remove support of non backed enums

Author: mtarld

src/Symfony/Component/SerDes/Internal/TypeFactory.php

@@ -110,8 +110,12 @@ public static function createFromString(string $string): Type|UnionType
             return self::$cache[$cacheKey] = new Type($string, $isNullable);
         }
 
-        if (is_subclass_of($string, \BackedEnum::class)) {
-            return self::$cache[$cacheKey] = new Type('enum', $isNullable, $string);
+        if (is_subclass_of($string, \UnitEnum::class)) {
+            if (is_subclass_of($string, \BackedEnum::class)) {
+                return self::$cache[$cacheKey] = new Type('enum', $isNullable, $string);
+            }
+
+            throw new InvalidTypeException($string);
         }
 
         if (class_exists($string) || interface_exists($string)) {

src/Symfony/Component/SerDes/Tests/Fixtures/Enum/DummyUnitEnum.php

@@ -0,0 +1,9 @@
+<?php
+
+namespace Symfony\Component\SerDes\Tests\Fixtures\Enum;
+
+enum DummyUnitEnum
+{
+    case ONE;
+    case TWO;
+}

src/Symfony/Component/SerDes/Tests/Internal/TypeFactoryTest.php

@@ -20,6 +20,7 @@
 use Symfony\Component\SerDes\Internal\UnionType;
 use Symfony\Component\SerDes\Tests\Fixtures\Dto\ClassicDummy;
 use Symfony\Component\SerDes\Tests\Fixtures\Enum\DummyBackedEnum;
+use Symfony\Component\SerDes\Tests\Fixtures\Enum\DummyUnitEnum;
 
 class TypeFactoryTest extends TestCase
 {
@@ -140,4 +141,11 @@ public function testCreateThrowOnRawArray()
 
         TypeFactory::createFromString('array');
     }
+
+    public function testCreateThrowOnUnitEnum()
+    {
+        $this->expectException(InvalidTypeException::class);
+
+        TypeFactory::createFromString(DummyUnitEnum::class);
+    }
 }