diff -u b/core/lib/Drupal/Core/Form/FormErrorInterface.php b/core/lib/Drupal/Core/Form/FormErrorInterface.php
--- b/core/lib/Drupal/Core/Form/FormErrorInterface.php
+++ b/core/lib/Drupal/Core/Form/FormErrorInterface.php
@@ -70,14 +70,15 @@
    *
    * This will require $form_state['values']['step1'] and everything within it
    * (for example, $form_state['values']['step1']['choice']) to be valid, so
-   * calls to FormBuilder::setErrorByName('step1', $form_state, $message) or
-   * FormBuilder::setErrorByName('step1][choice', $form_state, $message) will
-   * prevent the submit handlers from running, and result in the error message
-   * being displayed to the user. However, calls to
-   * FormBuilder::setErrorByName('step2', $form_state, $message) and
-   * FormBuilder::setErrorByName('step2][groupX][choiceY', $form_state, $message)
+   * calls to FormErrorInterface::setErrorByName('step1', $form_state, $message)
+   * or
+   * FormErrorInterface::setErrorByName('step1][choice', $form_state, $message)
+   * will prevent the submit handlers from running, and result in the error
+   * message being displayed to the user. However, calls to
+   * FormErrorInterface::setErrorByName('step2', $form_state, $message) and
+   * FormErrorInterface::setErrorByName('step2][groupX][choiceY', $form_state, $message)
    * will be suppressed, resulting in the message not being displayed to the
-   * user, and the FormBuilder::submitdoCheckErrors() handlers will run despite
+   * user, and the submit handlers will run despite
    * $form_state['values']['step2'] and
    * $form_state['values']['step2']['groupX']['choiceY'] containing invalid
    * values. Errors for an invalid $form_state['values']['foo'] will be
@@ -105,12 +106,12 @@
    *
    * @return mixed
    *   Return value is for internal use only. To get a list of errors, use
-   *   FormBuilder::getErrors() or FormBuilder::getError().
+   *   FormErrorInterface::getErrors() or FormErrorInterface::getError().
    */
   public function setErrorByName($name, array &$form_state, $message = '');
 
   /**
-   * Clears all errors against all form elements made by FormBuilder::setErrorByName().
+   * Clears all errors against all form elements made by FormErrorInterface::setErrorByName().
    *
    * @param array $form_state
    *   An associative array containing the current state of the form.