diff --git a/src/Symfony/Bridge/Doctrine/Validator/DoctrineInitializer.php b/src/Symfony/Bridge/Doctrine/Validator/DoctrineInitializer.php
index 010c051581..3b482565a8 100644
--- a/src/Symfony/Bridge/Doctrine/Validator/DoctrineInitializer.php
+++ b/src/Symfony/Bridge/Doctrine/Validator/DoctrineInitializer.php
@@ -28,7 +28,7 @@ class DoctrineInitializer implements ObjectInitializerInterface
         $this->registry = $registry;
     }
 
-    public function initialize($object)
+    public function initialize(object $object)
     {
         $manager = $this->registry->getManagerForClass(\get_class($object));
         if (null !== $manager) {
diff --git a/src/Symfony/Component/Validator/ConstraintViolationList.php b/src/Symfony/Component/Validator/ConstraintViolationList.php
index c30ee57cb2..d5bedd21e2 100644
--- a/src/Symfony/Component/Validator/ConstraintViolationList.php
+++ b/src/Symfony/Component/Validator/ConstraintViolationList.php
@@ -72,7 +72,7 @@ class ConstraintViolationList implements \IteratorAggregate, ConstraintViolation
     /**
      * {@inheritdoc}
      */
-    public function get($offset)
+    public function get(int $offset)
     {
         if (!isset($this->violations[$offset])) {
             throw new \OutOfBoundsException(sprintf('The offset "%s" does not exist.', $offset));
@@ -84,7 +84,7 @@ class ConstraintViolationList implements \IteratorAggregate, ConstraintViolation
     /**
      * {@inheritdoc}
      */
-    public function has($offset)
+    public function has(int $offset)
     {
         return isset($this->violations[$offset]);
     }
@@ -92,7 +92,7 @@ class ConstraintViolationList implements \IteratorAggregate, ConstraintViolation
     /**
      * {@inheritdoc}
      */
-    public function set($offset, ConstraintViolationInterface $violation)
+    public function set(int $offset, ConstraintViolationInterface $violation)
     {
         $this->violations[$offset] = $violation;
     }
@@ -100,7 +100,7 @@ class ConstraintViolationList implements \IteratorAggregate, ConstraintViolation
     /**
      * {@inheritdoc}
      */
-    public function remove($offset)
+    public function remove(int $offset)
     {
         unset($this->violations[$offset]);
     }
diff --git a/src/Symfony/Component/Validator/ConstraintViolationListInterface.php b/src/Symfony/Component/Validator/ConstraintViolationListInterface.php
index 47e986f51e..d253f688d3 100644
--- a/src/Symfony/Component/Validator/ConstraintViolationListInterface.php
+++ b/src/Symfony/Component/Validator/ConstraintViolationListInterface.php
@@ -37,7 +37,7 @@ interface ConstraintViolationListInterface extends \Traversable, \Countable, \Ar
      *
      * @throws \OutOfBoundsException if the offset does not exist
      */
-    public function get($offset);
+    public function get(int $offset);
 
     /**
      * Returns whether the given offset exists.
@@ -46,7 +46,7 @@ interface ConstraintViolationListInterface extends \Traversable, \Countable, \Ar
      *
      * @return bool Whether the offset exists
      */
-    public function has($offset);
+    public function has(int $offset);
 
     /**
      * Sets a violation at a given offset.
@@ -54,12 +54,12 @@ interface ConstraintViolationListInterface extends \Traversable, \Countable, \Ar
      * @param int                          $offset    The violation offset
      * @param ConstraintViolationInterface $violation The violation
      */
-    public function set($offset, ConstraintViolationInterface $violation);
+    public function set(int $offset, ConstraintViolationInterface $violation);
 
     /**
      * Removes a violation at a given offset.
      *
      * @param int $offset The offset to remove
      */
-    public function remove($offset);
+    public function remove(int $offset);
 }
diff --git a/src/Symfony/Component/Validator/Context/ExecutionContext.php b/src/Symfony/Component/Validator/Context/ExecutionContext.php
index bfb767a0d4..56c38d160e 100644
--- a/src/Symfony/Component/Validator/Context/ExecutionContext.php
+++ b/src/Symfony/Component/Validator/Context/ExecutionContext.php
@@ -143,7 +143,7 @@ class ExecutionContext implements ExecutionContextInterface
     /**
      * {@inheritdoc}
      */
-    public function setNode($value, $object, MetadataInterface $metadata = null, $propertyPath)
+    public function setNode($value, ?object $object, MetadataInterface $metadata = null, string $propertyPath)
     {
         $this->value = $value;
         $this->object = $object;
@@ -154,7 +154,7 @@ class ExecutionContext implements ExecutionContextInterface
     /**
      * {@inheritdoc}
      */
-    public function setGroup($group)
+    public function setGroup(?string $group)
     {
         $this->group = $group;
     }
@@ -170,7 +170,7 @@ class ExecutionContext implements ExecutionContextInterface
     /**
      * {@inheritdoc}
      */
-    public function addViolation($message, array $parameters = [])
+    public function addViolation(string $message, array $parameters = [])
     {
         $this->violations->add(new ConstraintViolation(
             $this->translator->trans($message, $parameters, $this->translationDomain),
@@ -188,7 +188,7 @@ class ExecutionContext implements ExecutionContextInterface
     /**
      * {@inheritdoc}
      */
-    public function buildViolation($message, array $parameters = [])
+    public function buildViolation(string $message, array $parameters = [])
     {
         return new ConstraintViolationBuilder(
             $this->violations,
@@ -283,7 +283,7 @@ class ExecutionContext implements ExecutionContextInterface
     /**
      * {@inheritdoc}
      */
-    public function getPropertyPath($subPath = '')
+    public function getPropertyPath(string $subPath = '')
     {
         return PropertyPath::append($this->propertyPath, $subPath);
     }
@@ -291,7 +291,7 @@ class ExecutionContext implements ExecutionContextInterface
     /**
      * {@inheritdoc}
      */
-    public function markGroupAsValidated($cacheKey, $groupHash)
+    public function markGroupAsValidated(string $cacheKey, string $groupHash)
     {
         if (!isset($this->validatedObjects[$cacheKey])) {
             $this->validatedObjects[$cacheKey] = [];
@@ -303,7 +303,7 @@ class ExecutionContext implements ExecutionContextInterface
     /**
      * {@inheritdoc}
      */
-    public function isGroupValidated($cacheKey, $groupHash)
+    public function isGroupValidated(string $cacheKey, string $groupHash)
     {
         return isset($this->validatedObjects[$cacheKey][$groupHash]);
     }
@@ -311,7 +311,7 @@ class ExecutionContext implements ExecutionContextInterface
     /**
      * {@inheritdoc}
      */
-    public function markConstraintAsValidated($cacheKey, $constraintHash)
+    public function markConstraintAsValidated(string $cacheKey, string $constraintHash)
     {
         $this->validatedConstraints[$cacheKey.':'.$constraintHash] = true;
     }
@@ -319,7 +319,7 @@ class ExecutionContext implements ExecutionContextInterface
     /**
      * {@inheritdoc}
      */
-    public function isConstraintValidated($cacheKey, $constraintHash)
+    public function isConstraintValidated(string $cacheKey, string $constraintHash)
     {
         return isset($this->validatedConstraints[$cacheKey.':'.$constraintHash]);
     }
@@ -327,7 +327,7 @@ class ExecutionContext implements ExecutionContextInterface
     /**
      * {@inheritdoc}
      */
-    public function markObjectAsInitialized($cacheKey)
+    public function markObjectAsInitialized(string $cacheKey)
     {
         $this->initializedObjects[$cacheKey] = true;
     }
@@ -335,7 +335,7 @@ class ExecutionContext implements ExecutionContextInterface
     /**
      * {@inheritdoc}
      */
-    public function isObjectInitialized($cacheKey)
+    public function isObjectInitialized(string $cacheKey)
     {
         return isset($this->initializedObjects[$cacheKey]);
     }
diff --git a/src/Symfony/Component/Validator/Context/ExecutionContextInterface.php b/src/Symfony/Component/Validator/Context/ExecutionContextInterface.php
index 2ab625b156..0f02e1f694 100644
--- a/src/Symfony/Component/Validator/Context/ExecutionContextInterface.php
+++ b/src/Symfony/Component/Validator/Context/ExecutionContextInterface.php
@@ -67,7 +67,7 @@ interface ExecutionContextInterface
      * @param string $message The error message
      * @param array  $params  The parameters substituted in the error message
      */
-    public function addViolation($message, array $params = []);
+    public function addViolation(string $message, array $params = []);
 
     /**
      * Returns a builder for adding a violation with extended information.
@@ -86,7 +86,7 @@ interface ExecutionContextInterface
      *
      * @return ConstraintViolationBuilderInterface The violation builder
      */
-    public function buildViolation($message, array $parameters = []);
+    public function buildViolation(string $message, array $parameters = []);
 
     /**
      * Returns the validator.
@@ -133,7 +133,7 @@ interface ExecutionContextInterface
      * @internal Used by the validator engine. Should not be called by user
      *           code.
      */
-    public function setNode($value, $object, MetadataInterface $metadata = null, $propertyPath);
+    public function setNode($value, ?object $object, MetadataInterface $metadata = null, string $propertyPath);
 
     /**
      * Sets the currently validated group.
@@ -143,7 +143,7 @@ interface ExecutionContextInterface
      * @internal Used by the validator engine. Should not be called by user
      *           code.
      */
-    public function setGroup($group);
+    public function setGroup(?string $group);
 
     /**
      * Sets the currently validated constraint.
@@ -165,7 +165,7 @@ interface ExecutionContextInterface
      * @internal Used by the validator engine. Should not be called by user
      *           code.
      */
-    public function markGroupAsValidated($cacheKey, $groupHash);
+    public function markGroupAsValidated(string $cacheKey, string $groupHash);
 
     /**
      * Returns whether an object was validated in a specific validation group.
@@ -180,7 +180,7 @@ interface ExecutionContextInterface
      * @internal Used by the validator engine. Should not be called by user
      *           code.
      */
-    public function isGroupValidated($cacheKey, $groupHash);
+    public function isGroupValidated(string $cacheKey, string $groupHash);
 
     /**
      * Marks a constraint as validated for an object.
@@ -191,7 +191,7 @@ interface ExecutionContextInterface
      * @internal Used by the validator engine. Should not be called by user
      *           code.
      */
-    public function markConstraintAsValidated($cacheKey, $constraintHash);
+    public function markConstraintAsValidated(string $cacheKey, string $constraintHash);
 
     /**
      * Returns whether a constraint was validated for an object.
@@ -204,7 +204,7 @@ interface ExecutionContextInterface
      * @internal Used by the validator engine. Should not be called by user
      *           code.
      */
-    public function isConstraintValidated($cacheKey, $constraintHash);
+    public function isConstraintValidated(string $cacheKey, string $constraintHash);
 
     /**
      * Marks that an object was initialized.
@@ -216,7 +216,7 @@ interface ExecutionContextInterface
      *
      * @see ObjectInitializerInterface
      */
-    public function markObjectAsInitialized($cacheKey);
+    public function markObjectAsInitialized(string $cacheKey);
 
     /**
      * Returns whether an object was initialized.
@@ -230,7 +230,7 @@ interface ExecutionContextInterface
      *
      * @see ObjectInitializerInterface
      */
-    public function isObjectInitialized($cacheKey);
+    public function isObjectInitialized(string $cacheKey);
 
     /**
      * Returns the violations generated by the validator so far.
@@ -340,5 +340,5 @@ interface ExecutionContextInterface
      *                string if the validator is currently validating the
      *                root value of the validation graph.
      */
-    public function getPropertyPath($subPath = '');
+    public function getPropertyPath(string $subPath = '');
 }
diff --git a/src/Symfony/Component/Validator/Mapping/Cache/CacheInterface.php b/src/Symfony/Component/Validator/Mapping/Cache/CacheInterface.php
index f770f46154..cf2541deb3 100644
--- a/src/Symfony/Component/Validator/Mapping/Cache/CacheInterface.php
+++ b/src/Symfony/Component/Validator/Mapping/Cache/CacheInterface.php
@@ -25,7 +25,7 @@ interface CacheInterface
      *
      * @param string $class
      */
-    public function has($class);
+    public function has(string $class);
 
     /**
      * Returns the metadata for the given class from the cache.
@@ -34,7 +34,7 @@ interface CacheInterface
      *
      * @return ClassMetadata|false A ClassMetadata instance or false on miss
      */
-    public function read($class);
+    public function read(string $class);
 
     /**
      * Stores a class metadata in the cache.
diff --git a/src/Symfony/Component/Validator/Mapping/Cache/DoctrineCache.php b/src/Symfony/Component/Validator/Mapping/Cache/DoctrineCache.php
index 2f54019328..17b46e9823 100644
--- a/src/Symfony/Component/Validator/Mapping/Cache/DoctrineCache.php
+++ b/src/Symfony/Component/Validator/Mapping/Cache/DoctrineCache.php
@@ -36,7 +36,7 @@ final class DoctrineCache implements CacheInterface
     /**
      * {@inheritdoc}
      */
-    public function has($class): bool
+    public function has(string $class): bool
     {
         return $this->cache->contains($class);
     }
@@ -44,7 +44,7 @@ final class DoctrineCache implements CacheInterface
     /**
      * {@inheritdoc}
      */
-    public function read($class)
+    public function read(string $class)
     {
         return $this->cache->fetch($class);
     }
diff --git a/src/Symfony/Component/Validator/Mapping/Cache/Psr6Cache.php b/src/Symfony/Component/Validator/Mapping/Cache/Psr6Cache.php
index 7d1cdd8003..e913e280e6 100644
--- a/src/Symfony/Component/Validator/Mapping/Cache/Psr6Cache.php
+++ b/src/Symfony/Component/Validator/Mapping/Cache/Psr6Cache.php
@@ -31,7 +31,7 @@ class Psr6Cache implements CacheInterface
     /**
      * {@inheritdoc}
      */
-    public function has($class)
+    public function has(string $class)
     {
         return $this->cacheItemPool->hasItem($this->escapeClassName($class));
     }
@@ -39,7 +39,7 @@ class Psr6Cache implements CacheInterface
     /**
      * {@inheritdoc}
      */
-    public function read($class)
+    public function read(string $class)
     {
         $item = $this->cacheItemPool->getItem($this->escapeClassName($class));
 
diff --git a/src/Symfony/Component/Validator/Mapping/ClassMetadata.php b/src/Symfony/Component/Validator/Mapping/ClassMetadata.php
index 6e0256c290..d1ee1212ba 100644
--- a/src/Symfony/Component/Validator/Mapping/ClassMetadata.php
+++ b/src/Symfony/Component/Validator/Mapping/ClassMetadata.php
@@ -364,7 +364,7 @@ class ClassMetadata extends GenericMetadata implements ClassMetadataInterface
     /**
      * {@inheritdoc}
      */
-    public function hasPropertyMetadata($property)
+    public function hasPropertyMetadata(string $property)
     {
         return \array_key_exists($property, $this->members);
     }
@@ -372,7 +372,7 @@ class ClassMetadata extends GenericMetadata implements ClassMetadataInterface
     /**
      * {@inheritdoc}
      */
-    public function getPropertyMetadata($property)
+    public function getPropertyMetadata(string $property)
     {
         if (!isset($this->members[$property])) {
             return [];
diff --git a/src/Symfony/Component/Validator/Mapping/ClassMetadataInterface.php b/src/Symfony/Component/Validator/Mapping/ClassMetadataInterface.php
index 1b6f07ac8e..b25fc018bb 100644
--- a/src/Symfony/Component/Validator/Mapping/ClassMetadataInterface.php
+++ b/src/Symfony/Component/Validator/Mapping/ClassMetadataInterface.php
@@ -81,7 +81,7 @@ interface ClassMetadataInterface extends MetadataInterface
      *
      * @return bool
      */
-    public function hasPropertyMetadata($property);
+    public function hasPropertyMetadata(string $property);
 
     /**
      * Returns all metadata instances for the given named property.
@@ -94,7 +94,7 @@ interface ClassMetadataInterface extends MetadataInterface
      * @return PropertyMetadataInterface[] A list of metadata instances. Empty if
      *                                     no metadata exists for the property.
      */
-    public function getPropertyMetadata($property);
+    public function getPropertyMetadata(string $property);
 
     /**
      * Returns the name of the backing PHP class.
diff --git a/src/Symfony/Component/Validator/Mapping/GenericMetadata.php b/src/Symfony/Component/Validator/Mapping/GenericMetadata.php
index 139d252fc0..9a2a2d6db7 100644
--- a/src/Symfony/Component/Validator/Mapping/GenericMetadata.php
+++ b/src/Symfony/Component/Validator/Mapping/GenericMetadata.php
@@ -185,7 +185,7 @@ class GenericMetadata implements MetadataInterface
      *
      * Aware of the global group (* group).
      */
-    public function findConstraints($group)
+    public function findConstraints(string $group)
     {
         return isset($this->constraintsByGroup[$group])
             ? $this->constraintsByGroup[$group]
diff --git a/src/Symfony/Component/Validator/Mapping/MetadataInterface.php b/src/Symfony/Component/Validator/Mapping/MetadataInterface.php
index 514beb9492..f46af2fcce 100644
--- a/src/Symfony/Component/Validator/Mapping/MetadataInterface.php
+++ b/src/Symfony/Component/Validator/Mapping/MetadataInterface.php
@@ -62,5 +62,5 @@ interface MetadataInterface
      *
      * @return Constraint[] A list of constraint instances
      */
-    public function findConstraints($group);
+    public function findConstraints(string $group);
 }
diff --git a/src/Symfony/Component/Validator/ObjectInitializerInterface.php b/src/Symfony/Component/Validator/ObjectInitializerInterface.php
index 1bd55f0cda..8d0688cece 100644
--- a/src/Symfony/Component/Validator/ObjectInitializerInterface.php
+++ b/src/Symfony/Component/Validator/ObjectInitializerInterface.php
@@ -27,5 +27,5 @@ interface ObjectInitializerInterface
      *
      * @param object $object The object to validate
      */
-    public function initialize($object);
+    public function initialize(object $object);
 }
diff --git a/src/Symfony/Component/Validator/Tests/Fixtures/FakeClassMetadata.php b/src/Symfony/Component/Validator/Tests/Fixtures/FakeClassMetadata.php
index 39f5477779..e5e200a5ba 100644
--- a/src/Symfony/Component/Validator/Tests/Fixtures/FakeClassMetadata.php
+++ b/src/Symfony/Component/Validator/Tests/Fixtures/FakeClassMetadata.php
@@ -15,7 +15,7 @@ use Symfony\Component\Validator\Mapping\ClassMetadata;
 
 class FakeClassMetadata extends ClassMetadata
 {
-    public function addCustomPropertyMetadata($propertyName, $metadata)
+    public function addCustomPropertyMetadata(string $propertyName, $metadata)
     {
         if (!isset($this->members[$propertyName])) {
             $this->members[$propertyName] = [];
diff --git a/src/Symfony/Component/Validator/Validator/ContextualValidatorInterface.php b/src/Symfony/Component/Validator/Validator/ContextualValidatorInterface.php
index c8b545b54b..68cd36eac9 100644
--- a/src/Symfony/Component/Validator/Validator/ContextualValidatorInterface.php
+++ b/src/Symfony/Component/Validator/Validator/ContextualValidatorInterface.php
@@ -32,7 +32,7 @@ interface ContextualValidatorInterface
      *
      * @return $this
      */
-    public function atPath($path);
+    public function atPath(string $path);
 
     /**
      * Validates a value against a constraint or a list of constraints.
@@ -58,7 +58,7 @@ interface ContextualValidatorInterface
      *
      * @return $this
      */
-    public function validateProperty($object, $propertyName, $groups = null);
+    public function validateProperty($object, string $propertyName, $groups = null);
 
     /**
      * Validates a value against the constraints specified for an object's
@@ -71,7 +71,7 @@ interface ContextualValidatorInterface
      *
      * @return $this
      */
-    public function validatePropertyValue($objectOrClass, $propertyName, $value, $groups = null);
+    public function validatePropertyValue($objectOrClass, string $propertyName, $value, $groups = null);
 
     /**
      * Returns the violations that have been generated so far in the context
diff --git a/src/Symfony/Component/Validator/Validator/RecursiveContextualValidator.php b/src/Symfony/Component/Validator/Validator/RecursiveContextualValidator.php
index 33e207af47..cad3acc154 100644
--- a/src/Symfony/Component/Validator/Validator/RecursiveContextualValidator.php
+++ b/src/Symfony/Component/Validator/Validator/RecursiveContextualValidator.php
@@ -71,7 +71,7 @@ class RecursiveContextualValidator implements ContextualValidatorInterface
     /**
      * {@inheritdoc}
      */
-    public function atPath($path)
+    public function atPath(string $path)
     {
         $this->defaultPropertyPath = $this->context->getPropertyPath($path);
 
@@ -169,7 +169,7 @@ class RecursiveContextualValidator implements ContextualValidatorInterface
     /**
      * {@inheritdoc}
      */
-    public function validateProperty($object, $propertyName, $groups = null)
+    public function validateProperty($object, string $propertyName, $groups = null)
     {
         $classMetadata = $this->metadataFactory->getMetadataFor($object);
 
@@ -213,7 +213,7 @@ class RecursiveContextualValidator implements ContextualValidatorInterface
     /**
      * {@inheritdoc}
      */
-    public function validatePropertyValue($objectOrClass, $propertyName, $value, $groups = null)
+    public function validatePropertyValue($objectOrClass, string $propertyName, $value, $groups = null)
     {
         $classMetadata = $this->metadataFactory->getMetadataFor($objectOrClass);
 
@@ -295,7 +295,7 @@ class RecursiveContextualValidator implements ContextualValidatorInterface
      * traversal, the object will be iterated and each nested object will be
      * validated instead.
      *
-     * @param object                    $object            The object to cascade
+     * @param object|int|float|string   $object            The object to cascade
      * @param string                    $propertyPath      The current property path
      * @param (string|GroupSequence)[]  $groups            The validated groups
      * @param int                       $traversalStrategy The strategy for traversing the
@@ -437,7 +437,7 @@ class RecursiveContextualValidator implements ContextualValidatorInterface
      *
      * @see TraversalStrategy
      */
-    private function validateClassNode($object, $cacheKey, ClassMetadataInterface $metadata = null, $propertyPath, array $groups, $cascadedGroups, $traversalStrategy, ExecutionContextInterface $context)
+    private function validateClassNode(object $object, $cacheKey, ClassMetadataInterface $metadata = null, $propertyPath, array $groups, $cascadedGroups, $traversalStrategy, ExecutionContextInterface $context)
     {
         $context->setNode($object, $object, $metadata, $propertyPath);
 
@@ -616,7 +616,7 @@ class RecursiveContextualValidator implements ContextualValidatorInterface
      *
      * @see TraversalStrategy
      */
-    private function validateGenericNode($value, $object, $cacheKey, MetadataInterface $metadata = null, $propertyPath, array $groups, $cascadedGroups, $traversalStrategy, ExecutionContextInterface $context)
+    private function validateGenericNode($value, ?object $object, $cacheKey, MetadataInterface $metadata = null, $propertyPath, array $groups, $cascadedGroups, $traversalStrategy, ExecutionContextInterface $context)
     {
         $context->setNode($value, $object, $metadata, $propertyPath);
 
@@ -724,7 +724,7 @@ class RecursiveContextualValidator implements ContextualValidatorInterface
      *                                                     the group sequence
      * @param ExecutionContextInterface $context           The execution context
      */
-    private function stepThroughGroupSequence($value, $object, $cacheKey, MetadataInterface $metadata = null, $propertyPath, $traversalStrategy, GroupSequence $groupSequence, $cascadedGroup, ExecutionContextInterface $context)
+    private function stepThroughGroupSequence($value, ?object $object, $cacheKey, MetadataInterface $metadata = null, $propertyPath, $traversalStrategy, GroupSequence $groupSequence, $cascadedGroup, ExecutionContextInterface $context)
     {
         $violationCount = \count($context->getViolations());
         $cascadedGroups = $cascadedGroup ? [$cascadedGroup] : null;
diff --git a/src/Symfony/Component/Validator/Validator/RecursiveValidator.php b/src/Symfony/Component/Validator/Validator/RecursiveValidator.php
index a258fd4a77..8a04e1d197 100644
--- a/src/Symfony/Component/Validator/Validator/RecursiveValidator.php
+++ b/src/Symfony/Component/Validator/Validator/RecursiveValidator.php
@@ -104,7 +104,7 @@ class RecursiveValidator implements ValidatorInterface
     /**
      * {@inheritdoc}
      */
-    public function validateProperty($object, $propertyName, $groups = null)
+    public function validateProperty($object, string $propertyName, $groups = null)
     {
         return $this->startContext($object)
             ->validateProperty($object, $propertyName, $groups)
@@ -114,7 +114,7 @@ class RecursiveValidator implements ValidatorInterface
     /**
      * {@inheritdoc}
      */
-    public function validatePropertyValue($objectOrClass, $propertyName, $value, $groups = null)
+    public function validatePropertyValue($objectOrClass, string $propertyName, $value, $groups = null)
     {
         // If a class name is passed, take $value as root
         return $this->startContext(\is_object($objectOrClass) ? $objectOrClass : $value)
diff --git a/src/Symfony/Component/Validator/Validator/TraceableValidator.php b/src/Symfony/Component/Validator/Validator/TraceableValidator.php
index c08910d8de..be7daf48c8 100644
--- a/src/Symfony/Component/Validator/Validator/TraceableValidator.php
+++ b/src/Symfony/Component/Validator/Validator/TraceableValidator.php
@@ -105,7 +105,7 @@ class TraceableValidator implements ValidatorInterface, ResetInterface
     /**
      * {@inheritdoc}
      */
-    public function validateProperty($object, $propertyName, $groups = null)
+    public function validateProperty($object, string $propertyName, $groups = null)
     {
         return $this->validator->validateProperty($object, $propertyName, $groups);
     }
@@ -113,7 +113,7 @@ class TraceableValidator implements ValidatorInterface, ResetInterface
     /**
      * {@inheritdoc}
      */
-    public function validatePropertyValue($objectOrClass, $propertyName, $value, $groups = null)
+    public function validatePropertyValue($objectOrClass, string $propertyName, $value, $groups = null)
     {
         return $this->validator->validatePropertyValue($objectOrClass, $propertyName, $value, $groups);
     }
diff --git a/src/Symfony/Component/Validator/Validator/ValidatorInterface.php b/src/Symfony/Component/Validator/Validator/ValidatorInterface.php
index 78157465ab..23356638be 100644
--- a/src/Symfony/Component/Validator/Validator/ValidatorInterface.php
+++ b/src/Symfony/Component/Validator/Validator/ValidatorInterface.php
@@ -52,7 +52,7 @@ interface ValidatorInterface extends MetadataFactoryInterface
      *                                          If the list is empty, validation
      *                                          succeeded
      */
-    public function validateProperty($object, $propertyName, $groups = null);
+    public function validateProperty($object, string $propertyName, $groups = null);
 
     /**
      * Validates a value against the constraints specified for an object's
@@ -67,7 +67,7 @@ interface ValidatorInterface extends MetadataFactoryInterface
      *                                          If the list is empty, validation
      *                                          succeeded
      */
-    public function validatePropertyValue($objectOrClass, $propertyName, $value, $groups = null);
+    public function validatePropertyValue($objectOrClass, string $propertyName, $value, $groups = null);
 
     /**
      * Starts a new validation context and returns a validator for that context.
diff --git a/src/Symfony/Component/Validator/Violation/ConstraintViolationBuilder.php b/src/Symfony/Component/Validator/Violation/ConstraintViolationBuilder.php
index 151a815815..2291132050 100644
--- a/src/Symfony/Component/Validator/Violation/ConstraintViolationBuilder.php
+++ b/src/Symfony/Component/Validator/Violation/ConstraintViolationBuilder.php
@@ -59,7 +59,7 @@ class ConstraintViolationBuilder implements ConstraintViolationBuilderInterface
     /**
      * {@inheritdoc}
      */
-    public function atPath($path)
+    public function atPath(string $path)
     {
         $this->propertyPath = PropertyPath::append($this->propertyPath, $path);
 
@@ -69,7 +69,7 @@ class ConstraintViolationBuilder implements ConstraintViolationBuilderInterface
     /**
      * {@inheritdoc}
      */
-    public function setParameter($key, $value)
+    public function setParameter(string $key, string $value)
     {
         $this->parameters[$key] = $value;
 
@@ -89,7 +89,7 @@ class ConstraintViolationBuilder implements ConstraintViolationBuilderInterface
     /**
      * {@inheritdoc}
      */
-    public function setTranslationDomain($translationDomain)
+    public function setTranslationDomain(string $translationDomain)
     {
         $this->translationDomain = $translationDomain;
 
@@ -109,7 +109,7 @@ class ConstraintViolationBuilder implements ConstraintViolationBuilderInterface
     /**
      * {@inheritdoc}
      */
-    public function setPlural($number)
+    public function setPlural(int $number)
     {
         $this->plural = $number;
 
@@ -119,7 +119,7 @@ class ConstraintViolationBuilder implements ConstraintViolationBuilderInterface
     /**
      * {@inheritdoc}
      */
-    public function setCode($code)
+    public function setCode(?string $code)
     {
         $this->code = $code;
 
diff --git a/src/Symfony/Component/Validator/Violation/ConstraintViolationBuilderInterface.php b/src/Symfony/Component/Validator/Violation/ConstraintViolationBuilderInterface.php
index cb007b6e65..9ac1b8b4c4 100644
--- a/src/Symfony/Component/Validator/Violation/ConstraintViolationBuilderInterface.php
+++ b/src/Symfony/Component/Validator/Violation/ConstraintViolationBuilderInterface.php
@@ -33,7 +33,7 @@ interface ConstraintViolationBuilderInterface
      *
      * @return $this
      */
-    public function atPath($path);
+    public function atPath(string $path);
 
     /**
      * Sets a parameter to be inserted into the violation message.
@@ -43,7 +43,7 @@ interface ConstraintViolationBuilderInterface
      *
      * @return $this
      */
-    public function setParameter($key, $value);
+    public function setParameter(string $key, string $value);
 
     /**
      * Sets all parameters to be inserted into the violation message.
@@ -66,7 +66,7 @@ interface ConstraintViolationBuilderInterface
      *
      * @see \Symfony\Contracts\Translation\TranslatorInterface
      */
-    public function setTranslationDomain($translationDomain);
+    public function setTranslationDomain(string $translationDomain);
 
     /**
      * Sets the invalid value that caused this violation.
@@ -87,7 +87,7 @@ interface ConstraintViolationBuilderInterface
      *
      * @see \Symfony\Contracts\Translation\TranslatorInterface::trans()
      */
-    public function setPlural($number);
+    public function setPlural(int $number);
 
     /**
      * Sets the violation code.
@@ -96,7 +96,7 @@ interface ConstraintViolationBuilderInterface
      *
      * @return $this
      */
-    public function setCode($code);
+    public function setCode(?string $code);
 
     /**
      * Sets the cause of the violation.