[DI] Fixed custom services definition BC break introduced in ec7e70fb…

src/Symfony/Component/DependencyInjection/ContainerBuilder.php

@@ -840,8 +840,8 @@ class ContainerBuilder extends Container implements TaggedContainerInterface
      */
     public function createService(Definition $definition, $id, $tryProxy = true)
     {
-        if ('Symfony\Component\DependencyInjection\Definition' !== get_class($definition)) {
-            throw new RuntimeException(sprintf('Constructing service "%s" from a %s is not supported at build time.', $id, get_class($definition)));
+        if ($definition instanceof DefinitionDecorator) {
+            throw new RuntimeException(sprintf('Constructing decorated service "%s" from a %s is not supported at build time.', $id, get_class($definition)));
         }
 
         if ($definition->isSynthetic()) {

src/Symfony/Component/DependencyInjection/Tests/ContainerBuilderTest.php

@@ -29,6 +29,7 @@ use Symfony\Component\DependencyInjection\Reference;
 use Symfony\Component\DependencyInjection\ParameterBag\ParameterBag;
 use Symfony\Component\DependencyInjection\Scope;
 use Symfony\Component\Config\Resource\FileResource;
+use Symfony\Component\DependencyInjection\Tests\Fixtures\CustomDefinition;
 use Symfony\Component\ExpressionLanguage\Expression;
 
 class ContainerBuilderTest extends \PHPUnit_Framework_TestCase
@@ -407,7 +408,7 @@ class ContainerBuilderTest extends \PHPUnit_Framework_TestCase
 
     /**
      * @expectedException \Symfony\Component\DependencyInjection\Exception\RuntimeException
-     * @expectedExceptionMessage Constructing service "foo" from a Symfony\Component\DependencyInjection\DefinitionDecorator is not supported at build time.
+     * @expectedExceptionMessage Constructing decorated service "foo" from a Symfony\Component\DependencyInjection\DefinitionDecorator is not supported at build time.
      */
     public function testResolveServicesWithDecoratedDefinition()
     {
@@ -419,6 +420,14 @@ class ContainerBuilderTest extends \PHPUnit_Framework_TestCase
         $builder->get('foo');
     }
 
+    public function testResolveServicesWithCustomDefinitionClass()
+    {
+        $builder = new ContainerBuilder();
+        $builder->setDefinition('foo', new CustomDefinition('stdClass'));
+
+        $this->assertInstanceOf('stdClass', $builder->get('foo'));
+    }
+
     public function testMerge()
     {
         $container = new ContainerBuilder(new ParameterBag(array('bar' => 'foo')));

src/Symfony/Component/DependencyInjection/Tests/Fixtures/CustomDefinition.php

@@ -0,0 +1,18 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\DependencyInjection\Tests\Fixtures;
+
+use Symfony\Component\DependencyInjection\Definition;
+
+class CustomDefinition extends Definition
+{
+}