diff --git a/src/Symfony/Bridge/Doctrine/ContainerAwareEventManager.php b/src/Symfony/Bridge/Doctrine/ContainerAwareEventManager.php
index 0c1ad35f0b..67ba6abf3d 100644
--- a/src/Symfony/Bridge/Doctrine/ContainerAwareEventManager.php
+++ b/src/Symfony/Bridge/Doctrine/ContainerAwareEventManager.php
@@ -39,6 +39,8 @@ class ContainerAwareEventManager extends EventManager
 
     /**
      * {@inheritdoc}
+     *
+     * @return void
      */
     public function dispatchEvent($eventName, EventArgs $eventArgs = null)
     {
@@ -59,6 +61,8 @@ class ContainerAwareEventManager extends EventManager
 
     /**
      * {@inheritdoc}
+     *
+     * @return object[][]
      */
     public function getListeners($event = null)
     {
@@ -81,6 +85,8 @@ class ContainerAwareEventManager extends EventManager
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function hasListeners($event)
     {
@@ -89,6 +95,8 @@ class ContainerAwareEventManager extends EventManager
 
     /**
      * {@inheritdoc}
+     *
+     * @return void
      */
     public function addEventListener($events, $listener)
     {
@@ -109,6 +117,8 @@ class ContainerAwareEventManager extends EventManager
 
     /**
      * {@inheritdoc}
+     *
+     * @return void
      */
     public function removeEventListener($events, $listener)
     {
diff --git a/src/Symfony/Bridge/Doctrine/Logger/DbalLogger.php b/src/Symfony/Bridge/Doctrine/Logger/DbalLogger.php
index b64a82faa2..e3bd6e1319 100644
--- a/src/Symfony/Bridge/Doctrine/Logger/DbalLogger.php
+++ b/src/Symfony/Bridge/Doctrine/Logger/DbalLogger.php
@@ -34,6 +34,8 @@ class DbalLogger implements SQLLogger
 
     /**
      * {@inheritdoc}
+     *
+     * @return void
      */
     public function startQuery($sql, array $params = null, array $types = null)
     {
@@ -48,6 +50,8 @@ class DbalLogger implements SQLLogger
 
     /**
      * {@inheritdoc}
+     *
+     * @return void
      */
     public function stopQuery()
     {
diff --git a/src/Symfony/Bridge/Doctrine/ManagerRegistry.php b/src/Symfony/Bridge/Doctrine/ManagerRegistry.php
index ae481b5726..a81357a121 100644
--- a/src/Symfony/Bridge/Doctrine/ManagerRegistry.php
+++ b/src/Symfony/Bridge/Doctrine/ManagerRegistry.php
@@ -29,6 +29,8 @@ abstract class ManagerRegistry extends AbstractManagerRegistry
 
     /**
      * {@inheritdoc}
+     *
+     * @return object
      */
     protected function getService($name)
     {
@@ -37,6 +39,8 @@ abstract class ManagerRegistry extends AbstractManagerRegistry
 
     /**
      * {@inheritdoc}
+     *
+     * @return void
      */
     protected function resetService($name)
     {
diff --git a/src/Symfony/Bridge/Doctrine/Tests/Fixtures/Type/StringWrapperType.php b/src/Symfony/Bridge/Doctrine/Tests/Fixtures/Type/StringWrapperType.php
index 0af4271ba7..9e1cd621fe 100644
--- a/src/Symfony/Bridge/Doctrine/Tests/Fixtures/Type/StringWrapperType.php
+++ b/src/Symfony/Bridge/Doctrine/Tests/Fixtures/Type/StringWrapperType.php
@@ -34,6 +34,8 @@ class StringWrapperType extends StringType
 
     /**
      * {@inheritdoc}
+     *
+     * @return string
      */
     public function getName()
     {
diff --git a/src/Symfony/Bridge/Doctrine/Tests/PropertyInfo/Fixtures/DoctrineFooType.php b/src/Symfony/Bridge/Doctrine/Tests/PropertyInfo/Fixtures/DoctrineFooType.php
index 1b8cba50f3..68629066f5 100644
--- a/src/Symfony/Bridge/Doctrine/Tests/PropertyInfo/Fixtures/DoctrineFooType.php
+++ b/src/Symfony/Bridge/Doctrine/Tests/PropertyInfo/Fixtures/DoctrineFooType.php
@@ -27,6 +27,8 @@ class DoctrineFooType extends Type
 
     /**
      * {@inheritdoc}
+     *
+     * @return string
      */
     public function getName()
     {
@@ -35,6 +37,8 @@ class DoctrineFooType extends Type
 
     /**
      * {@inheritdoc}
+     *
+     * @return string
      */
     public function getSQLDeclaration(array $fieldDeclaration, AbstractPlatform $platform)
     {
@@ -76,6 +80,8 @@ class DoctrineFooType extends Type
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function requiresSQLCommentHint(AbstractPlatform $platform)
     {
diff --git a/src/Symfony/Bridge/Monolog/Handler/ServerLogHandler.php b/src/Symfony/Bridge/Monolog/Handler/ServerLogHandler.php
index 8f2b6b7749..b0d3676e9b 100644
--- a/src/Symfony/Bridge/Monolog/Handler/ServerLogHandler.php
+++ b/src/Symfony/Bridge/Monolog/Handler/ServerLogHandler.php
@@ -11,6 +11,7 @@
 
 namespace Symfony\Bridge\Monolog\Handler;
 
+use Monolog\Formatter\FormatterInterface;
 use Monolog\Handler\AbstractHandler;
 use Monolog\Logger;
 use Symfony\Bridge\Monolog\Formatter\VarDumperFormatter;
@@ -77,6 +78,8 @@ class ServerLogHandler extends AbstractHandler
 
     /**
      * {@inheritdoc}
+     *
+     * @return FormatterInterface
      */
     protected function getDefaultFormatter()
     {
diff --git a/src/Symfony/Bridge/Monolog/Handler/SwiftMailerHandler.php b/src/Symfony/Bridge/Monolog/Handler/SwiftMailerHandler.php
index d7bcb59796..85b3c9229e 100644
--- a/src/Symfony/Bridge/Monolog/Handler/SwiftMailerHandler.php
+++ b/src/Symfony/Bridge/Monolog/Handler/SwiftMailerHandler.php
@@ -63,6 +63,8 @@ class SwiftMailerHandler extends BaseSwiftMailerHandler
 
     /**
      * {@inheritdoc}
+     *
+     * @return void
      */
     public function reset()
     {
diff --git a/src/Symfony/Bridge/ProxyManager/LazyProxy/PhpDumper/LazyLoadingValueHolderGenerator.php b/src/Symfony/Bridge/ProxyManager/LazyProxy/PhpDumper/LazyLoadingValueHolderGenerator.php
index 545a736711..de81bcb291 100644
--- a/src/Symfony/Bridge/ProxyManager/LazyProxy/PhpDumper/LazyLoadingValueHolderGenerator.php
+++ b/src/Symfony/Bridge/ProxyManager/LazyProxy/PhpDumper/LazyLoadingValueHolderGenerator.php
@@ -29,6 +29,8 @@ class LazyLoadingValueHolderGenerator extends BaseGenerator
 
     /**
      * {@inheritdoc}
+     *
+     * @return void
      */
     public function generate(\ReflectionClass $originalClass, ClassGenerator $classGenerator)
     {
diff --git a/src/Symfony/Bridge/Twig/Extension/AssetExtension.php b/src/Symfony/Bridge/Twig/Extension/AssetExtension.php
index 2093553629..2b861a8ecf 100644
--- a/src/Symfony/Bridge/Twig/Extension/AssetExtension.php
+++ b/src/Symfony/Bridge/Twig/Extension/AssetExtension.php
@@ -31,6 +31,8 @@ class AssetExtension extends AbstractExtension
 
     /**
      * {@inheritdoc}
+     *
+     * @return TwigFunction[]
      */
     public function getFunctions()
     {
diff --git a/src/Symfony/Bridge/Twig/Extension/CodeExtension.php b/src/Symfony/Bridge/Twig/Extension/CodeExtension.php
index 7dc490a7e6..ed81d0561f 100644
--- a/src/Symfony/Bridge/Twig/Extension/CodeExtension.php
+++ b/src/Symfony/Bridge/Twig/Extension/CodeExtension.php
@@ -40,6 +40,8 @@ class CodeExtension extends AbstractExtension
 
     /**
      * {@inheritdoc}
+     *
+     * @return TwigFilter[]
      */
     public function getFilters()
     {
diff --git a/src/Symfony/Bridge/Twig/Extension/DumpExtension.php b/src/Symfony/Bridge/Twig/Extension/DumpExtension.php
index a4ad4a1bc4..c384a7c69b 100644
--- a/src/Symfony/Bridge/Twig/Extension/DumpExtension.php
+++ b/src/Symfony/Bridge/Twig/Extension/DumpExtension.php
@@ -17,6 +17,7 @@ use Symfony\Component\VarDumper\Dumper\HtmlDumper;
 use Twig\Environment;
 use Twig\Extension\AbstractExtension;
 use Twig\Template;
+use Twig\TokenParser\TokenParserInterface;
 use Twig\TwigFunction;
 
 /**
@@ -35,6 +36,9 @@ class DumpExtension extends AbstractExtension
         $this->dumper = $dumper;
     }
 
+    /**
+     * @return TwigFunction[]
+     */
     public function getFunctions()
     {
         return [
@@ -42,6 +46,9 @@ class DumpExtension extends AbstractExtension
         ];
     }
 
+    /**
+     * @return TokenParserInterface[]
+     */
     public function getTokenParsers()
     {
         return [new DumpTokenParser()];
diff --git a/src/Symfony/Bridge/Twig/Extension/ExpressionExtension.php b/src/Symfony/Bridge/Twig/Extension/ExpressionExtension.php
index 4ed79ea009..57320d291e 100644
--- a/src/Symfony/Bridge/Twig/Extension/ExpressionExtension.php
+++ b/src/Symfony/Bridge/Twig/Extension/ExpressionExtension.php
@@ -24,6 +24,8 @@ class ExpressionExtension extends AbstractExtension
 {
     /**
      * {@inheritdoc}
+     *
+     * @return TwigFunction[]
      */
     public function getFunctions()
     {
diff --git a/src/Symfony/Bridge/Twig/Extension/FormExtension.php b/src/Symfony/Bridge/Twig/Extension/FormExtension.php
index 909e20d58d..38dd348fe7 100644
--- a/src/Symfony/Bridge/Twig/Extension/FormExtension.php
+++ b/src/Symfony/Bridge/Twig/Extension/FormExtension.php
@@ -15,6 +15,7 @@ use Symfony\Bridge\Twig\TokenParser\FormThemeTokenParser;
 use Symfony\Component\Form\ChoiceList\View\ChoiceView;
 use Symfony\Component\Form\FormView;
 use Twig\Extension\AbstractExtension;
+use Twig\TokenParser\TokenParserInterface;
 use Twig\TwigFilter;
 use Twig\TwigFunction;
 use Twig\TwigTest;
@@ -29,6 +30,8 @@ class FormExtension extends AbstractExtension
 {
     /**
      * {@inheritdoc}
+     *
+     * @return TokenParserInterface[]
      */
     public function getTokenParsers()
     {
@@ -40,6 +43,8 @@ class FormExtension extends AbstractExtension
 
     /**
      * {@inheritdoc}
+     *
+     * @return TwigFunction[]
      */
     public function getFunctions()
     {
@@ -60,6 +65,8 @@ class FormExtension extends AbstractExtension
 
     /**
      * {@inheritdoc}
+     *
+     * @return TwigFilter[]
      */
     public function getFilters()
     {
@@ -71,6 +78,8 @@ class FormExtension extends AbstractExtension
 
     /**
      * {@inheritdoc}
+     *
+     * @return TwigTest[]
      */
     public function getTests()
     {
diff --git a/src/Symfony/Bridge/Twig/Extension/HttpFoundationExtension.php b/src/Symfony/Bridge/Twig/Extension/HttpFoundationExtension.php
index e03676d34f..fa0ad7ad2f 100644
--- a/src/Symfony/Bridge/Twig/Extension/HttpFoundationExtension.php
+++ b/src/Symfony/Bridge/Twig/Extension/HttpFoundationExtension.php
@@ -32,6 +32,8 @@ class HttpFoundationExtension extends AbstractExtension
 
     /**
      * {@inheritdoc}
+     *
+     * @return TwigFunction[]
      */
     public function getFunctions()
     {
diff --git a/src/Symfony/Bridge/Twig/Extension/HttpKernelExtension.php b/src/Symfony/Bridge/Twig/Extension/HttpKernelExtension.php
index ac9cacca2a..20f8b93e52 100644
--- a/src/Symfony/Bridge/Twig/Extension/HttpKernelExtension.php
+++ b/src/Symfony/Bridge/Twig/Extension/HttpKernelExtension.php
@@ -22,6 +22,9 @@ use Twig\TwigFunction;
  */
 class HttpKernelExtension extends AbstractExtension
 {
+    /**
+     * @return TwigFunction[]
+     */
     public function getFunctions()
     {
         return [
diff --git a/src/Symfony/Bridge/Twig/Extension/LogoutUrlExtension.php b/src/Symfony/Bridge/Twig/Extension/LogoutUrlExtension.php
index b409216b60..02c5ae838c 100644
--- a/src/Symfony/Bridge/Twig/Extension/LogoutUrlExtension.php
+++ b/src/Symfony/Bridge/Twig/Extension/LogoutUrlExtension.php
@@ -31,6 +31,8 @@ class LogoutUrlExtension extends AbstractExtension
 
     /**
      * {@inheritdoc}
+     *
+     * @return TwigFunction[]
      */
     public function getFunctions()
     {
diff --git a/src/Symfony/Bridge/Twig/Extension/RoutingExtension.php b/src/Symfony/Bridge/Twig/Extension/RoutingExtension.php
index f3df81c1ee..15d3536068 100644
--- a/src/Symfony/Bridge/Twig/Extension/RoutingExtension.php
+++ b/src/Symfony/Bridge/Twig/Extension/RoutingExtension.php
@@ -34,6 +34,8 @@ class RoutingExtension extends AbstractExtension
 
     /**
      * {@inheritdoc}
+     *
+     * @return TwigFunction[]
      */
     public function getFunctions()
     {
diff --git a/src/Symfony/Bridge/Twig/Extension/SecurityExtension.php b/src/Symfony/Bridge/Twig/Extension/SecurityExtension.php
index 3fa35e290a..41b2cf9e1e 100644
--- a/src/Symfony/Bridge/Twig/Extension/SecurityExtension.php
+++ b/src/Symfony/Bridge/Twig/Extension/SecurityExtension.php
@@ -50,6 +50,8 @@ class SecurityExtension extends AbstractExtension
 
     /**
      * {@inheritdoc}
+     *
+     * @return TwigFunction[]
      */
     public function getFunctions()
     {
diff --git a/src/Symfony/Bridge/Twig/Extension/StopwatchExtension.php b/src/Symfony/Bridge/Twig/Extension/StopwatchExtension.php
index 19dfed23e3..fb67ad92c6 100644
--- a/src/Symfony/Bridge/Twig/Extension/StopwatchExtension.php
+++ b/src/Symfony/Bridge/Twig/Extension/StopwatchExtension.php
@@ -14,6 +14,7 @@ namespace Symfony\Bridge\Twig\Extension;
 use Symfony\Bridge\Twig\TokenParser\StopwatchTokenParser;
 use Symfony\Component\Stopwatch\Stopwatch;
 use Twig\Extension\AbstractExtension;
+use Twig\TokenParser\TokenParserInterface;
 
 /**
  * Twig extension for the stopwatch helper.
@@ -36,6 +37,9 @@ class StopwatchExtension extends AbstractExtension
         return $this->stopwatch;
     }
 
+    /**
+     * @return TokenParserInterface[]
+     */
     public function getTokenParsers()
     {
         return [
diff --git a/src/Symfony/Bridge/Twig/Extension/TranslationExtension.php b/src/Symfony/Bridge/Twig/Extension/TranslationExtension.php
index b25fa47655..dbdb177eef 100644
--- a/src/Symfony/Bridge/Twig/Extension/TranslationExtension.php
+++ b/src/Symfony/Bridge/Twig/Extension/TranslationExtension.php
@@ -57,6 +57,8 @@ class TranslationExtension extends AbstractExtension
 
     /**
      * {@inheritdoc}
+     *
+     * @return TwigFilter[]
      */
     public function getFilters(): array
     {
@@ -83,6 +85,8 @@ class TranslationExtension extends AbstractExtension
 
     /**
      * {@inheritdoc}
+     *
+     * @return NodeVisitorInterface[]
      */
     public function getNodeVisitors(): array
     {
diff --git a/src/Symfony/Bridge/Twig/Extension/WebLinkExtension.php b/src/Symfony/Bridge/Twig/Extension/WebLinkExtension.php
index 116c5fbbb8..1f77c26762 100644
--- a/src/Symfony/Bridge/Twig/Extension/WebLinkExtension.php
+++ b/src/Symfony/Bridge/Twig/Extension/WebLinkExtension.php
@@ -33,6 +33,8 @@ class WebLinkExtension extends AbstractExtension
 
     /**
      * {@inheritdoc}
+     *
+     * @return TwigFunction[]
      */
     public function getFunctions()
     {
diff --git a/src/Symfony/Bridge/Twig/Extension/WorkflowExtension.php b/src/Symfony/Bridge/Twig/Extension/WorkflowExtension.php
index 14a5ec4258..6e075d7035 100644
--- a/src/Symfony/Bridge/Twig/Extension/WorkflowExtension.php
+++ b/src/Symfony/Bridge/Twig/Extension/WorkflowExtension.php
@@ -31,6 +31,9 @@ class WorkflowExtension extends AbstractExtension
         $this->workflowRegistry = $workflowRegistry;
     }
 
+    /**
+     * @return TwigFunction[]
+     */
     public function getFunctions()
     {
         return [
diff --git a/src/Symfony/Bridge/Twig/Extension/YamlExtension.php b/src/Symfony/Bridge/Twig/Extension/YamlExtension.php
index 1c543137a1..700148361e 100644
--- a/src/Symfony/Bridge/Twig/Extension/YamlExtension.php
+++ b/src/Symfony/Bridge/Twig/Extension/YamlExtension.php
@@ -25,6 +25,8 @@ class YamlExtension extends AbstractExtension
 {
     /**
      * {@inheritdoc}
+     *
+     * @return TwigFilter[]
      */
     public function getFilters()
     {
diff --git a/src/Symfony/Bridge/Twig/NodeVisitor/TranslationDefaultDomainNodeVisitor.php b/src/Symfony/Bridge/Twig/NodeVisitor/TranslationDefaultDomainNodeVisitor.php
index d98b87b2b3..bcc88f1933 100644
--- a/src/Symfony/Bridge/Twig/NodeVisitor/TranslationDefaultDomainNodeVisitor.php
+++ b/src/Symfony/Bridge/Twig/NodeVisitor/TranslationDefaultDomainNodeVisitor.php
@@ -39,6 +39,8 @@ class TranslationDefaultDomainNodeVisitor extends AbstractNodeVisitor
 
     /**
      * {@inheritdoc}
+     *
+     * @return Node
      */
     protected function doEnterNode(Node $node, Environment $env)
     {
@@ -91,6 +93,8 @@ class TranslationDefaultDomainNodeVisitor extends AbstractNodeVisitor
 
     /**
      * {@inheritdoc}
+     *
+     * @return Node|null
      */
     protected function doLeaveNode(Node $node, Environment $env)
     {
diff --git a/src/Symfony/Bridge/Twig/NodeVisitor/TranslationNodeVisitor.php b/src/Symfony/Bridge/Twig/NodeVisitor/TranslationNodeVisitor.php
index 3da4141cdd..2d3e1d1ba1 100644
--- a/src/Symfony/Bridge/Twig/NodeVisitor/TranslationNodeVisitor.php
+++ b/src/Symfony/Bridge/Twig/NodeVisitor/TranslationNodeVisitor.php
@@ -49,6 +49,8 @@ class TranslationNodeVisitor extends AbstractNodeVisitor
 
     /**
      * {@inheritdoc}
+     *
+     * @return Node
      */
     protected function doEnterNode(Node $node, Environment $env)
     {
@@ -89,6 +91,8 @@ class TranslationNodeVisitor extends AbstractNodeVisitor
 
     /**
      * {@inheritdoc}
+     *
+     * @return Node|null
      */
     protected function doLeaveNode(Node $node, Environment $env)
     {
diff --git a/src/Symfony/Bridge/Twig/TokenParser/DumpTokenParser.php b/src/Symfony/Bridge/Twig/TokenParser/DumpTokenParser.php
index a4d7d6f690..1a7326d555 100644
--- a/src/Symfony/Bridge/Twig/TokenParser/DumpTokenParser.php
+++ b/src/Symfony/Bridge/Twig/TokenParser/DumpTokenParser.php
@@ -12,6 +12,7 @@
 namespace Symfony\Bridge\Twig\TokenParser;
 
 use Symfony\Bridge\Twig\Node\DumpNode;
+use Twig\Node\Node;
 use Twig\Token;
 use Twig\TokenParser\AbstractTokenParser;
 
@@ -30,6 +31,8 @@ class DumpTokenParser extends AbstractTokenParser
 {
     /**
      * {@inheritdoc}
+     *
+     * @return Node
      */
     public function parse(Token $token)
     {
@@ -44,6 +47,8 @@ class DumpTokenParser extends AbstractTokenParser
 
     /**
      * {@inheritdoc}
+     *
+     * @return string
      */
     public function getTag()
     {
diff --git a/src/Symfony/Bridge/Twig/TokenParser/StopwatchTokenParser.php b/src/Symfony/Bridge/Twig/TokenParser/StopwatchTokenParser.php
index 54dcf6d391..2c306b1a86 100644
--- a/src/Symfony/Bridge/Twig/TokenParser/StopwatchTokenParser.php
+++ b/src/Symfony/Bridge/Twig/TokenParser/StopwatchTokenParser.php
@@ -13,6 +13,7 @@ namespace Symfony\Bridge\Twig\TokenParser;
 
 use Symfony\Bridge\Twig\Node\StopwatchNode;
 use Twig\Node\Expression\AssignNameExpression;
+use Twig\Node\Node;
 use Twig\Token;
 use Twig\TokenParser\AbstractTokenParser;
 
@@ -30,6 +31,9 @@ class StopwatchTokenParser extends AbstractTokenParser
         $this->stopwatchIsAvailable = $stopwatchIsAvailable;
     }
 
+    /**
+     * @return Node
+     */
     public function parse(Token $token)
     {
         $lineno = $token->getLine();
@@ -56,6 +60,9 @@ class StopwatchTokenParser extends AbstractTokenParser
         return $token->test('endstopwatch');
     }
 
+    /**
+     * @return string
+     */
     public function getTag()
     {
         return 'stopwatch';
diff --git a/src/Symfony/Bridge/Twig/TokenParser/TransDefaultDomainTokenParser.php b/src/Symfony/Bridge/Twig/TokenParser/TransDefaultDomainTokenParser.php
index 72fbda77b8..1f03c6ab89 100644
--- a/src/Symfony/Bridge/Twig/TokenParser/TransDefaultDomainTokenParser.php
+++ b/src/Symfony/Bridge/Twig/TokenParser/TransDefaultDomainTokenParser.php
@@ -12,6 +12,7 @@
 namespace Symfony\Bridge\Twig\TokenParser;
 
 use Symfony\Bridge\Twig\Node\TransDefaultDomainNode;
+use Twig\Node\Node;
 use Twig\Token;
 use Twig\TokenParser\AbstractTokenParser;
 
@@ -24,6 +25,8 @@ class TransDefaultDomainTokenParser extends AbstractTokenParser
 {
     /**
      * {@inheritdoc}
+     *
+     * @return Node
      */
     public function parse(Token $token)
     {
@@ -36,6 +39,8 @@ class TransDefaultDomainTokenParser extends AbstractTokenParser
 
     /**
      * {@inheritdoc}
+     *
+     * @return string
      */
     public function getTag()
     {
diff --git a/src/Symfony/Bridge/Twig/TokenParser/TransTokenParser.php b/src/Symfony/Bridge/Twig/TokenParser/TransTokenParser.php
index 44f10cb6af..1d60eda34a 100644
--- a/src/Symfony/Bridge/Twig/TokenParser/TransTokenParser.php
+++ b/src/Symfony/Bridge/Twig/TokenParser/TransTokenParser.php
@@ -15,6 +15,7 @@ use Symfony\Bridge\Twig\Node\TransNode;
 use Twig\Error\SyntaxError;
 use Twig\Node\Expression\AbstractExpression;
 use Twig\Node\Expression\ArrayExpression;
+use Twig\Node\Node;
 use Twig\Node\TextNode;
 use Twig\Token;
 use Twig\TokenParser\AbstractTokenParser;
@@ -28,6 +29,8 @@ class TransTokenParser extends AbstractTokenParser
 {
     /**
      * {@inheritdoc}
+     *
+     * @return Node
      */
     public function parse(Token $token)
     {
@@ -86,6 +89,8 @@ class TransTokenParser extends AbstractTokenParser
 
     /**
      * {@inheritdoc}
+     *
+     * @return string
      */
     public function getTag()
     {
diff --git a/src/Symfony/Bundle/FrameworkBundle/Controller/AbstractController.php b/src/Symfony/Bundle/FrameworkBundle/Controller/AbstractController.php
index d18665e1fa..68fc1fff56 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Controller/AbstractController.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Controller/AbstractController.php
@@ -364,12 +364,12 @@ abstract class AbstractController implements ServiceSubscriberInterface
         }
 
         if (null === $token = $this->container->get('security.token_storage')->getToken()) {
-            return;
+            return null;
         }
 
         if (!\is_object($user = $token->getUser())) {
             // e.g. anonymous authentication
-            return;
+            return null;
         }
 
         return $user;
diff --git a/src/Symfony/Bundle/WebProfilerBundle/Twig/WebProfilerExtension.php b/src/Symfony/Bundle/WebProfilerBundle/Twig/WebProfilerExtension.php
index d5689701f4..4c123c1d44 100644
--- a/src/Symfony/Bundle/WebProfilerBundle/Twig/WebProfilerExtension.php
+++ b/src/Symfony/Bundle/WebProfilerBundle/Twig/WebProfilerExtension.php
@@ -62,6 +62,8 @@ class WebProfilerExtension extends ProfilerExtension
 
     /**
      * {@inheritdoc}
+     *
+     * @return TwigFunction[]
      */
     public function getFunctions()
     {
diff --git a/src/Symfony/Component/BrowserKit/AbstractBrowser.php b/src/Symfony/Component/BrowserKit/AbstractBrowser.php
index 8cf0770347..e468c4313d 100644
--- a/src/Symfony/Component/BrowserKit/AbstractBrowser.php
+++ b/src/Symfony/Component/BrowserKit/AbstractBrowser.php
@@ -510,7 +510,7 @@ abstract class AbstractBrowser
     protected function createCrawlerFromContent(string $uri, string $content, string $type)
     {
         if (!class_exists('Symfony\Component\DomCrawler\Crawler')) {
-            return;
+            return null;
         }
 
         $crawler = new Crawler(null, $uri);
diff --git a/src/Symfony/Component/Cache/Adapter/AbstractAdapter.php b/src/Symfony/Component/Cache/Adapter/AbstractAdapter.php
index 2f91434575..0360b71b0b 100644
--- a/src/Symfony/Component/Cache/Adapter/AbstractAdapter.php
+++ b/src/Symfony/Component/Cache/Adapter/AbstractAdapter.php
@@ -136,6 +136,8 @@ abstract class AbstractAdapter implements AdapterInterface, CacheInterface, Logg
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function commit()
     {
diff --git a/src/Symfony/Component/Cache/Adapter/AbstractTagAwareAdapter.php b/src/Symfony/Component/Cache/Adapter/AbstractTagAwareAdapter.php
index 93f1105bc7..12c1dbcd15 100644
--- a/src/Symfony/Component/Cache/Adapter/AbstractTagAwareAdapter.php
+++ b/src/Symfony/Component/Cache/Adapter/AbstractTagAwareAdapter.php
@@ -151,6 +151,8 @@ abstract class AbstractTagAwareAdapter implements TagAwareAdapterInterface, TagA
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function commit()
     {
@@ -213,6 +215,8 @@ abstract class AbstractTagAwareAdapter implements TagAwareAdapterInterface, TagA
      * {@inheritdoc}
      *
      * Overloaded in order to deal with tags for adjusted doDelete() signature.
+     *
+     * @return bool
      */
     public function deleteItems(array $keys)
     {
diff --git a/src/Symfony/Component/Cache/Adapter/AdapterInterface.php b/src/Symfony/Component/Cache/Adapter/AdapterInterface.php
index 77efe14359..99c5cd1f9f 100644
--- a/src/Symfony/Component/Cache/Adapter/AdapterInterface.php
+++ b/src/Symfony/Component/Cache/Adapter/AdapterInterface.php
@@ -37,6 +37,8 @@ interface AdapterInterface extends CacheItemPoolInterface
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function clear(string $prefix = '');
 }
diff --git a/src/Symfony/Component/Cache/Adapter/ArrayAdapter.php b/src/Symfony/Component/Cache/Adapter/ArrayAdapter.php
index b7d7151121..05920d01a9 100644
--- a/src/Symfony/Component/Cache/Adapter/ArrayAdapter.php
+++ b/src/Symfony/Component/Cache/Adapter/ArrayAdapter.php
@@ -78,6 +78,8 @@ class ArrayAdapter implements AdapterInterface, CacheInterface, LoggerAwareInter
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function hasItem($key)
     {
@@ -120,6 +122,8 @@ class ArrayAdapter implements AdapterInterface, CacheInterface, LoggerAwareInter
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function deleteItem($key)
     {
@@ -133,6 +137,8 @@ class ArrayAdapter implements AdapterInterface, CacheInterface, LoggerAwareInter
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function deleteItems(array $keys)
     {
@@ -145,6 +151,8 @@ class ArrayAdapter implements AdapterInterface, CacheInterface, LoggerAwareInter
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function save(CacheItemInterface $item)
     {
@@ -176,6 +184,8 @@ class ArrayAdapter implements AdapterInterface, CacheInterface, LoggerAwareInter
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function saveDeferred(CacheItemInterface $item)
     {
@@ -184,6 +194,8 @@ class ArrayAdapter implements AdapterInterface, CacheInterface, LoggerAwareInter
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function commit()
     {
@@ -192,6 +204,8 @@ class ArrayAdapter implements AdapterInterface, CacheInterface, LoggerAwareInter
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function clear(string $prefix = '')
     {
diff --git a/src/Symfony/Component/Cache/Adapter/ChainAdapter.php b/src/Symfony/Component/Cache/Adapter/ChainAdapter.php
index 1746361444..78a65e9d6d 100644
--- a/src/Symfony/Component/Cache/Adapter/ChainAdapter.php
+++ b/src/Symfony/Component/Cache/Adapter/ChainAdapter.php
@@ -178,6 +178,8 @@ class ChainAdapter implements AdapterInterface, CacheInterface, PruneableInterfa
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function hasItem($key)
     {
@@ -192,6 +194,8 @@ class ChainAdapter implements AdapterInterface, CacheInterface, PruneableInterfa
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function clear(string $prefix = '')
     {
@@ -211,6 +215,8 @@ class ChainAdapter implements AdapterInterface, CacheInterface, PruneableInterfa
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function deleteItem($key)
     {
@@ -226,6 +232,8 @@ class ChainAdapter implements AdapterInterface, CacheInterface, PruneableInterfa
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function deleteItems(array $keys)
     {
@@ -241,6 +249,8 @@ class ChainAdapter implements AdapterInterface, CacheInterface, PruneableInterfa
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function save(CacheItemInterface $item)
     {
@@ -256,6 +266,8 @@ class ChainAdapter implements AdapterInterface, CacheInterface, PruneableInterfa
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function saveDeferred(CacheItemInterface $item)
     {
@@ -271,6 +283,8 @@ class ChainAdapter implements AdapterInterface, CacheInterface, PruneableInterfa
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function commit()
     {
diff --git a/src/Symfony/Component/Cache/Adapter/NullAdapter.php b/src/Symfony/Component/Cache/Adapter/NullAdapter.php
index 7839d5b644..44778d787b 100644
--- a/src/Symfony/Component/Cache/Adapter/NullAdapter.php
+++ b/src/Symfony/Component/Cache/Adapter/NullAdapter.php
@@ -67,6 +67,8 @@ class NullAdapter implements AdapterInterface, CacheInterface
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function hasItem($key)
     {
@@ -75,6 +77,8 @@ class NullAdapter implements AdapterInterface, CacheInterface
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function clear(string $prefix = '')
     {
@@ -83,6 +87,8 @@ class NullAdapter implements AdapterInterface, CacheInterface
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function deleteItem($key)
     {
@@ -91,6 +97,8 @@ class NullAdapter implements AdapterInterface, CacheInterface
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function deleteItems(array $keys)
     {
@@ -99,6 +107,8 @@ class NullAdapter implements AdapterInterface, CacheInterface
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function save(CacheItemInterface $item)
     {
@@ -107,6 +117,8 @@ class NullAdapter implements AdapterInterface, CacheInterface
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function saveDeferred(CacheItemInterface $item)
     {
@@ -115,6 +127,8 @@ class NullAdapter implements AdapterInterface, CacheInterface
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function commit()
     {
diff --git a/src/Symfony/Component/Cache/Adapter/PhpArrayAdapter.php b/src/Symfony/Component/Cache/Adapter/PhpArrayAdapter.php
index 4cd7342312..45c9cde144 100644
--- a/src/Symfony/Component/Cache/Adapter/PhpArrayAdapter.php
+++ b/src/Symfony/Component/Cache/Adapter/PhpArrayAdapter.php
@@ -169,6 +169,8 @@ class PhpArrayAdapter implements AdapterInterface, CacheInterface, PruneableInte
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function hasItem($key)
     {
@@ -184,6 +186,8 @@ class PhpArrayAdapter implements AdapterInterface, CacheInterface, PruneableInte
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function deleteItem($key)
     {
@@ -199,6 +203,8 @@ class PhpArrayAdapter implements AdapterInterface, CacheInterface, PruneableInte
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function deleteItems(array $keys)
     {
@@ -229,6 +235,8 @@ class PhpArrayAdapter implements AdapterInterface, CacheInterface, PruneableInte
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function save(CacheItemInterface $item)
     {
@@ -241,6 +249,8 @@ class PhpArrayAdapter implements AdapterInterface, CacheInterface, PruneableInte
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function saveDeferred(CacheItemInterface $item)
     {
@@ -253,6 +263,8 @@ class PhpArrayAdapter implements AdapterInterface, CacheInterface, PruneableInte
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function commit()
     {
@@ -261,6 +273,8 @@ class PhpArrayAdapter implements AdapterInterface, CacheInterface, PruneableInte
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function clear(string $prefix = '')
     {
diff --git a/src/Symfony/Component/Cache/Adapter/ProxyAdapter.php b/src/Symfony/Component/Cache/Adapter/ProxyAdapter.php
index c0a2e46aea..5e1b0276fc 100644
--- a/src/Symfony/Component/Cache/Adapter/ProxyAdapter.php
+++ b/src/Symfony/Component/Cache/Adapter/ProxyAdapter.php
@@ -139,6 +139,8 @@ class ProxyAdapter implements AdapterInterface, CacheInterface, PruneableInterfa
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function hasItem($key)
     {
@@ -147,6 +149,8 @@ class ProxyAdapter implements AdapterInterface, CacheInterface, PruneableInterfa
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function clear(string $prefix = '')
     {
@@ -159,6 +163,8 @@ class ProxyAdapter implements AdapterInterface, CacheInterface, PruneableInterfa
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function deleteItem($key)
     {
@@ -167,6 +173,8 @@ class ProxyAdapter implements AdapterInterface, CacheInterface, PruneableInterfa
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function deleteItems(array $keys)
     {
@@ -181,6 +189,8 @@ class ProxyAdapter implements AdapterInterface, CacheInterface, PruneableInterfa
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function save(CacheItemInterface $item)
     {
@@ -189,6 +199,8 @@ class ProxyAdapter implements AdapterInterface, CacheInterface, PruneableInterfa
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function saveDeferred(CacheItemInterface $item)
     {
@@ -197,6 +209,8 @@ class ProxyAdapter implements AdapterInterface, CacheInterface, PruneableInterfa
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function commit()
     {
diff --git a/src/Symfony/Component/Cache/Adapter/TagAwareAdapter.php b/src/Symfony/Component/Cache/Adapter/TagAwareAdapter.php
index 338ab345ef..00543d3b19 100644
--- a/src/Symfony/Component/Cache/Adapter/TagAwareAdapter.php
+++ b/src/Symfony/Component/Cache/Adapter/TagAwareAdapter.php
@@ -151,6 +151,8 @@ class TagAwareAdapter implements TagAwareAdapterInterface, TagAwareCacheInterfac
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function hasItem($key)
     {
@@ -213,6 +215,8 @@ class TagAwareAdapter implements TagAwareAdapterInterface, TagAwareCacheInterfac
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function clear(string $prefix = '')
     {
@@ -235,6 +239,8 @@ class TagAwareAdapter implements TagAwareAdapterInterface, TagAwareCacheInterfac
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function deleteItem($key)
     {
@@ -243,6 +249,8 @@ class TagAwareAdapter implements TagAwareAdapterInterface, TagAwareCacheInterfac
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function deleteItems(array $keys)
     {
@@ -257,6 +265,8 @@ class TagAwareAdapter implements TagAwareAdapterInterface, TagAwareCacheInterfac
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function save(CacheItemInterface $item)
     {
@@ -270,6 +280,8 @@ class TagAwareAdapter implements TagAwareAdapterInterface, TagAwareCacheInterfac
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function saveDeferred(CacheItemInterface $item)
     {
@@ -283,6 +295,8 @@ class TagAwareAdapter implements TagAwareAdapterInterface, TagAwareCacheInterfac
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function commit()
     {
diff --git a/src/Symfony/Component/Cache/Adapter/TraceableAdapter.php b/src/Symfony/Component/Cache/Adapter/TraceableAdapter.php
index 7371fcb1e7..16d819ee46 100644
--- a/src/Symfony/Component/Cache/Adapter/TraceableAdapter.php
+++ b/src/Symfony/Component/Cache/Adapter/TraceableAdapter.php
@@ -89,6 +89,8 @@ class TraceableAdapter implements AdapterInterface, CacheInterface, PruneableInt
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function hasItem($key)
     {
@@ -102,6 +104,8 @@ class TraceableAdapter implements AdapterInterface, CacheInterface, PruneableInt
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function deleteItem($key)
     {
@@ -115,6 +119,8 @@ class TraceableAdapter implements AdapterInterface, CacheInterface, PruneableInt
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function save(CacheItemInterface $item)
     {
@@ -128,6 +134,8 @@ class TraceableAdapter implements AdapterInterface, CacheInterface, PruneableInt
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function saveDeferred(CacheItemInterface $item)
     {
@@ -167,6 +175,8 @@ class TraceableAdapter implements AdapterInterface, CacheInterface, PruneableInt
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function clear(string $prefix = '')
     {
@@ -184,6 +194,8 @@ class TraceableAdapter implements AdapterInterface, CacheInterface, PruneableInt
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function deleteItems(array $keys)
     {
@@ -198,6 +210,8 @@ class TraceableAdapter implements AdapterInterface, CacheInterface, PruneableInt
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function commit()
     {
diff --git a/src/Symfony/Component/Cache/CacheItem.php b/src/Symfony/Component/Cache/CacheItem.php
index c7f5e00e42..056afbdffd 100644
--- a/src/Symfony/Component/Cache/CacheItem.php
+++ b/src/Symfony/Component/Cache/CacheItem.php
@@ -60,6 +60,8 @@ final class CacheItem implements ItemInterface
 
     /**
      * {@inheritdoc}
+     *
+     * @return static
      */
     public function set($value)
     {
@@ -70,6 +72,8 @@ final class CacheItem implements ItemInterface
 
     /**
      * {@inheritdoc}
+     *
+     * @return static
      */
     public function expiresAt($expiration)
     {
@@ -86,6 +90,8 @@ final class CacheItem implements ItemInterface
 
     /**
      * {@inheritdoc}
+     *
+     * @return static
      */
     public function expiresAfter($time)
     {
diff --git a/src/Symfony/Component/Cache/DoctrineProvider.php b/src/Symfony/Component/Cache/DoctrineProvider.php
index 3cc186962e..ee3102617e 100644
--- a/src/Symfony/Component/Cache/DoctrineProvider.php
+++ b/src/Symfony/Component/Cache/DoctrineProvider.php
@@ -58,6 +58,8 @@ class DoctrineProvider extends CacheProvider implements PruneableInterface, Rese
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     protected function doContains($id)
     {
@@ -66,6 +68,8 @@ class DoctrineProvider extends CacheProvider implements PruneableInterface, Rese
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     protected function doSave($id, $data, $lifeTime = 0)
     {
@@ -80,6 +84,8 @@ class DoctrineProvider extends CacheProvider implements PruneableInterface, Rese
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     protected function doDelete($id)
     {
@@ -88,6 +94,8 @@ class DoctrineProvider extends CacheProvider implements PruneableInterface, Rese
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     protected function doFlush()
     {
@@ -96,6 +104,8 @@ class DoctrineProvider extends CacheProvider implements PruneableInterface, Rese
 
     /**
      * {@inheritdoc}
+     *
+     * @return array|null
      */
     protected function doGetStats()
     {
diff --git a/src/Symfony/Component/Cache/Psr16Cache.php b/src/Symfony/Component/Cache/Psr16Cache.php
index d67615eb77..36d77a71a0 100644
--- a/src/Symfony/Component/Cache/Psr16Cache.php
+++ b/src/Symfony/Component/Cache/Psr16Cache.php
@@ -85,6 +85,8 @@ class Psr16Cache implements CacheInterface, PruneableInterface, ResettableInterf
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function set($key, $value, $ttl = null)
     {
@@ -108,6 +110,8 @@ class Psr16Cache implements CacheInterface, PruneableInterface, ResettableInterf
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function delete($key)
     {
@@ -122,6 +126,8 @@ class Psr16Cache implements CacheInterface, PruneableInterface, ResettableInterf
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function clear()
     {
@@ -130,6 +136,8 @@ class Psr16Cache implements CacheInterface, PruneableInterface, ResettableInterf
 
     /**
      * {@inheritdoc}
+     *
+     * @return iterable
      */
     public function getMultiple($keys, $default = null)
     {
@@ -178,6 +186,8 @@ class Psr16Cache implements CacheInterface, PruneableInterface, ResettableInterf
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function setMultiple($values, $ttl = null)
     {
@@ -229,6 +239,8 @@ class Psr16Cache implements CacheInterface, PruneableInterface, ResettableInterf
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function deleteMultiple($keys)
     {
@@ -249,6 +261,8 @@ class Psr16Cache implements CacheInterface, PruneableInterface, ResettableInterf
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function has($key)
     {
diff --git a/src/Symfony/Component/Cache/Tests/Adapter/ProxyAdapterTest.php b/src/Symfony/Component/Cache/Tests/Adapter/ProxyAdapterTest.php
index 24f92ca9a5..13e5aedad0 100644
--- a/src/Symfony/Component/Cache/Tests/Adapter/ProxyAdapterTest.php
+++ b/src/Symfony/Component/Cache/Tests/Adapter/ProxyAdapterTest.php
@@ -12,6 +12,7 @@
 namespace Symfony\Component\Cache\Tests\Adapter;
 
 use Psr\Cache\CacheItemInterface;
+use Psr\Cache\CacheItemPoolInterface;
 use Symfony\Component\Cache\Adapter\ArrayAdapter;
 use Symfony\Component\Cache\Adapter\FilesystemAdapter;
 use Symfony\Component\Cache\Adapter\ProxyAdapter;
@@ -28,6 +29,9 @@ class ProxyAdapterTest extends AdapterTestCase
         'testPrune' => 'ProxyAdapter just proxies',
     ];
 
+    /**
+     * @return CacheItemPoolInterface
+     */
     public function createCachePool($defaultLifetime = 0, $testMethod = null)
     {
         if ('testGetMetadata' === $testMethod) {
diff --git a/src/Symfony/Component/Cache/Tests/Fixtures/ArrayCache.php b/src/Symfony/Component/Cache/Tests/Fixtures/ArrayCache.php
index 95b39d54bd..c00a3aef05 100644
--- a/src/Symfony/Component/Cache/Tests/Fixtures/ArrayCache.php
+++ b/src/Symfony/Component/Cache/Tests/Fixtures/ArrayCache.php
@@ -13,6 +13,9 @@ class ArrayCache extends CacheProvider
         return $this->doContains($id) ? $this->data[$id][0] : false;
     }
 
+    /**
+     * @return bool
+     */
     protected function doContains($id)
     {
         if (!isset($this->data[$id])) {
@@ -24,6 +27,9 @@ class ArrayCache extends CacheProvider
         return !$expiry || microtime(true) < $expiry || !$this->doDelete($id);
     }
 
+    /**
+     * @return bool
+     */
     protected function doSave($id, $data, $lifeTime = 0)
     {
         $this->data[$id] = [$data, $lifeTime ? microtime(true) + $lifeTime : false];
@@ -31,6 +37,9 @@ class ArrayCache extends CacheProvider
         return true;
     }
 
+    /**
+     * @return bool
+     */
     protected function doDelete($id)
     {
         unset($this->data[$id]);
@@ -38,6 +47,9 @@ class ArrayCache extends CacheProvider
         return true;
     }
 
+    /**
+     * @return bool
+     */
     protected function doFlush()
     {
         $this->data = [];
@@ -45,6 +57,9 @@ class ArrayCache extends CacheProvider
         return true;
     }
 
+    /**
+     * @return array|null
+     */
     protected function doGetStats()
     {
         return null;
diff --git a/src/Symfony/Component/Cache/Tests/Fixtures/ExternalAdapter.php b/src/Symfony/Component/Cache/Tests/Fixtures/ExternalAdapter.php
index deb0b3bc34..0481b16bcd 100644
--- a/src/Symfony/Component/Cache/Tests/Fixtures/ExternalAdapter.php
+++ b/src/Symfony/Component/Cache/Tests/Fixtures/ExternalAdapter.php
@@ -29,46 +29,73 @@ class ExternalAdapter implements CacheItemPoolInterface
         $this->cache = new ArrayAdapter($defaultLifetime);
     }
 
+    /**
+     * @return CacheItemInterface
+     */
     public function getItem($key)
     {
         return $this->cache->getItem($key);
     }
 
+    /**
+     * @return iterable
+     */
     public function getItems(array $keys = [])
     {
         return $this->cache->getItems($keys);
     }
 
+    /**
+     * @return bool
+     */
     public function hasItem($key)
     {
         return $this->cache->hasItem($key);
     }
 
+    /**
+     * @return bool
+     */
     public function clear()
     {
         return $this->cache->clear();
     }
 
+    /**
+     * @return bool
+     */
     public function deleteItem($key)
     {
         return $this->cache->deleteItem($key);
     }
 
+    /**
+     * @return bool
+     */
     public function deleteItems(array $keys)
     {
         return $this->cache->deleteItems($keys);
     }
 
+    /**
+     * @return bool
+     */
     public function save(CacheItemInterface $item)
     {
         return $this->cache->save($item);
     }
 
+    /**
+     * @return bool
+     */
     public function saveDeferred(CacheItemInterface $item)
     {
         return $this->cache->saveDeferred($item);
     }
 
+    /**
+     * @return bool
+     */
     public function commit()
     {
         return $this->cache->commit();
diff --git a/src/Symfony/Component/Cache/Traits/AbstractAdapterTrait.php b/src/Symfony/Component/Cache/Traits/AbstractAdapterTrait.php
index fe4047ea8b..8f026f750d 100644
--- a/src/Symfony/Component/Cache/Traits/AbstractAdapterTrait.php
+++ b/src/Symfony/Component/Cache/Traits/AbstractAdapterTrait.php
@@ -93,6 +93,8 @@ trait AbstractAdapterTrait
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function hasItem($key)
     {
@@ -113,6 +115,8 @@ trait AbstractAdapterTrait
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function clear(string $prefix = '')
     {
@@ -141,6 +145,8 @@ trait AbstractAdapterTrait
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function deleteItem($key)
     {
@@ -149,6 +155,8 @@ trait AbstractAdapterTrait
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function deleteItems(array $keys)
     {
@@ -236,6 +244,8 @@ trait AbstractAdapterTrait
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function save(CacheItemInterface $item)
     {
@@ -249,6 +259,8 @@ trait AbstractAdapterTrait
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function saveDeferred(CacheItemInterface $item)
     {
diff --git a/src/Symfony/Component/Console/Logger/ConsoleLogger.php b/src/Symfony/Component/Console/Logger/ConsoleLogger.php
index 3a2853daee..32361189f2 100644
--- a/src/Symfony/Component/Console/Logger/ConsoleLogger.php
+++ b/src/Symfony/Component/Console/Logger/ConsoleLogger.php
@@ -61,6 +61,8 @@ class ConsoleLogger extends AbstractLogger
 
     /**
      * {@inheritdoc}
+     *
+     * @return void
      */
     public function log($level, $message, array $context = [])
     {
diff --git a/src/Symfony/Component/ErrorHandler/DebugClassLoader.php b/src/Symfony/Component/ErrorHandler/DebugClassLoader.php
index eec3c7051e..f1506a92ec 100644
--- a/src/Symfony/Component/ErrorHandler/DebugClassLoader.php
+++ b/src/Symfony/Component/ErrorHandler/DebugClassLoader.php
@@ -27,9 +27,47 @@ use PHPUnit\Framework\MockObject\Matcher\StatelessInvocation;
  */
 class DebugClassLoader
 {
+    private const SPECIAL_RETURN_TYPES = [
+        'mixed' => 'mixed',
+        'void' => 'void',
+        'null' => 'null',
+        'resource' => 'resource',
+        'static' => 'object',
+        '$this' => 'object',
+        'boolean' => 'bool',
+        'true' => 'bool',
+        'false' => 'bool',
+        'integer' => 'int',
+        'array' => 'array',
+        'bool' => 'bool',
+        'callable' => 'callable',
+        'float' => 'float',
+        'int' => 'integer',
+        'iterable' => 'iterable',
+        'object' => 'object',
+        'string' => 'string',
+        'self' => 'self',
+        'parent' => 'parent',
+    ];
+
+    private const BUILTIN_RETURN_TYPES = [
+        'void' => true,
+        'array' => true,
+        'bool' => true,
+        'callable' => true,
+        'float' => true,
+        'int' => true,
+        'iterable' => true,
+        'object' => true,
+        'string' => true,
+        'self' => true,
+        'parent' => true,
+    ];
+
     private $classLoader;
     private $isFinder;
     private $loaded = [];
+    private $compatPatch;
     private static $caseCheck;
     private static $checkedClasses = [];
     private static $final = [];
@@ -40,11 +78,14 @@ class DebugClassLoader
     private static $annotatedParameters = [];
     private static $darwinCache = ['/' => ['/', []]];
     private static $method = [];
+    private static $returnTypes = [];
+    private static $methodTraits = [];
 
     public function __construct(callable $classLoader)
     {
         $this->classLoader = $classLoader;
         $this->isFinder = \is_array($classLoader) && method_exists($classLoader[0], 'findFile');
+        $this->compatPatch = getenv('SYMFONY_PATCH_TYPE_DECLARATIONS_COMPAT') ?: null;
 
         if (!isset(self::$caseCheck)) {
             $file = file_exists(__FILE__) ? __FILE__ : rtrim(realpath('.'), \DIRECTORY_SEPARATOR);
@@ -218,11 +259,11 @@ class DebugClassLoader
         $deprecations = [];
 
         // Don't trigger deprecations for classes in the same vendor
-        if (2 > $len = 1 + (strpos($class, '\\') ?: strpos($class, '_'))) {
-            $len = 0;
-            $ns = '';
+        if (2 > $vendorLen = 1 + (strpos($class, '\\') ?: strpos($class, '_'))) {
+            $vendorLen = 0;
+            $vendor = '';
         } else {
-            $ns = str_replace('_', '\\', substr($class, 0, $len));
+            $vendor = str_replace('_', '\\', substr($class, 0, $vendorLen));
         }
 
         // Detect annotations on the class
@@ -252,7 +293,7 @@ class DebugClassLoader
             }
         }
 
-        $parent = get_parent_class($class);
+        $parent = get_parent_class($class) ?: null;
         $parentAndOwnInterfaces = $this->getOwnInterfaces($class, $parent);
         if ($parent) {
             $parentAndOwnInterfaces[$parent] = $parent;
@@ -271,13 +312,13 @@ class DebugClassLoader
             if (!isset(self::$checkedClasses[$use])) {
                 $this->checkClass($use);
             }
-            if (isset(self::$deprecated[$use]) && strncmp($ns, str_replace('_', '\\', $use), $len) && !isset(self::$deprecated[$class])) {
+            if (isset(self::$deprecated[$use]) && strncmp($vendor, str_replace('_', '\\', $use), $vendorLen) && !isset(self::$deprecated[$class])) {
                 $type = class_exists($class, false) ? 'class' : (interface_exists($class, false) ? 'interface' : 'trait');
                 $verb = class_exists($use, false) || interface_exists($class, false) ? 'extends' : (interface_exists($use, false) ? 'implements' : 'uses');
 
                 $deprecations[] = sprintf('The "%s" %s %s "%s" that is deprecated%s.', $class, $type, $verb, $use, self::$deprecated[$use]);
             }
-            if (isset(self::$internal[$use]) && strncmp($ns, str_replace('_', '\\', $use), $len)) {
+            if (isset(self::$internal[$use]) && strncmp($vendor, str_replace('_', '\\', $use), $vendorLen)) {
                 $deprecations[] = sprintf('The "%s" %s is considered internal%s. It may change without further notice. You should not use it from "%s".', $use, class_exists($use, false) ? 'class' : (interface_exists($use, false) ? 'interface' : 'trait'), self::$internal[$use], $class);
             }
             if (isset(self::$method[$use])) {
@@ -305,15 +346,24 @@ class DebugClassLoader
         }
 
         if (trait_exists($class)) {
+            $file = $refl->getFileName();
+
+            foreach ($refl->getMethods(\ReflectionMethod::IS_PUBLIC | \ReflectionMethod::IS_PROTECTED) as $method) {
+                if ($method->getFileName() === $file) {
+                    self::$methodTraits[$file][$method->getStartLine()] = $class;
+                }
+            }
+
             return $deprecations;
         }
 
-        // Inherit @final, @internal and @param annotations for methods
+        // Inherit @final, @internal, @param and @return annotations for methods
         self::$finalMethods[$class] = [];
         self::$internalMethods[$class] = [];
         self::$annotatedParameters[$class] = [];
+        self::$returnTypes[$class] = [];
         foreach ($parentAndOwnInterfaces as $use) {
-            foreach (['finalMethods', 'internalMethods', 'annotatedParameters'] as $property) {
+            foreach (['finalMethods', 'internalMethods', 'annotatedParameters', 'returnTypes'] as $property) {
                 if (isset(self::${$property}[$use])) {
                     self::${$property}[$class] = self::${$property}[$class] ? self::${$property}[$use] + self::${$property}[$class] : self::${$property}[$use];
                 }
@@ -325,6 +375,16 @@ class DebugClassLoader
                 continue;
             }
 
+            if (null === $ns = self::$methodTraits[$method->getFileName()][$method->getStartLine()] ?? null) {
+                $ns = $vendor;
+                $len = $vendorLen;
+            } elseif (2 > $len = 1 + (strpos($ns, '\\') ?: strpos($ns, '_'))) {
+                $len = 0;
+                $ns = '';
+            } else {
+                $ns = str_replace('_', '\\', substr($ns, 0, $len));
+            }
+
             if ($parent && isset(self::$finalMethods[$parent][$method->name])) {
                 list($declaringClass, $message) = self::$finalMethods[$parent][$method->name];
                 $deprecations[] = sprintf('The "%s::%s()" method is considered final%s. It may change without further notice as of its next major version. You should not extend it from "%s".', $declaringClass, $method->name, $message, $class);
@@ -353,10 +413,34 @@ class DebugClassLoader
                 }
             }
 
+            if (isset(self::$returnTypes[$class][$method->name]) && !$method->hasReturnType() && !($doc && preg_match('/\n\s+\* @return +(\S+)/', $doc))) {
+                list($normalizedType, $returnType, $declaringClass, $declaringFile) = self::$returnTypes[$class][$method->name];
+
+                if (null !== $this->compatPatch && 0 === strpos($class, $this->compatPatch)) {
+                    self::fixReturnStatements($method, $normalizedType);
+                }
+
+                if (strncmp($ns, $declaringClass, $len)) {
+                    if (null !== $this->compatPatch && 0 === strpos($class, $this->compatPatch)) {
+                        self::patchMethod($method, $returnType, $declaringFile);
+                    }
+
+                    $deprecations[] = sprintf('Method "%s::%s()" will return "%s" as of its next major version. Doing the same in child class "%s" will be required when upgrading.', $declaringClass, $method->name, $normalizedType, $class);
+                }
+            }
+
             if (!$doc) {
                 continue;
             }
 
+            if (!$method->hasReturnType() && false !== strpos($doc, '@return') && preg_match('/\n\s+\* @return +(\S+)/', $doc, $matches)) {
+                $this->setReturnType($matches[1], $method, $parent);
+
+                if (null !== $this->compatPatch && 0 === strpos($class, $this->compatPatch)) {
+                    self::fixReturnStatements($method, self::$returnTypes[$class][$method->name][0] ?? '?');
+                }
+            }
+
             $finalOrInternal = false;
 
             foreach (['final', 'internal'] as $annotation) {
@@ -382,7 +466,7 @@ class DebugClassLoader
             foreach ($matches as list(, $parameterType, $parameterName)) {
                 if (!isset($definedParameters[$parameterName])) {
                     $parameterType = trim($parameterType);
-                    self::$annotatedParameters[$class][$method->name][$parameterName] = sprintf('The "%%s::%s()" method will require a new "%s$%s" argument in the next major version of its parent class "%s", not defining it is deprecated.', $method->name, $parameterType ? $parameterType.' ' : '', $parameterName, $method->class);
+                    self::$annotatedParameters[$class][$method->name][$parameterName] = sprintf('The "%%s::%s()" method will require a new "%s$%s" argument in the next major version of its parent class "%s", not defining it is deprecated.', $method->name, $parameterType ? $parameterType.' ' : '', $parameterName, $class);
                 }
             }
         }
@@ -496,11 +580,9 @@ class DebugClassLoader
     /**
      * `class_implements` includes interfaces from the parents so we have to manually exclude them.
      *
-     * @param string|false $parent
-     *
      * @return string[]
      */
-    private function getOwnInterfaces(string $class, $parent): array
+    private function getOwnInterfaces(string $class, ?string $parent): array
     {
         $ownInterfaces = class_implements($class, false);
 
@@ -518,4 +600,234 @@ class DebugClassLoader
 
         return $ownInterfaces;
     }
+
+    private function setReturnType(string $types, \ReflectionMethod $method, ?string $parent): void
+    {
+        $nullable = false;
+        $typesMap = [];
+        foreach (explode('|', $types) as $t) {
+            $typesMap[$this->normalizeType($t, $method->class, $parent)] = $t;
+        }
+
+        if (isset($typesMap['array']) && (isset($typesMap['Traversable']) || isset($typesMap['\Traversable']))) {
+            $typesMap['iterable'] = 'array' !== $typesMap['array'] ? $typesMap['array'] : 'iterable';
+            unset($typesMap['array'], $typesMap['Traversable'], $typesMap['\Traversable']);
+        }
+
+        if (isset($typesMap['array']) && isset($typesMap['iterable'])) {
+            if ('[]' === substr($typesMap['array'], -2)) {
+                $typesMap['iterable'] = $typesMap['array'];
+            }
+            unset($typesMap['array']);
+        }
+
+        $normalizedType = key($typesMap);
+        $returnType = current($typesMap);
+
+        foreach ($typesMap as $n => $t) {
+            if ('null' === $n) {
+                $nullable = true;
+            } elseif ('null' === $normalizedType) {
+                $normalizedType = $t;
+                $returnType = $t;
+            } elseif ($n !== $normalizedType) {
+                // ignore multi-types return declarations
+                return;
+            }
+        }
+
+        if ('void' === $normalizedType) {
+            $nullable = false;
+        } elseif (!isset(self::BUILTIN_RETURN_TYPES[$normalizedType]) && isset(self::SPECIAL_RETURN_TYPES[$normalizedType])) {
+            // ignore other special return types
+            return;
+        }
+
+        if ($nullable) {
+            $normalizedType = '?'.$normalizedType;
+            $returnType .= '|null';
+        }
+
+        self::$returnTypes[$method->class][$method->name] = [$normalizedType, $returnType, $method->class, $method->getFileName()];
+    }
+
+    private function normalizeType(string $type, string $class, ?string $parent): string
+    {
+        if (isset(self::SPECIAL_RETURN_TYPES[$lcType = strtolower($type)])) {
+            if ('parent' === $lcType = self::SPECIAL_RETURN_TYPES[$lcType]) {
+                $lcType = null !== $parent ? '\\'.$parent : 'parent';
+            } elseif ('self' === $lcType) {
+                $lcType = '\\'.$class;
+            }
+
+            return $lcType;
+        }
+
+        if ('[]' === substr($type, -2)) {
+            return 'array';
+        }
+
+        if (preg_match('/^(array|iterable|callable) *[<(]/', $lcType, $m)) {
+            return $m[1];
+        }
+
+        // We could resolve "use" statements to return the FQDN
+        // but this would be too expensive for a runtime checker
+
+        return $type;
+    }
+
+    /**
+     * Utility method to add @return annotations to the Symfony code-base where it triggers a self-deprecations.
+     */
+    private static function patchMethod(\ReflectionMethod $method, string $returnType, string $declaringFile)
+    {
+        static $patchedMethods = [];
+        static $useStatements = [];
+
+        if (!file_exists($file = $method->getFileName()) || isset($patchedMethods[$file][$startLine = $method->getStartLine()])) {
+            return;
+        }
+
+        $patchedMethods[$file][$startLine] = true;
+        $patchedMethods[$file][0] = $patchedMethods[$file][0] ?? 0;
+        $startLine += $patchedMethods[$file][0] - 2;
+        $returnType = explode('|', $returnType);
+        $code = file($file);
+
+        foreach ($returnType as $i => $type) {
+            if (preg_match('/((?:\[\])+)$/', $type, $m)) {
+                $type = substr($type, 0, -\strlen($m[1]));
+                $format = '%s'.$m[1];
+            } elseif (preg_match('/^(array|iterable)<([^,>]++)>$/', $type, $m)) {
+                $type = $m[2];
+                $format = $m[1].'<%s>';
+            } else {
+                $format = null;
+            }
+
+            if (isset(self::SPECIAL_RETURN_TYPES[$type]) || ('\\' === $type[0] && !$p = strrpos($type, '\\', 1))) {
+                continue;
+            }
+
+            list($namespace, $useOffset, $useMap) = $useStatements[$file] ?? $useStatements[$file] = self::getUseStatements($file);
+
+            if ('\\' !== $type[0]) {
+                list($declaringNamespace, , $declaringUseMap) = $useStatements[$declaringFile] ?? $useStatements[$declaringFile] = self::getUseStatements($declaringFile);
+
+                $p = strpos($type, '\\', 1);
+                $alias = $p ? substr($type, 0, $p) : $type;
+
+                if (isset($declaringUseMap[$alias])) {
+                    $type = '\\'.$declaringUseMap[$alias].($p ? substr($type, $p) : '');
+                } else {
+                    $type = '\\'.$declaringNamespace.$type;
+                }
+
+                $p = strrpos($type, '\\', 1);
+            }
+
+            $alias = substr($type, 1 + $p);
+            $type = substr($type, 1);
+
+            if (!isset($useMap[$alias]) && (class_exists($c = $namespace.$alias) || interface_exists($c) || trait_exists($c))) {
+                $useMap[$alias] = $c;
+            }
+
+            if (!isset($useMap[$alias])) {
+                $useStatements[$file][2][$alias] = $type;
+                $code[$useOffset] = "use $type;\n".$code[$useOffset];
+                ++$patchedMethods[$file][0];
+            } elseif ($useMap[$alias] !== $type) {
+                $alias .= 'FIXME';
+                $useStatements[$file][2][$alias] = $type;
+                $code[$useOffset] = "use $type as $alias;\n".$code[$useOffset];
+                ++$patchedMethods[$file][0];
+            }
+
+            $returnType[$i] = null !== $format ? sprintf($format, $alias) : $alias;
+        }
+
+        $returnType = implode('|', $returnType);
+
+        if ($method->getDocComment()) {
+            $code[$startLine] = "     * @return $returnType\n".$code[$startLine];
+        } else {
+            $code[$startLine] .= <<<EOTXT
+    /**
+     * @return $returnType
+     */
+
+EOTXT;
+        }
+
+        $patchedMethods[$file][0] += substr_count($code[$startLine], "\n") - 1;
+        file_put_contents($file, $code);
+    }
+
+    private static function getUseStatements(string $file): array
+    {
+        $namespace = '';
+        $useMap = [];
+        $useOffset = 0;
+
+        if (!file_exists($file)) {
+            return [$namespace, $useOffset, $useMap];
+        }
+
+        $file = file($file);
+
+        for ($i = 0; $i < \count($file); ++$i) {
+            if (preg_match('/^(class|interface|trait|abstract) /', $file[$i])) {
+                break;
+            }
+
+            if (0 === strpos($file[$i], 'namespace ')) {
+                $namespace = substr($file[$i], \strlen('namespace '), -2).'\\';
+                $useOffset = $i + 2;
+            }
+
+            if (0 === strpos($file[$i], 'use ')) {
+                $useOffset = $i;
+
+                for (; 0 === strpos($file[$i], 'use '); ++$i) {
+                    $u = explode(' as ', substr($file[$i], 4, -2), 2);
+
+                    if (1 === \count($u)) {
+                        $p = strrpos($u[0], '\\');
+                        $useMap[substr($u[0], false !== $p ? 1 + $p : 0)] = $u[0];
+                    } else {
+                        $useMap[$u[1]] = $u[0];
+                    }
+                }
+
+                break;
+            }
+        }
+
+        return [$namespace, $useOffset, $useMap];
+    }
+
+    private static function fixReturnStatements(\ReflectionMethod $method, string $returnType)
+    {
+        if (!file_exists($file = $method->getFileName())) {
+            return;
+        }
+
+        $fixedCode = $code = file($file);
+        $end = $method->getEndLine();
+        for ($i = $method->getStartLine(); $i < $end; ++$i) {
+            if ('void' === $returnType) {
+                $fixedCode[$i] = str_replace('    return null;', '    return;', $code[$i]);
+            } elseif ('mixed' === $returnType || '?' === $returnType[0]) {
+                $fixedCode[$i] = str_replace('    return;', '    return null;', $code[$i]);
+            } else {
+                $fixedCode[$i] = str_replace('    return;', "    return $returnType!?;", $code[$i]);
+            }
+        }
+
+        if ($fixedCode !== $code) {
+            file_put_contents($file, $fixedCode);
+        }
+    }
 }
diff --git a/src/Symfony/Component/ErrorHandler/FatalErrorHandler/ClassNotFoundFatalErrorHandler.php b/src/Symfony/Component/ErrorHandler/FatalErrorHandler/ClassNotFoundFatalErrorHandler.php
index b59b0d4517..ee9930c097 100644
--- a/src/Symfony/Component/ErrorHandler/FatalErrorHandler/ClassNotFoundFatalErrorHandler.php
+++ b/src/Symfony/Component/ErrorHandler/FatalErrorHandler/ClassNotFoundFatalErrorHandler.php
@@ -33,11 +33,11 @@ class ClassNotFoundFatalErrorHandler implements FatalErrorHandlerInterface
         $notFoundSuffix = '\' not found';
         $notFoundSuffixLen = \strlen($notFoundSuffix);
         if ($notFoundSuffixLen > $messageLen) {
-            return;
+            return null;
         }
 
         if (0 !== substr_compare($error['message'], $notFoundSuffix, -$notFoundSuffixLen)) {
-            return;
+            return null;
         }
 
         foreach (['class', 'interface', 'trait'] as $typeName) {
diff --git a/src/Symfony/Component/ErrorHandler/FatalErrorHandler/UndefinedFunctionFatalErrorHandler.php b/src/Symfony/Component/ErrorHandler/FatalErrorHandler/UndefinedFunctionFatalErrorHandler.php
index 9e3affb14d..b944b8e11c 100644
--- a/src/Symfony/Component/ErrorHandler/FatalErrorHandler/UndefinedFunctionFatalErrorHandler.php
+++ b/src/Symfony/Component/ErrorHandler/FatalErrorHandler/UndefinedFunctionFatalErrorHandler.php
@@ -30,17 +30,17 @@ class UndefinedFunctionFatalErrorHandler implements FatalErrorHandlerInterface
         $notFoundSuffix = '()';
         $notFoundSuffixLen = \strlen($notFoundSuffix);
         if ($notFoundSuffixLen > $messageLen) {
-            return;
+            return null;
         }
 
         if (0 !== substr_compare($error['message'], $notFoundSuffix, -$notFoundSuffixLen)) {
-            return;
+            return null;
         }
 
         $prefix = 'Call to undefined function ';
         $prefixLen = \strlen($prefix);
         if (0 !== strpos($error['message'], $prefix)) {
-            return;
+            return null;
         }
 
         $fullyQualifiedFunctionName = substr($error['message'], $prefixLen, -$notFoundSuffixLen);
diff --git a/src/Symfony/Component/ErrorHandler/FatalErrorHandler/UndefinedMethodFatalErrorHandler.php b/src/Symfony/Component/ErrorHandler/FatalErrorHandler/UndefinedMethodFatalErrorHandler.php
index 49de274469..90bb09837e 100644
--- a/src/Symfony/Component/ErrorHandler/FatalErrorHandler/UndefinedMethodFatalErrorHandler.php
+++ b/src/Symfony/Component/ErrorHandler/FatalErrorHandler/UndefinedMethodFatalErrorHandler.php
@@ -28,7 +28,7 @@ class UndefinedMethodFatalErrorHandler implements FatalErrorHandlerInterface
     {
         preg_match('/^Call to undefined method (.*)::(.*)\(\)$/', $error['message'], $matches);
         if (!$matches) {
-            return;
+            return null;
         }
 
         $className = $matches[1];
diff --git a/src/Symfony/Component/ErrorHandler/Tests/DebugClassLoaderTest.php b/src/Symfony/Component/ErrorHandler/Tests/DebugClassLoaderTest.php
index a0d92a680a..753e1a9624 100644
--- a/src/Symfony/Component/ErrorHandler/Tests/DebugClassLoaderTest.php
+++ b/src/Symfony/Component/ErrorHandler/Tests/DebugClassLoaderTest.php
@@ -353,6 +353,40 @@ class DebugClassLoaderTest extends TestCase
     {
         $this->assertTrue(class_exists(__NAMESPACE__.'\Fixtures\DefinitionInEvaluatedCode', true));
     }
+
+    public function testReturnType()
+    {
+        $deprecations = [];
+        set_error_handler(function ($type, $msg) use (&$deprecations) { $deprecations[] = $msg; });
+        $e = error_reporting(E_USER_DEPRECATED);
+
+        class_exists('Test\\'.__NAMESPACE__.'\\ReturnType', true);
+
+        error_reporting($e);
+        restore_error_handler();
+
+        $this->assertSame([
+           'Method "Symfony\Component\ErrorHandler\Tests\Fixtures\ReturnTypeGrandParent::returnTypeGrandParent()" will return "string" as of its next major version. Doing the same in child class "Test\Symfony\Component\ErrorHandler\Tests\ReturnType" will be required when upgrading.',
+           'Method "Symfony\Component\ErrorHandler\Tests\Fixtures\ReturnTypeParentInterface::returnTypeParentInterface()" will return "string" as of its next major version. Doing the same in child class "Test\Symfony\Component\ErrorHandler\Tests\ReturnType" will be required when upgrading.',
+           'Method "Symfony\Component\ErrorHandler\Tests\Fixtures\ReturnTypeInterface::returnTypeInterface()" will return "string" as of its next major version. Doing the same in child class "Test\Symfony\Component\ErrorHandler\Tests\ReturnType" will be required when upgrading.',
+           'Method "Symfony\Component\ErrorHandler\Tests\Fixtures\ReturnTypeParent::oneNonNullableReturnableType()" will return "void" as of its next major version. Doing the same in child class "Test\Symfony\Component\ErrorHandler\Tests\ReturnType" will be required when upgrading.',
+           'Method "Symfony\Component\ErrorHandler\Tests\Fixtures\ReturnTypeParent::oneNonNullableReturnableTypeWithNull()" will return "void" as of its next major version. Doing the same in child class "Test\Symfony\Component\ErrorHandler\Tests\ReturnType" will be required when upgrading.',
+           'Method "Symfony\Component\ErrorHandler\Tests\Fixtures\ReturnTypeParent::oneNullableReturnableType()" will return "array" as of its next major version. Doing the same in child class "Test\Symfony\Component\ErrorHandler\Tests\ReturnType" will be required when upgrading.',
+           'Method "Symfony\Component\ErrorHandler\Tests\Fixtures\ReturnTypeParent::oneNullableReturnableTypeWithNull()" will return "?bool" as of its next major version. Doing the same in child class "Test\Symfony\Component\ErrorHandler\Tests\ReturnType" will be required when upgrading.',
+           'Method "Symfony\Component\ErrorHandler\Tests\Fixtures\ReturnTypeParent::oneOtherType()" will return "\ArrayIterator" as of its next major version. Doing the same in child class "Test\Symfony\Component\ErrorHandler\Tests\ReturnType" will be required when upgrading.',
+           'Method "Symfony\Component\ErrorHandler\Tests\Fixtures\ReturnTypeParent::oneOtherTypeWithNull()" will return "?\ArrayIterator" as of its next major version. Doing the same in child class "Test\Symfony\Component\ErrorHandler\Tests\ReturnType" will be required when upgrading.',
+           'Method "Symfony\Component\ErrorHandler\Tests\Fixtures\ReturnTypeParent::manyIterables()" will return "array" as of its next major version. Doing the same in child class "Test\Symfony\Component\ErrorHandler\Tests\ReturnType" will be required when upgrading.',
+           'Method "Symfony\Component\ErrorHandler\Tests\Fixtures\ReturnTypeParent::nullableReturnableTypeNormalization()" will return "object" as of its next major version. Doing the same in child class "Test\Symfony\Component\ErrorHandler\Tests\ReturnType" will be required when upgrading.',
+           'Method "Symfony\Component\ErrorHandler\Tests\Fixtures\ReturnTypeParent::nonNullableReturnableTypeNormalization()" will return "void" as of its next major version. Doing the same in child class "Test\Symfony\Component\ErrorHandler\Tests\ReturnType" will be required when upgrading.',
+           'Method "Symfony\Component\ErrorHandler\Tests\Fixtures\ReturnTypeParent::commonNonObjectReturnedTypeNormalization()" will return "object" as of its next major version. Doing the same in child class "Test\Symfony\Component\ErrorHandler\Tests\ReturnType" will be required when upgrading.',
+           'Method "Symfony\Component\ErrorHandler\Tests\Fixtures\ReturnTypeParent::bracketsNormalization()" will return "array" as of its next major version. Doing the same in child class "Test\Symfony\Component\ErrorHandler\Tests\ReturnType" will be required when upgrading.',
+           'Method "Symfony\Component\ErrorHandler\Tests\Fixtures\ReturnTypeParent::booleanNormalization()" will return "bool" as of its next major version. Doing the same in child class "Test\Symfony\Component\ErrorHandler\Tests\ReturnType" will be required when upgrading.',
+           'Method "Symfony\Component\ErrorHandler\Tests\Fixtures\ReturnTypeParent::callableNormalization1()" will return "callable" as of its next major version. Doing the same in child class "Test\Symfony\Component\ErrorHandler\Tests\ReturnType" will be required when upgrading.',
+           'Method "Symfony\Component\ErrorHandler\Tests\Fixtures\ReturnTypeParent::callableNormalization2()" will return "callable" as of its next major version. Doing the same in child class "Test\Symfony\Component\ErrorHandler\Tests\ReturnType" will be required when upgrading.',
+           'Method "Symfony\Component\ErrorHandler\Tests\Fixtures\ReturnTypeParent::otherTypeNormalization()" will return "\ArrayIterator" as of its next major version. Doing the same in child class "Test\Symfony\Component\ErrorHandler\Tests\ReturnType" will be required when upgrading.',
+           'Method "Symfony\Component\ErrorHandler\Tests\Fixtures\ReturnTypeParent::arrayWithLessThanSignNormalization()" will return "array" as of its next major version. Doing the same in child class "Test\Symfony\Component\ErrorHandler\Tests\ReturnType" will be required when upgrading.',
+        ], $deprecations);
+    }
 }
 
 class ClassLoader
@@ -435,6 +469,10 @@ class ClassLoader
         } elseif ('Test\\'.__NAMESPACE__.'\ExtendsVirtualMagicCall' === $class) {
             eval('namespace Test\\'.__NAMESPACE__.'; class ExtendsVirtualMagicCall extends \\'.__NAMESPACE__.'\Fixtures\VirtualClassMagicCall implements \\'.__NAMESPACE__.'\Fixtures\VirtualInterface {
             }');
+        } elseif ('Test\\'.__NAMESPACE__.'\ReturnType' === $class) {
+            return $fixtureDir.\DIRECTORY_SEPARATOR.'ReturnType.php';
+        } elseif ('Test\\'.__NAMESPACE__.'\Fixtures\OutsideInterface' === $class) {
+            return $fixtureDir.\DIRECTORY_SEPARATOR.'OutsideInterface.php';
         }
     }
 }
diff --git a/src/Symfony/Component/ErrorHandler/Tests/Fixtures/OutsideInterface.php b/src/Symfony/Component/ErrorHandler/Tests/Fixtures/OutsideInterface.php
new file mode 100644
index 0000000000..43989a9060
--- /dev/null
+++ b/src/Symfony/Component/ErrorHandler/Tests/Fixtures/OutsideInterface.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace Test\Symfony\Component\ErrorHandler\Tests\Fixtures;
+
+interface OutsideInterface
+{
+    /**
+     * @return string - should not be reported as it's in a non-Symfony namespace
+     */
+    public function outsideMethod();
+}
diff --git a/src/Symfony/Component/ErrorHandler/Tests/Fixtures/ReturnType.php b/src/Symfony/Component/ErrorHandler/Tests/Fixtures/ReturnType.php
new file mode 100644
index 0000000000..28682763b7
--- /dev/null
+++ b/src/Symfony/Component/ErrorHandler/Tests/Fixtures/ReturnType.php
@@ -0,0 +1,46 @@
+<?php
+
+namespace Test\Symfony\Component\ErrorHandler\Tests;
+
+use Symfony\Component\ErrorHandler\Tests\Fixtures\ReturnTypeParent;
+use Symfony\Component\ErrorHandler\Tests\Fixtures\ReturnTypeInterface;
+
+class ReturnType extends ReturnTypeParent implements ReturnTypeInterface, Fixtures\OutsideInterface
+{
+    public function returnTypeGrandParent() { }
+    public function returnTypeParentInterface() { }
+    public function returnTypeInterface() { }
+    public function realReturnTypeMustBeThere(): string { }
+    public function realReturnTypeIsAlreadyThere(): float { }
+    public function realReturnTypeIsAlreadyThereWithNull(): ?iterable { }
+    public function oneCommonNonObjectReturnedType() { }
+    public function oneCommonNonObjectReturnedTypeWithNull() { }
+    public function oneNonNullableReturnableType() { }
+    public function oneNonNullableReturnableTypeWithNull() { }
+    public function oneNullableReturnableType() { }
+    public function oneNullableReturnableTypeWithNull() { }
+    public function oneOtherType() { }
+    public function oneOtherTypeWithNull() { }
+    public function twoNullableReturnableTypes() { }
+    public function twoNullEdgeCase() { }
+    public function threeReturnTypes() { }
+    /**
+     * @return anything - should not trigger
+     */
+    public function throughDoc() { }
+    /**
+     * @return parent - same as parent
+     */
+    public function optOutThroughDoc() { }
+    public function manyIterables() { }
+    public function nullableReturnableTypeNormalization() { }
+    public function nonNullableReturnableTypeNormalization() { }
+    public function commonNonObjectReturnedTypeNormalization() { }
+    public function bracketsNormalization() { }
+    public function booleanNormalization() { }
+    public function callableNormalization1() { }
+    public function callableNormalization2() { }
+    public function otherTypeNormalization() { }
+    public function arrayWithLessThanSignNormalization() { }
+    public function outsideMethod() { }
+}
diff --git a/src/Symfony/Component/ErrorHandler/Tests/Fixtures/ReturnTypeGrandParent.php b/src/Symfony/Component/ErrorHandler/Tests/Fixtures/ReturnTypeGrandParent.php
new file mode 100644
index 0000000000..3fc14ee59d
--- /dev/null
+++ b/src/Symfony/Component/ErrorHandler/Tests/Fixtures/ReturnTypeGrandParent.php
@@ -0,0 +1,13 @@
+<?php
+
+namespace Symfony\Component\ErrorHandler\Tests\Fixtures;
+
+abstract class ReturnTypeGrandParent
+{
+    /**
+     * @return string
+     */
+    public function returnTypeGrandParent()
+    {
+    }
+}
diff --git a/src/Symfony/Component/ErrorHandler/Tests/Fixtures/ReturnTypeInterface.php b/src/Symfony/Component/ErrorHandler/Tests/Fixtures/ReturnTypeInterface.php
new file mode 100644
index 0000000000..30c4f5de5d
--- /dev/null
+++ b/src/Symfony/Component/ErrorHandler/Tests/Fixtures/ReturnTypeInterface.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace Symfony\Component\ErrorHandler\Tests\Fixtures;
+
+interface ReturnTypeInterface
+{
+    /**
+     * @return string
+     */
+    public function returnTypeInterface();
+}
diff --git a/src/Symfony/Component/ErrorHandler/Tests/Fixtures/ReturnTypeParent.php b/src/Symfony/Component/ErrorHandler/Tests/Fixtures/ReturnTypeParent.php
new file mode 100644
index 0000000000..45f8abad74
--- /dev/null
+++ b/src/Symfony/Component/ErrorHandler/Tests/Fixtures/ReturnTypeParent.php
@@ -0,0 +1,201 @@
+<?php
+
+namespace Symfony\Component\ErrorHandler\Tests\Fixtures;
+
+abstract class ReturnTypeParent extends ReturnTypeGrandParent implements ReturnTypeParentInterface
+{
+    /**
+     * No return declared here
+     */
+    public function returnTypeGrandParent()
+    {
+    }
+
+    /**
+     * @return string
+     */
+    abstract public function realReturnTypeMustBeThere(): string;
+
+    /**
+     * @return float
+     */
+    public function realReturnTypeIsAlreadyThere()
+    {
+    }
+
+    /**
+     * @return iterable|null
+     */
+    abstract public function realReturnTypeIsAlreadyThereWithNull();
+
+    /**
+     * @return mixed
+     */
+    public function oneCommonNonObjectReturnedType()
+    {
+    }
+
+    /**
+     *  @return resource|null
+     */
+    public function oneCommonNonObjectReturnedTypeWithNull()
+    {
+    }
+
+    /**
+     * @return void
+     */
+    public function oneNonNullableReturnableType()
+    {
+    }
+
+    /**
+     * @return void|null
+     */
+    public function oneNonNullableReturnableTypeWithNull()
+    {
+    }
+
+    /**
+     * @return array The array
+     */
+    public function oneNullableReturnableType()
+    {
+    }
+
+    /**
+     * @return bool|null
+     */
+    public function oneNullableReturnableTypeWithNull()
+    {
+    }
+
+    /**
+     * @return \ArrayIterator
+     */
+    public function oneOtherType()
+    {
+    }
+
+    /**
+     * @return \ArrayIterator|null
+     */
+    public function oneOtherTypeWithNull()
+    {
+    }
+
+    /**
+     * @return int|self
+     */
+    public function twoNullableReturnableTypes()
+    {
+    }
+
+    /**
+     * @return null|null
+     */
+    public function twoNullEdgeCase()
+    {
+    }
+
+    /**
+     * @return bool|string|null
+     */
+    public function threeReturnTypes()
+    {
+    }
+
+    /**
+     * @return self
+     */
+    public function throughDoc()
+    {
+    }
+
+    /**
+     * @return self
+     */
+    public function optOutThroughDoc()
+    {
+    }
+
+    /**
+     * @return \ArrayIterator[]|\DirectoryIterator[]
+     */
+    public function manyIterables()
+    {
+    }
+
+    /**
+     * Something before.
+     *
+     * @return object
+     */
+    public function nullableReturnableTypeNormalization()
+    {
+    }
+
+    /**
+     * @annotation before
+     * @return VOID
+     */
+    public function nonNullableReturnableTypeNormalization()
+    {
+    }
+
+    /**
+     * @return $this
+     */
+    public function commonNonObjectReturnedTypeNormalization()
+    {
+    }
+
+    /**
+     * @return \ArrayIterator[]
+     */
+    public function bracketsNormalization()
+    {
+    }
+
+    /**
+     * @return false
+     */
+    public function booleanNormalization()
+    {
+    }
+
+    /**
+     * @return callable(\Throwable $reason, mixed $value)
+     */
+    public function callableNormalization1()
+    {
+    }
+
+    /**
+     * @return callable ($a, $b)
+     */
+    public function callableNormalization2()
+    {
+    }
+
+    /**
+     * @return \ArrayIterator
+     */
+    public function otherTypeNormalization()
+    {
+    }
+
+    /**
+     * @return array<string, int>
+     */
+    public function arrayWithLessThanSignNormalization()
+    {
+    }
+
+    /**
+     * @return int
+     */
+    public function notExtended()
+    {
+    }
+}
diff --git a/src/Symfony/Component/ErrorHandler/Tests/Fixtures/ReturnTypeParentInterface.php b/src/Symfony/Component/ErrorHandler/Tests/Fixtures/ReturnTypeParentInterface.php
new file mode 100644
index 0000000000..d63e31165d
--- /dev/null
+++ b/src/Symfony/Component/ErrorHandler/Tests/Fixtures/ReturnTypeParentInterface.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace Symfony\Component\ErrorHandler\Tests\Fixtures;
+
+interface ReturnTypeParentInterface
+{
+    /**
+     * @return string
+     */
+    public function returnTypeParentInterface();
+}
diff --git a/src/Symfony/Component/HttpKernel/Log/Logger.php b/src/Symfony/Component/HttpKernel/Log/Logger.php
index 3969487b77..c27bb3f070 100644
--- a/src/Symfony/Component/HttpKernel/Log/Logger.php
+++ b/src/Symfony/Component/HttpKernel/Log/Logger.php
@@ -65,6 +65,8 @@ class Logger extends AbstractLogger
 
     /**
      * {@inheritdoc}
+     *
+     * @return void
      */
     public function log($level, $message, array $context = [])
     {
diff --git a/src/Symfony/Component/HttpKernel/Tests/Logger.php b/src/Symfony/Component/HttpKernel/Tests/Logger.php
index 8ae756132c..1f80e48ae9 100644
--- a/src/Symfony/Component/HttpKernel/Tests/Logger.php
+++ b/src/Symfony/Component/HttpKernel/Tests/Logger.php
@@ -41,46 +41,73 @@ class Logger implements LoggerInterface
         ];
     }
 
+    /**
+     * @return void
+     */
     public function log($level, $message, array $context = [])
     {
         $this->logs[$level][] = $message;
     }
 
+    /**
+     * @return void
+     */
     public function emergency($message, array $context = [])
     {
         $this->log('emergency', $message, $context);
     }
 
+    /**
+     * @return void
+     */
     public function alert($message, array $context = [])
     {
         $this->log('alert', $message, $context);
     }
 
+    /**
+     * @return void
+     */
     public function critical($message, array $context = [])
     {
         $this->log('critical', $message, $context);
     }
 
+    /**
+     * @return void
+     */
     public function error($message, array $context = [])
     {
         $this->log('error', $message, $context);
     }
 
+    /**
+     * @return void
+     */
     public function warning($message, array $context = [])
     {
         $this->log('warning', $message, $context);
     }
 
+    /**
+     * @return void
+     */
     public function notice($message, array $context = [])
     {
         $this->log('notice', $message, $context);
     }
 
+    /**
+     * @return void
+     */
     public function info($message, array $context = [])
     {
         $this->log('info', $message, $context);
     }
 
+    /**
+     * @return void
+     */
     public function debug($message, array $context = [])
     {
         $this->log('debug', $message, $context);
diff --git a/src/Symfony/Component/Intl/Data/Generator/TimezoneDataGenerator.php b/src/Symfony/Component/Intl/Data/Generator/TimezoneDataGenerator.php
index 7b22deb88d..e5c0d0c479 100644
--- a/src/Symfony/Component/Intl/Data/Generator/TimezoneDataGenerator.php
+++ b/src/Symfony/Component/Intl/Data/Generator/TimezoneDataGenerator.php
@@ -84,13 +84,13 @@ class TimezoneDataGenerator extends AbstractDataGenerator
         // Don't generate aliases, as they are resolved during runtime
         // Unless an alias is needed as fallback for de-duplication purposes
         if (isset($this->localeAliases[$displayLocale]) && !$this->generatingFallback) {
-            return;
+            return null;
         }
 
         $localeBundle = $reader->read($tempDir, $displayLocale);
 
         if (!isset($localeBundle['zoneStrings']) || null === $localeBundle['zoneStrings']) {
-            return;
+            return null;
         }
 
         $data = [
@@ -115,7 +115,7 @@ class TimezoneDataGenerator extends AbstractDataGenerator
             $data['Meta'] = array_diff($data['Meta'], $fallback['Meta']);
         }
         if (!$data['Names'] && !$data['Meta']) {
-            return;
+            return null;
         }
 
         $this->zoneIds = array_merge($this->zoneIds, array_keys($data['Names']));
diff --git a/src/Symfony/Component/WebLink/GenericLinkProvider.php b/src/Symfony/Component/WebLink/GenericLinkProvider.php
index 5c8b2e7114..9dd0e6733f 100644
--- a/src/Symfony/Component/WebLink/GenericLinkProvider.php
+++ b/src/Symfony/Component/WebLink/GenericLinkProvider.php
@@ -61,6 +61,8 @@ class GenericLinkProvider implements EvolvableLinkProviderInterface
 
     /**
      * {@inheritdoc}
+     *
+     * @return static
      */
     public function withLink(LinkInterface $link)
     {
@@ -72,6 +74,8 @@ class GenericLinkProvider implements EvolvableLinkProviderInterface
 
     /**
      * {@inheritdoc}
+     *
+     * @return static
      */
     public function withoutLink(LinkInterface $link)
     {
diff --git a/src/Symfony/Component/WebLink/Link.php b/src/Symfony/Component/WebLink/Link.php
index a7d034c1fa..a43028443c 100644
--- a/src/Symfony/Component/WebLink/Link.php
+++ b/src/Symfony/Component/WebLink/Link.php
@@ -92,6 +92,8 @@ class Link implements EvolvableLinkInterface
 
     /**
      * {@inheritdoc}
+     *
+     * @return static
      */
     public function withHref($href)
     {
@@ -104,6 +106,8 @@ class Link implements EvolvableLinkInterface
 
     /**
      * {@inheritdoc}
+     *
+     * @return static
      */
     public function withRel($rel)
     {
@@ -115,6 +119,8 @@ class Link implements EvolvableLinkInterface
 
     /**
      * {@inheritdoc}
+     *
+     * @return static
      */
     public function withoutRel($rel)
     {
@@ -126,6 +132,8 @@ class Link implements EvolvableLinkInterface
 
     /**
      * {@inheritdoc}
+     *
+     * @return static
      */
     public function withAttribute($attribute, $value)
     {
@@ -137,6 +145,8 @@ class Link implements EvolvableLinkInterface
 
     /**
      * {@inheritdoc}
+     *
+     * @return static
      */
     public function withoutAttribute($attribute)
     {
diff --git a/src/Symfony/Contracts/Service/ServiceLocatorTrait.php b/src/Symfony/Contracts/Service/ServiceLocatorTrait.php
index 71b1b7460d..4ec6eb4276 100644
--- a/src/Symfony/Contracts/Service/ServiceLocatorTrait.php
+++ b/src/Symfony/Contracts/Service/ServiceLocatorTrait.php
@@ -36,6 +36,8 @@ trait ServiceLocatorTrait
 
     /**
      * {@inheritdoc}
+     *
+     * @return bool
      */
     public function has($id)
     {