bug symfony#17942 Fix bug when using an private aliased factory service (WouterJ)

This PR was squashed before being merged into the 2.3 branch (closes symfony#17942).

Discussion
----------

Fix bug when using an private aliased factory service

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | symfony#17910, symfony#17915
| License       | MIT
| Doc PR        | -

/cc @xabbuh

Commits
-------

de406c0 Fix bug when using an private aliased factory service

Author: fabpot

src/Symfony/Component/DependencyInjection/Compiler/ReplaceAliasByActualDefinitionPass.php

@@ -131,6 +131,6 @@ private function updateFactoryServiceReference($factoryService, $currentId, $new
             return;
         }
 
-        return $currentId === $factoryService ? $newId : $currentId;
+        return $currentId === $factoryService ? $newId : $factoryService;
     }
 }

src/Symfony/Component/DependencyInjection/Tests/Compiler/ReplaceAliasByActualDefinitionPassTest.php

@@ -15,6 +15,8 @@
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\Definition;
 
+require_once __DIR__.'/../Fixtures/includes/foo.php';
+
 class ReplaceAliasByActualDefinitionPassTest extends \PHPUnit_Framework_TestCase
 {
     public function testProcess()
@@ -44,6 +46,26 @@ public function testProcess()
         $this->assertSame('b_alias', $aDefinition->getFactoryService());
     }
 
+    /**
+     * @group legacy
+     */
+    public function testPrivateAliasesInFactory()
+    {
+        $container = new ContainerBuilder();
+
+        $container->register('a', 'FooClass');
+        $container->register('b', 'FooClass')
+            ->setFactoryService('a')
+            ->setFactoryMethod('getInstance');
+
+        $container->register('c', 'stdClass')->setPublic(false);
+        $container->setAlias('c_alias', 'c');
+
+        $this->process($container);
+
+        $this->assertInstanceOf('FooClass', $container->get('b'));
+    }
+
     /**
      * @expectedException \InvalidArgumentException
      */