diff --git a/src/Symfony/Component/Config/Definition/ArrayNode.php b/src/Symfony/Component/Config/Definition/ArrayNode.php
index 96f38dcc92..c3c837a412 100644
--- a/src/Symfony/Component/Config/Definition/ArrayNode.php
+++ b/src/Symfony/Component/Config/Definition/ArrayNode.php
@@ -203,11 +203,7 @@ class ArrayNode extends BaseNode implements PrototypeNodeInterface
     }
 
     /**
-     * Finalizes the value of this node.
-     *
-     * @param mixed $value
-     *
-     * @return mixed The finalised value
+     * {@inheritdoc}
      *
      * @throws UnsetKeyException
      * @throws InvalidConfigurationException if the node doesn't have enough children
@@ -249,11 +245,7 @@ class ArrayNode extends BaseNode implements PrototypeNodeInterface
     }
 
     /**
-     * Validates the type of the value.
-     *
-     * @param mixed $value
-     *
-     * @throws InvalidTypeException
+     * {@inheritdoc}
      */
     protected function validateType($value)
     {
@@ -269,11 +261,7 @@ class ArrayNode extends BaseNode implements PrototypeNodeInterface
     }
 
     /**
-     * Normalizes the value.
-     *
-     * @param mixed $value The value to normalize
-     *
-     * @return mixed The normalized value
+     * {@inheritdoc}
      *
      * @throws InvalidConfigurationException
      */
@@ -355,12 +343,7 @@ class ArrayNode extends BaseNode implements PrototypeNodeInterface
     }
 
     /**
-     * Merges values together.
-     *
-     * @param mixed $leftSide  The left side to merge
-     * @param mixed $rightSide The right side to merge
-     *
-     * @return mixed The merged values
+     * {@inheritdoc}
      *
      * @throws InvalidConfigurationException
      * @throws \RuntimeException
diff --git a/src/Symfony/Component/Config/Definition/Builder/ArrayNodeDefinition.php b/src/Symfony/Component/Config/Definition/Builder/ArrayNodeDefinition.php
index bec08b0db6..61348387be 100644
--- a/src/Symfony/Component/Config/Definition/Builder/ArrayNodeDefinition.php
+++ b/src/Symfony/Component/Config/Definition/Builder/ArrayNodeDefinition.php
@@ -280,7 +280,7 @@ class ArrayNodeDefinition extends NodeDefinition implements ParentNodeDefinition
             ->treatNullLike(['enabled' => true])
             ->beforeNormalization()
                 ->ifArray()
-                ->then(function ($v) {
+                ->then(function (array $v) {
                     $v['enabled'] = $v['enabled'] ?? true;
 
                     return $v;
diff --git a/src/Symfony/Component/Config/Definition/Builder/ExprBuilder.php b/src/Symfony/Component/Config/Definition/Builder/ExprBuilder.php
index 5db229dcca..0cf47c162c 100644
--- a/src/Symfony/Component/Config/Definition/Builder/ExprBuilder.php
+++ b/src/Symfony/Component/Config/Definition/Builder/ExprBuilder.php
@@ -37,7 +37,7 @@ class ExprBuilder
      */
     public function always(\Closure $then = null)
     {
-        $this->ifPart = function ($v) { return true; };
+        $this->ifPart = function () { return true; };
 
         if (null !== $then) {
             $this->thenPart = $then;
@@ -168,7 +168,7 @@ class ExprBuilder
      */
     public function thenEmptyArray()
     {
-        $this->thenPart = function ($v) { return []; };
+        $this->thenPart = function () { return []; };
 
         return $this;
     }
@@ -200,7 +200,7 @@ class ExprBuilder
      */
     public function thenUnset()
     {
-        $this->thenPart = function ($v) { throw new UnsetKeyException('Unsetting key.'); };
+        $this->thenPart = function () { throw new UnsetKeyException('Unsetting key.'); };
 
         return $this;
     }
diff --git a/src/Symfony/Component/Config/Definition/Builder/NumericNodeDefinition.php b/src/Symfony/Component/Config/Definition/Builder/NumericNodeDefinition.php
index 390b113656..c4bff1756f 100644
--- a/src/Symfony/Component/Config/Definition/Builder/NumericNodeDefinition.php
+++ b/src/Symfony/Component/Config/Definition/Builder/NumericNodeDefinition.php
@@ -26,7 +26,7 @@ abstract class NumericNodeDefinition extends ScalarNodeDefinition
     /**
      * Ensures that the value is smaller than the given reference.
      *
-     * @param mixed $max
+     * @param int|float $max
      *
      * @return $this
      *
@@ -45,7 +45,7 @@ abstract class NumericNodeDefinition extends ScalarNodeDefinition
     /**
      * Ensures that the value is bigger than the given reference.
      *
-     * @param mixed $min
+     * @param int|float $min
      *
      * @return $this
      *
diff --git a/src/Symfony/Component/Config/Definition/Dumper/XmlReferenceDumper.php b/src/Symfony/Component/Config/Definition/Dumper/XmlReferenceDumper.php
index 29e4076f97..a6b6240c77 100644
--- a/src/Symfony/Component/Config/Definition/Dumper/XmlReferenceDumper.php
+++ b/src/Symfony/Component/Config/Definition/Dumper/XmlReferenceDumper.php
@@ -49,7 +49,7 @@ class XmlReferenceDumper
 
         // xml remapping
         if ($node->getParent()) {
-            $remapping = array_filter($node->getParent()->getXmlRemappings(), function ($mapping) use ($rootName) {
+            $remapping = array_filter($node->getParent()->getXmlRemappings(), function (array $mapping) use ($rootName) {
                 return $rootName === $mapping[1];
             });
 
diff --git a/src/Symfony/Component/Config/Definition/EnumNode.php b/src/Symfony/Component/Config/Definition/EnumNode.php
index 23fc508a78..822e6b57f1 100644
--- a/src/Symfony/Component/Config/Definition/EnumNode.php
+++ b/src/Symfony/Component/Config/Definition/EnumNode.php
@@ -38,6 +38,9 @@ class EnumNode extends ScalarNode
         return $this->values;
     }
 
+    /**
+     * {@inheritdoc}
+     */
     protected function finalizeValue($value)
     {
         $value = parent::finalizeValue($value);
diff --git a/src/Symfony/Component/Config/Definition/NumericNode.php b/src/Symfony/Component/Config/Definition/NumericNode.php
index 19c96e8af7..50d137c2d7 100644
--- a/src/Symfony/Component/Config/Definition/NumericNode.php
+++ b/src/Symfony/Component/Config/Definition/NumericNode.php
@@ -23,6 +23,10 @@ class NumericNode extends ScalarNode
     protected $min;
     protected $max;
 
+    /**
+     * @param int|float|null $min
+     * @param int|float|null $max
+     */
     public function __construct(?string $name, NodeInterface $parent = null, $min = null, $max = null, string $pathSeparator = BaseNode::DEFAULT_PATH_SEPARATOR)
     {
         parent::__construct($name, $parent, $pathSeparator);
diff --git a/src/Symfony/Component/Config/Definition/PrototypedArrayNode.php b/src/Symfony/Component/Config/Definition/PrototypedArrayNode.php
index 72d3578be7..0382223677 100644
--- a/src/Symfony/Component/Config/Definition/PrototypedArrayNode.php
+++ b/src/Symfony/Component/Config/Definition/PrototypedArrayNode.php
@@ -173,14 +173,7 @@ class PrototypedArrayNode extends ArrayNode
     }
 
     /**
-     * Finalizes the value of this node.
-     *
-     * @param mixed $value
-     *
-     * @return mixed The finalized value
-     *
-     * @throws UnsetKeyException
-     * @throws InvalidConfigurationException if the node doesn't have enough children
+     * {@inheritdoc}
      */
     protected function finalizeValue($value)
     {
@@ -208,13 +201,8 @@ class PrototypedArrayNode extends ArrayNode
     }
 
     /**
-     * Normalizes the value.
+     * {@inheritdoc}
      *
-     * @param mixed $value The value to normalize
-     *
-     * @return mixed The normalized value
-     *
-     * @throws InvalidConfigurationException
      * @throws DuplicateKeyException
      */
     protected function normalizeValue($value)
@@ -282,15 +270,7 @@ class PrototypedArrayNode extends ArrayNode
     }
 
     /**
-     * Merges values together.
-     *
-     * @param mixed $leftSide  The left side to merge
-     * @param mixed $rightSide The right side to merge
-     *
-     * @return mixed The merged values
-     *
-     * @throws InvalidConfigurationException
-     * @throws \RuntimeException
+     * {@inheritdoc}
      */
     protected function mergeValues($leftSide, $rightSide)
     {
diff --git a/src/Symfony/Component/Config/Tests/ConfigCacheTest.php b/src/Symfony/Component/Config/Tests/ConfigCacheTest.php
index cfb2403a82..ff72302a46 100644
--- a/src/Symfony/Component/Config/Tests/ConfigCacheTest.php
+++ b/src/Symfony/Component/Config/Tests/ConfigCacheTest.php
@@ -38,7 +38,7 @@ class ConfigCacheTest extends TestCase
     /**
      * @dataProvider debugModes
      */
-    public function testCacheIsNotValidIfNothingHasBeenCached($debug)
+    public function testCacheIsNotValidIfNothingHasBeenCached(bool $debug)
     {
         unlink($this->cacheFile); // remove tempnam() side effect
         $cache = new ConfigCache($this->cacheFile, $debug);
@@ -60,7 +60,7 @@ class ConfigCacheTest extends TestCase
     /**
      * @dataProvider debugModes
      */
-    public function testIsFreshWhenNoResourceProvided($debug)
+    public function testIsFreshWhenNoResourceProvided(bool $debug)
     {
         $cache = new ConfigCache($this->cacheFile, $debug);
         $cache->write('', []);
@@ -89,7 +89,7 @@ class ConfigCacheTest extends TestCase
         $this->assertFalse($cache->isFresh());
     }
 
-    public function debugModes()
+    public function debugModes(): array
     {
         return [
             [true],
diff --git a/src/Symfony/Component/Config/Tests/Definition/ArrayNodeTest.php b/src/Symfony/Component/Config/Tests/Definition/ArrayNodeTest.php
index 54a966f177..95f8480316 100644
--- a/src/Symfony/Component/Config/Tests/Definition/ArrayNodeTest.php
+++ b/src/Symfony/Component/Config/Tests/Definition/ArrayNodeTest.php
@@ -55,7 +55,7 @@ class ArrayNodeTest extends TestCase
         $node->normalize(['beta' => 'foo']);
     }
 
-    public function ignoreAndRemoveMatrixProvider()
+    public function ignoreAndRemoveMatrixProvider(): array
     {
         $unrecognizedOptionException = new InvalidConfigurationException('Unrecognized option "foo" under "root"');
 
@@ -68,9 +68,11 @@ class ArrayNodeTest extends TestCase
     }
 
     /**
+     * @param array|\Exception $expected
+     *
      * @dataProvider ignoreAndRemoveMatrixProvider
      */
-    public function testIgnoreAndRemoveBehaviors($ignore, $remove, $expected, $message = '')
+    public function testIgnoreAndRemoveBehaviors(bool $ignore, bool $remove, $expected, string $message = '')
     {
         if ($expected instanceof \Exception) {
             $this->expectException(\get_class($expected));
@@ -85,7 +87,7 @@ class ArrayNodeTest extends TestCase
     /**
      * @dataProvider getPreNormalizationTests
      */
-    public function testPreNormalize($denormalized, $normalized)
+    public function testPreNormalize(array $denormalized, array $normalized)
     {
         $node = new ArrayNode('foo');
 
@@ -95,7 +97,7 @@ class ArrayNodeTest extends TestCase
         $this->assertSame($normalized, $r->invoke($node, $denormalized));
     }
 
-    public function getPreNormalizationTests()
+    public function getPreNormalizationTests(): array
     {
         return [
             [
@@ -120,7 +122,7 @@ class ArrayNodeTest extends TestCase
     /**
      * @dataProvider getZeroNamedNodeExamplesData
      */
-    public function testNodeNameCanBeZero($denormalized, $normalized)
+    public function testNodeNameCanBeZero(array $denormalized, array $normalized)
     {
         $zeroNode = new ArrayNode(0);
         $zeroNode->addChild(new ScalarNode('name'));
@@ -137,7 +139,7 @@ class ArrayNodeTest extends TestCase
         $this->assertSame($normalized, $r->invoke($rootNode, $denormalized));
     }
 
-    public function getZeroNamedNodeExamplesData()
+    public function getZeroNamedNodeExamplesData(): array
     {
         return [
             [
@@ -168,7 +170,7 @@ class ArrayNodeTest extends TestCase
     /**
      * @dataProvider getPreNormalizedNormalizedOrderedData
      */
-    public function testChildrenOrderIsMaintainedOnNormalizeValue($prenormalized, $normalized)
+    public function testChildrenOrderIsMaintainedOnNormalizeValue(array $prenormalized, array $normalized)
     {
         $scalar1 = new ScalarNode('1');
         $scalar2 = new ScalarNode('2');
@@ -184,7 +186,7 @@ class ArrayNodeTest extends TestCase
         $this->assertSame($normalized, $r->invoke($node, $prenormalized));
     }
 
-    public function getPreNormalizedNormalizedOrderedData()
+    public function getPreNormalizedNormalizedOrderedData(): array
     {
         return [
             [
@@ -260,7 +262,7 @@ class ArrayNodeTest extends TestCase
     /**
      * @dataProvider getDataWithIncludedExtraKeys
      */
-    public function testMergeWithoutIgnoringExtraKeys($prenormalizeds, $merged)
+    public function testMergeWithoutIgnoringExtraKeys(array $prenormalizeds)
     {
         $this->expectException(\RuntimeException::class);
         $this->expectExceptionMessage('merge() expects a normalized config array.');
@@ -278,7 +280,7 @@ class ArrayNodeTest extends TestCase
     /**
      * @dataProvider getDataWithIncludedExtraKeys
      */
-    public function testMergeWithIgnoringAndRemovingExtraKeys($prenormalizeds, $merged)
+    public function testMergeWithIgnoringAndRemovingExtraKeys(array $prenormalizeds)
     {
         $this->expectException(\RuntimeException::class);
         $this->expectExceptionMessage('merge() expects a normalized config array.');
@@ -296,7 +298,7 @@ class ArrayNodeTest extends TestCase
     /**
      * @dataProvider getDataWithIncludedExtraKeys
      */
-    public function testMergeWithIgnoringExtraKeys($prenormalizeds, $merged)
+    public function testMergeWithIgnoringExtraKeys(array $prenormalizeds, array $merged)
     {
         $node = new ArrayNode('root');
         $node->addChild(new ScalarNode('foo'));
@@ -309,7 +311,7 @@ class ArrayNodeTest extends TestCase
         $this->assertEquals($merged, $r->invoke($node, ...$prenormalizeds));
     }
 
-    public function getDataWithIncludedExtraKeys()
+    public function getDataWithIncludedExtraKeys(): array
     {
         return [
             [
diff --git a/src/Symfony/Component/Config/Tests/Definition/BaseNodeTest.php b/src/Symfony/Component/Config/Tests/Definition/BaseNodeTest.php
index ea2ed639ff..afe3cdf691 100644
--- a/src/Symfony/Component/Config/Tests/Definition/BaseNodeTest.php
+++ b/src/Symfony/Component/Config/Tests/Definition/BaseNodeTest.php
@@ -20,7 +20,7 @@ class BaseNodeTest extends TestCase
     /**
      * @dataProvider providePath
      */
-    public function testGetPathForChildNode($expected, array $params)
+    public function testGetPathForChildNode(string $expected, array $params)
     {
         $constructorArgs = [];
         $constructorArgs[] = $params[0];
@@ -41,7 +41,7 @@ class BaseNodeTest extends TestCase
         $this->assertSame($expected, $node->getPath());
     }
 
-    public function providePath()
+    public function providePath(): array
     {
         return [
             'name only' => ['root', ['root']],
diff --git a/src/Symfony/Component/Config/Tests/Definition/BooleanNodeTest.php b/src/Symfony/Component/Config/Tests/Definition/BooleanNodeTest.php
index 3a05e3efd8..bec3b5996d 100644
--- a/src/Symfony/Component/Config/Tests/Definition/BooleanNodeTest.php
+++ b/src/Symfony/Component/Config/Tests/Definition/BooleanNodeTest.php
@@ -20,7 +20,7 @@ class BooleanNodeTest extends TestCase
     /**
      * @dataProvider getValidValues
      */
-    public function testNormalize($value)
+    public function testNormalize(bool $value)
     {
         $node = new BooleanNode('test');
         $this->assertSame($value, $node->normalize($value));
@@ -28,10 +28,8 @@ class BooleanNodeTest extends TestCase
 
     /**
      * @dataProvider getValidValues
-     *
-     * @param bool $value
      */
-    public function testValidNonEmptyValues($value)
+    public function testValidNonEmptyValues(bool $value)
     {
         $node = new BooleanNode('test');
         $node->setAllowEmptyValue(false);
@@ -39,7 +37,7 @@ class BooleanNodeTest extends TestCase
         $this->assertSame($value, $node->finalize($value));
     }
 
-    public function getValidValues()
+    public function getValidValues(): array
     {
         return [
             [false],
@@ -57,7 +55,7 @@ class BooleanNodeTest extends TestCase
         $node->normalize($value);
     }
 
-    public function getInvalidValues()
+    public function getInvalidValues(): array
     {
         return [
             [null],
diff --git a/src/Symfony/Component/Config/Tests/Definition/Builder/ArrayNodeDefinitionTest.php b/src/Symfony/Component/Config/Tests/Definition/Builder/ArrayNodeDefinitionTest.php
index 0e489ac910..0f111826d3 100644
--- a/src/Symfony/Component/Config/Tests/Definition/Builder/ArrayNodeDefinitionTest.php
+++ b/src/Symfony/Component/Config/Tests/Definition/Builder/ArrayNodeDefinitionTest.php
@@ -42,7 +42,7 @@ class ArrayNodeDefinitionTest extends TestCase
     /**
      * @dataProvider providePrototypeNodeSpecificCalls
      */
-    public function testPrototypeNodeSpecificOption($method, $args)
+    public function testPrototypeNodeSpecificOption(string $method, array $args)
     {
         $this->expectException(InvalidDefinitionException::class);
         $node = new ArrayNodeDefinition('root');
@@ -52,7 +52,7 @@ class ArrayNodeDefinitionTest extends TestCase
         $node->getNode();
     }
 
-    public function providePrototypeNodeSpecificCalls()
+    public function providePrototypeNodeSpecificCalls(): array
     {
         return [
             ['defaultValue', [[]]],
@@ -98,9 +98,11 @@ class ArrayNodeDefinitionTest extends TestCase
     }
 
     /**
+     * @param int|array|string|null $args
+     *
      * @dataProvider providePrototypedArrayNodeDefaults
      */
-    public function testPrototypedArrayNodeDefault($args, $shouldThrowWhenUsingAttrAsKey, $shouldThrowWhenNotUsingAttrAsKey, $defaults)
+    public function testPrototypedArrayNodeDefault($args, bool $shouldThrowWhenUsingAttrAsKey, bool $shouldThrowWhenNotUsingAttrAsKey, array $defaults)
     {
         $node = new ArrayNodeDefinition('root');
         $node
@@ -132,7 +134,7 @@ class ArrayNodeDefinitionTest extends TestCase
         }
     }
 
-    public function providePrototypedArrayNodeDefaults()
+    public function providePrototypedArrayNodeDefaults(): array
     {
         return [
             [null, true, false, [[]]],
@@ -173,7 +175,7 @@ class ArrayNodeDefinitionTest extends TestCase
     /**
      * @dataProvider getEnableableNodeFixtures
      */
-    public function testTrueEnableEnabledNode($expected, $config, $message)
+    public function testTrueEnableEnabledNode(array $expected, array $config, string $message)
     {
         $processor = new Processor();
         $node = new ArrayNodeDefinition('root');
@@ -293,7 +295,7 @@ class ArrayNodeDefinitionTest extends TestCase
         $this->assertEquals($node->prototype('enum'), $node->enumPrototype());
     }
 
-    public function getEnableableNodeFixtures()
+    public function getEnableableNodeFixtures(): array
     {
         return [
             [['enabled' => true, 'foo' => 'bar'], [true], 'true enables an enableable node'],
@@ -432,7 +434,10 @@ class ArrayNodeDefinitionTest extends TestCase
         $this->assertSame($expectedName, $this->getField($actualNode, 'name'));
     }
 
-    protected function getField($object, $field)
+    /**
+     * @param object $object
+     */
+    protected function getField($object, string $field)
     {
         $reflection = new \ReflectionProperty($object, $field);
         $reflection->setAccessible(true);
diff --git a/src/Symfony/Component/Config/Tests/Definition/Builder/ExprBuilderTest.php b/src/Symfony/Component/Config/Tests/Definition/Builder/ExprBuilderTest.php
index c634f08877..74ae972e54 100644
--- a/src/Symfony/Component/Config/Tests/Definition/Builder/ExprBuilderTest.php
+++ b/src/Symfony/Component/Config/Tests/Definition/Builder/ExprBuilderTest.php
@@ -13,6 +13,7 @@ namespace Symfony\Component\Config\Tests\Definition\Builder;
 
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\Config\Definition\Builder\ExprBuilder;
+use Symfony\Component\Config\Definition\Builder\NodeDefinition;
 use Symfony\Component\Config\Definition\Builder\TreeBuilder;
 use Symfony\Component\Config\Definition\Exception\InvalidConfigurationException;
 
@@ -36,13 +37,13 @@ class ExprBuilderTest extends TestCase
         $this->assertFinalizedValueIs('new_value', $test, ['key' => true]);
 
         $test = $this->getTestBuilder()
-            ->ifTrue(function ($v) { return true; })
+            ->ifTrue(function () { return true; })
             ->then($this->returnClosure('new_value'))
         ->end();
         $this->assertFinalizedValueIs('new_value', $test);
 
         $test = $this->getTestBuilder()
-            ->ifTrue(function ($v) { return false; })
+            ->ifTrue(function () { return false; })
             ->then($this->returnClosure('new_value'))
         ->end();
         $this->assertFinalizedValueIs('value', $test);
@@ -150,7 +151,7 @@ class ExprBuilderTest extends TestCase
     /**
      * @dataProvider castToArrayValues
      */
-    public function testCastToArrayExpression($configValue, $expectedValue)
+    public function testCastToArrayExpression($configValue, array $expectedValue)
     {
         $test = $this->getTestBuilder()
             ->castToArray()
@@ -158,7 +159,7 @@ class ExprBuilderTest extends TestCase
         $this->assertFinalizedValueIs($expectedValue, $test, ['key' => $configValue]);
     }
 
-    public function castToArrayValues()
+    public function castToArrayValues(): iterable
     {
         yield ['value', ['value']];
         yield [-3.14, [-3.14]];
@@ -219,20 +220,19 @@ class ExprBuilderTest extends TestCase
     /**
      * Close the validation process and finalize with the given config.
      *
-     * @param TreeBuilder $testBuilder The tree builder to finalize
-     * @param array       $config      The config you want to use for the finalization, if nothing provided
-     *                                 a simple ['key'=>'value'] will be used
+     * @param array|null $config The config you want to use for the finalization, if nothing provided
+     *                           a simple ['key'=>'value'] will be used
      *
      * @return array The finalized config values
      */
-    protected function finalizeTestBuilder($testBuilder, $config = null): array
+    protected function finalizeTestBuilder(NodeDefinition $nodeDefinition, ?array $config = null): array
     {
-        return $testBuilder
+        return $nodeDefinition
             ->end()
             ->end()
             ->end()
             ->buildTree()
-            ->finalize(null === $config ? ['key' => 'value'] : $config)
+            ->finalize($config ?? ['key' => 'value'])
         ;
     }
 
@@ -243,7 +243,7 @@ class ExprBuilderTest extends TestCase
      */
     protected function returnClosure($val): \Closure
     {
-        return function ($v) use ($val) {
+        return function () use ($val) {
             return $val;
         };
     }
@@ -251,12 +251,11 @@ class ExprBuilderTest extends TestCase
     /**
      * Assert that the given test builder, will return the given value.
      *
-     * @param mixed       $value       The value to test
-     * @param TreeBuilder $treeBuilder The tree builder to finalize
-     * @param mixed       $config      The config values that new to be finalized
+     * @param mixed $value  The value to test
+     * @param mixed $config The config values that new to be finalized
      */
-    protected function assertFinalizedValueIs($value, $treeBuilder, $config = null)
+    protected function assertFinalizedValueIs($value, NodeDefinition $nodeDefinition, $config = null)
     {
-        $this->assertEquals(['key' => $value], $this->finalizeTestBuilder($treeBuilder, $config));
+        $this->assertEquals(['key' => $value], $this->finalizeTestBuilder($nodeDefinition, $config));
     }
 }
diff --git a/src/Symfony/Component/Config/Tests/Definition/Dumper/YamlReferenceDumperTest.php b/src/Symfony/Component/Config/Tests/Definition/Dumper/YamlReferenceDumperTest.php
index 146917aaa7..f1871d4972 100644
--- a/src/Symfony/Component/Config/Tests/Definition/Dumper/YamlReferenceDumperTest.php
+++ b/src/Symfony/Component/Config/Tests/Definition/Dumper/YamlReferenceDumperTest.php
@@ -26,7 +26,7 @@ class YamlReferenceDumperTest extends TestCase
         $this->assertEquals($this->getConfigurationAsString(), $dumper->dump($configuration));
     }
 
-    public function provideDumpAtPath()
+    public function provideDumpAtPath(): array
     {
         return [
             'Regular node' => ['scalar_true', <<<EOL
@@ -72,7 +72,7 @@ EOL
     /**
      * @dataProvider provideDumpAtPath
      */
-    public function testDumpAtPath($path, $expected)
+    public function testDumpAtPath(string $path, string $expected)
     {
         $configuration = new ExampleConfiguration();
 
@@ -81,7 +81,7 @@ EOL
         $this->assertSame(trim($expected), trim($dumper->dumpAtPath($configuration, $path)));
     }
 
-    private function getConfigurationAsString()
+    private function getConfigurationAsString(): string
     {
         return <<<'EOL'
 acme_root:
diff --git a/src/Symfony/Component/Config/Tests/Definition/FloatNodeTest.php b/src/Symfony/Component/Config/Tests/Definition/FloatNodeTest.php
index 68ed8a7521..d675f47046 100644
--- a/src/Symfony/Component/Config/Tests/Definition/FloatNodeTest.php
+++ b/src/Symfony/Component/Config/Tests/Definition/FloatNodeTest.php
@@ -19,6 +19,8 @@ class FloatNodeTest extends TestCase
 {
     /**
      * @dataProvider getValidValues
+     *
+     * @param int|float $value
      */
     public function testNormalize($value)
     {
@@ -29,7 +31,7 @@ class FloatNodeTest extends TestCase
     /**
      * @dataProvider getValidValues
      *
-     * @param int $value
+     * @param int|float $value
      */
     public function testValidNonEmptyValues($value)
     {
@@ -39,7 +41,7 @@ class FloatNodeTest extends TestCase
         $this->assertSame($value, $node->finalize($value));
     }
 
-    public function getValidValues()
+    public function getValidValues(): array
     {
         return [
             [1798.0],
@@ -63,7 +65,7 @@ class FloatNodeTest extends TestCase
         $node->normalize($value);
     }
 
-    public function getInvalidValues()
+    public function getInvalidValues(): array
     {
         return [
             [null],
diff --git a/src/Symfony/Component/Config/Tests/Definition/IntegerNodeTest.php b/src/Symfony/Component/Config/Tests/Definition/IntegerNodeTest.php
index c4dd57b8f4..7c843b38f3 100644
--- a/src/Symfony/Component/Config/Tests/Definition/IntegerNodeTest.php
+++ b/src/Symfony/Component/Config/Tests/Definition/IntegerNodeTest.php
@@ -20,7 +20,7 @@ class IntegerNodeTest extends TestCase
     /**
      * @dataProvider getValidValues
      */
-    public function testNormalize($value)
+    public function testNormalize(int $value)
     {
         $node = new IntegerNode('test');
         $this->assertSame($value, $node->normalize($value));
@@ -28,10 +28,8 @@ class IntegerNodeTest extends TestCase
 
     /**
      * @dataProvider getValidValues
-     *
-     * @param int $value
      */
-    public function testValidNonEmptyValues($value)
+    public function testValidNonEmptyValues(int $value)
     {
         $node = new IntegerNode('test');
         $node->setAllowEmptyValue(false);
@@ -39,7 +37,7 @@ class IntegerNodeTest extends TestCase
         $this->assertSame($value, $node->finalize($value));
     }
 
-    public function getValidValues()
+    public function getValidValues(): array
     {
         return [
             [1798],
@@ -58,7 +56,7 @@ class IntegerNodeTest extends TestCase
         $node->normalize($value);
     }
 
-    public function getInvalidValues()
+    public function getInvalidValues(): array
     {
         return [
             [null],
diff --git a/src/Symfony/Component/Config/Tests/Definition/NormalizationTest.php b/src/Symfony/Component/Config/Tests/Definition/NormalizationTest.php
index 3fecac2e3e..0b497707e4 100644
--- a/src/Symfony/Component/Config/Tests/Definition/NormalizationTest.php
+++ b/src/Symfony/Component/Config/Tests/Definition/NormalizationTest.php
@@ -51,7 +51,7 @@ class NormalizationTest extends TestCase
         $this->assertNormalized($tree, $denormalized, $normalized);
     }
 
-    public function getEncoderTests()
+    public function getEncoderTests(): array
     {
         $configs = [];
 
@@ -120,7 +120,7 @@ class NormalizationTest extends TestCase
         $this->assertNormalized($tree, $denormalized, $normalized);
     }
 
-    public function getAnonymousKeysTests()
+    public function getAnonymousKeysTests(): array
     {
         $configs = [];
 
@@ -151,7 +151,7 @@ class NormalizationTest extends TestCase
         $this->assertNormalized($this->getNumericKeysTestTree(), $denormalized, $normalized);
     }
 
-    public function getNumericKeysTests()
+    public function getNumericKeysTests(): array
     {
         $configs = [];
 
@@ -233,10 +233,9 @@ class NormalizationTest extends TestCase
         self::assertSame($normalized, $tree->normalize($denormalized));
     }
 
-    private function getNumericKeysTestTree()
+    private function getNumericKeysTestTree(): NodeInterface
     {
-        $tb = new TreeBuilder('root', 'array');
-        $tree = $tb
+        return (new TreeBuilder('root', 'array'))
             ->getRootNode()
                 ->children()
                     ->node('thing', 'array')
@@ -247,9 +246,6 @@ class NormalizationTest extends TestCase
                     ->end()
                 ->end()
             ->end()
-            ->buildTree()
-        ;
-
-        return $tree;
+            ->buildTree();
     }
 }
diff --git a/src/Symfony/Component/Config/Tests/Definition/PrototypedArrayNodeTest.php b/src/Symfony/Component/Config/Tests/Definition/PrototypedArrayNodeTest.php
index 58d2408a71..b02d6ce6df 100644
--- a/src/Symfony/Component/Config/Tests/Definition/PrototypedArrayNodeTest.php
+++ b/src/Symfony/Component/Config/Tests/Definition/PrototypedArrayNodeTest.php
@@ -264,7 +264,7 @@ class PrototypedArrayNodeTest extends TestCase
      *
      * @dataProvider getDataForKeyRemovedLeftValueOnly
      */
-    public function testMappedAttributeKeyIsRemovedLeftValueOnly($value, $children, $expected)
+    public function testMappedAttributeKeyIsRemovedLeftValueOnly($value, $children, array $expected)
     {
         $node = new PrototypedArrayNode('root');
         $node->setKeyAttribute('id', true);
@@ -280,7 +280,7 @@ class PrototypedArrayNodeTest extends TestCase
         $this->assertEquals($expected, $normalized);
     }
 
-    public function getDataForKeyRemovedLeftValueOnly()
+    public function getDataForKeyRemovedLeftValueOnly(): array
     {
         $scalarValue = new ScalarNode('value');
 
@@ -342,7 +342,7 @@ class PrototypedArrayNodeTest extends TestCase
     /**
      * @dataProvider getPrototypedArrayNodeDataToMerge
      */
-    public function testPrototypedArrayNodeMerge($left, $right, $expected)
+    public function testPrototypedArrayNodeMerge(array $left, array $right, array $expected)
     {
         $node = new PrototypedArrayNode('options');
         $node->setNormalizeKeys(false);
@@ -354,7 +354,7 @@ class PrototypedArrayNodeTest extends TestCase
         self::assertSame($result, $expected);
     }
 
-    public function getPrototypedArrayNodeDataToMerge()
+    public function getPrototypedArrayNodeDataToMerge(): array
     {
         return [
             // data to merged is a plain array
diff --git a/src/Symfony/Component/Config/Tests/Definition/ScalarNodeTest.php b/src/Symfony/Component/Config/Tests/Definition/ScalarNodeTest.php
index 0eb66963eb..0ddd1104fa 100644
--- a/src/Symfony/Component/Config/Tests/Definition/ScalarNodeTest.php
+++ b/src/Symfony/Component/Config/Tests/Definition/ScalarNodeTest.php
@@ -28,7 +28,7 @@ class ScalarNodeTest extends TestCase
         $this->assertSame($value, $node->normalize($value));
     }
 
-    public function getValidValues()
+    public function getValidValues(): array
     {
         return [
             [false],
@@ -84,7 +84,7 @@ class ScalarNodeTest extends TestCase
         $node->normalize($value);
     }
 
-    public function getInvalidValues()
+    public function getInvalidValues(): array
     {
         return [
             [[]],
@@ -127,7 +127,7 @@ class ScalarNodeTest extends TestCase
         $this->assertSame($value, $node->finalize($value));
     }
 
-    public function getValidNonEmptyValues()
+    public function getValidNonEmptyValues(): array
     {
         return [
             [false],
@@ -153,7 +153,7 @@ class ScalarNodeTest extends TestCase
         $node->finalize($value);
     }
 
-    public function getEmptyValues()
+    public function getEmptyValues(): array
     {
         return [
             [null],
diff --git a/src/Symfony/Component/Config/Tests/FileLocatorTest.php b/src/Symfony/Component/Config/Tests/FileLocatorTest.php
index 44ef5ac9e3..b8419d9a1a 100644
--- a/src/Symfony/Component/Config/Tests/FileLocatorTest.php
+++ b/src/Symfony/Component/Config/Tests/FileLocatorTest.php
@@ -20,7 +20,7 @@ class FileLocatorTest extends TestCase
     /**
      * @dataProvider getIsAbsolutePathTests
      */
-    public function testIsAbsolutePath($path)
+    public function testIsAbsolutePath(string $path)
     {
         $loader = new FileLocator([]);
         $r = new \ReflectionObject($loader);
@@ -30,7 +30,7 @@ class FileLocatorTest extends TestCase
         $this->assertTrue($m->invoke($loader, $path), '->isAbsolutePath() returns true for an absolute path');
     }
 
-    public function getIsAbsolutePathTests()
+    public function getIsAbsolutePathTests(): array
     {
         return [
             ['/foo.xml'],
diff --git a/src/Symfony/Component/Config/Tests/Fixtures/Builder/NodeBuilder.php b/src/Symfony/Component/Config/Tests/Fixtures/Builder/NodeBuilder.php
index 26323e9805..5a0a8fe6f3 100644
--- a/src/Symfony/Component/Config/Tests/Fixtures/Builder/NodeBuilder.php
+++ b/src/Symfony/Component/Config/Tests/Fixtures/Builder/NodeBuilder.php
@@ -12,10 +12,11 @@
 namespace Symfony\Component\Config\Tests\Fixtures\Builder;
 
 use Symfony\Component\Config\Definition\Builder\NodeBuilder as BaseNodeBuilder;
+use Symfony\Component\Config\Definition\Builder\NodeDefinition;
 
 class NodeBuilder extends BaseNodeBuilder
 {
-    public function barNode($name)
+    public function barNode($name): NodeDefinition
     {
         return $this->node($name, 'bar');
     }
@@ -23,9 +24,8 @@ class NodeBuilder extends BaseNodeBuilder
     protected function getNodeClass($type): string
     {
         switch ($type) {
-            case 'variable':
-                return __NAMESPACE__.'\\'.ucfirst($type).'NodeDefinition';
             case 'bar':
+            case 'variable':
                 return __NAMESPACE__.'\\'.ucfirst($type).'NodeDefinition';
             default:
                 return parent::getNodeClass($type);
diff --git a/src/Symfony/Component/Config/Tests/Fixtures/Configuration/CustomNode.php b/src/Symfony/Component/Config/Tests/Fixtures/Configuration/CustomNode.php
index 1270eb6a68..f6c53ceeeb 100644
--- a/src/Symfony/Component/Config/Tests/Fixtures/Configuration/CustomNode.php
+++ b/src/Symfony/Component/Config/Tests/Fixtures/Configuration/CustomNode.php
@@ -7,22 +7,22 @@ use Symfony\Component\Config\Definition\NodeInterface;
 
 class CustomNode implements NodeInterface
 {
-    public function getName()
+    public function getName(): string
     {
         return 'custom_node';
     }
 
-    public function getPath()
+    public function getPath(): string
     {
         return 'custom';
     }
 
-    public function isRequired()
+    public function isRequired(): bool
     {
         return false;
     }
 
-    public function hasDefaultValue()
+    public function hasDefaultValue(): bool
     {
         return true;
     }
diff --git a/src/Symfony/Component/Config/Tests/Loader/FileLoaderTest.php b/src/Symfony/Component/Config/Tests/Loader/FileLoaderTest.php
index 023bbe0f31..9c74f6d60a 100644
--- a/src/Symfony/Component/Config/Tests/Loader/FileLoaderTest.php
+++ b/src/Symfony/Component/Config/Tests/Loader/FileLoaderTest.php
@@ -165,22 +165,12 @@ class TestFileLoader extends FileLoader
         return $this->supports;
     }
 
-    public function addLoading($resource)
+    public function addLoading(string $resource): void
     {
         self::$loading[$resource] = true;
     }
 
-    public function removeLoading($resource)
-    {
-        unset(self::$loading[$resource]);
-    }
-
-    public function clearLoading()
-    {
-        self::$loading = [];
-    }
-
-    public function setSupports($supports)
+    public function setSupports(bool $supports): void
     {
         $this->supports = $supports;
     }
diff --git a/src/Symfony/Component/Config/Tests/Resource/DirectoryResourceTest.php b/src/Symfony/Component/Config/Tests/Resource/DirectoryResourceTest.php
index 3de58f4be0..a114f214ab 100644
--- a/src/Symfony/Component/Config/Tests/Resource/DirectoryResourceTest.php
+++ b/src/Symfony/Component/Config/Tests/Resource/DirectoryResourceTest.php
@@ -35,7 +35,7 @@ class DirectoryResourceTest extends TestCase
         $this->removeDirectory($this->directory);
     }
 
-    protected function removeDirectory($directory)
+    protected function removeDirectory(string $directory): void
     {
         $iterator = new \RecursiveIteratorIterator(new \RecursiveDirectoryIterator($directory), \RecursiveIteratorIterator::CHILD_FIRST);
         foreach ($iterator as $path) {
diff --git a/src/Symfony/Component/Config/Tests/Resource/ReflectionClassResourceTest.php b/src/Symfony/Component/Config/Tests/Resource/ReflectionClassResourceTest.php
index af0c2cd2c9..64cfbf129a 100644
--- a/src/Symfony/Component/Config/Tests/Resource/ReflectionClassResourceTest.php
+++ b/src/Symfony/Component/Config/Tests/Resource/ReflectionClassResourceTest.php
@@ -64,7 +64,7 @@ class ReflectionClassResourceTest extends TestCase
     /**
      * @dataProvider provideHashedSignature
      */
-    public function testHashedSignature($changeExpected, $changedLine, $changedCode, $setContext = null)
+    public function testHashedSignature(bool $changeExpected, int $changedLine, ?string $changedCode, ?\Closure $setContext = null)
     {
         if ($setContext) {
             $setContext();
@@ -117,43 +117,43 @@ EOPHP;
         }
     }
 
-    public function provideHashedSignature()
+    public function provideHashedSignature(): iterable
     {
-        yield [0, 0, "// line change\n\n"];
-        yield [1, 0, '/** class docblock */'];
-        yield [1, 1, 'abstract class %s'];
-        yield [1, 1, 'final class %s'];
-        yield [1, 1, 'class %s extends Exception'];
-        yield [1, 1, 'class %s implements '.DummyInterface::class];
-        yield [1, 3, 'const FOO = 456;'];
-        yield [1, 3, 'const BAR = 123;'];
-        yield [1, 4, '/** pub docblock */'];
-        yield [1, 5, 'protected $pub = [];'];
-        yield [1, 5, 'public $pub = [123];'];
-        yield [1, 6, '/** prot docblock */'];
-        yield [1, 7, 'private $prot;'];
-        yield [0, 8, '/** priv docblock */'];
-        yield [0, 9, 'private $priv = 123;'];
-        yield [1, 10, '/** pub docblock */'];
-        yield [1, 11, 'public function pub(...$arg) {}'];
-        yield [1, 11, 'public function pub($arg = null): Foo {}'];
-        yield [0, 11, "public function pub(\$arg = null) {\nreturn 123;\n}"];
-        yield [1, 12, '/** prot docblock */'];
-        yield [1, 13, 'protected function prot($a = [123]) {}'];
-        yield [0, 14, '/** priv docblock */'];
-        yield [0, 15, ''];
+        yield [false, 0, "// line change\n\n"];
+        yield [true, 0, '/** class docblock */'];
+        yield [true, 1, 'abstract class %s'];
+        yield [true, 1, 'final class %s'];
+        yield [true, 1, 'class %s extends Exception'];
+        yield [true, 1, 'class %s implements '.DummyInterface::class];
+        yield [true, 3, 'const FOO = 456;'];
+        yield [true, 3, 'const BAR = 123;'];
+        yield [true, 4, '/** pub docblock */'];
+        yield [true, 5, 'protected $pub = [];'];
+        yield [true, 5, 'public $pub = [123];'];
+        yield [true, 6, '/** prot docblock */'];
+        yield [true, 7, 'private $prot;'];
+        yield [false, 8, '/** priv docblock */'];
+        yield [false, 9, 'private $priv = 123;'];
+        yield [true, 10, '/** pub docblock */'];
+        yield [true, 11, 'public function pub(...$arg) {}'];
+        yield [true, 11, 'public function pub($arg = null): Foo {}'];
+        yield [false, 11, "public function pub(\$arg = null) {\nreturn 123;\n}"];
+        yield [true, 12, '/** prot docblock */'];
+        yield [true, 13, 'protected function prot($a = [123]) {}'];
+        yield [false, 14, '/** priv docblock */'];
+        yield [false, 15, ''];
 
         if (\PHP_VERSION_ID >= 70400) {
             // PHP7.4 typed properties without default value are
             // undefined, make sure this doesn't throw an error
-            yield [1, 5, 'public array $pub;'];
-            yield [0, 7, 'protected int $prot;'];
-            yield [0, 9, 'private string $priv;'];
+            yield [true, 5, 'public array $pub;'];
+            yield [false, 7, 'protected int $prot;'];
+            yield [false, 9, 'private string $priv;'];
         }
 
-        yield [1, 17, 'public function ccc($bar = 187) {}'];
-        yield [1, 17, 'public function ccc($bar = ANOTHER_ONE_THAT_WILL_NEVER_BE_DEFINED_CCCCCCCCC) {}'];
-        yield [1, 17, null, static function () { \define('A_CONSTANT_THAT_FOR_SURE_WILL_NEVER_BE_DEFINED_CCCCCC', 'foo'); }];
+        yield [true, 17, 'public function ccc($bar = 187) {}'];
+        yield [true, 17, 'public function ccc($bar = ANOTHER_ONE_THAT_WILL_NEVER_BE_DEFINED_CCCCCCCCC) {}'];
+        yield [true, 17, null, static function () { \define('A_CONSTANT_THAT_FOR_SURE_WILL_NEVER_BE_DEFINED_CCCCCC', 'foo'); }];
     }
 
     public function testEventSubscriber()
diff --git a/src/Symfony/Component/Config/Tests/Resource/ResourceStub.php b/src/Symfony/Component/Config/Tests/Resource/ResourceStub.php
index 959b00290e..4073566d19 100644
--- a/src/Symfony/Component/Config/Tests/Resource/ResourceStub.php
+++ b/src/Symfony/Component/Config/Tests/Resource/ResourceStub.php
@@ -17,7 +17,7 @@ class ResourceStub implements SelfCheckingResourceInterface
 {
     private $fresh = true;
 
-    public function setFresh($isFresh)
+    public function setFresh(bool $isFresh): void
     {
         $this->fresh = $isFresh;
     }
diff --git a/src/Symfony/Component/Config/Tests/Util/XmlUtilsTest.php b/src/Symfony/Component/Config/Tests/Util/XmlUtilsTest.php
index 481603763a..a7a8ae980d 100644
--- a/src/Symfony/Component/Config/Tests/Util/XmlUtilsTest.php
+++ b/src/Symfony/Component/Config/Tests/Util/XmlUtilsTest.php
@@ -116,7 +116,7 @@ class XmlUtilsTest extends TestCase
     /**
      * @dataProvider getDataForConvertDomToArray
      */
-    public function testConvertDomToArray($expected, $xml, $root = false, $checkPrefix = true)
+    public function testConvertDomToArray($expected, string $xml, bool $root = false, bool $checkPrefix = true)
     {
         $dom = new \DOMDocument();
         $dom->loadXML($root ? $xml : '<root>'.$xml.'</root>');
@@ -124,7 +124,7 @@ class XmlUtilsTest extends TestCase
         $this->assertSame($expected, XmlUtils::convertDomElementToArray($dom->documentElement, $checkPrefix));
     }
 
-    public function getDataForConvertDomToArray()
+    public function getDataForConvertDomToArray(): array
     {
         return [
             [null, ''],
@@ -155,7 +155,7 @@ class XmlUtilsTest extends TestCase
         $this->assertSame($expected, XmlUtils::phpize($value));
     }
 
-    public function getDataForPhpize()
+    public function getDataForPhpize(): array
     {
         return [
             ['', ''],