diff --git a/src/Symfony/Bundle/FrameworkBundle/Translation/Translator.php b/src/Symfony/Bundle/FrameworkBundle/Translation/Translator.php
index 78ad390e07..721c020370 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Translation/Translator.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Translation/Translator.php
@@ -126,7 +126,7 @@ class Translator extends BaseTranslator implements WarmableInterface
     /**
      * @internal
      */
-    protected function doLoadCatalogue($locale): void
+    protected function doLoadCatalogue(string $locale): void
     {
         parent::doLoadCatalogue($locale);
 
diff --git a/src/Symfony/Bundle/FrameworkBundle/composer.json b/src/Symfony/Bundle/FrameworkBundle/composer.json
index 21c06c2394..02bf50913b 100644
--- a/src/Symfony/Bundle/FrameworkBundle/composer.json
+++ b/src/Symfony/Bundle/FrameworkBundle/composer.json
@@ -50,7 +50,7 @@
         "symfony/security-http": "^3.4|^4.0|^5.0",
         "symfony/serializer": "^4.3|^5.0",
         "symfony/stopwatch": "^3.4|^4.0|^5.0",
-        "symfony/translation": "^4.3|^5.0",
+        "symfony/translation": "^4.4|^5.0",
         "symfony/templating": "^3.4|^4.0|^5.0",
         "symfony/twig-bundle": "^4.4|^5.0",
         "symfony/validator": "^4.4|^5.0",
@@ -80,7 +80,7 @@
         "symfony/property-info": "<3.4",
         "symfony/serializer": "<4.2",
         "symfony/stopwatch": "<3.4",
-        "symfony/translation": "<4.3",
+        "symfony/translation": "<4.4",
         "symfony/twig-bridge": "<4.1.1",
         "symfony/twig-bundle": "<4.4",
         "symfony/validator": "<4.4",
diff --git a/src/Symfony/Component/Form/ChoiceList/ArrayChoiceList.php b/src/Symfony/Component/Form/ChoiceList/ArrayChoiceList.php
index 9ed002a9cc..49b991a465 100644
--- a/src/Symfony/Component/Form/ChoiceList/ArrayChoiceList.php
+++ b/src/Symfony/Component/Form/ChoiceList/ArrayChoiceList.php
@@ -182,7 +182,7 @@ class ArrayChoiceList implements ChoiceListInterface
      *
      * @internal
      */
-    protected function flatten(array $choices, $value, &$choicesByValues, &$keysByValues, &$structuredValues)
+    protected function flatten(array $choices, callable $value, ?array &$choicesByValues, ?array &$keysByValues, ?array &$structuredValues)
     {
         if (null === $choicesByValues) {
             $choicesByValues = [];
diff --git a/src/Symfony/Component/Form/Command/DebugCommand.php b/src/Symfony/Component/Form/Command/DebugCommand.php
index 341329b70b..ea5ef2e5d1 100644
--- a/src/Symfony/Component/Form/Command/DebugCommand.php
+++ b/src/Symfony/Component/Form/Command/DebugCommand.php
@@ -154,7 +154,7 @@ EOF
         $helper->describe($io, $object, $options);
     }
 
-    private function getFqcnTypeClass(InputInterface $input, SymfonyStyle $io, string $shortClassName)
+    private function getFqcnTypeClass(InputInterface $input, SymfonyStyle $io, string $shortClassName): string
     {
         $classes = [];
         sort($this->namespaces);
@@ -195,7 +195,7 @@ EOF
         return $io->choice(sprintf("The type \"%s\" is ambiguous.\n\nSelect one of the following form types to display its information:", $shortClassName), $classes, $classes[0]);
     }
 
-    private function getCoreTypes()
+    private function getCoreTypes(): array
     {
         $coreExtension = new CoreExtension();
         $loadTypesRefMethod = (new \ReflectionObject($coreExtension))->getMethod('loadTypes');
@@ -223,7 +223,7 @@ EOF
         return $typesWithDeprecatedOptions;
     }
 
-    private function findAlternatives(string $name, array $collection)
+    private function findAlternatives(string $name, array $collection): array
     {
         $alternatives = [];
         foreach ($collection as $item) {
diff --git a/src/Symfony/Component/Form/Console/Descriptor/Descriptor.php b/src/Symfony/Component/Form/Console/Descriptor/Descriptor.php
index e209e34d53..17828344c4 100644
--- a/src/Symfony/Component/Form/Console/Descriptor/Descriptor.php
+++ b/src/Symfony/Component/Form/Console/Descriptor/Descriptor.php
@@ -167,7 +167,7 @@ abstract class Descriptor implements DescriptorInterface
         $this->extensionOptions = $filterByDeprecated($this->extensionOptions);
     }
 
-    private function getParentOptionsResolver(ResolvedFormTypeInterface $type)
+    private function getParentOptionsResolver(ResolvedFormTypeInterface $type): OptionsResolver
     {
         $this->parents[$class = \get_class($type->getInnerType())] = [];
 
diff --git a/src/Symfony/Component/Form/Console/Descriptor/TextDescriptor.php b/src/Symfony/Component/Form/Console/Descriptor/TextDescriptor.php
index 219bd69c62..6dc9ac48ac 100644
--- a/src/Symfony/Component/Form/Console/Descriptor/TextDescriptor.php
+++ b/src/Symfony/Component/Form/Console/Descriptor/TextDescriptor.php
@@ -155,7 +155,7 @@ class TextDescriptor extends Descriptor
         return $tableRows;
     }
 
-    private function normalizeAndSortOptionsColumns(array $options)
+    private function normalizeAndSortOptionsColumns(array $options): array
     {
         foreach ($options as $group => $opts) {
             $sorted = false;
diff --git a/src/Symfony/Component/Form/DependencyInjection/FormPass.php b/src/Symfony/Component/Form/DependencyInjection/FormPass.php
index 7e10a5b13f..2be2a59d60 100644
--- a/src/Symfony/Component/Form/DependencyInjection/FormPass.php
+++ b/src/Symfony/Component/Form/DependencyInjection/FormPass.php
@@ -11,6 +11,7 @@
 
 namespace Symfony\Component\Form\DependencyInjection;
 
+use Symfony\Component\DependencyInjection\Argument\ArgumentInterface;
 use Symfony\Component\DependencyInjection\Argument\IteratorArgument;
 use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
 use Symfony\Component\DependencyInjection\Compiler\PriorityTaggedServiceTrait;
@@ -60,7 +61,7 @@ class FormPass implements CompilerPassInterface
         $definition->replaceArgument(2, $this->processFormTypeGuessers($container));
     }
 
-    private function processFormTypes(ContainerBuilder $container)
+    private function processFormTypes(ContainerBuilder $container): Reference
     {
         // Get service locator argument
         $servicesMap = [];
@@ -83,7 +84,7 @@ class FormPass implements CompilerPassInterface
         return ServiceLocatorTagPass::register($container, $servicesMap);
     }
 
-    private function processFormTypeExtensions(ContainerBuilder $container)
+    private function processFormTypeExtensions(ContainerBuilder $container): array
     {
         $typeExtensions = [];
         $typeExtensionsClasses = [];
@@ -130,7 +131,7 @@ class FormPass implements CompilerPassInterface
         return $typeExtensions;
     }
 
-    private function processFormTypeGuessers(ContainerBuilder $container)
+    private function processFormTypeGuessers(ContainerBuilder $container): ArgumentInterface
     {
         $guessers = [];
         $guessersClasses = [];
diff --git a/src/Symfony/Component/Form/Extension/Core/DataTransformer/DateIntervalToStringTransformer.php b/src/Symfony/Component/Form/Extension/Core/DataTransformer/DateIntervalToStringTransformer.php
index 7ec61e747c..a06a244b0f 100644
--- a/src/Symfony/Component/Form/Extension/Core/DataTransformer/DateIntervalToStringTransformer.php
+++ b/src/Symfony/Component/Form/Extension/Core/DataTransformer/DateIntervalToStringTransformer.php
@@ -94,7 +94,7 @@ class DateIntervalToStringTransformer implements DataTransformerInterface
         return $dateInterval;
     }
 
-    private function isISO8601(string $string)
+    private function isISO8601(string $string): bool
     {
         return preg_match('/^P(?=\w*(?:\d|%\w))(?:\d+Y|%[yY]Y)?(?:\d+M|%[mM]M)?(?:(?:\d+D|%[dD]D)|(?:\d+W|%[wW]W))?(?:T(?:\d+H|[hH]H)?(?:\d+M|[iI]M)?(?:\d+S|[sS]S)?)?$/', $string);
     }
diff --git a/src/Symfony/Component/Form/Extension/Validator/Constraints/FormValidator.php b/src/Symfony/Component/Form/Extension/Validator/Constraints/FormValidator.php
index 05a2d8bca7..01488217c8 100644
--- a/src/Symfony/Component/Form/Extension/Validator/Constraints/FormValidator.php
+++ b/src/Symfony/Component/Form/Extension/Validator/Constraints/FormValidator.php
@@ -188,7 +188,7 @@ class FormValidator extends ConstraintValidator
      *
      * @param string|GroupSequence|(string|GroupSequence)[]|callable $groups The validation groups
      *
-     * @return (string|GroupSequence)[] The validation groups
+     * @return GroupSequence|(string|GroupSequence)[] The validation groups
      */
     private static function resolveValidationGroups($groups, FormInterface $form)
     {
diff --git a/src/Symfony/Component/Form/FormRenderer.php b/src/Symfony/Component/Form/FormRenderer.php
index 91e6faa9cc..034dc41cc3 100644
--- a/src/Symfony/Component/Form/FormRenderer.php
+++ b/src/Symfony/Component/Form/FormRenderer.php
@@ -290,7 +290,7 @@ class FormRenderer implements FormRendererInterface
     /**
      * @internal
      */
-    public function encodeCurrency(Environment $environment, $text, $widget = '')
+    public function encodeCurrency(Environment $environment, string $text, string $widget = ''): string
     {
         if ('UTF-8' === $charset = $environment->getCharset()) {
             $text = htmlspecialchars($text, ENT_QUOTES | (\defined('ENT_SUBSTITUTE') ? ENT_SUBSTITUTE : 0), 'UTF-8');
diff --git a/src/Symfony/Component/HttpClient/Tests/DataCollector/HttpClientDataCollectorTest.php b/src/Symfony/Component/HttpClient/Tests/DataCollector/HttpClientDataCollectorTest.php
index f4f94156a3..d173c17250 100755
--- a/src/Symfony/Component/HttpClient/Tests/DataCollector/HttpClientDataCollectorTest.php
+++ b/src/Symfony/Component/HttpClient/Tests/DataCollector/HttpClientDataCollectorTest.php
@@ -164,7 +164,7 @@ class HttpClientDataCollectorTest extends TestCase
         $this->assertEquals(0, $sut->getRequestCount());
     }
 
-    private function httpClientThatHasTracedRequests($tracedRequests)
+    private function httpClientThatHasTracedRequests($tracedRequests): TraceableHttpClient
     {
         $httpClient = new TraceableHttpClient(new NativeHttpClient());
 
diff --git a/src/Symfony/Component/HttpClient/Tests/Exception/HttpExceptionTraitTest.php b/src/Symfony/Component/HttpClient/Tests/Exception/HttpExceptionTraitTest.php
index 38afb212dc..ac6c30df1f 100644
--- a/src/Symfony/Component/HttpClient/Tests/Exception/HttpExceptionTraitTest.php
+++ b/src/Symfony/Component/HttpClient/Tests/Exception/HttpExceptionTraitTest.php
@@ -20,7 +20,7 @@ use Symfony\Contracts\HttpClient\ResponseInterface;
  */
 class HttpExceptionTraitTest extends TestCase
 {
-    public function provideParseError()
+    public function provideParseError(): iterable
     {
         yield ['application/ld+json', '{"hydra:title": "An error occurred", "hydra:description": "Some details"}'];
         yield ['application/problem+json', '{"title": "An error occurred", "detail": "Some details"}'];
diff --git a/src/Symfony/Component/HttpClient/Tests/HttpClientTraitTest.php b/src/Symfony/Component/HttpClient/Tests/HttpClientTraitTest.php
index 559f2b6227..1b964f5f69 100644
--- a/src/Symfony/Component/HttpClient/Tests/HttpClientTraitTest.php
+++ b/src/Symfony/Component/HttpClient/Tests/HttpClientTraitTest.php
@@ -24,7 +24,7 @@ class HttpClientTraitTest extends TestCase
     /**
      * @dataProvider providePrepareRequestUrl
      */
-    public function testPrepareRequestUrl($expected, $url, $query = [])
+    public function testPrepareRequestUrl(string $expected, string $url, array $query = [])
     {
         $defaults = [
             'base_uri' => 'http://example.com?c=c',
@@ -36,7 +36,7 @@ class HttpClientTraitTest extends TestCase
         $this->assertSame($expected, implode('', $url));
     }
 
-    public function providePrepareRequestUrl()
+    public function providePrepareRequestUrl(): iterable
     {
         yield ['http://example.com/', 'http://example.com/'];
         yield ['http://example.com/?a=1&b=b', '.'];
@@ -48,7 +48,7 @@ class HttpClientTraitTest extends TestCase
     /**
      * @dataProvider provideResolveUrl
      */
-    public function testResolveUrl($base, $url, $expected)
+    public function testResolveUrl(string $base, string $url, string $expected)
     {
         $this->assertSame($expected, implode('', self::resolveUrl(self::parseUrl($url), self::parseUrl($base))));
     }
@@ -56,7 +56,7 @@ class HttpClientTraitTest extends TestCase
     /**
      * From https://github.com/guzzle/psr7/blob/master/tests/UriResoverTest.php.
      */
-    public function provideResolveUrl()
+    public function provideResolveUrl(): array
     {
         return [
             [self::RFC3986_BASE, 'http:h',        'http:h'],
@@ -123,14 +123,14 @@ class HttpClientTraitTest extends TestCase
     /**
      * @dataProvider provideParseUrl
      */
-    public function testParseUrl($expected, $url, $query = [])
+    public function testParseUrl(array $expected, string $url, array $query = [])
     {
         $expected = array_combine(['scheme', 'authority', 'path', 'query', 'fragment'], $expected);
 
         $this->assertSame($expected, self::parseUrl($url, $query));
     }
 
-    public function provideParseUrl()
+    public function provideParseUrl(): iterable
     {
         yield [['http:', '//example.com', null, null, null], 'http://Example.coM:80'];
         yield [['https:', '//xn--dj-kia8a.example.com:8000', '/', null, null], 'https://DÉjà.Example.com:8000/'];
diff --git a/src/Symfony/Component/HttpClient/Tests/HttpOptionsTest.php b/src/Symfony/Component/HttpClient/Tests/HttpOptionsTest.php
index 65d0ae59db..df5cb394df 100644
--- a/src/Symfony/Component/HttpClient/Tests/HttpOptionsTest.php
+++ b/src/Symfony/Component/HttpClient/Tests/HttpOptionsTest.php
@@ -19,7 +19,7 @@ use Symfony\Component\HttpClient\HttpOptions;
  */
 class HttpOptionsTest extends TestCase
 {
-    public function provideSetAuthBasic()
+    public function provideSetAuthBasic(): iterable
     {
         yield ['user:password', 'user', 'password'];
         yield ['user:password', 'user:password'];
diff --git a/src/Symfony/Component/HttpKernel/Controller/ControllerResolver.php b/src/Symfony/Component/HttpKernel/Controller/ControllerResolver.php
index 7291c25da7..22907ce58f 100644
--- a/src/Symfony/Component/HttpKernel/Controller/ControllerResolver.php
+++ b/src/Symfony/Component/HttpKernel/Controller/ControllerResolver.php
@@ -151,7 +151,7 @@ class ControllerResolver implements ControllerResolverInterface
         return new $class();
     }
 
-    private function getControllerError($callable)
+    private function getControllerError($callable): string
     {
         if (\is_string($callable)) {
             if (false !== strpos($callable, '::')) {
@@ -213,7 +213,7 @@ class ControllerResolver implements ControllerResolverInterface
         return $message;
     }
 
-    private function getClassMethodsWithoutMagicMethods($classOrObject)
+    private function getClassMethodsWithoutMagicMethods($classOrObject): array
     {
         $methods = get_class_methods($classOrObject);
 
diff --git a/src/Symfony/Component/HttpKernel/DataCollector/LoggerDataCollector.php b/src/Symfony/Component/HttpKernel/DataCollector/LoggerDataCollector.php
index af7b1bc3db..d91f77cc33 100644
--- a/src/Symfony/Component/HttpKernel/DataCollector/LoggerDataCollector.php
+++ b/src/Symfony/Component/HttpKernel/DataCollector/LoggerDataCollector.php
@@ -118,7 +118,7 @@ class LoggerDataCollector extends DataCollector implements LateDataCollectorInte
         return 'logger';
     }
 
-    private function getContainerDeprecationLogs()
+    private function getContainerDeprecationLogs(): array
     {
         if (null === $this->containerPathPrefix || !file_exists($file = $this->containerPathPrefix.'Deprecations.log')) {
             return [];
@@ -212,7 +212,7 @@ class LoggerDataCollector extends DataCollector implements LateDataCollectorInte
         return array_values($sanitizedLogs);
     }
 
-    private function isSilencedOrDeprecationErrorLog(array $log)
+    private function isSilencedOrDeprecationErrorLog(array $log): bool
     {
         if (!isset($log['context']['exception'])) {
             return false;
@@ -231,7 +231,7 @@ class LoggerDataCollector extends DataCollector implements LateDataCollectorInte
         return false;
     }
 
-    private function computeErrorsCount(array $containerDeprecationLogs)
+    private function computeErrorsCount(array $containerDeprecationLogs): array
     {
         $silencedLogs = [];
         $count = [
diff --git a/src/Symfony/Component/HttpKernel/DataCollector/MemoryDataCollector.php b/src/Symfony/Component/HttpKernel/DataCollector/MemoryDataCollector.php
index 5d394888df..c101fe406a 100644
--- a/src/Symfony/Component/HttpKernel/DataCollector/MemoryDataCollector.php
+++ b/src/Symfony/Component/HttpKernel/DataCollector/MemoryDataCollector.php
@@ -89,7 +89,7 @@ class MemoryDataCollector extends DataCollector implements LateDataCollectorInte
         return 'memory';
     }
 
-    private function convertToBytes(string $memoryLimit)
+    private function convertToBytes(string $memoryLimit): int
     {
         if ('-1' === $memoryLimit) {
             return -1;
diff --git a/src/Symfony/Component/HttpKernel/DependencyInjection/AddAnnotatedClassesToCachePass.php b/src/Symfony/Component/HttpKernel/DependencyInjection/AddAnnotatedClassesToCachePass.php
index c236eeae4e..70a987ebf4 100644
--- a/src/Symfony/Component/HttpKernel/DependencyInjection/AddAnnotatedClassesToCachePass.php
+++ b/src/Symfony/Component/HttpKernel/DependencyInjection/AddAnnotatedClassesToCachePass.php
@@ -82,7 +82,7 @@ class AddAnnotatedClassesToCachePass implements CompilerPassInterface
         return array_unique($expanded);
     }
 
-    private function getClassesInComposerClassMaps()
+    private function getClassesInComposerClassMaps(): array
     {
         $classes = [];
 
@@ -103,7 +103,7 @@ class AddAnnotatedClassesToCachePass implements CompilerPassInterface
         return array_keys($classes);
     }
 
-    private function patternsToRegexps(array $patterns)
+    private function patternsToRegexps(array $patterns): array
     {
         $regexps = [];
 
@@ -125,7 +125,7 @@ class AddAnnotatedClassesToCachePass implements CompilerPassInterface
         return $regexps;
     }
 
-    private function matchAnyRegexps(string $class, array $regexps)
+    private function matchAnyRegexps(string $class, array $regexps): bool
     {
         $blacklisted = false !== strpos($class, 'Test');
 
diff --git a/src/Symfony/Component/HttpKernel/EventListener/RouterListener.php b/src/Symfony/Component/HttpKernel/EventListener/RouterListener.php
index b040b692dc..9d8e83bc71 100644
--- a/src/Symfony/Component/HttpKernel/EventListener/RouterListener.php
+++ b/src/Symfony/Component/HttpKernel/EventListener/RouterListener.php
@@ -161,7 +161,7 @@ class RouterListener implements EventSubscriberInterface
         ];
     }
 
-    private function createWelcomeResponse()
+    private function createWelcomeResponse(): Response
     {
         $version = Kernel::VERSION;
         $projectDir = realpath($this->projectDir).\DIRECTORY_SEPARATOR;
diff --git a/src/Symfony/Component/HttpKernel/UriSigner.php b/src/Symfony/Component/HttpKernel/UriSigner.php
index 82cbeac8cc..c66caa6e89 100644
--- a/src/Symfony/Component/HttpKernel/UriSigner.php
+++ b/src/Symfony/Component/HttpKernel/UriSigner.php
@@ -82,12 +82,12 @@ class UriSigner
         return $this->computeHash($this->buildUrl($url, $params)) === $hash;
     }
 
-    private function computeHash(string $uri)
+    private function computeHash(string $uri): string
     {
         return base64_encode(hash_hmac('sha256', $uri, $this->secret, true));
     }
 
-    private function buildUrl(array $url, array $params = [])
+    private function buildUrl(array $url, array $params = []): string
     {
         ksort($params, SORT_STRING);
         $url['query'] = http_build_query($params, '', '&');
diff --git a/src/Symfony/Component/Intl/Data/Generator/LanguageDataGenerator.php b/src/Symfony/Component/Intl/Data/Generator/LanguageDataGenerator.php
index 847fb9932c..2af1b0682b 100644
--- a/src/Symfony/Component/Intl/Data/Generator/LanguageDataGenerator.php
+++ b/src/Symfony/Component/Intl/Data/Generator/LanguageDataGenerator.php
@@ -205,7 +205,7 @@ class LanguageDataGenerator extends AbstractDataGenerator
         return array_keys($alpha3Codes);
     }
 
-    private function generateAlpha2ToAlpha3Mapping(ArrayAccessibleResourceBundle $metadataBundle)
+    private function generateAlpha2ToAlpha3Mapping(ArrayAccessibleResourceBundle $metadataBundle): array
     {
         $aliases = iterator_to_array($metadataBundle['alias']['language']);
         $alpha2ToAlpha3 = [];
diff --git a/src/Symfony/Component/Intl/Locale.php b/src/Symfony/Component/Intl/Locale.php
index 3b9eba3a75..0373844e76 100644
--- a/src/Symfony/Component/Intl/Locale.php
+++ b/src/Symfony/Component/Intl/Locale.php
@@ -65,7 +65,7 @@ final class Locale extends \Locale
      * @return string|null The ICU locale code of the fallback locale, or null
      *                     if no fallback exists
      */
-    public static function getFallback($locale): ?string
+    public static function getFallback(string $locale): ?string
     {
         if (\function_exists('locale_parse')) {
             $localeSubTags = locale_parse($locale);
diff --git a/src/Symfony/Component/Intl/Util/GitRepository.php b/src/Symfony/Component/Intl/Util/GitRepository.php
index bd043bc3ba..3f24c6a463 100644
--- a/src/Symfony/Component/Intl/Util/GitRepository.php
+++ b/src/Symfony/Component/Intl/Util/GitRepository.php
@@ -44,32 +44,32 @@ final class GitRepository
         return new self(realpath($targetDir));
     }
 
-    public function getPath()
+    public function getPath(): string
     {
         return $this->path;
     }
 
-    public function getUrl()
+    public function getUrl(): string
     {
         return $this->getLastLine($this->execInPath('git config --get remote.origin.url'));
     }
 
-    public function getLastCommitHash()
+    public function getLastCommitHash(): string
     {
         return $this->getLastLine($this->execInPath('git log -1 --format="%H"'));
     }
 
-    public function getLastAuthor()
+    public function getLastAuthor(): string
     {
         return $this->getLastLine($this->execInPath('git log -1 --format="%an"'));
     }
 
-    public function getLastAuthoredDate()
+    public function getLastAuthoredDate(): \DateTime
     {
         return new \DateTime($this->getLastLine($this->execInPath('git log -1 --format="%ai"')));
     }
 
-    public function getLastTag(callable $filter = null)
+    public function getLastTag(callable $filter = null): string
     {
         $tags = $this->execInPath('git tag -l --sort=v:refname');
 
@@ -80,17 +80,17 @@ final class GitRepository
         return $this->getLastLine($tags);
     }
 
-    public function checkout($branch)
+    public function checkout(string $branch)
     {
         $this->execInPath(sprintf('git checkout %s', escapeshellarg($branch)));
     }
 
-    private function execInPath(string $command)
+    private function execInPath(string $command): array
     {
         return self::exec(sprintf('cd %s && %s', escapeshellarg($this->path), $command));
     }
 
-    private static function exec($command, $customErrorMessage = null)
+    private static function exec(string $command, string $customErrorMessage = null): array
     {
         exec(sprintf('%s 2>&1', $command), $output, $result);
 
@@ -101,7 +101,7 @@ final class GitRepository
         return $output;
     }
 
-    private function getLastLine(array $output)
+    private function getLastLine(array $output): string
     {
         return array_pop($output);
     }
diff --git a/src/Symfony/Component/Ldap/Adapter/ExtLdap/Collection.php b/src/Symfony/Component/Ldap/Adapter/ExtLdap/Collection.php
index 2f3d22743d..573ab0ce99 100644
--- a/src/Symfony/Component/Ldap/Adapter/ExtLdap/Collection.php
+++ b/src/Symfony/Component/Ldap/Adapter/ExtLdap/Collection.php
@@ -118,7 +118,7 @@ class Collection implements CollectionInterface
         unset($this->entries[$offset]);
     }
 
-    private function getSingleEntry($con, $current)
+    private function getSingleEntry($con, $current): Entry
     {
         $attributes = ldap_get_attributes($con, $current);
 
@@ -137,7 +137,7 @@ class Collection implements CollectionInterface
         return new Entry($dn, $attributes);
     }
 
-    private function cleanupAttributes(array $entry)
+    private function cleanupAttributes(array $entry): array
     {
         $attributes = array_diff_key($entry, array_flip(range(0, $entry['count'] - 1)) + [
                 'count' => null,
diff --git a/src/Symfony/Component/Ldap/Adapter/ExtLdap/ConnectionOptions.php b/src/Symfony/Component/Ldap/Adapter/ExtLdap/ConnectionOptions.php
index 949770e88f..225f107ffd 100644
--- a/src/Symfony/Component/Ldap/Adapter/ExtLdap/ConnectionOptions.php
+++ b/src/Symfony/Component/Ldap/Adapter/ExtLdap/ConnectionOptions.php
@@ -62,7 +62,7 @@ final class ConnectionOptions
     const X_KEEPALIVE_PROBES = 0x6301;
     const X_KEEPALIVE_INTERVAL = 0x6302;
 
-    public static function getOptionName($name)
+    public static function getOptionName(string $name): string
     {
         return sprintf('%s::%s', self::class, strtoupper($name));
     }
@@ -71,11 +71,9 @@ final class ConnectionOptions
      * Fetches an option's corresponding constant value from an option name.
      * The option name can either be in snake or camel case.
      *
-     * @param string $name
-     *
      * @throws LdapException
      */
-    public static function getOption($name): int
+    public static function getOption(string $name): int
     {
         // Convert
         $constantName = self::getOptionName($name);
@@ -87,7 +85,7 @@ final class ConnectionOptions
         return \constant($constantName);
     }
 
-    public static function isOption($name)
+    public static function isOption(string $name): bool
     {
         return \defined(self::getOptionName($name));
     }
diff --git a/src/Symfony/Component/Ldap/Adapter/ExtLdap/EntryManager.php b/src/Symfony/Component/Ldap/Adapter/ExtLdap/EntryManager.php
index d64e4b3289..20055c2f3b 100644
--- a/src/Symfony/Component/Ldap/Adapter/ExtLdap/EntryManager.php
+++ b/src/Symfony/Component/Ldap/Adapter/ExtLdap/EntryManager.php
@@ -156,7 +156,7 @@ class EntryManager implements EntryManagerInterface
         }
     }
 
-    private function parseRdnFromEntry(Entry $entry)
+    private function parseRdnFromEntry(Entry $entry): string
     {
         if (!preg_match('/^([^,]+),/', $entry->getDn(), $matches)) {
             throw new LdapException(sprintf('Entry "%s" malformed, could not parse RDN.', $entry->getDn()));
diff --git a/src/Symfony/Component/Lock/Key.php b/src/Symfony/Component/Lock/Key.php
index c53892ab6b..bc09b88888 100644
--- a/src/Symfony/Component/Lock/Key.php
+++ b/src/Symfony/Component/Lock/Key.php
@@ -60,7 +60,7 @@ final class Key
     /**
      * @param float $ttl the expiration delay of locks in seconds
      */
-    public function reduceLifetime($ttl)
+    public function reduceLifetime(float $ttl)
     {
         $newTime = microtime(true) + $ttl;
 
diff --git a/src/Symfony/Component/Lock/Store/MemcachedStore.php b/src/Symfony/Component/Lock/Store/MemcachedStore.php
index 215e3496bd..23e2ee8121 100644
--- a/src/Symfony/Component/Lock/Store/MemcachedStore.php
+++ b/src/Symfony/Component/Lock/Store/MemcachedStore.php
@@ -161,7 +161,7 @@ class MemcachedStore implements StoreInterface
         return $key->getState(__CLASS__);
     }
 
-    private function getValueAndCas(Key $key)
+    private function getValueAndCas(Key $key): array
     {
         if (null === $this->useExtendedReturn) {
             $this->useExtendedReturn = version_compare(phpversion('memcached'), '2.9.9', '>');
diff --git a/src/Symfony/Component/Messenger/Command/AbstractFailedMessagesCommand.php b/src/Symfony/Component/Messenger/Command/AbstractFailedMessagesCommand.php
index 136a20e94c..69b30d781d 100644
--- a/src/Symfony/Component/Messenger/Command/AbstractFailedMessagesCommand.php
+++ b/src/Symfony/Component/Messenger/Command/AbstractFailedMessagesCommand.php
@@ -39,7 +39,7 @@ abstract class AbstractFailedMessagesCommand extends Command
         parent::__construct();
     }
 
-    protected function getReceiverName()
+    protected function getReceiverName(): string
     {
         return $this->receiverName;
     }
diff --git a/src/Symfony/Component/Messenger/Handler/HandlerDescriptor.php b/src/Symfony/Component/Messenger/Handler/HandlerDescriptor.php
index 6178f89fba..a0dac29cd0 100644
--- a/src/Symfony/Component/Messenger/Handler/HandlerDescriptor.php
+++ b/src/Symfony/Component/Messenger/Handler/HandlerDescriptor.php
@@ -49,7 +49,7 @@ final class HandlerDescriptor
         return $this->options[$option] ?? null;
     }
 
-    private function callableName(callable $handler)
+    private function callableName(callable $handler): string
     {
         if (\is_array($handler)) {
             if (\is_object($handler[0])) {
diff --git a/src/Symfony/Component/Messenger/Handler/HandlersLocator.php b/src/Symfony/Component/Messenger/Handler/HandlersLocator.php
index 39b12f53d1..6252bcc52a 100644
--- a/src/Symfony/Component/Messenger/Handler/HandlersLocator.php
+++ b/src/Symfony/Component/Messenger/Handler/HandlersLocator.php
@@ -74,7 +74,7 @@ class HandlersLocator implements HandlersLocatorInterface
             + ['*' => '*'];
     }
 
-    private function shouldHandle(Envelope $envelope, HandlerDescriptor $handlerDescriptor)
+    private function shouldHandle(Envelope $envelope, HandlerDescriptor $handlerDescriptor): bool
     {
         if (null === $received = $envelope->last(ReceivedStamp::class)) {
             return true;
diff --git a/src/Symfony/Component/Messenger/Tests/Handler/HandleDescriptorTest.php b/src/Symfony/Component/Messenger/Tests/Handler/HandleDescriptorTest.php
index 61e080b034..4f76d379dd 100644
--- a/src/Symfony/Component/Messenger/Tests/Handler/HandleDescriptorTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Handler/HandleDescriptorTest.php
@@ -18,7 +18,7 @@ class HandleDescriptorTest extends TestCase
         $this->assertStringMatchesFormat($expectedHandlerString, $descriptor->getName());
     }
 
-    public function provideHandlers()
+    public function provideHandlers(): iterable
     {
         yield [function () {}, 'Closure'];
         yield ['var_dump', 'var_dump'];
diff --git a/src/Symfony/Component/Messenger/Tests/MessageBusTest.php b/src/Symfony/Component/Messenger/Tests/MessageBusTest.php
index e47b57c104..4e1c2f6982 100644
--- a/src/Symfony/Component/Messenger/Tests/MessageBusTest.php
+++ b/src/Symfony/Component/Messenger/Tests/MessageBusTest.php
@@ -148,7 +148,7 @@ class MessageBusTest extends TestCase
         $this->assertCount(2, $finalEnvelope->all());
     }
 
-    public function provideConstructorDataStucture()
+    public function provideConstructorDataStucture(): iterable
     {
         yield 'iterator' => [new \ArrayObject([
             new SimpleMiddleware(),
@@ -167,7 +167,7 @@ class MessageBusTest extends TestCase
     }
 
     /** @dataProvider provideConstructorDataStucture */
-    public function testConstructDataStructure($dataStructure)
+    public function testConstructDataStructure(iterable $dataStructure)
     {
         $bus = new MessageBus($dataStructure);
         $envelope = new Envelope(new DummyMessage('Hello'));
diff --git a/src/Symfony/Component/Messenger/Tests/Middleware/HandleMessageMiddlewareTest.php b/src/Symfony/Component/Messenger/Tests/Middleware/HandleMessageMiddlewareTest.php
index 3ed20e0601..400060bc86 100644
--- a/src/Symfony/Component/Messenger/Tests/Middleware/HandleMessageMiddlewareTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Middleware/HandleMessageMiddlewareTest.php
@@ -60,7 +60,7 @@ class HandleMessageMiddlewareTest extends MiddlewareTestCase
         $this->assertEquals($expectedStamps, $envelope->all(HandledStamp::class));
     }
 
-    public function itAddsHandledStampsProvider()
+    public function itAddsHandledStampsProvider(): iterable
     {
         $first = $this->createPartialMock(HandleMessageMiddlewareTestCallable::class, ['__invoke']);
         $first->method('__invoke')->willReturn('first result');
diff --git a/src/Symfony/Component/Messenger/Tests/Middleware/SendMessageMiddlewareTest.php b/src/Symfony/Component/Messenger/Tests/Middleware/SendMessageMiddlewareTest.php
index 0dd857afc3..82c3b0ac05 100644
--- a/src/Symfony/Component/Messenger/Tests/Middleware/SendMessageMiddlewareTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Middleware/SendMessageMiddlewareTest.php
@@ -241,7 +241,7 @@ class SendMessageMiddlewareTest extends MiddlewareTestCase
         $middleware->handle($envelope, $this->getStackMock(false));
     }
 
-    private function createSendersLocator(array $sendersMap, array $senders)
+    private function createSendersLocator(array $sendersMap, array $senders): SendersLocator
     {
         $container = $this->createMock(ContainerInterface::class);
         $container->expects($this->any())
diff --git a/src/Symfony/Component/Messenger/Tests/Retry/MultiplierRetryStrategyTest.php b/src/Symfony/Component/Messenger/Tests/Retry/MultiplierRetryStrategyTest.php
index d1c201955d..433590d7fc 100644
--- a/src/Symfony/Component/Messenger/Tests/Retry/MultiplierRetryStrategyTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Retry/MultiplierRetryStrategyTest.php
@@ -70,7 +70,7 @@ class MultiplierRetryStrategyTest extends TestCase
         $this->assertSame($expectedDelay, $strategy->getWaitingTime($envelope));
     }
 
-    public function getWaitTimeTests()
+    public function getWaitTimeTests(): iterable
     {
         // delay, multiplier, maxDelay, retries, expectedDelay
         yield [1000, 1, 5000, 0, 1000];
diff --git a/src/Symfony/Component/Messenger/Tests/Transport/AmqpExt/AmqpReceiverTest.php b/src/Symfony/Component/Messenger/Tests/Transport/AmqpExt/AmqpReceiverTest.php
index 8e0b9da29a..8e9aebbce8 100644
--- a/src/Symfony/Component/Messenger/Tests/Transport/AmqpExt/AmqpReceiverTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Transport/AmqpExt/AmqpReceiverTest.php
@@ -73,7 +73,7 @@ class AmqpReceiverTest extends TestCase
         $receiver->reject(new Envelope(new \stdClass(), [new AmqpReceivedStamp($amqpEnvelope, 'queueName')]));
     }
 
-    private function createAMQPEnvelope()
+    private function createAMQPEnvelope(): \AMQPEnvelope
     {
         $envelope = $this->getMockBuilder(\AMQPEnvelope::class)->getMock();
         $envelope->method('getBody')->willReturn('{"message": "Hi"}');
diff --git a/src/Symfony/Component/Messenger/Tests/Transport/AmqpExt/AmqpTransportTest.php b/src/Symfony/Component/Messenger/Tests/Transport/AmqpExt/AmqpTransportTest.php
index 4afdabca69..6618d2fc76 100644
--- a/src/Symfony/Component/Messenger/Tests/Transport/AmqpExt/AmqpTransportTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Transport/AmqpExt/AmqpTransportTest.php
@@ -52,7 +52,7 @@ class AmqpTransportTest extends TestCase
         $this->assertSame($decodedMessage, $envelopes[0]->getMessage());
     }
 
-    private function getTransport(SerializerInterface $serializer = null, Connection $connection = null)
+    private function getTransport(SerializerInterface $serializer = null, Connection $connection = null): AmqpTransport
     {
         $serializer = $serializer ?: $this->getMockBuilder(SerializerInterface::class)->getMock();
         $connection = $connection ?: $this->getMockBuilder(Connection::class)->disableOriginalConstructor()->getMock();
diff --git a/src/Symfony/Component/Messenger/Tests/Transport/Doctrine/ConnectionTest.php b/src/Symfony/Component/Messenger/Tests/Transport/Doctrine/ConnectionTest.php
index 6e7724d506..29c1135ec5 100644
--- a/src/Symfony/Component/Messenger/Tests/Transport/Doctrine/ConnectionTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Transport/Doctrine/ConnectionTest.php
@@ -135,7 +135,7 @@ class ConnectionTest extends TestCase
         return $queryBuilder;
     }
 
-    private function getStatementMock($expectedResult)
+    private function getStatementMock($expectedResult): Statement
     {
         $stmt = $this->createMock(Statement::class);
         $stmt->expects($this->once())
@@ -145,7 +145,7 @@ class ConnectionTest extends TestCase
         return $stmt;
     }
 
-    private function getSchemaSynchronizerMock()
+    private function getSchemaSynchronizerMock(): SchemaSynchronizer
     {
         return $this->createMock(SchemaSynchronizer::class);
     }
@@ -153,7 +153,7 @@ class ConnectionTest extends TestCase
     /**
      * @dataProvider buildConfigurationProvider
      */
-    public function testBuildConfiguration($dsn, $options, $expectedConnection, $expectedTableName, $expectedRedeliverTimeout, $expectedQueue, $expectedAutoSetup)
+    public function testBuildConfiguration(string $dsn, array $options, string $expectedConnection, string $expectedTableName, int $expectedRedeliverTimeout, string $expectedQueue, bool $expectedAutoSetup)
     {
         $config = Connection::buildConfiguration($dsn, $options);
         $this->assertEquals($expectedConnection, $config['connection']);
@@ -163,7 +163,7 @@ class ConnectionTest extends TestCase
         $this->assertEquals($expectedAutoSetup, $config['auto_setup']);
     }
 
-    public function buildConfigurationProvider()
+    public function buildConfigurationProvider(): iterable
     {
         yield 'no options' => [
             'dsn' => 'doctrine://default',
diff --git a/src/Symfony/Component/Messenger/Tests/Transport/Doctrine/DoctrineReceiverTest.php b/src/Symfony/Component/Messenger/Tests/Transport/Doctrine/DoctrineReceiverTest.php
index 9c8b359f09..45e4dd3b91 100644
--- a/src/Symfony/Component/Messenger/Tests/Transport/Doctrine/DoctrineReceiverTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Transport/Doctrine/DoctrineReceiverTest.php
@@ -119,7 +119,7 @@ class DoctrineReceiverTest extends TestCase
         $this->assertEquals(new DummyMessage('Hi'), $actualEnvelope->getMessage());
     }
 
-    private function createDoctrineEnvelope()
+    private function createDoctrineEnvelope(): array
     {
         return [
             'id' => 1,
diff --git a/src/Symfony/Component/Messenger/Tests/Transport/Doctrine/DoctrineTransportTest.php b/src/Symfony/Component/Messenger/Tests/Transport/Doctrine/DoctrineTransportTest.php
index 2ed5d34db4..96b5078b3a 100644
--- a/src/Symfony/Component/Messenger/Tests/Transport/Doctrine/DoctrineTransportTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Transport/Doctrine/DoctrineTransportTest.php
@@ -50,7 +50,7 @@ class DoctrineTransportTest extends TestCase
         $this->assertSame($decodedMessage, $envelopes[0]->getMessage());
     }
 
-    private function getTransport(SerializerInterface $serializer = null, Connection $connection = null)
+    private function getTransport(SerializerInterface $serializer = null, Connection $connection = null): DoctrineTransport
     {
         $serializer = $serializer ?: $this->createMock(SerializerInterface::class);
         $connection = $connection ?: $this->createMock(Connection::class);
diff --git a/src/Symfony/Component/Messenger/Tests/Transport/RedisExt/RedisReceiverTest.php b/src/Symfony/Component/Messenger/Tests/Transport/RedisExt/RedisReceiverTest.php
index 28c299258c..0da0e78ff8 100644
--- a/src/Symfony/Component/Messenger/Tests/Transport/RedisExt/RedisReceiverTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Transport/RedisExt/RedisReceiverTest.php
@@ -54,7 +54,7 @@ class RedisReceiverTest extends TestCase
         $receiver->get();
     }
 
-    private function createRedisEnvelope()
+    private function createRedisEnvelope(): array
     {
         return [
             'id' => 1,
diff --git a/src/Symfony/Component/Messenger/Tests/Transport/RedisExt/RedisTransportTest.php b/src/Symfony/Component/Messenger/Tests/Transport/RedisExt/RedisTransportTest.php
index fce73e50d3..8ca97243ae 100644
--- a/src/Symfony/Component/Messenger/Tests/Transport/RedisExt/RedisTransportTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Transport/RedisExt/RedisTransportTest.php
@@ -50,7 +50,7 @@ class RedisTransportTest extends TestCase
         $this->assertSame($decodedMessage, $envelopes[0]->getMessage());
     }
 
-    private function getTransport(SerializerInterface $serializer = null, Connection $connection = null)
+    private function getTransport(SerializerInterface $serializer = null, Connection $connection = null): RedisTransport
     {
         $serializer = $serializer ?: $this->getMockBuilder(SerializerInterface::class)->getMock();
         $connection = $connection ?: $this->getMockBuilder(Connection::class)->disableOriginalConstructor()->getMock();
diff --git a/src/Symfony/Component/Messenger/Tests/Transport/Sender/SendersLocatorTest.php b/src/Symfony/Component/Messenger/Tests/Transport/Sender/SendersLocatorTest.php
index 4c9be63c1c..d284861c3b 100644
--- a/src/Symfony/Component/Messenger/Tests/Transport/Sender/SendersLocatorTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Transport/Sender/SendersLocatorTest.php
@@ -90,7 +90,7 @@ class SendersLocatorTest extends TestCase
         $this->assertSame(['dummy' => $sender], iterator_to_array($locator->getSenders(new Envelope(new DummyMessage('a')))));
     }
 
-    private function createContainer(array $senders)
+    private function createContainer(array $senders): ContainerInterface
     {
         $container = $this->createMock(ContainerInterface::class);
         $container->expects($this->any())
diff --git a/src/Symfony/Component/Messenger/Tests/Transport/Serialization/SerializerTest.php b/src/Symfony/Component/Messenger/Tests/Transport/Serialization/SerializerTest.php
index 73cbfb6cb9..ae9a76fe22 100644
--- a/src/Symfony/Component/Messenger/Tests/Transport/Serialization/SerializerTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Transport/Serialization/SerializerTest.php
@@ -166,7 +166,7 @@ class SerializerTest extends TestCase
         $serializer->decode($data);
     }
 
-    public function getMissingKeyTests()
+    public function getMissingKeyTests(): iterable
     {
         yield 'no_body' => [
             ['headers' => ['type' => 'bar']],
diff --git a/src/Symfony/Component/Messenger/Tests/Worker/StopWhenMemoryUsageIsExceededWorkerTest.php b/src/Symfony/Component/Messenger/Tests/Worker/StopWhenMemoryUsageIsExceededWorkerTest.php
index d8a80e37a1..54f28b9f02 100644
--- a/src/Symfony/Component/Messenger/Tests/Worker/StopWhenMemoryUsageIsExceededWorkerTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Worker/StopWhenMemoryUsageIsExceededWorkerTest.php
@@ -44,7 +44,7 @@ class StopWhenMemoryUsageIsExceededWorkerTest extends TestCase
         $this->assertSame($shouldStop, $decoratedWorker->isStopped());
     }
 
-    public function memoryProvider()
+    public function memoryProvider(): iterable
     {
         yield [2048, 1024, true];
         yield [1024, 1024, false];
diff --git a/src/Symfony/Component/Messenger/Tests/Worker/StopWhenMessageCountIsExceededWorkerTest.php b/src/Symfony/Component/Messenger/Tests/Worker/StopWhenMessageCountIsExceededWorkerTest.php
index f22d4524bf..5aae0db212 100644
--- a/src/Symfony/Component/Messenger/Tests/Worker/StopWhenMessageCountIsExceededWorkerTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Worker/StopWhenMessageCountIsExceededWorkerTest.php
@@ -23,7 +23,7 @@ class StopWhenMessageCountIsExceededWorkerTest extends TestCase
     /**
      * @dataProvider countProvider
      */
-    public function testWorkerStopsWhenMaximumCountExceeded($max, $shouldStop)
+    public function testWorkerStopsWhenMaximumCountExceeded(int $max, bool $shouldStop)
     {
         $handlerCalledTimes = 0;
         $handledCallback = function () use (&$handlerCalledTimes) {
@@ -44,7 +44,7 @@ class StopWhenMessageCountIsExceededWorkerTest extends TestCase
         $this->assertSame($shouldStop, $decoratedWorker->isStopped());
     }
 
-    public function countProvider()
+    public function countProvider(): iterable
     {
         yield [1, true];
         yield [2, true];
diff --git a/src/Symfony/Component/Messenger/Transport/AmqpExt/Connection.php b/src/Symfony/Component/Messenger/Transport/AmqpExt/Connection.php
index 63c1fafdd5..edb0be43f8 100644
--- a/src/Symfony/Component/Messenger/Transport/AmqpExt/Connection.php
+++ b/src/Symfony/Component/Messenger/Transport/AmqpExt/Connection.php
@@ -266,7 +266,7 @@ class Connection
      * which is the original exchange, resulting on it being put back into
      * the original queue.
      */
-    private function createDelayQueue(int $delay, ?string $routingKey)
+    private function createDelayQueue(int $delay, ?string $routingKey): \AMQPQueue
     {
         $queue = $this->amqpFactory->createQueue($this->channel());
         $queue->setName(str_replace(
diff --git a/src/Symfony/Component/Messenger/Transport/Doctrine/Connection.php b/src/Symfony/Component/Messenger/Transport/Doctrine/Connection.php
index 9ef44d6973..ea42b0a6fd 100644
--- a/src/Symfony/Component/Messenger/Transport/Doctrine/Connection.php
+++ b/src/Symfony/Component/Messenger/Transport/Doctrine/Connection.php
@@ -13,6 +13,7 @@ namespace Symfony\Component\Messenger\Transport\Doctrine;
 
 use Doctrine\DBAL\Connection as DBALConnection;
 use Doctrine\DBAL\DBALException;
+use Doctrine\DBAL\Driver\Statement;
 use Doctrine\DBAL\Exception\TableNotFoundException;
 use Doctrine\DBAL\Query\QueryBuilder;
 use Doctrine\DBAL\Schema\Schema;
@@ -63,7 +64,7 @@ class Connection
         return $this->configuration;
     }
 
-    public static function buildConfiguration($dsn, array $options = [])
+    public static function buildConfiguration(string $dsn, array $options = []): array
     {
         if (false === $components = parse_url($dsn)) {
             throw new InvalidArgumentException(sprintf('The given Doctrine Messenger DSN "%s" is invalid.', $dsn));
@@ -279,7 +280,7 @@ class Connection
             ->from($this->configuration['table_name'], 'm');
     }
 
-    private function executeQuery(string $sql, array $parameters = [])
+    private function executeQuery(string $sql, array $parameters = []): Statement
     {
         $stmt = null;
         try {
@@ -327,7 +328,7 @@ class Connection
         return $schema;
     }
 
-    public static function formatDateTime(\DateTimeInterface $dateTime)
+    public static function formatDateTime(\DateTimeInterface $dateTime): string
     {
         return $dateTime->format('Y-m-d\TH:i:s');
     }
diff --git a/src/Symfony/Component/Process/Process.php b/src/Symfony/Component/Process/Process.php
index bc92dcfeab..b71d4dadb5 100644
--- a/src/Symfony/Component/Process/Process.php
+++ b/src/Symfony/Component/Process/Process.php
@@ -248,7 +248,7 @@ class Process implements \IteratorAggregate
      *
      * @final
      */
-    public function mustRun(callable $callback = null, array $env = [])
+    public function mustRun(callable $callback = null, array $env = []): self
     {
         if (0 !== $this->run($callback, $env)) {
             throw new ProcessFailedException($this);
@@ -370,7 +370,7 @@ class Process implements \IteratorAggregate
      *
      * @final
      */
-    public function restart(callable $callback = null, array $env = [])
+    public function restart(callable $callback = null, array $env = []): self
     {
         if ($this->isRunning()) {
             throw new RuntimeException('Process is already running');
@@ -1549,7 +1549,7 @@ class Process implements \IteratorAggregate
         return true;
     }
 
-    private function prepareWindowsCommandLine(string $cmd, array &$env)
+    private function prepareWindowsCommandLine(string $cmd, array &$env): string
     {
         $uid = uniqid('', true);
         $varCount = 0;
@@ -1652,7 +1652,7 @@ class Process implements \IteratorAggregate
         }, $commandline);
     }
 
-    private function getDefaultEnv()
+    private function getDefaultEnv(): array
     {
         $env = [];
 
diff --git a/src/Symfony/Component/PropertyInfo/Extractor/ReflectionExtractor.php b/src/Symfony/Component/PropertyInfo/Extractor/ReflectionExtractor.php
index fa8b7a85f9..510bcf82a5 100644
--- a/src/Symfony/Component/PropertyInfo/Extractor/ReflectionExtractor.php
+++ b/src/Symfony/Component/PropertyInfo/Extractor/ReflectionExtractor.php
@@ -294,7 +294,7 @@ class ReflectionExtractor implements PropertyListExtractorInterface, PropertyTyp
         return null;
     }
 
-    private function extractFromDefaultValue(string $class, string $property)
+    private function extractFromDefaultValue(string $class, string $property): ?array
     {
         try {
             $reflectionClass = new \ReflectionClass($class);
diff --git a/src/Symfony/Component/Routing/Loader/Configurator/CollectionConfigurator.php b/src/Symfony/Component/Routing/Loader/Configurator/CollectionConfigurator.php
index 4e1e234774..79c1100a82 100644
--- a/src/Symfony/Component/Routing/Loader/Configurator/CollectionConfigurator.php
+++ b/src/Symfony/Component/Routing/Loader/Configurator/CollectionConfigurator.php
@@ -48,7 +48,7 @@ class CollectionConfigurator
     /**
      * Creates a sub-collection.
      */
-    final public function collection($name = ''): self
+    final public function collection(string $name = ''): self
     {
         return new self($this->collection, $this->name.$name, $this, $this->prefixes);
     }
diff --git a/src/Symfony/Component/Routing/Loader/XmlFileLoader.php b/src/Symfony/Component/Routing/Loader/XmlFileLoader.php
index 19c75ef12d..c371f74a80 100644
--- a/src/Symfony/Component/Routing/Loader/XmlFileLoader.php
+++ b/src/Symfony/Component/Routing/Loader/XmlFileLoader.php
@@ -409,7 +409,7 @@ class XmlFileLoader extends FileLoader
         }
     }
 
-    private function isElementValueNull(\DOMElement $element)
+    private function isElementValueNull(\DOMElement $element): bool
     {
         $namespaceUri = 'http://www.w3.org/2001/XMLSchema-instance';
 
diff --git a/src/Symfony/Component/Routing/Matcher/Dumper/CompiledUrlMatcherDumper.php b/src/Symfony/Component/Routing/Matcher/Dumper/CompiledUrlMatcherDumper.php
index 85d70ee792..f26ca2b3b5 100644
--- a/src/Symfony/Component/Routing/Matcher/Dumper/CompiledUrlMatcherDumper.php
+++ b/src/Symfony/Component/Routing/Matcher/Dumper/CompiledUrlMatcherDumper.php
@@ -443,7 +443,7 @@ EOF;
         ];
     }
 
-    private function getExpressionLanguage()
+    private function getExpressionLanguage(): ExpressionLanguage
     {
         if (null === $this->expressionLanguage) {
             if (!class_exists('Symfony\Component\ExpressionLanguage\ExpressionLanguage')) {
@@ -455,7 +455,7 @@ EOF;
         return $this->expressionLanguage;
     }
 
-    private function indent(string $code, int $level = 1)
+    private function indent(string $code, int $level = 1): string
     {
         return preg_replace('/^./m', str_repeat('    ', $level).'$0', $code);
     }
diff --git a/src/Symfony/Component/Routing/Matcher/Dumper/CompiledUrlMatcherTrait.php b/src/Symfony/Component/Routing/Matcher/Dumper/CompiledUrlMatcherTrait.php
index 0528a7b213..8ef76df8f8 100644
--- a/src/Symfony/Component/Routing/Matcher/Dumper/CompiledUrlMatcherTrait.php
+++ b/src/Symfony/Component/Routing/Matcher/Dumper/CompiledUrlMatcherTrait.php
@@ -32,7 +32,7 @@ trait CompiledUrlMatcherTrait
     private $dynamicRoutes = [];
     private $checkCondition;
 
-    public function match($pathinfo)
+    public function match($pathinfo): array
     {
         $allow = $allowSchemes = [];
         if ($ret = $this->doMatch($pathinfo, $allow, $allowSchemes)) {
diff --git a/src/Symfony/Component/Routing/Matcher/UrlMatcher.php b/src/Symfony/Component/Routing/Matcher/UrlMatcher.php
index d40deff709..f471ce4bc9 100644
--- a/src/Symfony/Component/Routing/Matcher/UrlMatcher.php
+++ b/src/Symfony/Component/Routing/Matcher/UrlMatcher.php
@@ -276,7 +276,7 @@ class UrlMatcher implements UrlMatcherInterface, RequestMatcherInterface
     /**
      * @internal
      */
-    protected function createRequest($pathinfo)
+    protected function createRequest(string $pathinfo): ?Request
     {
         if (!class_exists('Symfony\Component\HttpFoundation\Request')) {
             return null;
diff --git a/src/Symfony/Component/Routing/RouteCompiler.php b/src/Symfony/Component/Routing/RouteCompiler.php
index cfea642769..59f3a327e0 100644
--- a/src/Symfony/Component/Routing/RouteCompiler.php
+++ b/src/Symfony/Component/Routing/RouteCompiler.php
@@ -92,7 +92,7 @@ class RouteCompiler implements RouteCompilerInterface
         );
     }
 
-    private static function compilePattern(Route $route, $pattern, $isHost)
+    private static function compilePattern(Route $route, string $pattern, bool $isHost): array
     {
         $tokens = [];
         $variables = [];
diff --git a/src/Symfony/Component/Security/Core/Authentication/Token/AbstractToken.php b/src/Symfony/Component/Security/Core/Authentication/Token/AbstractToken.php
index 3a71bff2b0..d39e99c336 100644
--- a/src/Symfony/Component/Security/Core/Authentication/Token/AbstractToken.php
+++ b/src/Symfony/Component/Security/Core/Authentication/Token/AbstractToken.php
@@ -299,7 +299,7 @@ abstract class AbstractToken implements TokenInterface
         return sprintf('%s(user="%s", authenticated=%s, roles="%s")', $class, $this->getUsername(), json_encode($this->authenticated), implode(', ', $roles));
     }
 
-    private function hasUserChanged(UserInterface $user)
+    private function hasUserChanged(UserInterface $user): bool
     {
         if (!($this->user instanceof UserInterface)) {
             throw new \BadMethodCallException('Method "hasUserChanged" should be called when current user class is instance of "UserInterface".');
diff --git a/src/Symfony/Component/Security/Core/Authorization/Voter/ExpressionVoter.php b/src/Symfony/Component/Security/Core/Authorization/Voter/ExpressionVoter.php
index 0e1074b7c4..66867af96a 100644
--- a/src/Symfony/Component/Security/Core/Authorization/Voter/ExpressionVoter.php
+++ b/src/Symfony/Component/Security/Core/Authorization/Voter/ExpressionVoter.php
@@ -93,7 +93,7 @@ class ExpressionVoter implements VoterInterface
         return $result;
     }
 
-    private function getVariables(TokenInterface $token, $subject)
+    private function getVariables(TokenInterface $token, $subject): array
     {
         if (method_exists($token, 'getRoleNames')) {
             $roleNames = $token->getRoleNames();
diff --git a/src/Symfony/Component/Security/Core/Encoder/Argon2iPasswordEncoder.php b/src/Symfony/Component/Security/Core/Encoder/Argon2iPasswordEncoder.php
index a8174e6a20..db046b7f3d 100644
--- a/src/Symfony/Component/Security/Core/Encoder/Argon2iPasswordEncoder.php
+++ b/src/Symfony/Component/Security/Core/Encoder/Argon2iPasswordEncoder.php
@@ -102,12 +102,12 @@ class Argon2iPasswordEncoder extends BasePasswordEncoder implements SelfSaltingE
         throw new \LogicException('Argon2i algorithm is not supported. Please install the libsodium extension or upgrade to PHP 7.2+.');
     }
 
-    private function encodePasswordNative(string $raw)
+    private function encodePasswordNative(string $raw): string
     {
         return password_hash($raw, \PASSWORD_ARGON2I, $this->config);
     }
 
-    private function encodePasswordSodiumFunction(string $raw)
+    private function encodePasswordSodiumFunction(string $raw): string
     {
         $hash = sodium_crypto_pwhash_str(
             $raw,
@@ -119,7 +119,7 @@ class Argon2iPasswordEncoder extends BasePasswordEncoder implements SelfSaltingE
         return $hash;
     }
 
-    private function encodePasswordSodiumExtension(string $raw)
+    private function encodePasswordSodiumExtension(string $raw): string
     {
         $hash = \Sodium\crypto_pwhash_str(
             $raw,
diff --git a/src/Symfony/Component/Security/Core/Encoder/EncoderFactory.php b/src/Symfony/Component/Security/Core/Encoder/EncoderFactory.php
index 36177c20cc..c3121a241f 100644
--- a/src/Symfony/Component/Security/Core/Encoder/EncoderFactory.php
+++ b/src/Symfony/Component/Security/Core/Encoder/EncoderFactory.php
@@ -80,7 +80,7 @@ class EncoderFactory implements EncoderFactoryInterface
         return $reflection->newInstanceArgs($config['arguments']);
     }
 
-    private function getEncoderConfigFromAlgorithm(array $config)
+    private function getEncoderConfigFromAlgorithm(array $config): array
     {
         if ('auto' === $config['algorithm']) {
             $encoderChain = [];
diff --git a/src/Symfony/Component/Security/Core/User/User.php b/src/Symfony/Component/Security/Core/User/User.php
index 31196abc79..67c6a84ad3 100644
--- a/src/Symfony/Component/Security/Core/User/User.php
+++ b/src/Symfony/Component/Security/Core/User/User.php
@@ -53,7 +53,7 @@ final class User implements UserInterface, EquatableInterface, AdvancedUserInter
     /**
      * {@inheritdoc}
      */
-    public function getRoles()
+    public function getRoles(): array
     {
         return $this->roles;
     }
diff --git a/src/Symfony/Component/Security/Csrf/CsrfTokenManager.php b/src/Symfony/Component/Security/Csrf/CsrfTokenManager.php
index 450387a057..d9d57a4aa8 100644
--- a/src/Symfony/Component/Security/Csrf/CsrfTokenManager.php
+++ b/src/Symfony/Component/Security/Csrf/CsrfTokenManager.php
@@ -114,7 +114,7 @@ class CsrfTokenManager implements CsrfTokenManagerInterface
         return hash_equals($this->storage->getToken($namespacedId), $token->getValue());
     }
 
-    private function getNamespace()
+    private function getNamespace(): string
     {
         return \is_callable($ns = $this->namespace) ? $ns() : $ns;
     }
diff --git a/src/Symfony/Component/Security/Csrf/Tests/CsrfTokenManagerTest.php b/src/Symfony/Component/Security/Csrf/Tests/CsrfTokenManagerTest.php
index 4759cf579b..3a7993c501 100644
--- a/src/Symfony/Component/Security/Csrf/Tests/CsrfTokenManagerTest.php
+++ b/src/Symfony/Component/Security/Csrf/Tests/CsrfTokenManagerTest.php
@@ -202,7 +202,7 @@ class CsrfTokenManagerTest extends TestCase
         return $data;
     }
 
-    private function getGeneratorAndStorage()
+    private function getGeneratorAndStorage(): array
     {
         return [
             $this->getMockBuilder('Symfony\Component\Security\Csrf\TokenGenerator\TokenGeneratorInterface')->getMock(),
diff --git a/src/Symfony/Component/Security/Guard/Provider/GuardAuthenticationProvider.php b/src/Symfony/Component/Security/Guard/Provider/GuardAuthenticationProvider.php
index 3212973d96..bbf3066a79 100644
--- a/src/Symfony/Component/Security/Guard/Provider/GuardAuthenticationProvider.php
+++ b/src/Symfony/Component/Security/Guard/Provider/GuardAuthenticationProvider.php
@@ -99,7 +99,7 @@ class GuardAuthenticationProvider implements AuthenticationProviderInterface
         return $this->authenticateViaGuard($guardAuthenticator, $token);
     }
 
-    private function authenticateViaGuard(AuthenticatorInterface $guardAuthenticator, PreAuthenticationGuardToken $token)
+    private function authenticateViaGuard(AuthenticatorInterface $guardAuthenticator, PreAuthenticationGuardToken $token): GuardTokenInterface
     {
         // get the user from the GuardAuthenticator
         $user = $guardAuthenticator->getUser($token->getCredentials(), $this->userProvider);
@@ -134,7 +134,7 @@ class GuardAuthenticationProvider implements AuthenticationProviderInterface
         return $authenticatedToken;
     }
 
-    private function findOriginatingAuthenticator(PreAuthenticationGuardToken $token)
+    private function findOriginatingAuthenticator(PreAuthenticationGuardToken $token): ?AuthenticatorInterface
     {
         // find the *one* GuardAuthenticator that this token originated from
         foreach ($this->guardAuthenticators as $key => $guardAuthenticator) {
diff --git a/src/Symfony/Component/Security/Http/Firewall/AbstractAuthenticationListener.php b/src/Symfony/Component/Security/Http/Firewall/AbstractAuthenticationListener.php
index 642be92c06..fed7785a61 100644
--- a/src/Symfony/Component/Security/Http/Firewall/AbstractAuthenticationListener.php
+++ b/src/Symfony/Component/Security/Http/Firewall/AbstractAuthenticationListener.php
@@ -171,7 +171,7 @@ abstract class AbstractAuthenticationListener implements ListenerInterface
      */
     abstract protected function attemptAuthentication(Request $request);
 
-    private function onFailure(Request $request, AuthenticationException $failed)
+    private function onFailure(Request $request, AuthenticationException $failed): Response
     {
         if (null !== $this->logger) {
             $this->logger->error('Authentication request failed.', ['exception' => $failed]);
@@ -191,7 +191,7 @@ abstract class AbstractAuthenticationListener implements ListenerInterface
         return $response;
     }
 
-    private function onSuccess(Request $request, TokenInterface $token)
+    private function onSuccess(Request $request, TokenInterface $token): Response
     {
         if (null !== $this->logger) {
             $this->logger->info('User has been authenticated successfully.', ['username' => $token->getUsername()]);
diff --git a/src/Symfony/Component/Security/Http/Firewall/UsernamePasswordJsonAuthenticationListener.php b/src/Symfony/Component/Security/Http/Firewall/UsernamePasswordJsonAuthenticationListener.php
index 5393fbef10..851e160beb 100644
--- a/src/Symfony/Component/Security/Http/Firewall/UsernamePasswordJsonAuthenticationListener.php
+++ b/src/Symfony/Component/Security/Http/Firewall/UsernamePasswordJsonAuthenticationListener.php
@@ -168,7 +168,7 @@ class UsernamePasswordJsonAuthenticationListener implements ListenerInterface
         return $response;
     }
 
-    private function onFailure(Request $request, AuthenticationException $failed)
+    private function onFailure(Request $request, AuthenticationException $failed): Response
     {
         if (null !== $this->logger) {
             $this->logger->info('Authentication request failed.', ['exception' => $failed]);
diff --git a/src/Symfony/Component/Serializer/Mapping/Loader/YamlFileLoader.php b/src/Symfony/Component/Serializer/Mapping/Loader/YamlFileLoader.php
index d21531b2c7..8833394109 100644
--- a/src/Symfony/Component/Serializer/Mapping/Loader/YamlFileLoader.php
+++ b/src/Symfony/Component/Serializer/Mapping/Loader/YamlFileLoader.php
@@ -128,7 +128,7 @@ class YamlFileLoader extends FileLoader
         return array_keys($this->classes);
     }
 
-    private function getClassesFromYaml()
+    private function getClassesFromYaml(): array
     {
         if (!stream_is_local($this->file)) {
             throw new MappingException(sprintf('This is not a local file "%s".', $this->file));
diff --git a/src/Symfony/Component/Serializer/NameConverter/MetadataAwareNameConverter.php b/src/Symfony/Component/Serializer/NameConverter/MetadataAwareNameConverter.php
index 3565106f95..970395efe1 100644
--- a/src/Symfony/Component/Serializer/NameConverter/MetadataAwareNameConverter.php
+++ b/src/Symfony/Component/Serializer/NameConverter/MetadataAwareNameConverter.php
@@ -69,7 +69,7 @@ final class MetadataAwareNameConverter implements AdvancedNameConverterInterface
         return self::$denormalizeCache[$class][$propertyName] ?? $this->denormalizeFallback($propertyName, $class, $format, $context);
     }
 
-    private function getCacheValueForNormalization(string $propertyName, string $class)
+    private function getCacheValueForNormalization(string $propertyName, string $class): ?string
     {
         if (!$this->metadataFactory->hasMetadataFor($class)) {
             return null;
@@ -83,12 +83,12 @@ final class MetadataAwareNameConverter implements AdvancedNameConverterInterface
         return $attributesMetadata[$propertyName]->getSerializedName() ?? null;
     }
 
-    private function normalizeFallback(string $propertyName, string $class = null, string $format = null, array $context = [])
+    private function normalizeFallback(string $propertyName, string $class = null, string $format = null, array $context = []): string
     {
         return $this->fallbackNameConverter ? $this->fallbackNameConverter->normalize($propertyName, $class, $format, $context) : $propertyName;
     }
 
-    private function getCacheValueForDenormalization(string $propertyName, string $class)
+    private function getCacheValueForDenormalization(string $propertyName, string $class): ?string
     {
         if (!isset(self::$attributesMetadataCache[$class])) {
             self::$attributesMetadataCache[$class] = $this->getCacheValueForAttributesMetadata($class);
@@ -97,7 +97,7 @@ final class MetadataAwareNameConverter implements AdvancedNameConverterInterface
         return self::$attributesMetadataCache[$class][$propertyName] ?? null;
     }
 
-    private function denormalizeFallback(string $propertyName, string $class = null, string $format = null, array $context = [])
+    private function denormalizeFallback(string $propertyName, string $class = null, string $format = null, array $context = []): string
     {
         return $this->fallbackNameConverter ? $this->fallbackNameConverter->denormalize($propertyName, $class, $format, $context) : $propertyName;
     }
diff --git a/src/Symfony/Component/Serializer/Normalizer/DateIntervalNormalizer.php b/src/Symfony/Component/Serializer/Normalizer/DateIntervalNormalizer.php
index b65e8e2639..f4d0045d84 100644
--- a/src/Symfony/Component/Serializer/Normalizer/DateIntervalNormalizer.php
+++ b/src/Symfony/Component/Serializer/Normalizer/DateIntervalNormalizer.php
@@ -132,7 +132,7 @@ class DateIntervalNormalizer implements NormalizerInterface, DenormalizerInterfa
         return \DateInterval::class === $type;
     }
 
-    private function isISO8601(string $string)
+    private function isISO8601(string $string): bool
     {
         return preg_match('/^[\-+]?P(?=\w*(?:\d|%\w))(?:\d+Y|%[yY]Y)?(?:\d+M|%[mM]M)?(?:(?:\d+D|%[dD]D)|(?:\d+W|%[wW]W))?(?:T(?:\d+H|[hH]H)?(?:\d+M|[iI]M)?(?:\d+S|[sS]S)?)?$/', $string);
     }
diff --git a/src/Symfony/Component/Serializer/Normalizer/DateTimeNormalizer.php b/src/Symfony/Component/Serializer/Normalizer/DateTimeNormalizer.php
index 4731d8fbee..0607ec1d7f 100644
--- a/src/Symfony/Component/Serializer/Normalizer/DateTimeNormalizer.php
+++ b/src/Symfony/Component/Serializer/Normalizer/DateTimeNormalizer.php
@@ -154,7 +154,7 @@ class DateTimeNormalizer implements NormalizerInterface, DenormalizerInterface,
         return $formattedErrors;
     }
 
-    private function getTimezone(array $context)
+    private function getTimezone(array $context): ?\DateTimeZone
     {
         $dateTimeZone = $context[self::TIMEZONE_KEY] ?? $this->defaultContext[self::TIMEZONE_KEY];
 
diff --git a/src/Symfony/Component/Stopwatch/StopwatchEvent.php b/src/Symfony/Component/Stopwatch/StopwatchEvent.php
index cb1e333db9..351e0f1e13 100644
--- a/src/Symfony/Component/Stopwatch/StopwatchEvent.php
+++ b/src/Symfony/Component/Stopwatch/StopwatchEvent.php
@@ -225,7 +225,7 @@ class StopwatchEvent
      *
      * @throws \InvalidArgumentException When the raw time is not valid
      */
-    private function formatTime(float $time)
+    private function formatTime(float $time): float
     {
         return round($time, 1);
     }
diff --git a/src/Symfony/Component/Translation/Dumper/IcuResFileDumper.php b/src/Symfony/Component/Translation/Dumper/IcuResFileDumper.php
index e88a4e3079..829e0d0c25 100644
--- a/src/Symfony/Component/Translation/Dumper/IcuResFileDumper.php
+++ b/src/Symfony/Component/Translation/Dumper/IcuResFileDumper.php
@@ -82,7 +82,7 @@ class IcuResFileDumper extends FileDumper
         return $header.$root.$data;
     }
 
-    private function writePadding(string $data)
+    private function writePadding(string $data): ?string
     {
         $padding = \strlen($data) % 4;
 
diff --git a/src/Symfony/Component/Translation/Dumper/MoFileDumper.php b/src/Symfony/Component/Translation/Dumper/MoFileDumper.php
index 27be16d573..5a96dacec0 100644
--- a/src/Symfony/Component/Translation/Dumper/MoFileDumper.php
+++ b/src/Symfony/Component/Translation/Dumper/MoFileDumper.php
@@ -75,7 +75,7 @@ class MoFileDumper extends FileDumper
         return 'mo';
     }
 
-    private function writeLong($str)
+    private function writeLong($str): string
     {
         return pack('V*', $str);
     }
diff --git a/src/Symfony/Component/Translation/Dumper/PoFileDumper.php b/src/Symfony/Component/Translation/Dumper/PoFileDumper.php
index 70a97c7768..2cc9e8895d 100644
--- a/src/Symfony/Component/Translation/Dumper/PoFileDumper.php
+++ b/src/Symfony/Component/Translation/Dumper/PoFileDumper.php
@@ -119,7 +119,7 @@ EOF;
         return 'po';
     }
 
-    private function escape(string $str)
+    private function escape(string $str): string
     {
         return addcslashes($str, "\0..\37\42\134");
     }
diff --git a/src/Symfony/Component/Translation/Extractor/PhpStringTokenParser.php b/src/Symfony/Component/Translation/Extractor/PhpStringTokenParser.php
index 8a8ccb1f1a..4531e91222 100644
--- a/src/Symfony/Component/Translation/Extractor/PhpStringTokenParser.php
+++ b/src/Symfony/Component/Translation/Extractor/PhpStringTokenParser.php
@@ -106,7 +106,7 @@ class PhpStringTokenParser
         );
     }
 
-    private static function parseCallback($matches)
+    private static function parseCallback(array $matches): string
     {
         $str = $matches[1];
 
diff --git a/src/Symfony/Component/Translation/Interval.php b/src/Symfony/Component/Translation/Interval.php
index a0e484da86..1adc43fbd5 100644
--- a/src/Symfony/Component/Translation/Interval.php
+++ b/src/Symfony/Component/Translation/Interval.php
@@ -99,7 +99,7 @@ class Interval
 EOF;
     }
 
-    private static function convertNumber($number)
+    private static function convertNumber(string $number): float
     {
         if ('-Inf' === $number) {
             return log(0);
diff --git a/src/Symfony/Component/Translation/Loader/XliffFileLoader.php b/src/Symfony/Component/Translation/Loader/XliffFileLoader.php
index fdb3c84217..15a6ee5cfb 100644
--- a/src/Symfony/Component/Translation/Loader/XliffFileLoader.php
+++ b/src/Symfony/Component/Translation/Loader/XliffFileLoader.php
@@ -72,8 +72,6 @@ class XliffFileLoader implements LoaderInterface
 
     /**
      * Extract messages and metadata from DOMDocument into a MessageCatalogue.
-     *
-     * @param string $domain The domain
      */
     private function extractXliff1(\DOMDocument $dom, MessageCatalogue $catalogue, string $domain)
     {
diff --git a/src/Symfony/Component/Translation/Translator.php b/src/Symfony/Component/Translation/Translator.php
index f98698d136..bb36ee184c 100644
--- a/src/Symfony/Component/Translation/Translator.php
+++ b/src/Symfony/Component/Translation/Translator.php
@@ -410,7 +410,7 @@ EOF
         return $fallbackContent;
     }
 
-    private function getCatalogueCachePath(string $locale)
+    private function getCatalogueCachePath(string $locale): string
     {
         return $this->cacheDir.'/catalogue.'.$locale.'.'.strtr(substr(base64_encode(hash('sha256', serialize($this->fallbackLocales), true)), 0, 7), '/', '_').'.php';
     }
@@ -418,7 +418,7 @@ EOF
     /**
      * @internal
      */
-    protected function doLoadCatalogue($locale): void
+    protected function doLoadCatalogue(string $locale): void
     {
         $this->catalogues[$locale] = new MessageCatalogue($locale);