Merge branch '7.4' into 8.0

* 7.4:
  [Mime] Deprecate implementing `__sleep/wakeup()` on `AbstractPart` implementations
  [Validator] Deprecate implementing `__sleep/wakeup()` on GenericMetadata implementations
  [String] Deprecate implementing `__sleep/wakeup()` on string implementations
  More cleanups related to internal sleep/wakeup usages
  [HttpKernel] Deprecate `__sleep/wakeup()` on kernels and data collectors and make `Profile` final
  [Serializer] Make `AttributeMetadata` and `ClassMetadata` final
  Replace __sleep/wakeup() by __(un)serialize() when BC isn't a concern
  chore: PHP CS Fixer - simplify config

Author: nicolas-grekas

Cloner/Internal/NoDefault.php

@@ -11,8 +11,6 @@
 
 namespace Symfony\Component\VarDumper\Cloner;
 
-use Symfony\Component\VarDumper\Cloner\Internal\NoDefault;
-
 /**
  * Represents the main properties of a PHP variable.
  *
@@ -42,34 +40,37 @@ class Stub
     public int $position = 0;
     public array $attr = [];
 
-    private static array $defaultProperties = [];
-
     /**
      * @internal
      */
-    public function __sleep(): array
-    {
-        $properties = [];
+    protected static array $propertyDefaults = [];
 
-        if (!isset(self::$defaultProperties[$c = static::class])) {
-            $reflection = new \ReflectionClass($c);
-            self::$defaultProperties[$c] = [];
+    public function __serialize(): array
+    {
+        static $noDefault = new \stdClass();
 
-            foreach ($reflection->getProperties() as $p) {
-                if ($p->isStatic()) {
-                    continue;
+        if (self::class === static::class) {
+            $data = [];
+            foreach ($this as $k => $v) {
+                $default = self::$propertyDefaults[$this::class][$k] ??= ($p = new \ReflectionProperty($this, $k))->hasDefaultValue() ? $p->getDefaultValue() : ($p->hasType() ? $noDefault : null);
+                if ($noDefault === $default || $default !== $v) {
+                    $data[$k] = $v;
                 }
-
-                self::$defaultProperties[$c][$p->name] = $p->hasDefaultValue() ? $p->getDefaultValue() : ($p->hasType() ? NoDefault::NoDefault : null);
             }
+
+            return $data;
         }
 
-        foreach (self::$defaultProperties[$c] as $k => $v) {
-            if (NoDefault::NoDefault === $v || $this->$k !== $v) {
-                $properties[] = $k;
+        return \Closure::bind(function () use ($noDefault) {
+            $data = [];
+            foreach ($this as $k => $v) {
+                $default = self::$propertyDefaults[$this::class][$k] ??= ($p = new \ReflectionProperty($this, $k))->hasDefaultValue() ? $p->getDefaultValue() : ($p->hasType() ? $noDefault : null);
+                if ($noDefault === $default || $default !== $v) {
+                    $data[$k] = $v;
+                }
             }
-        }
 
-        return $properties;
+            return $data;
+        }, $this, $this::class)();
     }
 }