diff --git a/core/modules/datetime/src/Plugin/Field/FieldWidget/DateTimeTimestampWidget.php b/core/modules/datetime/src/Plugin/Field/FieldWidget/DateTimeTimestampWidget.php
index 6c50058..828a7c5 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldWidget/DateTimeTimestampWidget.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldWidget/DateTimeTimestampWidget.php
@@ -9,6 +9,7 @@
 use Drupal\Core\Datetime\DrupalDateTime;
 use Drupal\Core\Field\FieldItemListInterface;
 use Drupal\Core\Field\WidgetBase;
+use Drupal\Core\Form\FormStateInterface;
 
 /**
  * Plugin implementation of the 'datetime timestamp' widget.
@@ -27,7 +28,7 @@ class DateTimeTimestampWidget extends WidgetBase {
   /**
    * {@inheritdoc}
    */
-  public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, array &$form_state) {
+  public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state) {
     $date_format = entity_load('date_format', 'html_date')->getPattern();
     $time_format = entity_load('date_format', 'html_time')->getPattern();
     $default_value = isset($items[$delta]->value) ? DrupalDateTime::createFromTimestamp($items[$delta]->value) : '';
diff --git a/core/modules/node/src/NodeForm.php b/core/modules/node/src/NodeForm.php
index 23b45b1..b96bf53 100644
--- a/core/modules/node/src/NodeForm.php
+++ b/core/modules/node/src/NodeForm.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\node;
 
+use Drupal\Core\Datetime\DrupalDateTime;
 use Drupal\Core\Entity\ContentEntityForm;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Language\LanguageInterface;
@@ -385,6 +386,8 @@ public function unpublish(array $form, FormStateInterface $form_state) {
   }
 
   /**
+   * {@inheritdoc}
+   */
   public function buildEntity(array $form, FormStateInterface $form_state) {
     /** @var \Drupal\node\NodeInterface $entity */
     $entity = parent::buildEntity($form, $form_state);
diff --git a/core/modules/node/src/Tests/MultiStepNodeFormBasicOptionsTest.php b/core/modules/node/src/Tests/MultiStepNodeFormBasicOptionsTest.php
index a2a181d..bbba4e9 100644
--- a/core/modules/node/src/Tests/MultiStepNodeFormBasicOptionsTest.php
+++ b/core/modules/node/src/Tests/MultiStepNodeFormBasicOptionsTest.php
@@ -61,8 +61,8 @@ function testMultiStepNodeFormBasicOptions() {
       "{$this->field_name}[0][value]" => $this->randomString(32),
     );
     $this->drupalPostForm('node/add/page', $edit, t('Add another item'));
-    $this->assertNoFieldChecked('edit-promote-value', 'promote stayed unchecked');
-    $this->assertFieldChecked('edit-sticky-value', 'sticky stayed checked');
+    $this->assertNoFieldChecked('edit-promote-value', 'Promote stayed unchecked');
+    $this->assertFieldChecked('edit-sticky-value', 'Sticky stayed checked');
   }
 
 }
diff --git a/core/modules/node/src/Tests/PageEditTest.php b/core/modules/node/src/Tests/PageEditTest.php
index 9147296..f87e7dd 100644
--- a/core/modules/node/src/Tests/PageEditTest.php
+++ b/core/modules/node/src/Tests/PageEditTest.php
@@ -7,8 +7,6 @@
 
 namespace Drupal\node\Tests;
 
-use Drupal\Component\Utility\String;
-
 /**
  * Create a node and test node edit functionality.
  *
diff --git a/core/modules/rdf/rdf.module b/core/modules/rdf/rdf.module
index 9abf2e6..95797f9 100644
--- a/core/modules/rdf/rdf.module
+++ b/core/modules/rdf/rdf.module
@@ -305,7 +305,7 @@ function rdf_preprocess_node(&$variables) {
   // Adds RDFa markup for the date.
   $created_mapping = $mapping->getPreparedFieldMapping('created');
   if (!empty($created_mapping) && $variables['display_submitted']) {
-    $date_attributes = rdf_rdfa_attributes($created_mapping, $variables['node']->get('created')[0]->getValue());
+    $date_attributes = rdf_rdfa_attributes($created_mapping, $variables['node']->get('created')->first()->getValue());
     $rdf_metadata = array(
       '#theme' => 'rdf_metadata',
       '#metadata' => array($date_attributes),