diff --git a/core/modules/rest/src/CacheableResourceResponse.php b/core/modules/rest/src/CacheableResourceResponse.php
index 897022d..9f58244 100644
--- a/core/modules/rest/src/CacheableResourceResponse.php
+++ b/core/modules/rest/src/CacheableResourceResponse.php
@@ -11,7 +11,6 @@
 use Drupal\Core\Cache\CacheableResponseTrait;
 use Symfony\Component\HttpFoundation\Response;
 
-
 class CacheableResourceResponse extends Response implements CacheableResponseInterface, ResourceResponseInterface {
 
   use CacheableResponseTrait;
diff --git a/core/modules/rest/src/Plugin/rest/resource/UserRegistrationResource.php b/core/modules/rest/src/Plugin/rest/resource/UserRegistrationResource.php
index 4ee9df2..545516a 100644
--- a/core/modules/rest/src/Plugin/rest/resource/UserRegistrationResource.php
+++ b/core/modules/rest/src/Plugin/rest/resource/UserRegistrationResource.php
@@ -102,7 +102,7 @@ public function post(UserInterface $account = NULL) {
     // POSTed user accounts must not have an ID set, because we always
     // want to create new entities here.
     if (!$account->isNew()) {
-      throw new BadRequestHttpException('Only new user accounts can be registered.');
+      throw new BadRequestHttpException('An ID has been set and only new user accounts can be registered.');
     }
 
     // The current resource only allows anonymous users to register users.
@@ -120,9 +120,9 @@ public function post(UserInterface $account = NULL) {
       $account->block();
     }
 
-    // Only check 'edit' permissions for fields that were actually
-    // submitted by the user. Field access makes no difference between 'create'
-    // and 'update', so the 'edit' operation is used here.
+    // Only check 'edit' permissions for fields that were actually submitted by
+    // the user. Field access makes no difference between 'create'and 'update',
+    // so the 'edit' operation is used here.
     foreach ($account->_restSubmittedFields as $key => $field_name) {
       if (!$account->get($field_name)->access('edit')) {
         throw new AccessDeniedHttpException("Access denied on creating field '$field_name'.");
@@ -135,7 +135,7 @@ public function post(UserInterface $account = NULL) {
     $account->save();
 
     $register = $this->userSettings->get('register');
-    // No email verification is required. Activating the user.
+    // No E-mail verification is required. Activating the user.
     if ($register == 'visitors') {
       if (!$this->userSettings->get('verify_mail')) {
         // Notification will be sent if activated.
@@ -167,9 +167,9 @@ public function routes() {
 
     $route = $this->getBaseRoute('/entity/user/register', 'POST');
 
-    // Restrict the incoming HTTP Content-type header to the known
-    // serialization formats.
-    $route->addRequirements(array('_content_type_format' => implode('|', $this->serializerFormats)));
+    // Restrict the incoming HTTP Content-type header to the known serialization
+    // formats.
+    $route->addRequirements(['_content_type_format' => implode('|', $this->serializerFormats)]));
     $collection->add("$this->pluginId", $route);
 
     return $collection;
diff --git a/core/modules/rest/src/UncacheableResourceResponse.php b/core/modules/rest/src/UncacheableResourceResponse.php
index 0c4eb9b..308275d 100644
--- a/core/modules/rest/src/UncacheableResourceResponse.php
+++ b/core/modules/rest/src/UncacheableResourceResponse.php
@@ -23,8 +23,8 @@ class UncacheableResourceResponse extends Response implements ResourceResponseIn
    * @param array $headers
    *   An array of response headers.
    */
-  public function __construct($data = NULL, $status = 200, $headers = array()) {
+  public function __construct($data = NULL, $status = 200, $headers = []) {
     $this->responseData = $data;
     parent::__construct('', $status, $headers);
   }
-}
\ No newline at end of file
+}
diff --git a/core/modules/rest/tests/src/Unit/UserRegistrationResourceTest.php b/core/modules/rest/tests/src/Unit/UserRegistrationResourceTest.php
index 778b534..2facc31 100644
--- a/core/modules/rest/tests/src/Unit/UserRegistrationResourceTest.php
+++ b/core/modules/rest/tests/src/Unit/UserRegistrationResourceTest.php
@@ -145,7 +145,7 @@ public function testValidate() {
     $method = $this->getProtectedMethod('validate');
 
     // No exception is thrown.
-    $method->invokeArgs($this->testClass, array($entity));
+    $method->invokeArgs($this->testClass, [$entity]);
   }
 
   /**