Make paginator covariant (#10002)

lib/Doctrine/ORM/Tools/Pagination/Paginator.php

@@ -16,6 +16,7 @@
 use Doctrine\ORM\QueryBuilder;
 use IteratorAggregate;
 use ReturnTypeWillChange;
+use Traversable;
 
 use function array_key_exists;
 use function array_map;
@@ -25,7 +26,7 @@
 /**
  * The paginator can handle various complex scenarios with DQL.
  *
- * @template T
+ * @template-covariant T
  */
 class Paginator implements Countable, IteratorAggregate
 {
@@ -124,8 +125,8 @@ public function count()
     /**
      * {@inheritdoc}
      *
-     * @return ArrayIterator
-     * @psalm-return ArrayIterator<array-key, T>
+     * @return Traversable
+     * @psalm-return Traversable<array-key, T>
      */
     #[ReturnTypeWillChange]
     public function getIterator()

tests/Doctrine/StaticAnalysis/Tools/Pagination/paginator-covariant.php

@@ -0,0 +1,65 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Doctrine\StaticAnalysis\Tools\Pagination;
+
+use Doctrine\ORM\Tools\Pagination\Paginator;
+
+/**
+ * @template-covariant T of object
+ */
+abstract class PaginatorFactory
+{
+    /** @var class-string<T> */
+    private $class;
+
+    /**
+     * @param class-string<T> $class
+     */
+    final public function __construct(string $class)
+    {
+        $this->class = $class;
+    }
+
+    /**
+     * @return class-string<T>
+     */
+    public function getClass(): string
+    {
+        return $this->class;
+    }
+
+    /**
+     * @psalm-return Paginator<T>
+     */
+    abstract public function createPaginator(): Paginator;
+}
+
+interface Animal
+{
+}
+
+class Cat implements Animal
+{
+}
+
+/**
+ * @param Paginator<Animal> $paginator
+ */
+function getFirstAnimal(Paginator $paginator): ?Animal
+{
+    foreach ($paginator as $result) {
+        return $result;
+    }
+
+    return null;
+}
+
+/**
+ * @param PaginatorFactory<Cat> $catPaginatorFactory
+ */
+function test(PaginatorFactory $catPaginatorFactory): ?Animal
+{
+    return getFirstAnimal($catPaginatorFactory->createPaginator());
+}