diff --git c/core/lib/Drupal/Component/Gettext/PoItem.php w/core/lib/Drupal/Component/Gettext/PoItem.php
index e7edbff..c268c2c 100644
--- c/core/lib/Drupal/Component/Gettext/PoItem.php
+++ w/core/lib/Drupal/Component/Gettext/PoItem.php
@@ -40,7 +40,7 @@ class PoItem {
   /**
    * Flag indicating if this translation has plurals.
    *
-   * @var boolean
+   * @var bool
    */
   private $_plural;
 
@@ -138,7 +138,7 @@ function setTranslation($translation) {
   /**
    * Set if the translation has plural values.
    *
-   * @param boolean $plural
+   * @param bool $plural
    */
   function setPlural($plural) {
     $this->_plural = $plural;
diff --git c/core/lib/Drupal/Component/Gettext/PoStreamReader.php w/core/lib/Drupal/Component/Gettext/PoStreamReader.php
index 94218e6..c72ddd1 100644
--- c/core/lib/Drupal/Component/Gettext/PoStreamReader.php
+++ w/core/lib/Drupal/Component/Gettext/PoStreamReader.php
@@ -94,7 +94,7 @@ class PoStreamReader implements PoStreamInterface, PoReaderInterface {
   /**
    * Indicator of whether the stream reading is finished.
    *
-   * @var boolean
+   * @var bool
    */
   private $_finished;
 
diff --git c/core/lib/Drupal/Core/Ajax/AjaxResponse.php w/core/lib/Drupal/Core/Ajax/AjaxResponse.php
index 1bc3d7e..6cd4df5 100644
--- c/core/lib/Drupal/Core/Ajax/AjaxResponse.php
+++ w/core/lib/Drupal/Core/Ajax/AjaxResponse.php
@@ -58,7 +58,7 @@ public function setAttachments(array $attachments) {
    *
    * @param \Drupal\Core\Ajax\CommandInterface $command
    *   An AJAX command object implementing CommandInterface.
-   * @param boolean $prepend
+   * @param bool $prepend
    *   A boolean which determines whether the new command should be executed
    *   before previously added commands. Defaults to FALSE.
    *
diff --git c/core/lib/Drupal/Core/Ajax/SettingsCommand.php w/core/lib/Drupal/Core/Ajax/SettingsCommand.php
index a5a8dc8..216ad46 100644
--- c/core/lib/Drupal/Core/Ajax/SettingsCommand.php
+++ w/core/lib/Drupal/Core/Ajax/SettingsCommand.php
@@ -39,7 +39,7 @@ class SettingsCommand implements CommandInterface {
    * By default (FALSE), the settings that are passed to Drupal.attachBehaviors
    * will not include the global drupalSettings.
    *
-   * @var boolean
+   * @var bool
    */
   protected $merge;
 
@@ -48,7 +48,7 @@ class SettingsCommand implements CommandInterface {
    *
    * @param array $settings
    *   An array of key/value pairs of JavaScript settings.
-   * @param boolean $merge
+   * @param bool $merge
    *   Whether the settings should be merged into the global drupalSettings.
    */
   public function __construct(array $settings, $merge = FALSE) {
diff --git c/core/lib/Drupal/Core/Database/Driver/fake/Install/Tasks.php w/core/lib/Drupal/Core/Database/Driver/fake/Install/Tasks.php
index 4ac7487..11ed2f3 100644
--- c/core/lib/Drupal/Core/Database/Driver/fake/Install/Tasks.php
+++ w/core/lib/Drupal/Core/Database/Driver/fake/Install/Tasks.php
@@ -22,7 +22,7 @@ class Tasks extends InstallTasks {
    * @TODO Looks like this is needed only if we define $pdoDriver to something valid e.g. mysql.
    * Not sure we need to do that. We may not need this file at all?
    *
-   * @var boolean
+   * @var bool
    */
   protected $error = TRUE;
 
diff --git c/core/lib/Drupal/Core/Database/Driver/mysql/Connection.php w/core/lib/Drupal/Core/Database/Driver/mysql/Connection.php
index 64e1511..8a70fb0 100644
--- c/core/lib/Drupal/Core/Database/Driver/mysql/Connection.php
+++ w/core/lib/Drupal/Core/Database/Driver/mysql/Connection.php
@@ -30,7 +30,7 @@ class Connection extends DatabaseConnection {
   /**
    * Flag to indicate if the cleanup function in __destruct() should run.
    *
-   * @var boolean
+   * @var bool
    */
   protected $needsCleanup = FALSE;
 
diff --git c/core/lib/Drupal/Core/Database/Driver/sqlite/Connection.php w/core/lib/Drupal/Core/Database/Driver/sqlite/Connection.php
index 4c3f838..ad26cbf 100644
--- c/core/lib/Drupal/Core/Database/Driver/sqlite/Connection.php
+++ w/core/lib/Drupal/Core/Database/Driver/sqlite/Connection.php
@@ -26,7 +26,7 @@ class Connection extends DatabaseConnection {
    * Version of sqlite lower then 3.6.8 can't use savepoints.
    * See http://www.sqlite.org/releaselog/3_6_8.html
    *
-   * @var boolean
+   * @var bool
    */
   protected $savepointSupport = FALSE;
 
@@ -38,7 +38,7 @@ class Connection extends DatabaseConnection {
   /**
    * Whether or not the active transaction (if any) will be rolled back.
    *
-   * @var boolean
+   * @var bool
    */
   protected $willRollback;
 
@@ -58,7 +58,7 @@ class Connection extends DatabaseConnection {
    * This variable is set to public because Schema needs to
    * access it. However, it should not be manually set.
    *
-   * @var boolean
+   * @var bool
    */
   var $tableDropped = FALSE;
 
diff --git c/core/lib/Drupal/Core/Database/Query/Merge.php w/core/lib/Drupal/Core/Database/Query/Merge.php
index b2ed839..dfa50e3 100644
--- c/core/lib/Drupal/Core/Database/Query/Merge.php
+++ w/core/lib/Drupal/Core/Database/Query/Merge.php
@@ -119,7 +119,7 @@ class Merge extends Query implements ConditionInterface {
   /**
    * Flag indicating whether an UPDATE is necessary.
    *
-   * @var boolean
+   * @var bool
    */
   protected $needsUpdate = FALSE;
 
diff --git c/core/lib/Drupal/Core/Database/Query/Select.php w/core/lib/Drupal/Core/Database/Query/Select.php
index 70dc96f..d925a07 100644
--- c/core/lib/Drupal/Core/Database/Query/Select.php
+++ w/core/lib/Drupal/Core/Database/Query/Select.php
@@ -88,7 +88,7 @@ class Select extends Query implements SelectInterface {
   /**
    * Whether or not this query should be DISTINCT
    *
-   * @var boolean
+   * @var bool
    */
   protected $distinct = FALSE;
 
@@ -114,7 +114,7 @@ class Select extends Query implements SelectInterface {
 
   /**
    * Indicates if preExecute() has already been called.
-   * @var boolean
+   * @var bool
    */
   protected $prepared = FALSE;
 
diff --git c/core/lib/Drupal/Core/Database/Transaction.php w/core/lib/Drupal/Core/Database/Transaction.php
index 68a4fc4..52286e0 100644
--- c/core/lib/Drupal/Core/Database/Transaction.php
+++ w/core/lib/Drupal/Core/Database/Transaction.php
@@ -38,7 +38,7 @@ class Transaction {
   /**
    * A boolean value to indicate whether this transaction has been rolled back.
    *
-   * @var Boolean
+   * @var bool
    */
   protected $rolledBack = FALSE;
 
diff --git c/core/lib/Drupal/Core/Entity/EntityDisplayBase.php w/core/lib/Drupal/Core/Entity/EntityDisplayBase.php
index 1197801..f33c646 100644
--- c/core/lib/Drupal/Core/Entity/EntityDisplayBase.php
+++ w/core/lib/Drupal/Core/Entity/EntityDisplayBase.php
@@ -67,7 +67,7 @@
    * Whether this display is enabled or not. If the entity (form) display
    * is disabled, we'll fall back to the 'default' display.
    *
-   * @var boolean
+   * @var bool
    */
   protected $status;
 
diff --git c/core/lib/Drupal/Core/Entity/EntityReferenceSelection/SelectionInterface.php w/core/lib/Drupal/Core/Entity/EntityReferenceSelection/SelectionInterface.php
index 793279e..fb4ea5d 100644
--- c/core/lib/Drupal/Core/Entity/EntityReferenceSelection/SelectionInterface.php
+++ w/core/lib/Drupal/Core/Entity/EntityReferenceSelection/SelectionInterface.php
@@ -59,7 +59,7 @@ public function validateReferenceableEntities(array $ids);
    *   The current form state.
    * @param array $form
    *   The form.
-   * @param boolean $strict
+   * @param bool $strict
    *   Whether to trigger a form error if an element from $input (eg. an entity)
    *   is not found. Defaults to TRUE.
    *
diff --git c/core/lib/Drupal/Core/Entity/Query/QueryBase.php w/core/lib/Drupal/Core/Entity/Query/QueryBase.php
index f5d36a1..4465efd 100644
--- c/core/lib/Drupal/Core/Entity/Query/QueryBase.php
+++ w/core/lib/Drupal/Core/Entity/Query/QueryBase.php
@@ -40,7 +40,7 @@
   /**
    * TRUE if this is a count query, FALSE if it isn't.
    *
-   * @var boolean
+   * @var bool
    */
   protected $count = FALSE;
 
diff --git c/core/lib/Drupal/Core/Field/Annotation/FieldType.php w/core/lib/Drupal/Core/Field/Annotation/FieldType.php
index 7a630ab..880a222 100644
--- c/core/lib/Drupal/Core/Field/Annotation/FieldType.php
+++ w/core/lib/Drupal/Core/Field/Annotation/FieldType.php
@@ -87,7 +87,7 @@ class FieldType extends DataType {
   /**
    * A boolean stating that fields of this type cannot be created through the UI.
    *
-   * @var boolean
+   * @var bool
    */
   public $no_ui = FALSE;
 
diff --git c/core/lib/Drupal/Core/Path/AliasManager.php w/core/lib/Drupal/Core/Path/AliasManager.php
index d91ad69..d44fc45 100644
--- c/core/lib/Drupal/Core/Path/AliasManager.php
+++ w/core/lib/Drupal/Core/Path/AliasManager.php
@@ -38,7 +38,7 @@ class AliasManager implements AliasManagerInterface, CacheDecoratorInterface {
   /**
    * Whether the cache needs to be written.
    *
-   * @var boolean
+   * @var bool
    */
   protected $cacheNeedsWriting = FALSE;
 
diff --git c/core/modules/comment/src/CommentStatisticsInterface.php w/core/modules/comment/src/CommentStatisticsInterface.php
index f73dccd..6c0a8a9 100644
--- c/core/modules/comment/src/CommentStatisticsInterface.php
+++ w/core/modules/comment/src/CommentStatisticsInterface.php
@@ -32,7 +32,7 @@ public function getRankingInfo();
    *   Array of entities on which commenting is enabled, keyed by id
    * @param string $entity_type
    *   The entity type of the passed entities.
-   * @param boolean $accurate
+   * @param bool $accurate
    *   (optional) Indicates if results must be completely up to date. If set to
    *   FALSE, a replica database will used if available. Defaults to TRUE.
    *
diff --git c/core/modules/comment/src/Tests/CommentNonNodeTest.php w/core/modules/comment/src/Tests/CommentNonNodeTest.php
index 167381b..ac53270 100644
--- c/core/modules/comment/src/Tests/CommentNonNodeTest.php
+++ w/core/modules/comment/src/Tests/CommentNonNodeTest.php
@@ -173,7 +173,7 @@ function postComment(EntityInterface $entity, $comment, $subject = '', $contact
    *
    * @param \Drupal\comment\CommentInterface $comment
    *   The comment object.
-   * @param boolean $reply
+   * @param bool $reply
    *   Boolean indicating whether the comment is a reply to another comment.
    *
    * @return boolean
@@ -211,7 +211,7 @@ function commentContactInfoAvailable() {
    *   Comment to perform operation on.
    * @param string $operation
    *   Operation to perform.
-   * @param boolean $aproval
+   * @param bool $aproval
    *   Operation is found on approval page.
    */
   function performCommentOperation($comment, $operation, $approval = FALSE) {
diff --git c/core/modules/comment/src/Tests/CommentTestBase.php w/core/modules/comment/src/Tests/CommentTestBase.php
index 12d17c6..9aa2e07 100644
--- c/core/modules/comment/src/Tests/CommentTestBase.php
+++ w/core/modules/comment/src/Tests/CommentTestBase.php
@@ -179,7 +179,7 @@ public function postComment($entity, $comment, $subject = '', $contact = NULL, $
    *
    * @param \Drupal\comment\CommentInterface $comment
    *   The comment object.
-   * @param boolean $reply
+   * @param bool $reply
    *   Boolean indicating whether the comment is a reply to another comment.
    *
    * @return boolean
@@ -337,7 +337,7 @@ function commentContactInfoAvailable() {
    *   Comment to perform operation on.
    * @param string $operation
    *   Operation to perform.
-   * @param boolean $aproval
+   * @param bool $aproval
    *   Operation is found on approval page.
    */
   function performCommentOperation(CommentInterface $comment, $operation, $approval = FALSE) {
diff --git c/core/modules/content_translation/src/Tests/ContentTranslationSettingsTest.php w/core/modules/content_translation/src/Tests/ContentTranslationSettingsTest.php
index 9874574..8bde6ba 100644
--- c/core/modules/content_translation/src/Tests/ContentTranslationSettingsTest.php
+++ w/core/modules/content_translation/src/Tests/ContentTranslationSettingsTest.php
@@ -208,7 +208,7 @@ function testAccountLanguageSettingsUI() {
    *   The entity type for which to check translatibility.
    * @param string $bundle
    *   The bundle for which to check translatibility.
-   * @param boolean $enabled
+   * @param bool $enabled
    *   TRUE if translatibility should be enabled, FALSE otherwise.
    * @param array $edit
    *   An array of values to submit to the content translation settings page.
diff --git c/core/modules/content_translation/src/Tests/ContentTranslationUITest.php w/core/modules/content_translation/src/Tests/ContentTranslationUITest.php
index 9ed362b..0ec3280 100644
--- c/core/modules/content_translation/src/Tests/ContentTranslationUITest.php
+++ w/core/modules/content_translation/src/Tests/ContentTranslationUITest.php
@@ -28,7 +28,7 @@
   /**
    * Whether the behavior of the language selector should be tested.
    *
-   * @var boolean
+   * @var bool
    */
   protected $testLanguageSelector = TRUE;
 
diff --git c/core/modules/editor/src/Annotation/Editor.php w/core/modules/editor/src/Annotation/Editor.php
index 82dc738..58d2450 100644
--- c/core/modules/editor/src/Annotation/Editor.php
+++ w/core/modules/editor/src/Annotation/Editor.php
@@ -44,7 +44,7 @@ class Editor extends Plugin {
   /**
    * Whether the editor supports "allowed content only" filtering.
    *
-   * @var boolean
+   * @var bool
    */
   public $supports_content_filtering;
 
diff --git c/core/modules/editor/src/Tests/EditorAdminTest.php w/core/modules/editor/src/Tests/EditorAdminTest.php
index 7ffa122..a39d844 100644
--- c/core/modules/editor/src/Tests/EditorAdminTest.php
+++ w/core/modules/editor/src/Tests/EditorAdminTest.php
@@ -152,7 +152,7 @@ protected function selectUnicornEditor() {
    *
    * @param string $format_id
    *   The format machine name.
-   * @param boolean $ponies_too
+   * @param bool $ponies_too
    *   The expected value of the ponies_too setting.
    */
   protected function verifyUnicornEditorConfiguration($format_id, $ponies_too = TRUE) {
diff --git c/core/modules/forum/src/Tests/ForumTest.php w/core/modules/forum/src/Tests/ForumTest.php
index e75507a..97c4b38 100644
--- c/core/modules/forum/src/Tests/ForumTest.php
+++ w/core/modules/forum/src/Tests/ForumTest.php
@@ -511,7 +511,7 @@ function testForumWithNewPost() {
    *
    * @param array $forum
    *   A forum array.
-   * @param boolean $container
+   * @param bool $container
    *   TRUE if $forum is a container; FALSE otherwise.
    *
    * @return object
diff --git c/core/modules/migrate/src/Plugin/migrate/id_map/Sql.php w/core/modules/migrate/src/Plugin/migrate/id_map/Sql.php
index 06a026a..435907b 100644
--- c/core/modules/migrate/src/Plugin/migrate/id_map/Sql.php
+++ w/core/modules/migrate/src/Plugin/migrate/id_map/Sql.php
@@ -84,7 +84,7 @@ class Sql extends PluginBase implements MigrateIdMapInterface {
   /**
    * Whether the plugin is already initialized.
    *
-   * @var boolean
+   * @var bool
    */
   protected $initialized;
 
diff --git c/core/modules/migrate/src/Plugin/migrate/source/SourcePluginBase.php w/core/modules/migrate/src/Plugin/migrate/source/SourcePluginBase.php
index 6eb87c7..1efbc4a 100644
--- c/core/modules/migrate/src/Plugin/migrate/source/SourcePluginBase.php
+++ w/core/modules/migrate/src/Plugin/migrate/source/SourcePluginBase.php
@@ -93,7 +93,7 @@
   /**
    * Whether this instance should cache the source count.
    *
-   * @var boolean
+   * @var bool
    */
   protected $cacheCounts = FALSE;
 
@@ -107,7 +107,7 @@
   /**
    * Whether this instance should not attempt to count the source.
    *
-   * @var boolean
+   * @var bool
    */
   protected $skipCount = FALSE;
 
diff --git c/core/modules/migrate_drupal/src/Plugin/migrate/source/d6/File.php w/core/modules/migrate_drupal/src/Plugin/migrate/source/d6/File.php
index 9401dec..ff51c62 100644
--- c/core/modules/migrate_drupal/src/Plugin/migrate/source/d6/File.php
+++ w/core/modules/migrate_drupal/src/Plugin/migrate/source/d6/File.php
@@ -36,7 +36,7 @@ class File extends DrupalSqlBase {
   /**
    * Flag for private or public file storage.
    *
-   * @var boolean
+   * @var bool
    */
   protected $isPublic;
 
diff --git c/core/modules/simpletest/src/TestBase.php w/core/modules/simpletest/src/TestBase.php
index b621140..91d0e49 100644
--- c/core/modules/simpletest/src/TestBase.php
+++ w/core/modules/simpletest/src/TestBase.php
@@ -91,7 +91,7 @@
   /**
    * TRUE if verbose debugging is enabled.
    *
-   * @var boolean
+   * @var bool
    */
   public $verbose;
 
@@ -260,7 +260,7 @@
   /**
    * Whether to die in case any test assertion fails.
    *
-   * @var boolean
+   * @var bool
    *
    * @see run-tests.sh
    */
diff --git c/core/modules/system/src/Tests/KeyValueStore/StorageTestBase.php w/core/modules/system/src/Tests/KeyValueStore/StorageTestBase.php
index b59828e..cb82a72 100644
--- c/core/modules/system/src/Tests/KeyValueStore/StorageTestBase.php
+++ w/core/modules/system/src/Tests/KeyValueStore/StorageTestBase.php
@@ -31,7 +31,7 @@
   /**
    * Whether we are using an expirable key/value store.
    *
-   * @var boolean
+   * @var bool
    */
   protected $factory = 'keyvalue';
 
diff --git c/core/tests/Drupal/Tests/Component/Utility/NumberTest.php w/core/tests/Drupal/Tests/Component/Utility/NumberTest.php
index 4e6b967..7edf50c 100644
--- c/core/tests/Drupal/Tests/Component/Utility/NumberTest.php
+++ w/core/tests/Drupal/Tests/Component/Utility/NumberTest.php
@@ -31,7 +31,7 @@ class NumberTest extends UnitTestCase {
    *   The value argument for Number::validStep().
    * @param numeric $step
    *   The step argument for Number::validStep().
-   * @param boolean $expected
+   * @param bool $expected
    *   Expected return value from Number::validStep().
    */
   public function testValidStep($value, $step, $expected) {
@@ -51,7 +51,7 @@ public function testValidStep($value, $step, $expected) {
    *   The step argument for Number::validStep().
    * @param numeric $offset
    *   The offset argument for Number::validStep().
-   * @param boolean $expected
+   * @param bool $expected
    *   Expected return value from Number::validStep().
    */
   public function testValidStepOffset($value, $step, $offset, $expected) {
diff --git c/core/tests/Drupal/Tests/Component/Utility/UnicodeTest.php w/core/tests/Drupal/Tests/Component/Utility/UnicodeTest.php
index b9861c2..724d875 100644
--- c/core/tests/Drupal/Tests/Component/Utility/UnicodeTest.php
+++ w/core/tests/Drupal/Tests/Component/Utility/UnicodeTest.php
@@ -466,7 +466,7 @@ public function providerTestTruncateBytes() {
    *
    * @param string $text
    *   The text to validate.
-   * @param boolean $expected
+   * @param bool $expected
    *   The expected return value from Unicode::validateUtf8().
    * @param string $message
    *   The message to display on failure.