Make AbstractSchemaManager covariant to its template argument

src/Schema/AbstractSchemaManager.php

@@ -31,7 +31,7 @@
  * Base class for schema managers. Schema managers are used to inspect and/or
  * modify the database schema/structure.
  *
- * @template T of AbstractPlatform
+ * @template-covariant T of AbstractPlatform
  */
 abstract class AbstractSchemaManager
 {

static-analysis/abstract-schema-manager-covariant-template.php

@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Doctrine\StaticAnalysis\DBAL;
+
+use Doctrine\DBAL\Connection;
+use Doctrine\DBAL\Driver\PDO\PgSQL\Driver;
+use Doctrine\DBAL\Schema\DefaultSchemaManagerFactory;
+use Doctrine\DBAL\Schema\PostgreSQLSchemaManager;
+use Exception;
+
+$smf = new DefaultSchemaManagerFactory();
+$schemaManager = $smf->createSchemaManager(new Connection([], new Driver()));
+
+if (!$schemaManager instanceof PostgreSQLSchemaManager) {
+    throw new Exception('should not happen');
+}