diff -u b/core/modules/action/src/ActionFormBase.php b/core/modules/action/src/ActionFormBase.php
--- b/core/modules/action/src/ActionFormBase.php
+++ b/core/modules/action/src/ActionFormBase.php
@@ -50,7 +50,7 @@
       '#maxlength' => 64,
       '#description' => $this->t('A unique name for this action. It must only contain lowercase letters, numbers and underscores.'),
       '#machine_name' => array(
-        'exists' => [get_class($this), 'exists'],
+        'exists' => [static::class, 'exists'],
       ),
     );
     $form['plugin'] = array(
diff -u b/core/modules/block/src/BlockForm.php b/core/modules/block/src/BlockForm.php
--- b/core/modules/block/src/BlockForm.php
+++ b/core/modules/block/src/BlockForm.php
@@ -135,7 +135,7 @@
       '#description' => $this->t('A unique name for this block instance. Must be alpha-numeric and underscore separated.'),
       '#default_value' => !$entity->isNew() ? $entity->id() : $this->getUniqueMachineName($entity),
       '#machine_name' => array(
-        'exists' => [get_class($this), 'exists'],
+        'exists' => [static::class, 'exists'],
         'replace_pattern' => '[^a-z0-9_.]+',
         'source' => array('settings', 'label'),
       ),
diff -u b/core/modules/block_content/src/BlockContentTypeForm.php b/core/modules/block_content/src/BlockContentTypeForm.php
--- b/core/modules/block_content/src/BlockContentTypeForm.php
+++ b/core/modules/block_content/src/BlockContentTypeForm.php
@@ -45,7 +45,7 @@
       '#type' => 'machine_name',
       '#default_value' => $block_type->id(),
       '#machine_name' => array(
-        'exists' => [get_class($this), 'exists'],
+        'exists' => [static::class, 'exists'],
       ),
       '#maxlength' => EntityTypeInterface::BUNDLE_MAX_LENGTH,
     );
diff -u b/core/modules/comment/src/CommentTypeForm.php b/core/modules/comment/src/CommentTypeForm.php
--- b/core/modules/comment/src/CommentTypeForm.php
+++ b/core/modules/comment/src/CommentTypeForm.php
@@ -87,7 +87,7 @@
       '#type' => 'machine_name',
       '#default_value' => $comment_type->id(),
       '#machine_name' => array(
-        'exists' => [get_class($this), 'exists'],
+        'exists' => [static::class, 'exists'],
       ),
       '#maxlength' => EntityTypeInterface::BUNDLE_MAX_LENGTH,
       '#disabled' => !$comment_type->isNew(),
diff -u b/core/modules/config/tests/config_test/src/ConfigTestForm.php b/core/modules/config/tests/config_test/src/ConfigTestForm.php
--- b/core/modules/config/tests/config_test/src/ConfigTestForm.php
+++ b/core/modules/config/tests/config_test/src/ConfigTestForm.php
@@ -62,7 +62,7 @@
       '#default_value' => $entity->id(),
       '#required' => TRUE,
       '#machine_name' => array(
-        'exists' => [get_class($this), 'exists'],
+        'exists' => [static::class, 'exists'],
         'replace_pattern' => '[^a-z0-9_.]+',
       ),
     );
diff -u b/core/modules/contact/src/ContactFormEditForm.php b/core/modules/contact/src/ContactFormEditForm.php
--- b/core/modules/contact/src/ContactFormEditForm.php
+++ b/core/modules/contact/src/ContactFormEditForm.php
@@ -76,7 +76,7 @@
       '#default_value' => $contact_form->id(),
       '#maxlength' => EntityTypeInterface::BUNDLE_MAX_LENGTH,
       '#machine_name' => array(
-        'exists' => [get_class($this), 'exists'],
+        'exists' => [static::class, 'exists'],
       ),
       '#disabled' => !$contact_form->isNew(),
     );
diff -u b/core/modules/field_ui/src/Form/EntityDisplayModeFormBase.php b/core/modules/field_ui/src/Form/EntityDisplayModeFormBase.php
--- b/core/modules/field_ui/src/Form/EntityDisplayModeFormBase.php
+++ b/core/modules/field_ui/src/Form/EntityDisplayModeFormBase.php
@@ -88,7 +88,7 @@
       '#default_value' => $this->entity->id(),
       '#field_prefix' => $this->entity->isNew() ? $this->entity->getTargetType() . '.' : '',
       '#machine_name' => array(
-        'exists' => [get_class($this), 'exists'],
+        'exists' => [static::class, 'exists'],
         'replace_pattern' => '[^a-z0-9_.]+',
       ),
     );
diff -u b/core/modules/filter/src/FilterFormatFormBase.php b/core/modules/filter/src/FilterFormatFormBase.php
--- b/core/modules/filter/src/FilterFormatFormBase.php
+++ b/core/modules/filter/src/FilterFormatFormBase.php
@@ -67,7 +67,7 @@
       '#default_value' => $format->id(),
       '#maxlength' => 255,
       '#machine_name' => array(
-        'exists' => [get_class($this), 'exists'],
+        'exists' => [static::class, 'exists'],
         'source' => array('name'),
       ),
       '#disabled' => !$format->isNew(),
diff -u b/core/modules/image/src/Form/ImageStyleFormBase.php b/core/modules/image/src/Form/ImageStyleFormBase.php
--- b/core/modules/image/src/Form/ImageStyleFormBase.php
+++ b/core/modules/image/src/Form/ImageStyleFormBase.php
@@ -36,7 +36,7 @@
     $form['name'] = array(
       '#type' => 'machine_name',
       '#machine_name' => array(
-        'exists' => [get_class($this), 'exists'],
+        'exists' => [static::class, 'exists'],
       ),
       '#default_value' => $this->entity->id(),
       '#required' => TRUE,
diff -u b/core/modules/node/src/NodeTypeForm.php b/core/modules/node/src/NodeTypeForm.php
--- b/core/modules/node/src/NodeTypeForm.php
+++ b/core/modules/node/src/NodeTypeForm.php
@@ -83,7 +83,7 @@
       '#maxlength' => EntityTypeInterface::BUNDLE_MAX_LENGTH,
       '#disabled' => $type->isLocked(),
       '#machine_name' => array(
-        'exists' => [get_class($this), 'exists'],
+        'exists' => [static::class, 'exists'],
         'source' => array('name'),
       ),
       '#description' => t('A unique machine-readable name for this content type. It must only contain lowercase letters, numbers, and underscores. This name will be used for constructing the URL of the %node-add page, in which underscores will be converted into hyphens.', array(
diff -u b/core/modules/responsive_image/src/ResponsiveImageStyleForm.php b/core/modules/responsive_image/src/ResponsiveImageStyleForm.php
--- b/core/modules/responsive_image/src/ResponsiveImageStyleForm.php
+++ b/core/modules/responsive_image/src/ResponsiveImageStyleForm.php
@@ -77,7 +77,7 @@
       '#type' => 'machine_name',
       '#default_value' => $responsive_image_style->id(),
       '#machine_name' => array(
-        'exists' => [get_class($this), 'exists'],
+        'exists' => [static::class, 'exists'],
         'source' => array('label'),
       ),
       '#disabled' => (bool) $responsive_image_style->id() && $this->operation != 'duplicate',
diff -u b/core/modules/search/src/Form/SearchPageFormBase.php b/core/modules/search/src/Form/SearchPageFormBase.php
--- b/core/modules/search/src/Form/SearchPageFormBase.php
+++ b/core/modules/search/src/Form/SearchPageFormBase.php
@@ -103,7 +103,7 @@
       '#disabled' => !$this->entity->isNew(),
       '#maxlength' => 64,
       '#machine_name' => array(
-        'exists' => [get_class($this), 'exists'],
+        'exists' => [static::class, 'exists'],
       ),
     );
     $form['path'] = array(
diff -u b/core/modules/shortcut/src/Form/SwitchShortcutSet.php b/core/modules/shortcut/src/Form/SwitchShortcutSet.php
--- b/core/modules/shortcut/src/Form/SwitchShortcutSet.php
+++ b/core/modules/shortcut/src/Form/SwitchShortcutSet.php
@@ -7,7 +7,7 @@
 
 namespace Drupal\shortcut\Form;
 
-use Drupal\Core\Form\FormBase;
+use Drupal\Core\Entity\ConfigEntityForm;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\shortcut\Entity\ShortcutSet;
 use Drupal\shortcut\ShortcutSetStorageInterface;
@@ -17,7 +17,7 @@
 /**
  * Builds the shortcut set switch form.
  */
-class SwitchShortcutSet extends FormBase {
+class SwitchShortcutSet extends ConfigEntityForm {
 
   /**
    * The account the shortcut set is for.
@@ -106,7 +106,7 @@
       $form['id'] = array(
         '#type' => 'machine_name',
         '#machine_name' => array(
-          'exists' => ['\Drupal\shortcut\Entity\ShortcutSet', 'load'],
+          'exists' => [static::class, 'exists'],
           'replace_pattern' => '[^a-z0-9-]+',
           'replace' => '-',
         ),
diff -u b/core/modules/shortcut/src/ShortcutSetForm.php b/core/modules/shortcut/src/ShortcutSetForm.php
--- b/core/modules/shortcut/src/ShortcutSetForm.php
+++ b/core/modules/shortcut/src/ShortcutSetForm.php
@@ -32,7 +32,7 @@
     $form['id'] = array(
       '#type' => 'machine_name',
       '#machine_name' => array(
-        'exists' => [get_class($this), 'exists'],
+        'exists' => [static::class, 'exists'],
         'source' => array('label'),
         'replace_pattern' => '[^a-z0-9-]+',
         'replace' => '-',
diff -u b/core/modules/system/src/Form/DateFormatFormBase.php b/core/modules/system/src/Form/DateFormatFormBase.php
--- b/core/modules/system/src/Form/DateFormatFormBase.php
+++ b/core/modules/system/src/Form/DateFormatFormBase.php
@@ -84,7 +84,7 @@
       '#disabled' => !$this->entity->isNew(),
       '#default_value' => $this->entity->id(),
       '#machine_name' => array(
-        'exists' => array(get_class($this), 'exists'),
+        'exists' => array(static::class, 'exists'),
         'replace_pattern' =>'([^a-z0-9_]+)|(^custom$)',
         'error' => $this->t('The machine-readable name must be unique, and can only contain lowercase letters, numbers, and underscores. Additionally, it can not be the reserved word "custom".'),
       ),
diff -u b/core/modules/taxonomy/src/VocabularyForm.php b/core/modules/taxonomy/src/VocabularyForm.php
--- b/core/modules/taxonomy/src/VocabularyForm.php
+++ b/core/modules/taxonomy/src/VocabularyForm.php
@@ -42,7 +42,7 @@
       '#default_value' => $vocabulary->id(),
       '#maxlength' => EntityTypeInterface::BUNDLE_MAX_LENGTH,
       '#machine_name' => array(
-        'exists' => [get_class($this), 'exists'],
+        'exists' => [static::class, 'exists'],
         'source' => array('name'),
       ),
     );
diff -u b/core/modules/user/src/RoleForm.php b/core/modules/user/src/RoleForm.php
--- b/core/modules/user/src/RoleForm.php
+++ b/core/modules/user/src/RoleForm.php
@@ -37,7 +37,7 @@
       '#size' => 30,
       '#maxlength' => 64,
       '#machine_name' => array(
-        'exists' => [get_class($this), 'exists'],
+        'exists' => [static::class, 'exists'],
       ),
     );
     $form['weight'] = array(
only in patch2:
unchanged:
--- /dev/null
+++ b/core/lib/Drupal/Core/Entity/ConfigEntityForm.php
@@ -0,0 +1,41 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Entity\ConfigEntityForm.
+ */
+
+namespace Drupal\Core\Entity;
+
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Render\Element;
+
+/**
+ * Base class for config entity forms.
+ *
+ * @ingroup entity_api
+ */
+class ConfigEntityForm extends EntityForm {
+
+  /**
+   * Determines if the entity already exists.
+   *
+   * @param string|int $entity_id
+   *   The entity ID.
+   * @param array $element
+   *   The form element.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The current state of the form.
+   *
+   * @return bool
+   *   TRUE if the entity exists, FALSE otherwise.
+   */
+  public static function exists($entity_id, array $element, FormStateInterface $form_state) {
+    /** @var \Drupal\Core\Entity\EntityTypeInterface $entity_type */
+    $entity_type = $form_state->getFormObject()->getEntity()->getEntityType();
+    return (bool) \Drupal::entityQuery($entity_type->id())
+      ->condition($entity_type->getKey('id'), $entity_id)
+      ->execute();
+  }
+
+}