diff -u b/core/lib/Drupal/Component/Datetime/DateTimePlus.php b/core/lib/Drupal/Component/Datetime/DateTimePlus.php
--- b/core/lib/Drupal/Component/Datetime/DateTimePlus.php
+++ b/core/lib/Drupal/Component/Datetime/DateTimePlus.php
@@ -590,9 +590,8 @@
    *   - timezone: (optional) String timezone name. Defaults to the timezone
    *     of the date object.
    *
-   * @return string|null
-   *   The formatted value of the date
-   *   or NULL if there were construction errors.
+   * @return string
+   *   The formatted value of the date.
    */
   public function format($format, $settings = array()) {
 
@@ -625,8 +624,9 @@
    *   - timezone: (optional) String timezone name. Defaults to the timezone
    *     of the date object.
    *
-   * @return string
-   *   The formatted value of the date.
+   * @return string|null
+   *   The formatted value of the date or NULL if there were construction
+   *   errors.
    */
   public function format($format, $settings = array()) {
 
diff -u b/core/modules/dblog/src/Controller/DbLogController.php b/core/modules/dblog/src/Controller/DbLogController.php
--- b/core/modules/dblog/src/Controller/DbLogController.php
+++ b/core/modules/dblog/src/Controller/DbLogController.php
@@ -300,8 +300,8 @@
    * Builds a query for database log administration filters based on session.
    *
    * @return array|null
-   *   An associative array with keys 'where' and 'args'
-   *   or NULL if there were no filters set.
+   *   An associative array with keys 'where' and 'args' or NULL if there were
+   *   no filters set.
    */
   protected function buildFilterQuery() {
     if (empty($_SESSION['dblog_overview_filter'])) {
diff -u b/core/modules/forum/src/Tests/ForumTest.php b/core/modules/forum/src/Tests/ForumTest.php
--- b/core/modules/forum/src/Tests/ForumTest.php
+++ b/core/modules/forum/src/Tests/ForumTest.php
@@ -522,8 +522,7 @@
    *   TRUE if $forum is a container; FALSE otherwise.
    *
    * @return object|null
-   *   The created topic node
-   *   or NULL if there were errors.
+   *   The created topic node or NULL if there were errors.
    */
   function createForumTopic($forum, $container = FALSE) {
     // Generate a random subject/body.
diff -u b/core/modules/simpletest/simpletest.module b/core/modules/simpletest/simpletest.module
--- b/core/modules/simpletest/simpletest.module
+++ b/core/modules/simpletest/simpletest.module
@@ -691,8 +691,8 @@
  *
  * @return array[]|null
  *   The results as array of rows in a format that can be inserted into
- *   {simpletest}. If the phpunit_xml_file does not have any contents
- *   then the function will return NULL.
+ *   {simpletest}. If the phpunit_xml_file does not have any contents then the
+ *   function will return NULL.
  */
 function simpletest_phpunit_xml_to_rows($test_id, $phpunit_xml_file) {
   $contents = @file_get_contents($phpunit_xml_file);
diff -u b/core/modules/system/src/Tests/Module/ModuleTestBase.php b/core/modules/system/src/Tests/Module/ModuleTestBase.php
--- b/core/modules/system/src/Tests/Module/ModuleTestBase.php
+++ b/core/modules/system/src/Tests/Module/ModuleTestBase.php
@@ -88,8 +88,8 @@
    *   The name of the module.
    *
    * @return bool|NULL
-   *   TRUE if configuration has been installed, FALSE otherwise.
-   *   Returns NULL if the module configuration directory does not exist.
+   *   TRUE if configuration has been installed, FALSE otherwise. Returns NULL
+   *   if the module configuration directory does not exist.
    */
   function assertModuleConfig($module) {
     $module_config_dir = drupal_get_path('module', $module) . '/' . InstallStorage::CONFIG_INSTALL_DIRECTORY;