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

This PR was merged into the 4.4 branch.

Discussion
----------

[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

Intl.php

@@ -111,7 +111,7 @@ final class Intl
      */
     public static function isExtensionLoaded(): bool
     {
-        return class_exists('\ResourceBundle');
+        return class_exists(\ResourceBundle::class);
     }
 
     /**

Tests/Collator/CollatorTest.php

@@ -12,6 +12,7 @@
 namespace Symfony\Component\Intl\Tests\Collator;
 
 use Symfony\Component\Intl\Collator\Collator;
+use Symfony\Component\Intl\Exception\MethodNotImplementedException;
 use Symfony\Component\Intl\Globals\IntlGlobals;
 
 class CollatorTest extends AbstractCollatorTest
@@ -57,19 +58,19 @@ public function testGetLocale()
     public function testConstructWithoutLocale()
     {
         $collator = $this->getCollator(null);
-        $this->assertInstanceOf('\Symfony\Component\Intl\Collator\Collator', $collator);
+        $this->assertInstanceOf(Collator::class, $collator);
     }
 
     public function testGetSortKey()
     {
-        $this->expectException('Symfony\Component\Intl\Exception\MethodNotImplementedException');
+        $this->expectException(MethodNotImplementedException::class);
         $collator = $this->getCollator('en');
         $collator->getSortKey('Hello');
     }
 
     public function testGetStrength()
     {
-        $this->expectException('Symfony\Component\Intl\Exception\MethodNotImplementedException');
+        $this->expectException(MethodNotImplementedException::class);
         $collator = $this->getCollator('en');
         $collator->getStrength();
     }
@@ -92,7 +93,7 @@ public function testStaticCreate()
     {
         $collator = $this->getCollator('en');
         $collator = $collator::create('en');
-        $this->assertInstanceOf('\Symfony\Component\Intl\Collator\Collator', $collator);
+        $this->assertInstanceOf(Collator::class, $collator);
     }
 
     protected function getCollator(?string $locale): Collator

Tests/Data/Bundle/Reader/IntlBundleReaderTest.php

@@ -34,7 +34,7 @@ public function testReadReturnsArrayAccess()
     {
         $data = $this->reader->read(__DIR__.'/Fixtures/res', 'ro');
 
-        $this->assertInstanceOf('\ArrayAccess', $data);
+        $this->assertInstanceOf(\ArrayAccess::class, $data);
         $this->assertSame('Bar', $data['Foo']);
         $this->assertArrayNotHasKey('ExistsNot', $data);
     }
@@ -44,7 +44,7 @@ public function testReadFollowsAlias()
         // "alias" = "ro"
         $data = $this->reader->read(__DIR__.'/Fixtures/res', 'alias');
 
-        $this->assertInstanceOf('\ArrayAccess', $data);
+        $this->assertInstanceOf(\ArrayAccess::class, $data);
         $this->assertSame('Bar', $data['Foo']);
         $this->assertArrayNotHasKey('ExistsNot', $data);
     }
@@ -54,7 +54,7 @@ public function testReadDoesNotFollowFallback()
         // "ro_MD" -> "ro"
         $data = $this->reader->read(__DIR__.'/Fixtures/res', 'ro_MD');
 
-        $this->assertInstanceOf('\ArrayAccess', $data);
+        $this->assertInstanceOf(\ArrayAccess::class, $data);
         $this->assertSame('Bam', $data['Baz']);
         $this->assertArrayNotHasKey('Foo', $data);
         $this->assertNull($data['Foo']);

Tests/DateFormatter/IntlDateFormatterTest.php

@@ -44,7 +44,7 @@ public function testStaticCreate()
     {
         $formatter = $this->getDateFormatter('en', IntlDateFormatter::MEDIUM, IntlDateFormatter::SHORT);
         $formatter = $formatter::create('en', IntlDateFormatter::MEDIUM, IntlDateFormatter::SHORT);
-        $this->assertInstanceOf('\Symfony\Component\Intl\DateFormatter\IntlDateFormatter', $formatter);
+        $this->assertInstanceOf(IntlDateFormatter::class, $formatter);
     }
 
     public function testFormatWithUnsupportedTimestampArgument()

Tests/NumberFormatter/NumberFormatterTest.php

@@ -54,10 +54,7 @@ public function testSetAttributeInvalidRoundingMode()
 
     public function testConstructWithoutLocale()
     {
-        $this->assertInstanceOf(
-            '\Symfony\Component\Intl\NumberFormatter\NumberFormatter',
-            $this->getNumberFormatter(null, NumberFormatter::DECIMAL)
-        );
+        $this->assertInstanceOf(NumberFormatter::class, $this->getNumberFormatter(null, NumberFormatter::DECIMAL));
     }
 
     public function testCreate()

Tests/NumberFormatter/Verification/NumberFormatterTest.php

@@ -29,7 +29,7 @@ protected function setUp(): void
 
     public function testCreate()
     {
-        $this->assertInstanceOf('\NumberFormatter', \NumberFormatter::create('en', \NumberFormatter::DECIMAL));
+        $this->assertInstanceOf(\NumberFormatter::class, \NumberFormatter::create('en', \NumberFormatter::DECIMAL));
     }
 
     public function testGetTextAttribute()