Use property type hints

Not a BC break since all of them are private.

Had to change an initialization check in `MbTranscoder::__construct`, since PHPStan figured out it is not nullable.

Author: jtojnar

.php-cs-fixer.php

@@ -7,6 +7,7 @@
     '@Symfony' => true,
     '@PHP74Migration' => true,
     '@PHP74Migration:risky' => true,
+    'phpdoc_to_property_type' => true,
     // 'phpdoc_to_param_type' => true, // requires PHP 8.0
     'phpdoc_to_return_type' => true,
     // overwrite some Symfony rules

src/IconvTranscoder.php

@@ -10,10 +10,7 @@
 
 class IconvTranscoder implements TranscoderInterface
 {
-    /**
-     * @var string
-     */
-    private $defaultEncoding;
+    private string $defaultEncoding;
 
     /**
      * Create an Iconv-based transcoder.

src/MbTranscoder.php

@@ -13,12 +13,9 @@ class MbTranscoder implements TranscoderInterface
     /**
      * @var array<string, int>
      */
-    private static $encodings;
+    private static array $encodings;
 
-    /**
-     * @var string
-     */
-    private $defaultEncoding;
+    private string $defaultEncoding;
 
     /**
      * Create a Mb-based transcoder.
@@ -31,7 +28,7 @@ public function __construct(string $defaultEncoding = 'UTF-8')
             throw new ExtensionMissingException('mb');
         }
 
-        if (null === self::$encodings) {
+        if (!isset(self::$encodings)) {
             self::$encodings = array_change_key_case(
                 array_flip(mb_list_encodings()),
                 CASE_LOWER

src/Transcoder.php

@@ -12,12 +12,12 @@ class Transcoder implements TranscoderInterface
     /**
      * @var array<string, TranscoderInterface>
      */
-    private static $chain;
+    private static array $chain;
 
     /**
      * @var TranscoderInterface[]
      */
-    private $transcoders = [];
+    private array $transcoders = [];
 
     /**
      * @param TranscoderInterface[] $transcoders

tests/IconvTranscoderTest.php

@@ -8,10 +8,7 @@
 
 class IconvTranscoderTest extends \PHPUnit\Framework\TestCase
 {
-    /**
-     * @var IconvTranscoder
-     */
-    private $transcoder;
+    private IconvTranscoder $transcoder;
 
     /**
      * @before

tests/MbTranscoderTest.php

@@ -8,10 +8,7 @@
 
 class MbTranscoderTest extends \PHPUnit\Framework\TestCase
 {
-    /**
-     * @var MbTranscoder
-     */
-    private $transcoder;
+    private MbTranscoder $transcoder;
 
     /**
      * @before

tests/TranscoderTest.php

@@ -9,10 +9,7 @@
 
 class TranscoderTest extends \PHPUnit\Framework\TestCase
 {
-    /**
-     * @var TranscoderInterface
-     */
-    private $transcoder;
+    private TranscoderInterface $transcoder;
 
     /**
      * @before