Issue #3158708 by catch: RouteProvider::getAllRoutes no longer returns an iterable, breaking BC

core/lib/Drupal/Core/Routing/RouteProvider.php

@@ -408,7 +408,8 @@ public function getAllRoutes() {
       $result[$name] = unserialize($route);
     }
 
-    return $result;
+    $array_object = new \ArrayObject($result);
+    return $array_object->getIterator();
   }
 
   /**

core/tests/Drupal/KernelTests/Core/Routing/RouteProviderTest.php

@@ -311,6 +311,7 @@ public function testGetAllRoutes() {
 
     $returned_routes = $provider->getAllRoutes();
 
+    $this->assertInstanceOf(\Iterator::class, $returned_routes);
     $this->assertEqual($expected_route_count, count($returned_routes));
 
     foreach ($returned_routes as $route_name => $route) {