Add Rector

rector.php

@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+use Rector\Core\Configuration\Option;
+use Rector\Core\ValueObject\PhpVersion;
+use Rector\Set\ValueObject\LevelSetList;
+use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;
+
+return static function (ContainerConfigurator $containerConfigurator): void {
+    $parameters = $containerConfigurator->parameters();
+
+    // paths to refactor; solid alternative to CLI arguments
+    $parameters->set(Option::PATHS, [
+        __DIR__ . '/src',
+        __DIR__ . '/tests',
+    ]);
+
+    // Path to phpstan with extensions, that PHPSTan in Rector uses to determine types
+    $parameters->set(Option::PHPSTAN_FOR_RECTOR_PATH, __DIR__ . '/phpstan.neon');
+
+    $parameters->set(Option::BOOTSTRAP_FILES, [
+        __DIR__ . '/vendor/bin/.phpunit/phpunit-8.5-0/vendor/autoload.php',
+        __DIR__ . '/vendor/autoload.php',
+    ]);
+
+    // Define what rule sets will be applied
+    $containerConfigurator->import(LevelSetList::UP_TO_PHP_72);
+
+    // is your PHP version different from the one your refactor to?
+    $parameters->set(Option::PHP_VERSION_FEATURES, PhpVersion::PHP_72);
+};