Parser.php
+++ b/src/Symfony/Component/Yaml/Parser.php
@@ -1134,7 +1134,7 @@ private function getLineTag(string $value, int $flags, bool $nextLineCheck = tru
         throw new ParseException(sprintf('Tags support is not enabled. You must use the flag "Yaml::PARSE_CUSTOM_TAGS" to use "%s".', $matches['tag']), $this->getRealCurrentLineNb() + 1, $value, $this->filename);
     }
 
-    private function parseQuotedString($yaml)
+    private function parseQuotedString(string $yaml): ?string
     {
         if ('' === $yaml || ('"' !== $yaml[0] && "'" !== $yaml[0])) {
             throw new \InvalidArgumentException(sprintf('"%s" is not a quoted string.', $yaml));
@@ -1223,7 +1223,7 @@ private function lexInlineMapping(string $yaml): string
         return implode("\n", $lines);
     }
 
-    private function lexInlineSequence($yaml)
+    private function lexInlineSequence(string $yaml): string
     {
         if ('' === $yaml || '[' !== $yaml[0]) {
             throw new \InvalidArgumentException(sprintf('"%s" is not a sequence.', $yaml));