Fix for readonly properties that declared in parent

src/Serializers/Native.php

@@ -504,6 +504,10 @@ protected function mapByReference(&$data)
                         continue;
                     }
 
+                    if (PHP_VERSION >= 8.1 && $property->isReadOnly() && $property->class !== $reflection->name) {
+                        continue;
+                    }
+
                     $value = $property->getValue($instance);
 
                     if (is_array($value) || is_object($value)) {

tests/SerializerPhp81Test.php

@@ -183,6 +183,28 @@ enum SerializerScopedBackedEnum: string {
     );
 })->with('serializers');
 
+test('readonly properties declared in parent', function () {
+    $childWithDefaultValue = new SerializerPhp81Child();
+
+    $f = static function () use ($childWithDefaultValue) {
+        return $childWithDefaultValue;
+    };
+
+    $f = s($f);
+
+    expect($f()->property)->toBe(1);
+
+    $child = new SerializerPhp81Child(100);
+
+    $f = static function () use ($child) {
+        return $child;
+    };
+
+    $f = s($f);
+
+    expect($f()->property)->toBe(100);
+})->with('serializers');
+
 test('first-class callable with closures', function () {
     $f = function ($value) {
         return $value;
@@ -584,6 +606,15 @@ enum SerializerScopedBackedEnum: string {
 interface SerializerPhp81HasId {}
 interface SerializerPhp81HasName {}
 
+class SerializerPhp81Child extends SerializerPhp81Parent {}
+
+class SerializerPhp81Parent
+{
+    public function __construct(
+        public readonly int $property = 1,
+    ) {}
+}
+
 class SerializerPhp81Service implements SerializerPhp81HasId, SerializerPhp81HasName
 {
     final public const X = 'foo';