minor #20666 [FrameworkBundle] mark alias as private during creation …

…(xabbuh)

This PR was merged into the 3.1 branch.

Discussion
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[FrameworkBundle] mark alias as private during creation

| Q             | A
| ------------- | ---
| Branch?       | 3.1
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #20577 (comment)
| License       | MIT
| Doc PR        | n/a

Commits
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828c761 mark alias as private during creation

src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php

@@ -12,6 +12,7 @@
 namespace Symfony\Bundle\FrameworkBundle\DependencyInjection;
 
 use Doctrine\Common\Annotations\Reader;
+use Symfony\Component\DependencyInjection\Alias;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\DependencyInjection\Definition;
@@ -1044,8 +1045,7 @@ private function registerCacheConfiguration(array $config, ContainerBuilder $con
 
         foreach (array('doctrine', 'psr6', 'redis') as $name) {
             if (isset($config[$name = 'default_'.$name.'_provider'])) {
-                $container->setAlias('cache.'.$name, Compiler\CachePoolPass::getServiceProvider($container, $config[$name]));
-                $container->getAlias('cache.'.$name)->setPublic(false);
+                $container->setAlias('cache.'.$name, new Alias(Compiler\CachePoolPass::getServiceProvider($container, $config[$name]), false));
             }
         }
         foreach (array('app', 'system') as $name) {