minor #39775 [WIP] Use ::class keyword when possible (fabpot)

This PR was merged into the 4.4 branch.

Discussion
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[WIP] Use ::class keyword when possible

| Q             | A
| ------------- | ---
| Branch?       | 4.4 <!-- see below -->
| Bug fix?      | no
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| Deprecations? | no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tickets       | n/a  <!-- prefix each issue number with "Fix #", no need to create an issue if none exist, explain below instead -->
| License       | MIT
| Doc PR        | n/a

Commits
-------

036a36cb14 Use ::class keyword when possible

Author: fabpot

Tests/Matcher/Dumper/PhpMatcherDumperTest.php

@@ -480,7 +480,7 @@ private function generateDumpedMatcher(RouteCollection $collection, $redirectabl
         $options = ['class' => $this->matcherClass];
 
         if ($redirectableStub) {
-            $options['base_class'] = '\Symfony\Component\Routing\Tests\Matcher\Dumper\RedirectableUrlMatcherStub';
+            $options['base_class'] = RedirectableUrlMatcherStub::class;
         }
 
         $dumper = new PhpMatcherDumper($collection);

Tests/RouteCollectionTest.php

@@ -66,7 +66,7 @@ public function testIterator()
         $collection->addCollection($collection1);
         $collection->add('last', $last = new Route('/last'));
 
-        $this->assertInstanceOf('\ArrayIterator', $collection->getIterator());
+        $this->assertInstanceOf(\ArrayIterator::class, $collection->getIterator());
         $this->assertSame(['bar' => $bar, 'foo' => $foo, 'last' => $last], $collection->getIterator()->getArrayCopy());
     }
 

Tests/RouteTest.php

@@ -13,6 +13,8 @@
 
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\Routing\Route;
+use Symfony\Component\Routing\Tests\Fixtures\CustomCompiledRoute;
+use Symfony\Component\Routing\Tests\Fixtures\CustomRouteCompiler;
 
 class RouteTest extends TestCase
 {
@@ -243,13 +245,13 @@ public function testSerializeWhenCompiled()
      */
     public function testSerializeWhenCompiledWithClass()
     {
-        $route = new Route('/', [], [], ['compiler_class' => '\Symfony\Component\Routing\Tests\Fixtures\CustomRouteCompiler']);
-        $this->assertInstanceOf('\Symfony\Component\Routing\Tests\Fixtures\CustomCompiledRoute', $route->compile(), '->compile() returned a proper route');
+        $route = new Route('/', [], [], ['compiler_class' => CustomRouteCompiler::class]);
+        $this->assertInstanceOf(CustomCompiledRoute::class, $route->compile(), '->compile() returned a proper route');
 
         $serialized = serialize($route);
         try {
             $unserialized = unserialize($serialized);
-            $this->assertInstanceOf('\Symfony\Component\Routing\Tests\Fixtures\CustomCompiledRoute', $unserialized->compile(), 'the unserialized route compiled successfully');
+            $this->assertInstanceOf(CustomCompiledRoute::class, $unserialized->compile(), 'the unserialized route compiled successfully');
         } catch (\Exception $e) {
             $this->fail('unserializing a route which uses a custom compiled route class');
         }