diff --git a/core/core.services.yml b/core/core.services.yml
index fa58e3bbb9..d7a26aa861 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -503,7 +503,7 @@ services:
     lazy: true
   extension.list.module:
     class: Drupal\Core\Extension\ModuleExtensionList
-    arguments: ['@app.root', 'module', '@cache.default', '@info_parser', '@module_handler', '@state', '@config.factory', '@extension.list.profile', '%container.modules%', '%install_profile%']
+    arguments: ['@app.root', 'module', '@cache.default', '@info_parser', '@module_handler', '@state', '@config.factory', '@extension.list.profile', '%install_profile%', '%container.modules%']
   extension.list.profile:
     class: Drupal\Core\Extension\ProfileExtensionList
     arguments: ['@app.root', 'profile', '@cache.default', '@info_parser', '@module_handler', '@state', '%install_profile%']
diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index 6328f137df..b8e7b1a9a0 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -214,16 +214,16 @@ function drupal_get_filename($type, $name, $filename = NULL) {
     $extension_list = \Drupal::service($service_id);
     if (isset($filename)) {
       // Manually add the info file path of an extension.
-      $extension_list->setFilename($name, $filename);
+      $extension_list->setPathname($name, $filename);
       return;
     }
     else {
       try {
-        return $extension_list->getFilename($name);
+        return $extension_list->getPathname($name);
       }
       catch (\InvalidArgumentException $e) {
         // Catch the exception and trigger error to maintain existing behavior.
-        trigger_error(new FormattableMarkup('The following @type is missing from the file system: @name', array('@type' => $type, '@name' => $name)), E_USER_WARNING);
+        trigger_error(new FormattableMarkup('The following @type is missing from the file system: @name', ['@type' => $type, '@name' => $name]), E_USER_WARNING);
       }
     }
   }
diff --git a/core/lib/Drupal/Core/Extension/ExtensionList.php b/core/lib/Drupal/Core/Extension/ExtensionList.php
index 5e3bc921eb..b0b3460f21 100644
--- a/core/lib/Drupal/Core/Extension/ExtensionList.php
+++ b/core/lib/Drupal/Core/Extension/ExtensionList.php
@@ -78,7 +78,7 @@
    *
    * @var string[]|null
    */
-  protected $fileNames;
+  protected $pathNames;
 
   /**
    * A list of extension folder names directly added in code (not discovered).
@@ -90,7 +90,7 @@
    *
    * @internal
    */
-  protected $addedFileNames = [];
+  protected $addedPathNames = [];
 
   /**
    * Static version of the added file names during the installer.
@@ -99,7 +99,7 @@
    *
    * @internal
    */
-  protected static $staticAddedFileNames;
+  protected static $staticAddedPathNames;
 
   /**
    * The state.
@@ -160,17 +160,17 @@ public function reset() {
     $this->cache->delete($this->getListCacheId());
     $this->extensionInfo = NULL;
     $this->cache->delete($this->getInfoCacheId());
-    $this->fileNames = NULL;
+    $this->pathNames = NULL;
 
     try {
-      $this->state->delete($this->getFilenamesCacheId());
+      $this->state->delete($this->getPathnamesCacheId());
     }
     catch (\Exception $e) {
       // Ignore exceptions caused by a non existing {key_value} table in the
       // early installer.
     }
 
-    $this->cache->delete($this->getFilenamesCacheId());
+    $this->cache->delete($this->getPathnamesCacheId());
     // We explicitly don't reset the addedFileNames as it is sort of a static
     // cache.
     // @todo In the long run it would be great to add the reset, but the early
@@ -204,7 +204,7 @@ protected function getInfoCacheId() {
    * @return string
    *   The filename cache ID.
    */
-  protected function getFilenamesCacheId() {
+  protected function getPathnamesCacheId() {
     return "system.{$this->type}.files";
   }
 
@@ -410,27 +410,27 @@ protected function recalculateInfo() {
   }
 
   /**
-   * Returns a list of extension file name keyed by extension machine name.
+   * Returns a list of extension file paths keyed by extension machine name.
    *
    * @return string[]
    */
-  public function getFilenames() {
-    if ($this->fileNames === NULL) {
-      $cache_id = $this->getFilenamesCacheId();
+  public function getPathnames() {
+    if ($this->pathNames === NULL) {
+      $cache_id = $this->getPathnamesCacheId();
       if ($cache = $this->cache->get($cache_id)) {
-        $file_names = $cache->data;
+        $path_names = $cache->data;
       }
       // We use $file_names below.
-      elseif (!$file_names = $this->state->get($cache_id)) {
-        $file_names = $this->recalculateFilenames();
+      elseif (!$path_names = $this->state->get($cache_id)) {
+        $path_names = $this->recalculatePathnames();
         // Store filenames to allow static::getFilename() to retrieve them
         // without having to rebuild or scan the filesystem.
-        $this->state->set($cache_id, $file_names);
-        $this->cache->set($cache_id, $file_names);
+        $this->state->set($cache_id, $path_names);
+        $this->cache->set($cache_id, $path_names);
       }
-      $this->fileNames = $file_names;
+      $this->pathNames = $path_names;
     }
-    return $this->fileNames;
+    return $this->pathNames;
   }
 
   /**
@@ -439,7 +439,7 @@ public function getFilenames() {
    * @return string[]
    *   An array of .info.yml file locations keyed by the extension machine name.
    */
-  protected function recalculateFilenames() {
+  protected function recalculatePathnames() {
     $extensions = $this->listExtensions();
     ksort($extensions);
 
@@ -449,7 +449,7 @@ protected function recalculateFilenames() {
   }
 
   /**
-   * Sets the filename for an extension.
+   * Sets the pathname for an extension.
    *
    * This method is used in the Drupal bootstrapping phase, when the extension
    * system is not fully initialized, to manually set locations of modules and
@@ -459,23 +459,23 @@ protected function recalculateFilenames() {
    *
    * @param string $extension_name
    *   The name of the extension for which the filename is requested.
-   * @param string $filename
-   *   The filename of the extension which is to be set explicitly rather
+   * @param string $pathname
+   *   The pathname of the extension which is to be set explicitly rather
    *   than by consulting the dynamic extension listing.
    *
    * @internal
    *
    * @see ::getFilename
    */
-  public function setFilename($extension_name, $filename) {
-    $this->addedFileNames[$extension_name] = $filename;
+  public function setPathname($extension_name, $pathname) {
+    $this->addedPathNames[$extension_name] = $pathname;
 
     // In the early installer the container is rebuilt multiple times. Therefore
     // we have to keep the added filenames across those rebuilds. This is not a
     // final design, but rather just a workaround resolved at some point,
     // hopefully.
     if (!empty($GLOBALS['install_state'])) {
-      static::$staticAddedFileNames[$extension_name] = $filename;
+      static::$staticAddedPathNames[$extension_name] = $pathname;
     }
   }
 
@@ -519,18 +519,18 @@ public function setFilename($extension_name, $filename) {
    * @throws \InvalidArgumentException
    *   If there is no extension with the supplied name.
    */
-  public function getFilename($extension_name) {
-    if (isset($this->addedFileNames[$extension_name])) {
-      return $this->addedFileNames[$extension_name];
+  public function getPathname($extension_name) {
+    if (isset($this->addedPathNames[$extension_name])) {
+      return $this->addedPathNames[$extension_name];
     }
-    elseif (isset($this->fileNames[$extension_name])) {
-      return $this->fileNames[$extension_name];
+    elseif (isset($this->pathNames[$extension_name])) {
+      return $this->pathNames[$extension_name];
     }
-    elseif (isset(static::$staticAddedFileNames[$extension_name])) {
-      return static::$staticAddedFileNames[$extension_name];
+    elseif (isset(static::$staticAddedPathNames[$extension_name])) {
+      return static::$staticAddedPathNames[$extension_name];
     }
-    elseif (($file_names = $this->getFilenames()) && isset($file_names[$extension_name])) {
-      return $file_names[$extension_name];
+    elseif (($path_names = $this->getPathnames()) && isset($path_names[$extension_name])) {
+      return $path_names[$extension_name];
     }
     throw new \InvalidArgumentException("The {$this->type} $extension_name does not exist.");
   }
@@ -549,7 +549,7 @@ public function getFilename($extension_name) {
    *   If there is no extension with the supplied name.
    */
   public function getPath($extension_name) {
-    return dirname($this->getFilename($extension_name));
+    return dirname($this->getPathname($extension_name));
   }
 
 }
diff --git a/core/lib/Drupal/Core/Extension/ModuleExtensionList.php b/core/lib/Drupal/Core/Extension/ModuleExtensionList.php
index 84c4345f14..5fc30aa2a6 100644
--- a/core/lib/Drupal/Core/Extension/ModuleExtensionList.php
+++ b/core/lib/Drupal/Core/Extension/ModuleExtensionList.php
@@ -56,14 +56,14 @@ class ModuleExtensionList extends ExtensionList {
    *   The state.
    * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
    *   The config factory.
-   * @param string $install_profile
-   *   The install profile used by the site.
    * @param \Drupal\Core\Extension\ExtensionList $profile_list
    *   The site profile listing.
+   * @param string $install_profile
+   *   The install profile used by the site.
    * @param array[] $container_modules_info
    *   (optional) The module locations coming from the compiled container.
    */
-  public function __construct($root, $type, CacheBackendInterface $cache, InfoParserInterface $info_parser, ModuleHandlerInterface $module_handler, StateInterface $state, ConfigFactoryInterface $config_factory, $install_profile, ExtensionList $profile_list, array $container_modules_info = []) {
+  public function __construct($root, $type, CacheBackendInterface $cache, InfoParserInterface $info_parser, ModuleHandlerInterface $module_handler, StateInterface $state, ConfigFactoryInterface $config_factory, ExtensionList $profile_list, $install_profile, array $container_modules_info = []) {
     parent::__construct($root, $type, $cache, $info_parser, $module_handler, $state, $install_profile);
 
     $this->configFactory = $config_factory;
@@ -71,7 +71,7 @@ public function __construct($root, $type, CacheBackendInterface $cache, InfoPars
 
     // Use the information from the container. This is an optimization.
     foreach ($container_modules_info as $module_name => $info) {
-      $this->setFilename($module_name, $info['pathname']);
+      $this->setPathname($module_name, $info['pathname']);
     }
   }
 
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index aa404497ca..2c2c6b6ee5 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -12,7 +12,6 @@
 use Drupal\Core\Queue\QueueGarbageCollectionInterface;
 use Drupal\Core\Database\Query\AlterableInterface;
 use Drupal\Core\Extension\Extension;
-use Drupal\Core\Extension\ExtensionDiscovery;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\KeyValueStore\KeyValueDatabaseExpirableFactory;
 use Drupal\Core\PageCache\RequestPolicyInterface;
@@ -1007,11 +1006,11 @@ function _system_rebuild_module_data_ensure_required($module, &$modules) {
  *   An associative array of module information.
  *
  * @deprecated in Drupal 8.4.x and will be removed before Drupal 9.0.0.
- *   Use \Drupal::service(\'extension.list.module\')->reset()->listExtensions()
+ *   Use \Drupal::service('extension.list.module')->reset()->listExtensions()
  *   instead. Note: You probably don't need the reset() method.
  */
 function _system_rebuild_module_data() {
-  @trigger_error('_system_rebuild_module_data() is deprecated in Drupal 8.4.0 and will be removed before Drupal 9.0.0. Instead, you should use \Drupal::service(\'extension.list.module\')->reset()->listExtensions(). See https://www.drupal.org/node/2709919', E_USER_DEPRECATED);
+  @trigger_error("_system_rebuild_module_data() is deprecated in Drupal 8.4.0 and will be removed before Drupal 9.0.0. Instead, you should use \\Drupal::service('extension.list.module')->reset()->listExtensions(). See https://www.drupal.org/node/2709919", E_USER_DEPRECATED);
   return \Drupal::service('extension.list.module')->reset()->listExtensions();
 }
 
@@ -1024,7 +1023,7 @@ function _system_rebuild_module_data() {
  * @deprecated in Drupal 8.4.x and will be removed before Drupal 9.0.0.
  */
 function system_rebuild_module_data() {
-  @trigger_error('system_rebuild_module_data() is deprecated in Drupal 8.4.0 and will be removed before Drupal 9.0.0. Instead, you should use \Drupal::service(\'extension.list.module\')->reset()->listExtensions(). See https://www.drupal.org/node/2709919', E_USER_DEPRECATED);
+  @trigger_error("system_rebuild_module_data() is deprecated in Drupal 8.4.0 and will be removed before Drupal 9.0.0. Instead, you should use \\Drupal::service('extension.list.module')->reset()->listExtensions(). See https://www.drupal.org/node/2709919", E_USER_DEPRECATED);
   return \Drupal::service('extension.list.module')->reset()->listExtensions();
 }
 
diff --git a/core/tests/Drupal/Tests/Core/Extension/ExtensionListTest.php b/core/tests/Drupal/Tests/Core/Extension/ExtensionListTest.php
index 77f24c163e..c24729c58c 100644
--- a/core/tests/Drupal/Tests/Core/Extension/ExtensionListTest.php
+++ b/core/tests/Drupal/Tests/Core/Extension/ExtensionListTest.php
@@ -22,16 +22,16 @@ class ExtensionListTest extends UnitTestCase {
 
   /**
    * @covers ::getName
-   * @expectedException \InvalidArgumentException
    */
   public function testGetNameWithNonExistingExtension() {
     list($cache, $info_parser, $module_handler, $state) = $this->getMocks();
-    $test_extension_list = new TestExtension($this->root, 'test_extension', $cache->reveal(), $info_parser->reveal(), $module_handler->reveal(), $state->reveal());
+    $test_extension_list = new TestExtension($this->root, 'test_extension', $cache->reveal(), $info_parser->reveal(), $module_handler->reveal(), $state->reveal(), 'testing');
 
     $extension_discovery = $this->prophesize(ExtensionDiscovery::class);
     $extension_discovery->scan('test_extension')->willReturn([]);
     $test_extension_list->setExtensionDiscovery($extension_discovery->reveal());
 
+    $this->setExpectedException(\InvalidArgumentException::class);
     $test_extension_list->getName('test_name');
   }
 
@@ -46,16 +46,16 @@ public function testGetName() {
 
   /**
    * @covers ::getExtension
-   * @expectedException \InvalidArgumentException
    */
   public function testGetExtensionWithNonExistingExtension() {
     list($cache, $info_parser, $module_handler, $state) = $this->getMocks();
-    $test_extension_list = new TestExtension($this->root, 'test_extension', $cache->reveal(), $info_parser->reveal(), $module_handler->reveal(), $state->reveal());
+    $test_extension_list = new TestExtension($this->root, 'test_extension', $cache->reveal(), $info_parser->reveal(), $module_handler->reveal(), $state->reveal(), 'testing');
 
     $extension_discovery = $this->prophesize(ExtensionDiscovery::class);
     $extension_discovery->scan('test_extension')->willReturn([]);
     $test_extension_list->setExtensionDiscovery($extension_discovery->reveal());
 
+    $this->setExpectedException(\InvalidArgumentException::class);
     $test_extension_list->getExtension('test_name');
   }
 
@@ -130,37 +130,37 @@ public function testGetAllInstalledInfo() {
   }
 
   /**
-   * @covers ::getFilenames
+   * @covers ::getPathnames
    */
-  public function testGetFilenames() {
+  public function testGetPathnames() {
     $test_extension_list = $this->setupTestExtensionList();
 
-    $filenames = $test_extension_list->getFilenames();
+    $filenames = $test_extension_list->getPathnames();
     $this->assertEquals([
       'test_name' => 'vfs://drupal_root/example/test_name/test_name.info.yml',
     ], $filenames);
   }
 
   /**
-   * @covers ::getFilename
+   * @covers ::getPathname
    */
-  public function testGetFilename() {
+  public function testGetPathname() {
     $test_extension_list = $this->setupTestExtensionList();
 
-    $filename = $test_extension_list->getFilename('test_name');
-    $this->assertEquals('vfs://drupal_root/example/test_name/test_name.info.yml', $filename);
+    $pathname = $test_extension_list->getPathname('test_name');
+    $this->assertEquals('vfs://drupal_root/example/test_name/test_name.info.yml', $pathname);
   }
 
 
   /**
-   * @covers ::setFilename
-   * @covers ::getFilename
+   * @covers ::setPathname
+   * @covers ::getPathname
    */
-  public function testSetFilename() {
+  public function testSetPathname() {
     $test_extension_list = $this->setupTestExtensionList();
 
-    $test_extension_list->setFilename('test_name', 'vfs://drupal_root/example2/test_name/test_name.info.yml');
-    $this->assertEquals('vfs://drupal_root/example2/test_name/test_name.info.yml', $test_extension_list->getFilename('test_name'));
+    $test_extension_list->setPathname('test_name', 'vfs://drupal_root/example2/test_name/test_name.info.yml');
+    $this->assertEquals('vfs://drupal_root/example2/test_name/test_name.info.yml', $test_extension_list->getPathname('test_name'));
   }
 
   /**
@@ -197,7 +197,7 @@ protected function setupTestExtensionList($extension_names = ['test_name']) {
       return Yaml::decode(file_get_contents($args[0]));
     });
 
-    $test_extension_list = new TestExtension('vfs://drupal_root', 'test_extension', $cache->reveal(), $info_parser->reveal(), $module_handler->reveal(), $state->reveal());
+    $test_extension_list = new TestExtension('vfs://drupal_root', 'test_extension', $cache->reveal(), $info_parser->reveal(), $module_handler->reveal(), $state->reveal(), 'testing');
 
     $extension_discovery = $this->prophesize(ExtensionDiscovery::class);
     $extension_scan_result = [];
diff --git a/core/tests/Drupal/Tests/Core/Session/AccountProxyTest.php b/core/tests/Drupal/Tests/Core/Session/AccountProxyTest.php
index 0e575a07ec..f17858cf80 100644
--- a/core/tests/Drupal/Tests/Core/Session/AccountProxyTest.php
+++ b/core/tests/Drupal/Tests/Core/Session/AccountProxyTest.php
@@ -42,6 +42,17 @@ public function testSetInitialAccountIdException() {
     $account_proxy->setInitialAccountId(1);
   }
 
+  /**
+   * @covers ::hasAccount
+   */
+  public function testHasAccount() {
+    $account_proxy = new AccountProxy();
+    $this->assertFalse($account_proxy->hasAccount());
+
+    $account_proxy->getAccount();
+    $this->assertTrue($account_proxy->hasAccount());
+  }
+
 }
 
 namespace Drupal\Core\Session;