diff --git a/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigEntityReferenceItemBase.php b/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigEntityReferenceItemBase.php
index a72557a..951ed03 100644
--- a/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigEntityReferenceItemBase.php
+++ b/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigEntityReferenceItemBase.php
@@ -147,7 +147,9 @@ public function instanceSettingsForm(array $form, array &$form_state) {
   }
 
   /**
-   * Returns options provided via hook_options_list().
+   * Returns options provided via the legacy callback hook_options_list().
+   *
+   * @todo: Convert all legacy callback implementations to methods.
    *
    * @see \Drupal\Core\TypedData\AllowedValuesInterface
    */
diff --git a/core/modules/field/lib/Drupal/field/Plugin/Type/Widget/WidgetBase.php b/core/modules/field/lib/Drupal/field/Plugin/Type/Widget/WidgetBase.php
index 654cbbe..5f46930 100644
--- a/core/modules/field/lib/Drupal/field/Plugin/Type/Widget/WidgetBase.php
+++ b/core/modules/field/lib/Drupal/field/Plugin/Type/Widget/WidgetBase.php
@@ -375,7 +375,9 @@ public function flagErrors(EntityInterface $entity, $langcode, array $items, arr
           foreach ($delta_violations as $violation) {
             // @todo: Pass $violation->arrayPropertyPath as property path.
             $error_element = $this->errorElement($delta_element, $violation, $form, $form_state);
-            form_error($error_element, $violation->getMessage());
+            if ($error_element !== FALSE) {
+              form_error($error_element, $violation->getMessage());
+            }
           }
         }
         // Reinitialize the errors list for the next submit.
diff --git a/core/modules/field/lib/Drupal/field/Plugin/Type/Widget/WidgetInterface.php b/core/modules/field/lib/Drupal/field/Plugin/Type/Widget/WidgetInterface.php
index fbc939c..1866415 100644
--- a/core/modules/field/lib/Drupal/field/Plugin/Type/Widget/WidgetInterface.php
+++ b/core/modules/field/lib/Drupal/field/Plugin/Type/Widget/WidgetInterface.php
@@ -125,18 +125,19 @@ public function formElement(array $items, $delta, array $element, $langcode, arr
    * @param array $element
    *   An array containing the form element for the widget, as generated by
    *   formElement().
-   * @param \Symfony\Component\Validator\ConstraintViolationInterface $violations
-   *   The list of constraint violations reported during the validation phase.
+   * @param \Symfony\Component\Validator\ConstraintViolationInterface $violation
+   *   A constraint violation reported during the validation phase.
    * @param array $form
    *   The form structure where field elements are attached to. This might be a
    *   full form structure, or a sub-element of a larger form.
    * @param array $form_state
    *   An associative array containing the current state of the form.
    *
-   * @return array
-   *   The element on which the error should be flagged.
+   * @return array|false
+   *   The element on which the error should be flagged, or FALSE to completely
+   *   ignore the violation (use with care!).
    */
-  public function errorElement(array $element, ConstraintViolationInterface $violations, array $form, array &$form_state);
+  public function errorElement(array $element, ConstraintViolationInterface $violation, array $form, array &$form_state);
 
   /**
    * Massages the form values into the format expected for field values.
diff --git a/core/modules/field/lib/Drupal/field/Plugin/field/field_type/LegacyConfigFieldItem.php b/core/modules/field/lib/Drupal/field/Plugin/field/field_type/LegacyConfigFieldItem.php
index 7e0596a..1af9d4e 100644
--- a/core/modules/field/lib/Drupal/field/Plugin/field/field_type/LegacyConfigFieldItem.php
+++ b/core/modules/field/lib/Drupal/field/Plugin/field/field_type/LegacyConfigFieldItem.php
@@ -107,7 +107,9 @@ public function prepareCache() {
   }
 
   /**
-   * Returns options provided via hook_options_list().
+   * Returns options provided via the legacy callback hook_options_list().
+   *
+   * @todo: Convert all legacy callback implementations to methods.
    *
    * @see \Drupal\Core\TypedData\AllowedValuesInterface
    */
diff --git a/core/modules/filter/filter.module b/core/modules/filter/filter.module
index e2d0c55..1a7c8a6 100644
--- a/core/modules/filter/filter.module
+++ b/core/modules/filter/filter.module
@@ -118,19 +118,6 @@ function filter_element_info() {
 }
 
 /**
- * Implements hook_data_type_info().
- */
-function filter_data_type_info() {
-  return array(
-    'filter_format' => array(
-      'label' => t('Filter format'),
-      'class' => 'Drupal\filter\Type\FilterFormat',
-      'primitive type' => Primitive::STRING,
-    ),
-  );
-}
-
-/**
  * Implements hook_menu().
  */
 function filter_menu() {
diff --git a/core/modules/filter/lib/Drupal/filter/Plugin/DataType/FilterFormat.php b/core/modules/filter/lib/Drupal/filter/Plugin/DataType/FilterFormat.php
index c8ff730..bb4b567 100644
--- a/core/modules/filter/lib/Drupal/filter/Plugin/DataType/FilterFormat.php
+++ b/core/modules/filter/lib/Drupal/filter/Plugin/DataType/FilterFormat.php
@@ -17,8 +17,7 @@
  *
  * @DataType(
  *   id = "filter_format",
- *   label = @Translation("Filter format"),
- *   primitive_type = 2
+ *   label = @Translation("Filter format")
  * )
  */
 class FilterFormat extends String implements AllowedValuesInterface {
diff --git a/core/modules/filter/lib/Drupal/filter/Tests/FilterAPITest.php b/core/modules/filter/lib/Drupal/filter/Tests/FilterAPITest.php
index 08dabf1..afa0615 100644
--- a/core/modules/filter/lib/Drupal/filter/Tests/FilterAPITest.php
+++ b/core/modules/filter/lib/Drupal/filter/Tests/FilterAPITest.php
@@ -8,7 +8,7 @@
 namespace Drupal\filter\Tests;
 
 use Drupal\Core\TypedData\AllowedValuesInterface;
-use Drupal\filter\Type\FilterFormat;
+use Drupal\filter\Plugin\DataType\FilterFormat;
 use Drupal\system\Tests\Entity\EntityUnitTestBase;
 use Symfony\Component\Validator\ConstraintViolationListInterface;
 
diff --git a/core/modules/text/lib/Drupal/text/Plugin/field/widget/TextareaWidget.php b/core/modules/text/lib/Drupal/text/Plugin/field/widget/TextareaWidget.php
index 72eff19..6c11da3 100644
--- a/core/modules/text/lib/Drupal/text/Plugin/field/widget/TextareaWidget.php
+++ b/core/modules/text/lib/Drupal/text/Plugin/field/widget/TextareaWidget.php
@@ -10,6 +10,7 @@
 use Drupal\Component\Annotation\Plugin;
 use Drupal\Core\Annotation\Translation;
 use Drupal\field\Plugin\Type\Widget\WidgetBase;
+use Symfony\Component\Validator\ConstraintViolationInterface;
 
 /**
  * Plugin implementation of the 'text_textarea' widget.
@@ -89,4 +90,15 @@ public function formElement(array $items, $delta, array $element, $langcode, arr
     return $element;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function errorElement(array $element, ConstraintViolationInterface $violation, array $form, array &$form_state) {
+    if ($violation->arrayPropertyPath == array('format') && isset($element['format']['#access']) && !$element['format']['#access']) {
+      // Ignore validation errors for formats if formats may not be changed,
+      // i.e. when existing formats become invalid. See filter_process_format().
+      return FALSE;
+    }
+    return $element;
+  }
 }
diff --git a/core/modules/text/lib/Drupal/text/Plugin/field/widget/TextareaWithSummaryWidget.php b/core/modules/text/lib/Drupal/text/Plugin/field/widget/TextareaWithSummaryWidget.php
index 300af18..185ee19 100644
--- a/core/modules/text/lib/Drupal/text/Plugin/field/widget/TextareaWithSummaryWidget.php
+++ b/core/modules/text/lib/Drupal/text/Plugin/field/widget/TextareaWithSummaryWidget.php
@@ -85,6 +85,11 @@ function formElement(array $items, $delta, array $element, $langcode, array &$fo
    * {@inheritdoc}
    */
   public function errorElement(array $element, ConstraintViolationInterface $violation, array $form, array &$form_state) {
+    if ($violation->arrayPropertyPath == array('format') && isset($element['format']['#access']) && !$element['format']['#access']) {
+      // Ignore validation errors for formats if formats may not be changed,
+      // i.e. when existing formats become invalid. See filter_process_format().
+      return FALSE;
+    }
     return $element[$violation->arrayPropertyPath[0]];
   }
 
diff --git a/core/modules/text/lib/Drupal/text/Plugin/field/widget/TextfieldWidget.php b/core/modules/text/lib/Drupal/text/Plugin/field/widget/TextfieldWidget.php
index 5319aab..07e7542 100644
--- a/core/modules/text/lib/Drupal/text/Plugin/field/widget/TextfieldWidget.php
+++ b/core/modules/text/lib/Drupal/text/Plugin/field/widget/TextfieldWidget.php
@@ -10,6 +10,7 @@
 use Drupal\Component\Annotation\Plugin;
 use Drupal\Core\Annotation\Translation;
 use Drupal\field\Plugin\Type\Widget\WidgetBase;
+use Symfony\Component\Validator\ConstraintViolationInterface;
 
 /**
  * Plugin implementation of the 'text_textfield' widget.
@@ -90,4 +91,16 @@ public function formElement(array $items, $delta, array $element, $langcode, arr
     return $element;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function errorElement(array $element, ConstraintViolationInterface $violation, array $form, array &$form_state) {
+    if ($violation->arrayPropertyPath == array('format') && isset($element['format']['#access']) && !$element['format']['#access']) {
+      // Ignore validation errors for formats if formats may not be changed,
+      // i.e. when existing formats become invalid. See filter_process_format().
+      return FALSE;
+    }
+    return $element;
+  }
+
 }