diff --git a/core/modules/user/src/AccountForm.php b/core/modules/user/src/AccountForm.php
index 3a2b57d..3eb4ff2 100644
--- a/core/modules/user/src/AccountForm.php
+++ b/core/modules/user/src/AccountForm.php
@@ -412,40 +412,75 @@ public function submitForm(array &$form, FormStateInterface $form_state) {
    * {@inheritdoc}
    */
   public function validateForm(array &$form, FormStateInterface $form_state) {
-    $name_taken = FALSE;
     $mail_taken = FALSE;
+    $account = $this->entity;
+    $user = $this->currentUser();
 
     // For new registrations, make sure the username does not conflict with
     // an existing user's email address.
-    $name_taken = (bool) db_select('users_field_data', 'ufd')
-      ->condition(
-        db_or()
-        ->condition('ufd.name', db_like($form_state->getValue('name')), 'LIKE')
-        ->condition('ufd.mail', db_like($form_state->getValue('name')), 'LIKE')
-      )
-      ->condition('ufd.status', 1)
-      ->range(0, 1)
-      ->countQuery()
-      ->execute()
-      ->fetchField();
-
-    if ($name_taken) {
-      $form_state->setErrorByName('name', $this->t('The name @name is already taken.', array('@name' => $form_state->getValue('name'))));
+    if (!empty($form_state->getValue('name'))) {
+      $name_taken = FALSE;
+
+      if ($user->isAuthenticated()) {
+        $name_taken = (bool) db_select('users_field_data', 'ufd')
+          ->condition(
+            db_or()
+            ->condition('ufd.name', db_like($form_state->getValue('name')), 'LIKE')
+            ->condition('ufd.mail', db_like($form_state->getValue('name')), 'LIKE')
+          )
+          ->condition('ufd.uid', $user->id(), '<>')
+          ->range(0, 1)
+          ->countQuery()
+          ->execute()
+          ->fetchField();
+      }
+      else {
+        $name_taken = (bool) db_select('users_field_data', 'ufd')
+          ->condition(
+            db_or()
+            ->condition('ufd.name', db_like($form_state->getValue('name')), 'LIKE')
+            ->condition('ufd.mail', db_like($form_state->getValue('name')), 'LIKE')
+          )
+          ->condition('ufd.status', 1)
+          ->range(0, 1)
+          ->countQuery()
+          ->execute()
+          ->fetchField();
+      }
+
+      if ($name_taken) {
+        $form_state->setErrorByName('name', $this->t('The name @name is already taken.', array('@name' => $form_state->getValue('name'))));
+      }
     }
 
     // For new registrations, make sure the email address does not conflict
     // with an existing user's username.
-    $mail_taken = (bool) db_select('users_field_data', 'ufd')
-      ->condition(
-        db_or()
-        ->condition('ufd.mail', db_like($form_state->getValue('mail')), 'LIKE')
-        ->condition('ufd.name', db_like($form_state->getValue('mail')), 'LIKE')
-      )
-      ->condition('ufd.status', 1)
-      ->range(0, 1)
-      ->countQuery()
-      ->execute()
-      ->fetchField();
+    if ($user->isAuthenticated()) {
+      $mail_taken = (bool) db_select('users_field_data', 'ufd')
+        ->condition(
+          db_or()
+          ->condition('ufd.mail', db_like($form_state->getValue('mail')), 'LIKE')
+          ->condition('ufd.name', db_like($form_state->getValue('mail')), 'LIKE')
+        )
+        ->condition('ufd.uid', $user->id(), '<>')
+        ->range(0, 1)
+        ->countQuery()
+        ->execute()
+        ->fetchField();
+    }
+    else {
+      $mail_taken = (bool) db_select('users_field_data', 'ufd')
+        ->condition(
+          db_or()
+          ->condition('ufd.mail', db_like($form_state->getValue('mail')), 'LIKE')
+          ->condition('ufd.name', db_like($form_state->getValue('mail')), 'LIKE')
+        )
+        ->condition('ufd.status', 1)
+        ->range(0, 1)
+        ->countQuery()
+        ->execute()
+        ->fetchField();
+    }
 
     if ($mail_taken) {
       $form_state->setErrorByName('mail', $this->t('The email address @email is already registered.', array('@email' => $form_state->getValue('mail'))));
diff --git a/core/modules/user/user.module b/core/modules/user/user.module
index 370f95a..3e95399 100644
--- a/core/modules/user/user.module
+++ b/core/modules/user/user.module
@@ -50,91 +50,6 @@
 const USER_REGISTER_VISITORS_ADMINISTRATIVE_APPROVAL = 'visitors_admin_approval';
 
 /**
- * Menu callback; process one time login link and redirects to the user page on success.
- *
- * @deprecated Use \Drupal\user\Form\UserForm::resetPass()
- */
-function user_pass_reset($form, $form_state, $uid, $timestamp, $hashed_pass, $action = NULL) {
-  global $user;
-
-  // When processing the one-time login link, we have to make sure that a user
-  // isn't already logged in.
-  if ($user->isAuthenticated()) {
-    // The existing user is already logged in.
-    if ($user->id() == $uid) {
-      drupal_set_message(t('You are logged in as %user. <a href="!user_edit">Change your password.</a>', array('%user' => $user->getUsername(), '!user_edit' => url("user/" . $user->id() . "/edit"))));
-    }
-    // A different user is already logged in on the computer.
-    else {
-      $reset_link_account = user_load($uid);
-      if (!empty($reset_link_account)) {
-        drupal_set_message(t('Another user (%other_user) is already logged into the site on this computer, but you tried to use a one-time link for user %resetting_user. Please <a href="!logout">logout</a> and try using the link again.',
-          array('%other_user' => $user->getUsername(), '%resetting_user' => $reset_link_account->getUsername(), '!logout' => url('user/logout'))));
-      } else {
-        // Invalid one-time link specifies an unknown user.
-        drupal_set_message(t('The one-time login link you clicked is invalid.'));
-      }
-    }
-    return new RedirectResponse(url('<front>', array('absolute' => TRUE)));
-  }
-  else {
-    // Time out, in seconds, until login URL expires.
-    $timeout = \Drupal::config('user.settings')->get('password_reset_timeout');
-    $current = REQUEST_TIME;
-    $account = user_load($uid);
-    // Verify that the user exists and is active.
-    if ($timestamp <= $current && $account && $account->isActive()) {
-      // No time out for first time login.
-      if ($account->getLastLoginTime() && $current - $timestamp > $timeout) {
-        drupal_set_message(t('You have tried to use a one-time login link that has expired. Please request a new one using the form below.'));
-        return new RedirectResponse(url('user/password', array('absolute' => TRUE)));
-      }
-      elseif ($account->isAuthenticated() && $timestamp >= $account->getLastLoginTime() && $timestamp <= $current && $hashed_pass == user_pass_rehash($account->getPassword(), $timestamp, $account->getLastLoginTime())) {
-        // First stage is a confirmation form, then login
-        if ($action == 'login') {
-          // Set the new user.
-          // user_login_finalize() also updates the login timestamp of the
-          // user, which invalidates further use of the one-time login link.
-          user_login_finalize($account);
-          watchdog('user', 'User %name used one-time login link at time %timestamp.', array('%name' => $account->getUsername(), '%timestamp' => $timestamp));
-          drupal_set_message(t('You have just used your one-time login link. It is no longer necessary to use this link to log in. Please change your password.'));
-          // Let the user's password be changed without the current password check.
-          $token = Crypt::randomStringHashed(55);
-          $_SESSION['pass_reset_' . $user->id()] = $token;
-          return new RedirectResponse(url('user/' . $user->id() . '/edit', array(
-            'query' => array('pass-reset-token' => $token),
-            'absolute' => TRUE,
-          )));
-        }
-       else {
-          if (!$account->getLastLoginTime()) {
-            // No expiration for first time login.
-            $form['message'] = array('#markup' => t('<p>This is a one-time login for %user_name.</p><p>Click on this button to log in to the site and change your password.</p>', array('%user_name' => $account->getUsername())));
-          }
-          else {
-            $form['message'] = array('#markup' => t('<p>This is a one-time login for %user_name and will expire on %expiration_date.</p><p>Click on this button to log in to the site and change your password.</p>', array('%user_name' => $account->getUsername(), '%expiration_date' => format_date($timestamp + $timeout))));
-          }
-          $form['help'] = array('#markup' => '<p>' . t('This login can be used only once.') . '</p>');
-          $form['actions'] = array('#type' => 'actions');
-          $form['actions']['submit'] = array('#type' => 'submit', '#value' => t('Log in'));
-          $form['#action'] = url("user/reset/$uid/$timestamp/$hashed_pass/login");
-          return $form;
-        }
-      }
-      else {
-        drupal_set_message(t('You have tried to use a one-time login link that has either been used or is no longer valid. Please request a new one using the form below.'));
-        return new RedirectResponse(url('user/password', array('absolute' => TRUE)));
-      }
-    }
-    else {
-      // Deny access, no more clues.
-      // Everything will be in the watchdog's URL for the administrator to check.
-      throw new AccessDeniedHttpException();
-    }
-  }
-}
-
-/**
  * Implements hook_help().
  */
 function user_help($route_name, RouteMatchInterface $route_match) {