From d3ba963f62e250862dc3ebdc00c4dac67d41d289 Mon Sep 17 00:00:00 2001
From: George Steel <george@net-glue.co.uk>
Date: Tue, 5 May 2026 12:47:32 +0100
Subject: [PATCH] Failing test case for covariant templates

---
 tests/Unit/Fixture/CovariantTemplate.php | 19 +++++++++++++++++++
 tests/Unit/MetadataHydratorTest.php      | 15 +++++++++++++++
 2 files changed, 34 insertions(+)
 create mode 100644 tests/Unit/Fixture/CovariantTemplate.php

diff --git a/tests/Unit/Fixture/CovariantTemplate.php b/tests/Unit/Fixture/CovariantTemplate.php
new file mode 100644
index 0000000..6b00958
--- /dev/null
+++ b/tests/Unit/Fixture/CovariantTemplate.php
@@ -0,0 +1,19 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\Hydrator\Tests\Unit\Fixture;
+
+use Patchlevel\Hydrator\Normalizer\ArrayNormalizer;
+use Patchlevel\Hydrator\Normalizer\ObjectNormalizer;
+
+/** @template-covariant T of object */
+final readonly class CovariantTemplate
+{
+    /** @param list<T> $objects */
+    public function __construct(
+        #[ArrayNormalizer(new ObjectNormalizer())]
+        public array $objects,
+    ) {
+    }
+}
diff --git a/tests/Unit/MetadataHydratorTest.php b/tests/Unit/MetadataHydratorTest.php
index 88b66a7..dca4aee 100644
--- a/tests/Unit/MetadataHydratorTest.php
+++ b/tests/Unit/MetadataHydratorTest.php
@@ -23,6 +23,7 @@
 use Patchlevel\Hydrator\Tests\Unit\Fixture\Circle2Dto;
 use Patchlevel\Hydrator\Tests\Unit\Fixture\Circle3Dto;
 use Patchlevel\Hydrator\Tests\Unit\Fixture\ContextAwareDto;
+use Patchlevel\Hydrator\Tests\Unit\Fixture\CovariantTemplate;
 use Patchlevel\Hydrator\Tests\Unit\Fixture\DefaultDto;
 use Patchlevel\Hydrator\Tests\Unit\Fixture\DtoWithHooks;
 use Patchlevel\Hydrator\Tests\Unit\Fixture\Email;
@@ -666,4 +667,18 @@ public function guess(ObjectType $type): Normalizer|null
 
         self::assertSame(4, $guesser->count);
     }
+
+    public function testTypesWithCovariantTemplatesCanBeSerialisedAndHydrated(): void
+    {
+        $object = new CovariantTemplate([
+            (object)['foo' => 1],
+            (object)['foo' => 2],
+        ]);
+
+        $serialized = $this->hydrator->extract($object);
+        $hydrated = $this->hydrator->hydrate(CovariantTemplate::class, $serialized);
+
+        self::assertNotSame($object, $hydrated);
+        self::assertEquals($object, $hydrated);
+    }
 }