diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index d78a54d412e19092fa13e641c0ffe235f736d67e..292e918e33b0bb974c28f64ec7d66cbc99c489cb 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -599,7 +599,7 @@ function _drupal_exception_handler_additional($exception, $exception2) {
  * @param string $new_prefix
  *   Internal use only. A new prefix to be stored.
  *
- * @return string|FALSE
+ * @return string|false
  *   Either the simpletest prefix (the string "simpletest" followed by any
  *   number of digits) or FALSE if the user agent does not contain a valid
  *   HMAC and timestamp.
diff --git a/core/lib/Drupal/Component/PhpStorage/PhpStorageInterface.php b/core/lib/Drupal/Component/PhpStorage/PhpStorageInterface.php
index 71f47008be9d139be490e10db94d38781f594c8e..735341d6b1c4445ec094ef7826056edfa1901927 100644
--- a/core/lib/Drupal/Component/PhpStorage/PhpStorageInterface.php
+++ b/core/lib/Drupal/Component/PhpStorage/PhpStorageInterface.php
@@ -80,7 +80,7 @@ public function deleteAll();
    * @param string $name
    *   The virtual file name. Can be a relative path.
    *
-   * @return string|FALSE
+   * @return string|false
    *   The full file path for the provided name. Return FALSE if the
    *   implementation needs to prevent access to the file.
    */
diff --git a/core/lib/Drupal/Core/Access/AccessResultReasonInterface.php b/core/lib/Drupal/Core/Access/AccessResultReasonInterface.php
index 468d9988964cc936d7cb8c150c29846867d136c9..850194c54b22833f2d40cff20c02ba9ddb984468 100644
--- a/core/lib/Drupal/Core/Access/AccessResultReasonInterface.php
+++ b/core/lib/Drupal/Core/Access/AccessResultReasonInterface.php
@@ -17,7 +17,7 @@ interface AccessResultReasonInterface extends AccessResultInterface {
   /**
    * Gets the reason for this access result.
    *
-   * @return string|NULL
+   * @return string|null
    *   The reason of this access result or NULL if no reason is provided.
    */
   public function getReason();
@@ -25,7 +25,7 @@ public function getReason();
   /**
    * Sets the reason for this access result.
    *
-   * @param $reason string|NULL
+   * @param $reason string|null
    *   The reason of this access result or NULL if no reason is provided.
    *
    * @return \Drupal\Core\Access\AccessResultInterface
diff --git a/core/lib/Drupal/Core/Asset/LibraryDiscoveryInterface.php b/core/lib/Drupal/Core/Asset/LibraryDiscoveryInterface.php
index c8d18f06e8cdb1919e6e50eb7dceddb263b94cb4..0f4e70474b906df9bf71059c7159e6322dde8c77 100644
--- a/core/lib/Drupal/Core/Asset/LibraryDiscoveryInterface.php
+++ b/core/lib/Drupal/Core/Asset/LibraryDiscoveryInterface.php
@@ -39,7 +39,7 @@ public function getLibrariesByExtension($extension);
    * @param string $name
    *   The name of a registered library to retrieve.
    *
-   * @return array|FALSE
+   * @return array|false
    *   The definition of the requested library, if $name was passed and it
    *   exists, otherwise FALSE.
    */
diff --git a/core/lib/Drupal/Core/Authentication/AuthenticationCollectorInterface.php b/core/lib/Drupal/Core/Authentication/AuthenticationCollectorInterface.php
index 3d869e5f1ed6310579821a78b426be215034f607..37f245cc1c33e89f61a4838e51397b0e526c9e83 100644
--- a/core/lib/Drupal/Core/Authentication/AuthenticationCollectorInterface.php
+++ b/core/lib/Drupal/Core/Authentication/AuthenticationCollectorInterface.php
@@ -41,7 +41,7 @@ public function isGlobal($provider_id);
    * @param string $provider_id
    *   The provider ID.
    *
-   * @return \Drupal\Core\Authentication\AuthenticationProviderInterface|NULL
+   * @return \Drupal\Core\Authentication\AuthenticationProviderInterface|null
    *   The authentication provider which matches the ID.
    */
   public function getProvider($provider_id);
diff --git a/core/lib/Drupal/Core/Authentication/AuthenticationManager.php b/core/lib/Drupal/Core/Authentication/AuthenticationManager.php
index 10b0edc5c5c768c3d076db9176e132ee44fc93cc..1049c92bb6282deccdb57884e4fddf3388bcfd40 100644
--- a/core/lib/Drupal/Core/Authentication/AuthenticationManager.php
+++ b/core/lib/Drupal/Core/Authentication/AuthenticationManager.php
@@ -94,7 +94,7 @@ public function challengeException(Request $request, \Exception $previous) {
    * @param \Symfony\Component\HttpFoundation\Request $request
    *   The incoming request.
    *
-   * @return string|NULL
+   * @return string|null
    *   The id of the first authentication provider which applies to the request.
    *   If no application detects appropriate credentials, then NULL is returned.
    */
@@ -112,7 +112,7 @@ protected function getProvider(Request $request) {
    * @param \Symfony\Component\HttpFoundation\Request $request
    *   The incoming request.
    *
-   * @return string|NULL
+   * @return string|null
    *   The ID of the first authentication provider which applies to the request.
    *   If no application detects appropriate credentials, then NULL is returned.
    */
diff --git a/core/lib/Drupal/Core/Authentication/AuthenticationProviderChallengeInterface.php b/core/lib/Drupal/Core/Authentication/AuthenticationProviderChallengeInterface.php
index 47210507a45bcdb3b2c184c174e31fd85ae51270..db86cc1a321710ef7bff4929d97de302e3dc15b1 100644
--- a/core/lib/Drupal/Core/Authentication/AuthenticationProviderChallengeInterface.php
+++ b/core/lib/Drupal/Core/Authentication/AuthenticationProviderChallengeInterface.php
@@ -21,7 +21,7 @@ interface AuthenticationProviderChallengeInterface {
    * @param \Exception $previous
    *   The previous exception.
    *
-   * @return \Symfony\Component\HttpKernel\Exception\HttpExceptionInterface|NULL
+   * @return \Symfony\Component\HttpKernel\Exception\HttpExceptionInterface|null
    *   An exception to be used in order to generate an authentication challenge.
    */
   public function challengeException(Request $request, \Exception $previous);
diff --git a/core/lib/Drupal/Core/Authentication/AuthenticationProviderInterface.php b/core/lib/Drupal/Core/Authentication/AuthenticationProviderInterface.php
index 7ef18dfb33bd1dc0a635218b141bb706b2a19a79..02f049764724b33fd3065b96d43ef7f270632e5d 100644
--- a/core/lib/Drupal/Core/Authentication/AuthenticationProviderInterface.php
+++ b/core/lib/Drupal/Core/Authentication/AuthenticationProviderInterface.php
@@ -27,7 +27,7 @@ public function applies(Request $request);
    * @param \Symfony\Component\HttpFoundation\Request|null $request
    *   The request object.
    *
-   * @return \Drupal\Core\Session\AccountInterface|NULL
+   * @return \Drupal\Core\Session\AccountInterface|null
    *   AccountInterface - in case of a successful authentication.
    *   NULL - in case where authentication failed.
    */
diff --git a/core/lib/Drupal/Core/Composer/Composer.php b/core/lib/Drupal/Core/Composer/Composer.php
index 51a4917fd485e3a44c69e0d6bb7e7ef6ee3e1dcf..263be4c6e962b5f242f6a88582e9a9985d6f3240 100644
--- a/core/lib/Drupal/Core/Composer/Composer.php
+++ b/core/lib/Drupal/Core/Composer/Composer.php
@@ -196,7 +196,7 @@ public static function vendorTestCodeCleanup(PackageEvent $event) {
    * @param string $package_name
    *   The package name from composer. This is always already lower case.
    *
-   * @return NULL|string
+   * @return string|null
    *   The string key, or NULL if none was found.
    */
   protected static function findPackageKey($package_name) {
diff --git a/core/lib/Drupal/Core/Config/ConfigCollectionInfo.php b/core/lib/Drupal/Core/Config/ConfigCollectionInfo.php
index ca526cd7ea0631bd8fd7c65f05c1bf570bbccb12..0ec82f9f2543e453c380680fb68d7159aca68f6d 100644
--- a/core/lib/Drupal/Core/Config/ConfigCollectionInfo.php
+++ b/core/lib/Drupal/Core/Config/ConfigCollectionInfo.php
@@ -63,7 +63,7 @@ public function getCollectionNames($include_default = TRUE) {
    * @param string $collection
    *   The configuration collection.
    *
-   * @return \Drupal\Core\Config\ConfigFactoryOverrideInterface|NULL
+   * @return \Drupal\Core\Config\ConfigFactoryOverrideInterface|null
    *   The override service responsible for the collection if one exists. NULL
    *   if not.
    */
diff --git a/core/lib/Drupal/Core/Config/Entity/ConfigEntityTypeInterface.php b/core/lib/Drupal/Core/Config/Entity/ConfigEntityTypeInterface.php
index 2cb14342151c87b8cb07a4dc21ec582916dc5753..589a63d2c157263f8669752e019f283b6ae47f28 100644
--- a/core/lib/Drupal/Core/Config/Entity/ConfigEntityTypeInterface.php
+++ b/core/lib/Drupal/Core/Config/Entity/ConfigEntityTypeInterface.php
@@ -65,7 +65,7 @@ public function getConfigPrefix();
   /**
    * Gets the config entity properties to export if declared on the annotation.
    *
-   * @return array|NULL
+   * @return array|null
    *   The properties to export or NULL if they can not be determine from the
    *   config entity type annotation.
    */
diff --git a/core/lib/Drupal/Core/Config/Entity/Query/QueryFactory.php b/core/lib/Drupal/Core/Config/Entity/Query/QueryFactory.php
index 4396a39282387a1affa8a5f546aeec0de406b11d..80a41c4f0362fca2552e799f40ffbe6b0daaddd7 100644
--- a/core/lib/Drupal/Core/Config/Entity/Query/QueryFactory.php
+++ b/core/lib/Drupal/Core/Config/Entity/Query/QueryFactory.php
@@ -189,7 +189,7 @@ protected function getKeys(Config $config, $key, $get_method, ConfigEntityTypeIn
    * @param int $start
    *   Which position of $parts we are processing. Defaults to 0.
    *
-   * @return array|NULL
+   * @return array|null
    *   The array of configuration values the match the provided key. NULL if
    *   the configuration object does not have a value that corresponds to the
    *   key.
diff --git a/core/lib/Drupal/Core/DrupalKernelInterface.php b/core/lib/Drupal/Core/DrupalKernelInterface.php
index 4f7e9c46102ef5094e390b0e6028eed9f6a5ad42..862fbec59d0f5471c4176c9dc4f7ef142925b36e 100644
--- a/core/lib/Drupal/Core/DrupalKernelInterface.php
+++ b/core/lib/Drupal/Core/DrupalKernelInterface.php
@@ -58,7 +58,7 @@ public function getContainer();
    *
    * This also allows inspecting a built container for debugging purposes.
    *
-   * @return array|NULL
+   * @return array|null
    *   The cached container definition or NULL if not found in cache.
    */
   public function getCachedContainerDefinition();
diff --git a/core/lib/Drupal/Core/Entity/Controller/EntityController.php b/core/lib/Drupal/Core/Entity/Controller/EntityController.php
index ebee7cca60bc82c801cdaeaf2935e3e9cd159389..4ca97e43ee4460b2329d8c227284bf402bc4dd05 100644
--- a/core/lib/Drupal/Core/Entity/Controller/EntityController.php
+++ b/core/lib/Drupal/Core/Entity/Controller/EntityController.php
@@ -273,7 +273,7 @@ public function deleteTitle(RouteMatchInterface $route_match, EntityInterface $_
    *   (optional) The entity, set in
    *   \Drupal\Core\Entity\Enhancer\EntityRouteEnhancer.
    *
-   * @return \Drupal\Core\Entity\EntityInterface|NULL
+   * @return \Drupal\Core\Entity\EntityInterface|null
    *   The entity, if it is passed in directly or if the first parameter of the
    *   active route is an entity; otherwise, NULL.
    */
diff --git a/core/lib/Drupal/Core/EventSubscriber/AuthenticationSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/AuthenticationSubscriber.php
index 4f44409dfc7ffb51c42b073385f253d917accdc0..62f5486cfd0b00f4f4c07d36e38adeb378279676 100644
--- a/core/lib/Drupal/Core/EventSubscriber/AuthenticationSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/AuthenticationSubscriber.php
@@ -30,14 +30,14 @@ class AuthenticationSubscriber implements EventSubscriberInterface {
   /**
    * Authentication provider filter.
    *
-   * @var \Drupal\Core\Authentication\AuthenticationProviderFilterInterface|NULL
+   * @var \Drupal\Core\Authentication\AuthenticationProviderFilterInterface|null
    */
   protected $filter;
 
   /**
    * Authentication challenge provider.
    *
-   * @var \Drupal\Core\Authentication\AuthenticationProviderChallengeInterface|NULL
+   * @var \Drupal\Core\Authentication\AuthenticationProviderChallengeInterface|null
    */
   protected $challengeProvider;
 
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldWidget/OptionsWidgetBase.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldWidget/OptionsWidgetBase.php
index add9cd77ebe37c21063bab793979853391d7b986..ca00bcc6485c92404a13b9369ada1aff607ed1eb 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldWidget/OptionsWidgetBase.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldWidget/OptionsWidgetBase.php
@@ -190,7 +190,7 @@ protected function sanitizeLabel(&$label) {
   /**
    * Returns the empty option label to add to the list of options, if any.
    *
-   * @return string|NULL
+   * @return string|null
    *   Either a label of the empty option, or NULL.
    */
   protected function getEmptyLabel() { }
diff --git a/core/lib/Drupal/Core/Form/EnforcedResponse.php b/core/lib/Drupal/Core/Form/EnforcedResponse.php
index c28033fae98866b492262f279071d1b1ac2cb2ba..2b1466d0a3cc027a60d160a0ed69b6317a9eec4e 100644
--- a/core/lib/Drupal/Core/Form/EnforcedResponse.php
+++ b/core/lib/Drupal/Core/Form/EnforcedResponse.php
@@ -37,7 +37,7 @@ class EnforcedResponse extends Response {
    * @param \Exception $e
    *   The exception where the enforced response is to be extracted from.
    *
-   * @return \Drupal\Core\Form\EnforcedResponse|NULL
+   * @return \Drupal\Core\Form\EnforcedResponse|null
    *   The enforced response or NULL if the exception chain does not contain a
    *   \Drupal\Core\Form\EnforcedResponseException exception.
    */
diff --git a/core/lib/Drupal/Core/Menu/MenuActiveTrailInterface.php b/core/lib/Drupal/Core/Menu/MenuActiveTrailInterface.php
index ddcd39dd44358dc96d00d9f8b8b00ffdf82cc625..8410e5af3f7df2405cea8c79f8770bbf8e6ead25 100644
--- a/core/lib/Drupal/Core/Menu/MenuActiveTrailInterface.php
+++ b/core/lib/Drupal/Core/Menu/MenuActiveTrailInterface.php
@@ -29,7 +29,7 @@ public function getActiveTrailIds($menu_name);
    *   (optional) The menu within which to find the active link. If omitted, all
    *   menus will be searched.
    *
-   * @return \Drupal\Core\Menu\MenuLinkInterface|NULL
+   * @return \Drupal\Core\Menu\MenuLinkInterface|null
    *   The menu link for the given route name, parameters and menu, or NULL if
    *   there is no matching menu link or the current user cannot access the
    *   current page (i.e. we have a 403 response).
diff --git a/core/lib/Drupal/Core/Menu/MenuLinkTreeElement.php b/core/lib/Drupal/Core/Menu/MenuLinkTreeElement.php
index 1327c78c549450aa0a278870deae7164166c8f64..e7e12c42ba524838fc5082c49c3265b60cb1f196 100644
--- a/core/lib/Drupal/Core/Menu/MenuLinkTreeElement.php
+++ b/core/lib/Drupal/Core/Menu/MenuLinkTreeElement.php
@@ -68,7 +68,7 @@ class MenuLinkTreeElement {
    * If the value is NULL the access was not determined yet, if an access result
    * object, it was determined already.
    *
-   * @var \Drupal\Core\Access\AccessResultInterface|NULL
+   * @var \Drupal\Core\Access\AccessResultInterface|null
    */
   public $access;
 
diff --git a/core/lib/Drupal/Core/Menu/MenuTreeStorageInterface.php b/core/lib/Drupal/Core/Menu/MenuTreeStorageInterface.php
index 4ee308b96cb03639b002a9d2bab0f5f05a9815a7..0a580d64a391d3d72d7f9855b82205b7d14db1f2 100644
--- a/core/lib/Drupal/Core/Menu/MenuTreeStorageInterface.php
+++ b/core/lib/Drupal/Core/Menu/MenuTreeStorageInterface.php
@@ -41,7 +41,7 @@ public function rebuild(array $definitions);
    * @param string $id
    *   The menu link plugin ID.
    *
-   * @return array|FALSE
+   * @return array|false
    *   The plugin definition, or FALSE if no definition was found for the ID.
    */
   public function load($id);
diff --git a/core/lib/Drupal/Core/Menu/StaticMenuLinkOverridesInterface.php b/core/lib/Drupal/Core/Menu/StaticMenuLinkOverridesInterface.php
index a833a79a9dc0d42a3ec326593c48305e9df2af39..1a5c41de66cfc01f388feb592ef7d6d3da654e37 100644
--- a/core/lib/Drupal/Core/Menu/StaticMenuLinkOverridesInterface.php
+++ b/core/lib/Drupal/Core/Menu/StaticMenuLinkOverridesInterface.php
@@ -21,7 +21,7 @@ public function reload();
    * @param string $id
    *   A menu link plugin ID.
    *
-   * @return array|NULL
+   * @return array|null
    *   An override with following supported keys:
    *     - parent
    *     - weight
diff --git a/core/lib/Drupal/Core/PageCache/RequestPolicyInterface.php b/core/lib/Drupal/Core/PageCache/RequestPolicyInterface.php
index 9bd24a84d6387c2e7433c632613af29f8540656b..02b20cb781b1a44ad220014beb9ac9e4310f5b5a 100644
--- a/core/lib/Drupal/Core/PageCache/RequestPolicyInterface.php
+++ b/core/lib/Drupal/Core/PageCache/RequestPolicyInterface.php
@@ -39,7 +39,7 @@ interface RequestPolicyInterface {
    * @param \Symfony\Component\HttpFoundation\Request $request
    *   The incoming request object.
    *
-   * @return string|NULL
+   * @return string|null
    *   One of static::ALLOW, static::DENY or NULL. Calling code may attempt to
    *   deliver a cached page if static::ALLOW is returned. Returns NULL if the
    *   policy is not specified for the given request.
diff --git a/core/lib/Drupal/Core/PageCache/ResponsePolicyInterface.php b/core/lib/Drupal/Core/PageCache/ResponsePolicyInterface.php
index a82427b107f529b79123e5bbddebf9bf67db4551..0d3f96554766d470a04ab6107c8f62efaf4ce3a7 100644
--- a/core/lib/Drupal/Core/PageCache/ResponsePolicyInterface.php
+++ b/core/lib/Drupal/Core/PageCache/ResponsePolicyInterface.php
@@ -27,7 +27,7 @@ interface ResponsePolicyInterface {
    * @param \Symfony\Component\HttpFoundation\Request $request
    *   The request object.
    *
-   * @return string|NULL
+   * @return string|null
    *   Either static::DENY or NULL. Calling code may attempt to store a page in
    *   the cache unless static::DENY is returned. Returns NULL if the policy
    *   policy is not specified for the given response.
diff --git a/core/lib/Drupal/Core/Plugin/Context/Context.php b/core/lib/Drupal/Core/Plugin/Context/Context.php
index 87fab3a1d752901ebd780fcc2fd10aa78fba93a8..35eaacda59d92fc5b196bd3278626f3fc5e62917 100644
--- a/core/lib/Drupal/Core/Plugin/Context/Context.php
+++ b/core/lib/Drupal/Core/Plugin/Context/Context.php
@@ -42,7 +42,7 @@ class Context extends ComponentContext implements ContextInterface {
    *
    * @param \Drupal\Core\Plugin\Context\ContextDefinitionInterface $context_definition
    *   The context definition.
-   * @param mixed $context_value|NULL
+   * @param mixed $context_value|null
    *   The context value object.
    */
   public function __construct(ContextDefinitionInterface $context_definition, $context_value = NULL) {
diff --git a/core/lib/Drupal/Core/Routing/StackedRouteMatchInterface.php b/core/lib/Drupal/Core/Routing/StackedRouteMatchInterface.php
index 8cc4fb5bd6b6fb45e0a77cd7b65cb2f70c9eec35..986e900e4c8450e82319545f61de675b6a61a6e8 100644
--- a/core/lib/Drupal/Core/Routing/StackedRouteMatchInterface.php
+++ b/core/lib/Drupal/Core/Routing/StackedRouteMatchInterface.php
@@ -28,7 +28,7 @@ public function getMasterRouteMatch();
   /**
    * Returns the parent route match of the current.
    *
-   * @return \Drupal\Core\Routing\RouteMatchInterface|NULL
+   * @return \Drupal\Core\Routing\RouteMatchInterface|null
    *   The parent route match or NULL, if it the master route match.
    */
   public function getParentRouteMatch();
@@ -39,7 +39,7 @@ public function getParentRouteMatch();
    * @param \Symfony\Component\HttpFoundation\Request
    *   The request.
    *
-   * @return \Drupal\Core\Routing\RouteMatchInterface|NULL
+   * @return \Drupal\Core\Routing\RouteMatchInterface|null
    *   THe matching route match, or NULL if there is no matching one.
    */
   public function getRouteMatchFromRequest(Request $request);
diff --git a/core/lib/Drupal/Core/Session/AccountProxy.php b/core/lib/Drupal/Core/Session/AccountProxy.php
index a50a289fb0ebe21e8d5b971f88136cb5db077f4f..7aa95ae10a2caaf1815665c098286c29e7bbc6ba 100644
--- a/core/lib/Drupal/Core/Session/AccountProxy.php
+++ b/core/lib/Drupal/Core/Session/AccountProxy.php
@@ -179,7 +179,7 @@ public function setInitialAccountId($account_id) {
    * @param int $account_id
    *   The id of an account to load.
    *
-   * @return \Drupal\Core\Session\AccountInterface|NULL
+   * @return \Drupal\Core\Session\AccountInterface|null
    *   An account or NULL if none is found.
    */
   protected function loadUserEntity($account_id) {
diff --git a/core/lib/Drupal/Core/Session/SessionConfiguration.php b/core/lib/Drupal/Core/Session/SessionConfiguration.php
index 351e57d2693d582c7483a31273df3f531c4736db..49dc63e915e65b4a09c830ee121dfe208d394444 100644
--- a/core/lib/Drupal/Core/Session/SessionConfiguration.php
+++ b/core/lib/Drupal/Core/Session/SessionConfiguration.php
@@ -141,7 +141,7 @@ protected function getCookieDomain(Request $request) {
   /**
    * Wraps drupal_valid_test_ua().
    *
-   * @return string|FALSE
+   * @return string|false
    *   Either the simpletest prefix (the string "simpletest" followed by any
    *   number of digits) or FALSE if the user agent does not contain a valid
    *   HMAC and timestamp.
diff --git a/core/lib/Drupal/Core/StringTranslation/Translator/TranslatorInterface.php b/core/lib/Drupal/Core/StringTranslation/Translator/TranslatorInterface.php
index 367581bb14ac7f2e8b27c61885024624200bfac6..e0fee163d8da5de6a595a24917658ca4d714cf29 100644
--- a/core/lib/Drupal/Core/StringTranslation/Translator/TranslatorInterface.php
+++ b/core/lib/Drupal/Core/StringTranslation/Translator/TranslatorInterface.php
@@ -17,7 +17,7 @@ interface TranslatorInterface {
    * @param string $context
    *   The string context.
    *
-   * @return string|FALSE
+   * @return string|false
    *   Translated string if there is a translation, FALSE if not.
    */
   public function getStringTranslation($langcode, $string, $context);
diff --git a/core/lib/Drupal/Core/Theme/ThemeNegotiator.php b/core/lib/Drupal/Core/Theme/ThemeNegotiator.php
index 1d6b589a1ac2530a3ca913c07ff0d1010f4bdac4..3064eb073e6598c5e21bef6a22364ac6d35af8f1 100644
--- a/core/lib/Drupal/Core/Theme/ThemeNegotiator.php
+++ b/core/lib/Drupal/Core/Theme/ThemeNegotiator.php
@@ -24,7 +24,7 @@ class ThemeNegotiator implements ThemeNegotiatorInterface {
    *
    * Set to NULL if the array needs to be re-calculated.
    *
-   * @var array|NULL
+   * @var array|null
    */
   protected $sortedNegotiators;
 
diff --git a/core/modules/ckeditor/src/CKEditorPluginInterface.php b/core/modules/ckeditor/src/CKEditorPluginInterface.php
index 65475a094bb6e1aa38aac1941b87b8dd542af779..543a112dfb6300c652015fbf77cd0034b1773ae4 100644
--- a/core/modules/ckeditor/src/CKEditorPluginInterface.php
+++ b/core/modules/ckeditor/src/CKEditorPluginInterface.php
@@ -71,7 +71,7 @@ public function getLibraries(Editor $editor);
    * Note: this does not use a Drupal library because this uses CKEditor's API,
    * see http://docs.cksource.com/ckeditor_api/symbols/CKEDITOR.resourceManager.html#addExternal.
    *
-   * @return string|FALSE
+   * @return string|false
    *   The Drupal root-relative path to the file, FALSE if an internal plugin.
    */
   public function getFile();
diff --git a/core/modules/ckeditor/src/Plugin/CKEditorPlugin/StylesCombo.php b/core/modules/ckeditor/src/Plugin/CKEditorPlugin/StylesCombo.php
index 888fec0e9070c587bdd8f3c420be738f604dfb53..75b78a5a5e76de3e0472a9f3e3029240dca85eb2 100644
--- a/core/modules/ckeditor/src/Plugin/CKEditorPlugin/StylesCombo.php
+++ b/core/modules/ckeditor/src/Plugin/CKEditorPlugin/StylesCombo.php
@@ -115,7 +115,7 @@ public function validateStylesValue(array $element, FormStateInterface $form_sta
    *
    * @param string $styles
    *   The "styles" setting.
-   * @return array|FALSE
+   * @return array|false
    *   An array containing the "stylesSet" configuration, or FALSE when the
    *   syntax is invalid.
    */
diff --git a/core/modules/comment/src/CommentInterface.php b/core/modules/comment/src/CommentInterface.php
index 72a66524bff4de15d423dd3ad44f80dcabc5fa7f..28318eea1530ea1767df1632ad967d705fcc833e 100644
--- a/core/modules/comment/src/CommentInterface.php
+++ b/core/modules/comment/src/CommentInterface.php
@@ -32,7 +32,7 @@ public function hasParentComment();
   /**
    * Returns the parent comment entity if this is a reply to a comment.
    *
-   * @return \Drupal\comment\CommentInterface|NULL
+   * @return \Drupal\comment\CommentInterface|null
    *   A comment entity of the parent comment or NULL if there is no parent.
    */
   public function getParentComment();
diff --git a/core/modules/file/file.module b/core/modules/file/file.module
index 9f6e9fcfe01a257c410d681d56c1d5bb3f992b98..c63fff4358fce165fb3b4f74a03770d9b5df0bf3 100644
--- a/core/modules/file/file.module
+++ b/core/modules/file/file.module
@@ -1318,7 +1318,7 @@ function file_icon_class($mime_type) {
  * @param string $mime_type
  *   A MIME type.
  *
- * @return string|FALSE
+ * @return string|false
  *   The generic icon MIME package expected for this file.
  */
 function file_icon_map($mime_type) {
diff --git a/core/modules/filter/src/FilterFormatInterface.php b/core/modules/filter/src/FilterFormatInterface.php
index 30b612cc1ad243b594429fc8d2819bb0f4786645..6008f3fa4002133de6bfa42416808be505bd855e 100644
--- a/core/modules/filter/src/FilterFormatInterface.php
+++ b/core/modules/filter/src/FilterFormatInterface.php
@@ -70,7 +70,7 @@ public function getFilterTypes();
    * It is up to the caller to handle this in whatever way it sees fit; this way
    * no information granularity is lost.
    *
-   * @return array|FALSE
+   * @return array|false
    *   A structured array as returned by FilterInterface::getHTMLRestrictions(),
    *   but with the intersection of all filters in this text format.
    *   Will either indicate blacklisting of tags or whitelisting of tags. In
diff --git a/core/modules/filter/src/Plugin/FilterInterface.php b/core/modules/filter/src/Plugin/FilterInterface.php
index d42d5ccc6809d8c27430e8e602084a4c4f98e24f..18f1fde893e3d7520e849430cd0def7061ee1618 100644
--- a/core/modules/filter/src/Plugin/FilterInterface.php
+++ b/core/modules/filter/src/Plugin/FilterInterface.php
@@ -182,7 +182,7 @@ public function process($text, $langcode);
    * a generic manner into which HTML tags and attributes are allowed by a
    * format.
    *
-   * @return array|FALSE
+   * @return array|false
    *   A nested array with *either* of the following keys:
    *     - 'allowed': (optional) the allowed tags as keys, and for each of those
    *       tags (keys) either of the following values:
diff --git a/core/modules/locale/src/LocaleConfigManager.php b/core/modules/locale/src/LocaleConfigManager.php
index 2de875e29c6763e426c594c8f380fb65c7f4c546..bc598e21de73d2d7210e4e8cb5bfbabd6a280415 100644
--- a/core/modules/locale/src/LocaleConfigManager.php
+++ b/core/modules/locale/src/LocaleConfigManager.php
@@ -434,7 +434,7 @@ public function reset() {
    * @param string $context
    *   The string context.
    *
-   * @return \Drupal\locale\TranslationString|FALSE
+   * @return \Drupal\locale\TranslationString|false
    *   The translation object if the string was not empty or FALSE otherwise.
    */
   public function getStringTranslation($name, $langcode, $source, $context) {
diff --git a/core/modules/migrate/src/Plugin/migrate/destination/EntityContentBase.php b/core/modules/migrate/src/Plugin/migrate/destination/EntityContentBase.php
index 3617f38ed089fa56652f824c69d3d30722c625cd..d3adce883ff024fbee3f513d43410d132bf173aa 100644
--- a/core/modules/migrate/src/Plugin/migrate/destination/EntityContentBase.php
+++ b/core/modules/migrate/src/Plugin/migrate/destination/EntityContentBase.php
@@ -147,7 +147,7 @@ public function getIds() {
    * @param \Drupal\migrate\Row $row
    *   The row object to update from.
    *
-   * @return NULL|\Drupal\Core\Entity\EntityInterface
+   * @return \Drupal\Core\Entity\EntityInterface|null
    *   An updated entity, or NULL if it's the same as the one passed in.
    */
   protected function updateEntity(EntityInterface $entity, Row $row) {
diff --git a/core/modules/migrate_drupal/src/MigrationConfigurationTrait.php b/core/modules/migrate_drupal/src/MigrationConfigurationTrait.php
index a7aab64a156bda159f0c5e80aaf0d2a680a7ce75..683823296a8f61733a7c2a681d88d105f4fbd218 100644
--- a/core/modules/migrate_drupal/src/MigrationConfigurationTrait.php
+++ b/core/modules/migrate_drupal/src/MigrationConfigurationTrait.php
@@ -125,7 +125,7 @@ protected function getMigrations($database_state_key, $drupal_version) {
    * @param \Drupal\Core\Database\Connection $connection
    *   The database connection object.
    *
-   * @return int|FALSE
+   * @return int|false
    *   An integer representing the major branch of Drupal core (e.g. '6' for
    *   Drupal 6.x), or FALSE if no valid version is matched.
    */
diff --git a/core/modules/rdf/tests/src/Kernel/Field/FieldRdfaTestBase.php b/core/modules/rdf/tests/src/Kernel/Field/FieldRdfaTestBase.php
index 99e64acdd0882324d3a34102a519178b383a31c5..74311850a9b5930670380e7d3bda4f8d62b6fecd 100644
--- a/core/modules/rdf/tests/src/Kernel/Field/FieldRdfaTestBase.php
+++ b/core/modules/rdf/tests/src/Kernel/Field/FieldRdfaTestBase.php
@@ -167,7 +167,7 @@ protected function parseContent($content) {
    * @param array $arguments
    *   Some arguments for the xpath.
    *
-   * @return array|FALSE
+   * @return array|false
    *   The return value of the xpath search. For details on the xpath string
    *   format and return values see the SimpleXML documentation,
    *   http://php.net/manual/function.simplexml-element-xpath.php.
diff --git a/core/modules/rest/src/Tests/RESTTestBase.php b/core/modules/rest/src/Tests/RESTTestBase.php
index 7f67b9314bcdc82f671a85a55fb8738d7d2e02c0..4f8a0f196e73dc3ae16937a15035c58bd839f8fe 100644
--- a/core/modules/rest/src/Tests/RESTTestBase.php
+++ b/core/modules/rest/src/Tests/RESTTestBase.php
@@ -449,7 +449,7 @@ protected function entityPermissions($entity_type_id, $operation) {
    * @param string $location_url
    *   The URL returned in the Location header.
    *
-   * @return \Drupal\Core\Entity\Entity|FALSE.
+   * @return \Drupal\Core\Entity\Entity|false
    *   The entity or FALSE if there is no matching entity.
    */
   protected function loadEntityFromLocationHeader($location_url) {
diff --git a/core/modules/simpletest/src/AssertContentTrait.php b/core/modules/simpletest/src/AssertContentTrait.php
index e428e71f22e4d2f421ee23e5344017a137ba1cde..e19f319c7ce7435de122af8d4a81357800a77a6b 100644
--- a/core/modules/simpletest/src/AssertContentTrait.php
+++ b/core/modules/simpletest/src/AssertContentTrait.php
@@ -117,7 +117,7 @@ protected function setDrupalSettings($settings) {
   /**
    * Parse content returned from curlExec using DOM and SimpleXML.
    *
-   * @return \SimpleXMLElement|FALSE
+   * @return \SimpleXMLElement|false
    *   A SimpleXMLElement or FALSE on failure.
    */
   protected function parse() {
diff --git a/core/modules/statistics/statistics.module b/core/modules/statistics/statistics.module
index 5419645ad625d8814ccb24daad42e1b68f45c1e5..922ed57c37c9bff0c81272d69872390298b405ab 100644
--- a/core/modules/statistics/statistics.module
+++ b/core/modules/statistics/statistics.module
@@ -87,7 +87,7 @@ function statistics_cron() {
  * @param int $dbrows
  *   The number of rows to be returned.
  *
- * @return SelectQuery|FALSE
+ * @return SelectQuery|false
  *   A query result containing the node ID, title, user ID that owns the node,
  *   and the username for the selected node(s), or FALSE if the query could not
  *   be executed correctly.
diff --git a/core/modules/system/src/Tests/Theme/TwigTransTest.php b/core/modules/system/src/Tests/Theme/TwigTransTest.php
index bd0ca18ef174c6e9b32c3a7532fc36853b90cff5..b8718e7fa8701963accd221a2ad6718a6b0ba181 100644
--- a/core/modules/system/src/Tests/Theme/TwigTransTest.php
+++ b/core/modules/system/src/Tests/Theme/TwigTransTest.php
@@ -229,7 +229,7 @@ protected function installLanguages() {
    * @param string $langcode
    *   The langcode of the specified language.
    *
-   * @return string|FALSE
+   * @return string|false
    *   The .po contents for the specified language or FALSE if none exists.
    */
   protected function poFileContents($langcode) {
diff --git a/core/modules/user/src/Authentication/Provider/Cookie.php b/core/modules/user/src/Authentication/Provider/Cookie.php
index 2f8624e4c7a406d95d96ade7b2a0dba50b56b09a..ebcdae7517a7d65f3bce2be7a452de0347db03a7 100644
--- a/core/modules/user/src/Authentication/Provider/Cookie.php
+++ b/core/modules/user/src/Authentication/Provider/Cookie.php
@@ -62,7 +62,7 @@ public function authenticate(Request $request) {
    * @param \Symfony\Component\HttpFoundation\Session\SessionInterface $session
    *   The session.
    *
-   * @return \Drupal\Core\Session\AccountInterface|NULL
+   * @return \Drupal\Core\Session\AccountInterface|null
    *   The UserSession object for the current user, or NULL if this is an
    *   anonymous session.
    */
diff --git a/core/modules/views/src/Plugin/views/access/AccessPluginBase.php b/core/modules/views/src/Plugin/views/access/AccessPluginBase.php
index 7a9b27f9d784ad7bfc101421fd142fde9aeb97f9..ee568e118f3b5c7211fdab344a2bf7485e14ec69 100644
--- a/core/modules/views/src/Plugin/views/access/AccessPluginBase.php
+++ b/core/modules/views/src/Plugin/views/access/AccessPluginBase.php
@@ -58,7 +58,7 @@ public function summaryTitle() {
    * @param \Drupal\Core\Session\AccountInterface $account
    *   The user who wants to access this view.
    *
-   * @return TRUE
+   * @return bool
    *   Returns whether the user has access to the view.
    */
   abstract public function access(AccountInterface $account);
diff --git a/core/modules/views/src/Plugin/views/display/DisplayPluginInterface.php b/core/modules/views/src/Plugin/views/display/DisplayPluginInterface.php
index 982b4ce28ad6018753476f0938b0cd8ff909d740..d3b4c79b6597e1d09c1b2d5ab866644e428ba7a4 100644
--- a/core/modules/views/src/Plugin/views/display/DisplayPluginInterface.php
+++ b/core/modules/views/src/Plugin/views/display/DisplayPluginInterface.php
@@ -233,7 +233,7 @@ public function getPath();
    * block display links to a page display, the page display will be returned
    * in both cases.
    *
-   * @return \Drupal\views\Plugin\views\display\DisplayRouterInterface|NULL
+   * @return \Drupal\views\Plugin\views\display\DisplayRouterInterface|null
    */
   public function getRoutedDisplay();
 
diff --git a/core/modules/views/src/Plugin/views/filter/InOperator.php b/core/modules/views/src/Plugin/views/filter/InOperator.php
index 593e97b10c6bb100cb82192617fd73fe876e22f6..aa3e21f8dc4d3ae6446b3185c837301f911028f4 100644
--- a/core/modules/views/src/Plugin/views/filter/InOperator.php
+++ b/core/modules/views/src/Plugin/views/filter/InOperator.php
@@ -54,7 +54,7 @@ public function init(ViewExecutable $view, DisplayPluginBase $display, array &$o
    * This can use a guard to be used to reduce database hits as much as
    * possible.
    *
-   * @return array|NULL
+   * @return array|null
    *   The stored values from $this->valueOptions.
    */
   public function getValueOptions() {
diff --git a/core/modules/views/src/Tests/Handler/FieldWebTest.php b/core/modules/views/src/Tests/Handler/FieldWebTest.php
index a6ff1b49dbf6bfd085e8b903893821a4115e040b..e85206985a9bafe17740e7534dfd186ecb259004 100644
--- a/core/modules/views/src/Tests/Handler/FieldWebTest.php
+++ b/core/modules/views/src/Tests/Handler/FieldWebTest.php
@@ -169,7 +169,7 @@ protected function parseContent($content) {
    * @param array $arguments
    *   Some arguments for the xpath.
    *
-   * @return array|FALSE
+   * @return array|false
    *   The return value of the xpath search. For details on the xpath string
    *   format and return values see the SimpleXML documentation,
    *   http://php.net/manual/function.simplexml-element-xpath.php.
diff --git a/core/modules/views/src/Tests/Plugin/CacheTagTest.php b/core/modules/views/src/Tests/Plugin/CacheTagTest.php
index 057110e1ca276bc1863d72aa301153321c071536..eaee6569d1073972235f5401f3e3f896c1d23a82 100644
--- a/core/modules/views/src/Tests/Plugin/CacheTagTest.php
+++ b/core/modules/views/src/Tests/Plugin/CacheTagTest.php
@@ -97,7 +97,7 @@ protected function setUp() {
    * @param \Drupal\views\ViewExecutable $view
    *   The view.
    *
-   * @return array|FALSE
+   * @return array|false
    *   The render cache result or FALSE if not existent.
    */
   protected function getRenderCache(ViewExecutable $view) {
diff --git a/core/phpcs.xml.dist b/core/phpcs.xml.dist
index dae5b7a2930f5d4bf3abf50045dd43bf6c694f16..29468f754ce6ba4674b19a81ddee1696c8cad2d8 100644
--- a/core/phpcs.xml.dist
+++ b/core/phpcs.xml.dist
@@ -46,7 +46,6 @@
   <rule ref="Drupal.Commenting.FunctionComment">
     <exclude name="Drupal.Commenting.FunctionComment.IncorrectTypeHint"/>
     <exclude name="Drupal.Commenting.FunctionComment.InvalidNoReturn"/>
-    <exclude name="Drupal.Commenting.FunctionComment.InvalidReturn"/>
     <exclude name="Drupal.Commenting.FunctionComment.InvalidReturnNotVoid"/>
     <exclude name="Drupal.Commenting.FunctionComment.InvalidTypeHint"/>
     <exclude name="Drupal.Commenting.FunctionComment.Missing"/>