Add a test case showing the regression

tests/Doctrine/Tests/ORM/Functional/Ticket/GH8055Test.php

@@ -0,0 +1,71 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Doctrine\Tests\ORM\Functional\Ticket;
+
+use Doctrine\Tests\OrmFunctionalTestCase;
+
+/**
+ * @group GH8055
+ */
+final class GH8055Test extends OrmFunctionalTestCase
+{
+    /**
+     * {@inheritDoc}
+     */
+    protected function setUp() : void
+    {
+        parent::setUp();
+
+        $this->setUpEntitySchema([
+            GH8055BaseClass::class,
+            GH8055SubClass::class,
+        ]);
+    }
+
+    public function testNumericDescriminatorColumn() : void
+    {
+        $entity = new GH8055SubClass();
+        $entity->value = 'test';
+        $this->_em->persist($entity);
+        $this->_em->flush();
+        $this->_em->clear();
+
+        $repository = $this->_em->getRepository(GH8055SubClass::class);
+        $hydrated = $repository->find($entity->id);
+
+        self::assertSame('test', $hydrated->value);
+    }
+}
+
+/**
+ * @Entity()
+ * @Table(name="gh8055")
+ * @InheritanceType("JOINED")
+ * @DiscriminatorColumn(name="discr", type="integer")
+ * @DiscriminatorMap({
+ *     "1" = GH8055BaseClass::class,
+ *     "2" = GH8055SubClass::class
+ * })
+ */
+class GH8055BaseClass
+{
+    /**
+     * @Id @GeneratedValue
+     * @Column(type="integer")
+     */
+    public $id;
+}
+
+/**
+ * @Entity()
+ */
+class GH8055SubClass extends GH8055BaseClass
+{
+    /**
+     * @Column(name="test", type="string")
+     * @var string
+     */
+    public $value;
+}