Mark some/most implementations of Serializable as `@internal`

src/Symfony/Component/Config/Resource/ClassExistenceResource.php

@@ -97,7 +97,7 @@ class ClassExistenceResource implements SelfCheckingResourceInterface, \Serializ
     }
 
     /**
-     * {@inheritdoc}
+     * @internal
      */
     public function serialize()
     {
@@ -109,7 +109,7 @@ class ClassExistenceResource implements SelfCheckingResourceInterface, \Serializ
     }
 
     /**
-     * {@inheritdoc}
+     * @internal
      */
     public function unserialize($serialized)
     {

src/Symfony/Component/Config/Resource/ComposerResource.php

@@ -51,11 +51,17 @@ class ComposerResource implements SelfCheckingResourceInterface, \Serializable
         return self::$runtimeVendors === $this->vendors;
     }
 
+    /**
+     * @internal
+     */
     public function serialize()
     {
         return serialize($this->vendors);
     }
 
+    /**
+     * @internal
+     */
     public function unserialize($serialized)
     {
         $this->vendors = unserialize($serialized);

src/Symfony/Component/Config/Resource/DirectoryResource.php

@@ -104,11 +104,17 @@ class DirectoryResource implements SelfCheckingResourceInterface, \Serializable
         return true;
     }
 
+    /**
+     * @internal
+     */
     public function serialize()
     {
         return serialize([$this->resource, $this->pattern]);
     }
 
+    /**
+     * @internal
+     */
     public function unserialize($serialized)
     {
         list($this->resource, $this->pattern) = unserialize($serialized);

src/Symfony/Component/Config/Resource/FileExistenceResource.php

@@ -59,7 +59,7 @@ class FileExistenceResource implements SelfCheckingResourceInterface, \Serializa
     }
 
     /**
-     * {@inheritdoc}
+     * @internal
      */
     public function serialize()
     {
@@ -67,7 +67,7 @@ class FileExistenceResource implements SelfCheckingResourceInterface, \Serializa
     }
 
     /**
-     * {@inheritdoc}
+     * @internal
      */
     public function unserialize($serialized)
     {

src/Symfony/Component/Config/Resource/FileResource.php

@@ -63,11 +63,17 @@ class FileResource implements SelfCheckingResourceInterface, \Serializable
         return false !== ($filemtime = @filemtime($this->resource)) && $filemtime <= $timestamp;
     }
 
+    /**
+     * @internal
+     */
     public function serialize()
     {
         return serialize($this->resource);
     }
 
+    /**
+     * @internal
+     */
     public function unserialize($serialized)
     {
         $this->resource = unserialize($serialized);

src/Symfony/Component/Config/Resource/GlobResource.php

@@ -73,6 +73,9 @@ class GlobResource implements \IteratorAggregate, SelfCheckingResourceInterface,
         return $this->hash === $hash;
     }
 
+    /**
+     * @internal
+     */
     public function serialize()
     {
         if (null === $this->hash) {
@@ -82,6 +85,9 @@ class GlobResource implements \IteratorAggregate, SelfCheckingResourceInterface,
         return serialize([$this->prefix, $this->pattern, $this->recursive, $this->hash]);
     }
 
+    /**
+     * @internal
+     */
     public function unserialize($serialized)
     {
         list($this->prefix, $this->pattern, $this->recursive, $this->hash) = unserialize($serialized);

src/Symfony/Component/Config/Resource/ReflectionClassResource.php

@@ -57,6 +57,9 @@ class ReflectionClassResource implements SelfCheckingResourceInterface, \Seriali
         return 'reflection.'.$this->className;
     }
 
+    /**
+     * @internal
+     */
     public function serialize()
     {
         if (null === $this->hash) {
@@ -67,6 +70,9 @@ class ReflectionClassResource implements SelfCheckingResourceInterface, \Seriali
         return serialize([$this->files, $this->className, $this->hash]);
     }
 
+    /**
+     * @internal
+     */
     public function unserialize($serialized)
     {
         list($this->files, $this->className, $this->hash) = unserialize($serialized);

src/Symfony/Component/DependencyInjection/Config/AutowireServiceResource.php

@@ -58,11 +58,17 @@ class AutowireServiceResource implements SelfCheckingResourceInterface, \Seriali
         return 'service.autowire.'.$this->class;
     }
 
+    /**
+     * @internal
+     */
     public function serialize()
     {
         return serialize([$this->class, $this->filePath, $this->autowiringMetadata]);
     }
 
+    /**
+     * @internal
+     */
     public function unserialize($serialized)
     {
         if (\PHP_VERSION_ID >= 70000) {

src/Symfony/Component/DependencyInjection/Config/ContainerParametersResource.php

@@ -39,7 +39,7 @@ class ContainerParametersResource implements ResourceInterface, \Serializable
     }
 
     /**
-     * {@inheritdoc}
+     * @internal
      */
     public function serialize()
     {
@@ -47,7 +47,7 @@ class ContainerParametersResource implements ResourceInterface, \Serializable
     }
 
     /**
-     * {@inheritdoc}
+     * @internal
      */
     public function unserialize($serialized)
     {

src/Symfony/Component/Form/FormError.php

@@ -135,9 +135,7 @@ class FormError implements \Serializable
     }
 
     /**
-     * Serializes this error.
-     *
-     * @return string The serialized error
+     * @internal
      */
     public function serialize()
     {
@@ -151,9 +149,7 @@ class FormError implements \Serializable
     }
 
     /**
-     * Unserializes a serialized error.
-     *
-     * @param string $serialized The serialized error
+     * @internal
      */
     public function unserialize($serialized)
     {

src/Symfony/Component/HttpKernel/Config/EnvParametersResource.php

@@ -65,11 +65,17 @@ class EnvParametersResource implements SelfCheckingResourceInterface, \Serializa
         return $this->findVariables() === $this->variables;
     }
 
+    /**
+     * @internal
+     */
     public function serialize()
     {
         return serialize(['prefix' => $this->prefix, 'variables' => $this->variables]);
     }
 
+    /**
+     * @internal
+     */
     public function unserialize($serialized)
     {
         if (\PHP_VERSION_ID >= 70000) {

src/Symfony/Component/HttpKernel/DataCollector/DataCollector.php

@@ -40,6 +40,9 @@ abstract class DataCollector implements DataCollectorInterface, \Serializable
      */
     private $cloner;
 
+    /**
+     * @internal
+     */
     public function serialize()
     {
         $trace = debug_backtrace(DEBUG_BACKTRACE_PROVIDE_OBJECT, 2);
@@ -48,6 +51,9 @@ abstract class DataCollector implements DataCollectorInterface, \Serializable
         return $isCalledFromOverridingMethod ? $this->data : serialize($this->data);
     }
 
+    /**
+     * @internal
+     */
     public function unserialize($data)
     {
         $this->data = \is_array($data) ? $data : unserialize($data);

src/Symfony/Component/HttpKernel/Debug/FileLinkFormatter.php

@@ -61,11 +61,17 @@ class FileLinkFormatter implements \Serializable
         return false;
     }
 
+    /**
+     * @internal
+     */
     public function serialize()
     {
         return serialize($this->getFileLinkFormat());
     }
 
+    /**
+     * @internal
+     */
     public function unserialize($serialized)
     {
         if (\PHP_VERSION_ID >= 70000) {

src/Symfony/Component/Validator/Constraint.php

@@ -284,9 +284,7 @@ abstract class Constraint
      *
      * @return array The properties to serialize
      *
-     * @internal This method may be replaced by an implementation of
-     *           {@link \Serializable} in the future. Please don't use or
-     *           overwrite it.
+     * @internal
      */
     public function __sleep()
     {