diff --git a/core/config/schema/core.data_types.schema.yml b/core/config/schema/core.data_types.schema.yml
index c695934..3615197 100644
--- a/core/config/schema/core.data_types.schema.yml
+++ b/core/config/schema/core.data_types.schema.yml
@@ -364,9 +364,9 @@ field_config_base:
       label: 'Translatable'
     default_value:
       type: field.[%parent.field_type].value
-    default_value_callback:
+    default_value_function:
       type: string
-      label: 'Default value callback'
+      label: 'Default value function'
     settings:
       type: field.[%parent.field_type].field_settings
     third_party_settings:
diff --git a/core/includes/batch.inc b/core/includes/batch.inc
index 786ee3c..7e6e12f 100644
--- a/core/includes/batch.inc
+++ b/core/includes/batch.inc
@@ -157,7 +157,7 @@ function _batch_progress_page() {
   $batch['url_options']['query']['id'] = $batch['id'];
   $batch['url_options']['query']['op'] = $new_op;
 
-  $url = _url($batch['url'], $batch['url_options']);
+  $url = url($batch['url'], $batch['url_options']);
 
   $build = array(
     '#theme' => 'progress_bar',
@@ -452,18 +452,11 @@ function _batch_finished() {
     if ($_batch['form_state']->getRedirect() === NULL) {
       $redirect = $_batch['batch_redirect'] ?: $_batch['source_url'];
       $options = UrlHelper::parse($redirect);
-      // Any path with a scheme does not correspond to a route.
-      if (parse_url($options['path'], PHP_URL_SCHEME)) {
-        $redirect = Url::fromUri($options['path'], $options);
-      }
-      else {
-        $redirect = \Drupal::pathValidator()->getUrlIfValid($options['path']);
-        if (!$redirect) {
-          // Stay on the same page if the redirect was invalid.
-          $redirect = Url::fromRoute('<current>');
-        }
-        $redirect->setOptions($options);
+      if (!UrlHelper::isExternal($options['path'])) {
+        $options['path'] = $GLOBALS['base_url'] . '/' . $options['path'];
       }
+      $redirect = Url::createFromPath($options['path']);
+      $redirect->setOptions($options);
       $_batch['form_state']->setRedirectUrl($redirect);
     }
 
@@ -486,7 +479,7 @@ function _batch_finished() {
     }
     elseif ($callback === NULL) {
       // Default to RedirectResponse objects when nothing specified.
-      $url = _url($_batch['source_url'], array(
+      $url = url($_batch['source_url'], array(
         'absolute' => TRUE,
         'query' => array('op' => 'finish', 'id' => $_batch['id']),
       ));
diff --git a/core/includes/common.inc b/core/includes/common.inc
index 81c61b3..e57821e 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -638,24 +638,9 @@ function _format_date_callback(array $matches = NULL, $new_langcode = NULL) {
  * When creating links in modules, consider whether l() could be a better
  * alternative than url().
  *
- * @see \Drupal\Core\Url::fromUri()
- * @see \Drupal\Core\Url::fromRoute()
- * @see \Drupal\Core\Url::toString()
- *
- * @deprecated in Drupal 8.x-dev, will be removed before Drupal 8.0.0.
- *   Use \Drupal\Core\Url::fromRoute() for internal paths served by Drupal
- *   controllers or \Drupal\Core\Url::fromUri() for external paths or
- *   non-controller or sub-domain URIs such as core/install.php. Note that
- *   \Drupal\Core\Url::fromUri() expects a valid URI including the scheme. URIs
- *   from the same sub-domain that are not handled by Drupal controllers should
- *   be prepended with base://. For example:
- * @code
- * $installer_url = \Drupal\Core\Url::fromUri('base://core/install.php')->toString();
- * $external_url = \Drupal\Core\Url::fromUri('http://example.com', ['query' => ['foo' => 'bar']])->toString();
- * $internal_url = \Drupal\Core\Url::fromRoute('system.admin')->toString();
- * @endcode
+ * @see \Drupal\Core\Routing\UrlGeneratorInterface::generateFromPath().
  */
-function _url($path = NULL, array $options = array()) {
+function url($path = NULL, array $options = array()) {
   return \Drupal::urlGenerator()->generateFromPath($path, $options);
 }
 
@@ -745,27 +730,10 @@ function drupal_http_header_attributes(array $attributes = array()) {
  * @return string
  *   An HTML string containing a link to the given path.
  *
- * @see _url()
+ * @see url()
  * @see system_page_build()
- * @deprecated in Drupal 8.x-dev, will be removed before Drupal 8.0.0.
- *   Use \Drupal::linkGenerator()->generate($url) where $url is an instance of
- *   \Drupal\Core\Url. To build a \Drupal\Core\Url object for internal paths
- *   served by Drupal controllers use \Drupal\Core\Url::fromRoute(). For
- *   external paths or non-controller or sub-domain URIs such as
- *   core/install.php use \Drupal\Core\Url::fromUri(). Note that
- *   \Drupal\Core\Url::fromUri() expects a valid URI including the scheme. URIs
- *   from the same sub-domain that are not handled by Drupal controllers should
- *   be prepended with base://. For example:
- * @code
- * $installer_url = \Drupal\Core\Url::fromUri('base://core/install.php')->toString();
- * $installer_link = \Drupal::linkGenerator()->generate($installer_url);
- * $external_url = \Drupal\Core\Url::fromUri('http://example.com', ['query' => ['foo' => 'bar']])->toString();
- * $external_link = \Drupal::linkGenerator()->generate($external_url);
- * $internal_url = \Drupal\Core\Url::fromRoute('system.admin')->toString();
- * $internal_link = \Drupal::linkGenerator()->generate($internal_url);
- * @endcode
  */
-function _l($text, $path, array $options = array()) {
+function l($text, $path, array $options = array()) {
   // Start building a structured representation of our link to be altered later.
   $variables = array(
     'text' => is_array($text) ? drupal_render($text) : $text,
@@ -820,7 +788,7 @@ function _l($text, $path, array $options = array()) {
 
   // The result of url() is a plain-text URL. Because we are using it here
   // in an HTML argument context, we need to encode it properly.
-  $url = String::checkPlain(_url($variables['path'], $variables['options']));
+  $url = String::checkPlain(url($variables['path'], $variables['options']));
 
   // Sanitize the link text if necessary.
   $text = $variables['options']['html'] ? $variables['text'] : String::checkPlain($variables['text']);
@@ -1541,7 +1509,7 @@ function _drupal_add_js($data = NULL, $options = NULL) {
           $scriptPath = $GLOBALS['script_path'];
           $pathPrefix = '';
           $current_query = \Drupal::service('request_stack')->getCurrentRequest()->query->all();
-          _url('', array('script' => &$scriptPath, 'prefix' => &$pathPrefix));
+          url('', array('script' => &$scriptPath, 'prefix' => &$pathPrefix));
           $current_path = current_path();
           $current_path_is_admin = FALSE;
           // The function path_is_admin() is not available on update.php pages.
diff --git a/core/includes/form.inc b/core/includes/form.inc
index 5aafe81..260ffbe 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -949,7 +949,7 @@ function batch_process($redirect = NULL, $url = 'batch', $redirect_callback = NU
     if ($batch['progressive']) {
       // Now that we have a batch id, we can generate the redirection link in
       // the generic error message.
-      $batch['error_message'] = t('Please continue to <a href="@error_url">the error page</a>', array('@error_url' => _url($url, array('query' => array('id' => $batch['id'], 'op' => 'finished')))));
+      $batch['error_message'] = t('Please continue to <a href="@error_url">the error page</a>', array('@error_url' => url($url, array('query' => array('id' => $batch['id'], 'op' => 'finished')))));
 
       // Clear the way for the redirection to the batch processing page, by
       // saving and unsetting the 'destination', if there is any.
@@ -977,7 +977,7 @@ function batch_process($redirect = NULL, $url = 'batch', $redirect_callback = NU
       }
       else {
         $options['absolute'] = TRUE;
-        return new RedirectResponse(_url($batch['url'], $options));
+        return new RedirectResponse(url($batch['url'], $options));
       }
     }
     else {
diff --git a/core/includes/install.core.inc b/core/includes/install.core.inc
index 7c48116..5a6859d 100644
--- a/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -543,10 +543,7 @@ function install_run_task($task, &$install_state) {
       }
       // Process the batch. For progressive batches, this will redirect.
       // Otherwise, the batch will complete.
-      // install_redirect_url() returns core/install.php, so let's ensure to
-      // drop it from it and use base:// as batch_process() is using the
-      // unrouted URL assembler, which requires base://.
-      $response = batch_process(preg_replace('@^core/@', 'base://', install_redirect_url($install_state)), install_full_redirect_url($install_state));
+      $response = batch_process(install_redirect_url($install_state), install_full_redirect_url($install_state));
       if ($response instanceof Response) {
         // Save $_SESSION data from batch.
         \Drupal::service('session_manager')->save();
diff --git a/core/includes/pager.inc b/core/includes/pager.inc
index 0dcfcb7..730be44 100644
--- a/core/includes/pager.inc
+++ b/core/includes/pager.inc
@@ -219,7 +219,7 @@ function template_preprocess_pager(&$variables) {
     $options = array(
       'query' => pager_query_add_page($parameters, $element, 0),
     );
-    $items['first']['href'] = _url($current_path, $options);
+    $items['first']['href'] = url($current_path, $options);
     if (isset($tags[0])) {
       $items['first']['text'] = $tags[0];
     }
@@ -228,7 +228,7 @@ function template_preprocess_pager(&$variables) {
     $options = array(
       'query' => pager_query_add_page($parameters, $element, $pager_page_array[$element] - 1),
     );
-    $items['previous']['href'] = _url($current_path, $options);
+    $items['previous']['href'] = url($current_path, $options);
     if (isset($tags[1])) {
       $items['previous']['text'] = $tags[1];
     }
@@ -244,7 +244,7 @@ function template_preprocess_pager(&$variables) {
       $options = array(
         'query' => pager_query_add_page($parameters, $element, $i - 1),
       );
-      $items['pages'][$i]['href'] = _url($current_path, $options);
+      $items['pages'][$i]['href'] = url($current_path, $options);
       if ($i == $pager_current) {
         $variables['current'] = $i;
       }
@@ -261,7 +261,7 @@ function template_preprocess_pager(&$variables) {
     $options = array(
       'query' => pager_query_add_page($parameters, $element, $pager_page_array[$element] + 1),
     );
-    $items['next']['href'] = _url($current_path, $options);
+    $items['next']['href'] = url($current_path, $options);
     if (isset($tags[3])) {
       $items['next']['text'] = $tags[3];
     }
@@ -270,7 +270,7 @@ function template_preprocess_pager(&$variables) {
     $options = array(
       'query' => pager_query_add_page($parameters, $element, $pager_max - 1),
     );
-    $items['last']['href'] = _url($current_path, $options);
+    $items['last']['href'] = url($current_path, $options);
     if (isset($tags[4])) {
       $items['last']['text'] = $tags[4];
     }
diff --git a/core/includes/tablesort.inc b/core/includes/tablesort.inc
index 0c8d25b..0b3574f 100644
--- a/core/includes/tablesort.inc
+++ b/core/includes/tablesort.inc
@@ -61,7 +61,7 @@ function tablesort_header(&$cell_content, array &$cell_attributes, array $header
       $ts['sort'] = 'asc';
       $image = '';
     }
-    $cell_content = _l($cell_content . $image, current_path(), array(
+    $cell_content = l($cell_content . $image, current_path(), array(
       'attributes' => array('title' => $title),
       'query' => array_merge($ts['query'], array(
         'sort' => $ts['sort'],
diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index f136ca1..f2c3ac1 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -2296,6 +2296,7 @@ function drupal_common_theme() {
     ),
     'indentation' => array(
       'variables' => array('size' => 1),
+      'function' => 'theme_indentation',
     ),
     // From theme.maintenance.inc.
     'maintenance_page' => array(
@@ -2312,9 +2313,15 @@ function drupal_common_theme() {
     ),
     'authorize_message' => array(
       'variables' => array('message' => NULL, 'success' => TRUE),
+      'function' => 'theme_authorize_message',
+      'path' => 'core/includes',
+      'file' => 'theme.maintenance.inc',
     ),
     'authorize_report' => array(
       'variables' => array('messages' => array()),
+      'function' => 'theme_authorize_report',
+      'path' => 'core/includes',
+      'file' => 'theme.maintenance.inc',
     ),
     // From pager.inc.
     'pager' => array(
diff --git a/core/lib/Drupal/Component/Utility/UrlHelper.php b/core/lib/Drupal/Component/Utility/UrlHelper.php
index 45a8036..cf87435 100644
--- a/core/lib/Drupal/Component/Utility/UrlHelper.php
+++ b/core/lib/Drupal/Component/Utility/UrlHelper.php
@@ -134,7 +134,7 @@ public static function filterQueryParameters(array $query, array $exclude = arra
    *   - fragment: The fragment component from $url, if it exists.
    *
    * @see \Drupal\Core\Utility\LinkGenerator
-   * @see _url()
+   * @see url()
    * @see http://tools.ietf.org/html/rfc3986
    *
    * @ingroup php_wrappers
@@ -288,7 +288,7 @@ public static function setAllowedProtocols(array $protocols = array()) {
    * to being output to an HTML attribute value. It is often called as part of
    * check_url() or Drupal\Component\Utility\Xss::filter(), but those functions
    * return an HTML-encoded string, so this function can be called independently
-   * when the output needs to be a plain-text string for passing to t(), _l(),
+   * when the output needs to be a plain-text string for passing to t(), l(),
    * Drupal\Core\Template\Attribute, or another function that will call
    * \Drupal\Component\Utility\String::checkPlain() separately.
    *
diff --git a/core/lib/Drupal/Core/Ajax/RedirectCommand.php b/core/lib/Drupal/Core/Ajax/RedirectCommand.php
index 4b31e52..4b0914a 100644
--- a/core/lib/Drupal/Core/Ajax/RedirectCommand.php
+++ b/core/lib/Drupal/Core/Ajax/RedirectCommand.php
@@ -28,7 +28,7 @@ class RedirectCommand implements CommandInterface {
    *
    * @param string $url
    *   The URL that will be loaded into window.location. This should be a full
-   *   URL, one that has already been run through the _url() function.
+   *   URL, one that has already been run through the url() function.
    */
   public function __construct($url) {
     $this->url = $url;
diff --git a/core/lib/Drupal/Core/Asset/CssOptimizer.php b/core/lib/Drupal/Core/Asset/CssOptimizer.php
index baa2de4..1090d5a 100644
--- a/core/lib/Drupal/Core/Asset/CssOptimizer.php
+++ b/core/lib/Drupal/Core/Asset/CssOptimizer.php
@@ -119,7 +119,7 @@ public function loadFile($file, $optimize = NULL, $reset_basepath = TRUE) {
    * Loads stylesheets recursively and returns contents with corrected paths.
    *
    * This function is used for recursive loading of stylesheets and
-   * returns the stylesheet content with all _url() paths corrected.
+   * returns the stylesheet content with all url() paths corrected.
    *
    * @param array $matches
    *   An array of matches by a preg_replace_callback() call that scans for
@@ -138,10 +138,10 @@ protected function loadNestedFile($matches) {
     // Determine the file's directory.
     $directory = dirname($filename);
     // If the file is in the current directory, make sure '.' doesn't appear in
-    // the _url() path.
+    // the url() path.
     $directory = $directory == '.' ? '' : $directory .'/';
 
-    // Alter all internal _url() paths. Leave external paths alone. We don't need
+    // Alter all internal url() paths. Leave external paths alone. We don't need
     // to normalize absolute paths here (i.e. remove folder/... segments)
     // because that will be done later.
     return preg_replace('/url\(\s*([\'"]?)(?![a-z]+:|\/+)([^\'")]+)([\'"]?)\s*\)/i', 'url(\1' . $directory . '\2\3)', $file);
@@ -215,7 +215,7 @@ protected function processCss($contents, $optimize = FALSE) {
    *
    * @param array $matches
    *   An array of matches by a preg_replace_callback() call that scans for
-   *   _url() references in CSS files, except for external or absolute ones.
+   *   url() references in CSS files, except for external or absolute ones.
    *
    * Note: the only reason this method is public is so color.module can call it;
    * it is not on the AssetOptimizerInterface, so future refactorings can make
diff --git a/core/lib/Drupal/Core/Entity/Entity.php b/core/lib/Drupal/Core/Entity/Entity.php
index 07e50c7..de1d04f 100644
--- a/core/lib/Drupal/Core/Entity/Entity.php
+++ b/core/lib/Drupal/Core/Entity/Entity.php
@@ -192,7 +192,7 @@ public function urlInfo($rel = 'canonical', array $options = []) {
       }
     }
 
-    // Pass the entity data to _url() so that alter functions do not need to
+    // Pass the entity data to url() so that alter functions do not need to
     // look up this entity again.
     $uri
       ->setOption('entity_type', $this->getEntityTypeId())
diff --git a/core/lib/Drupal/Core/Field/BaseFieldDefinition.php b/core/lib/Drupal/Core/Field/BaseFieldDefinition.php
index 613f88f..7eb0d8a 100644
--- a/core/lib/Drupal/Core/Field/BaseFieldDefinition.php
+++ b/core/lib/Drupal/Core/Field/BaseFieldDefinition.php
@@ -397,7 +397,7 @@ public function getDefaultValue(ContentEntityInterface $entity) {
    *
    * If set, the callback overrides any set default value.
    *
-   * @param string|null $callback
+   * @param callable|null $callback
    *   The callback to invoke for getting the default value (pass NULL to unset
    *   a previously set callback). The callback will be invoked with the
    *   following arguments:
@@ -411,9 +411,6 @@ public function getDefaultValue(ContentEntityInterface $entity) {
    * @return $this
    */
   public function setDefaultValueCallback($callback) {
-    if (isset($callback) && !is_string($callback)) {
-      throw new \InvalidArgumentException('Default value callback must be a string, like "function_name" or "ClassName::methodName"');
-    }
     $this->definition['default_value_callback'] = $callback;
     return $this;
   }
diff --git a/core/lib/Drupal/Core/Field/FieldConfigBase.php b/core/lib/Drupal/Core/Field/FieldConfigBase.php
index e0764cd..69473f4 100644
--- a/core/lib/Drupal/Core/Field/FieldConfigBase.php
+++ b/core/lib/Drupal/Core/Field/FieldConfigBase.php
@@ -135,7 +135,7 @@
    * hook_field_schema(). If the number of items exceeds the cardinality of the
    * field, extraneous items will be ignored.
    *
-   * This property is overlooked if the $default_value_callback is non-empty.
+   * This property is overlooked if the $default_value_function is non-empty.
    *
    * Example for a integer field:
    * @code
@@ -165,7 +165,7 @@
    *
    * @var string
    */
-  public $default_value_callback = '';
+  public $default_value_function = '';
 
   /**
    * The field storage object.
@@ -334,8 +334,8 @@ public function isRequired() {
    */
   public function getDefaultValue(ContentEntityInterface $entity) {
     // Allow custom default values function.
-    if ($callback = $this->default_value_callback) {
-      $value = call_user_func($callback, $entity, $this);
+    if ($function = $this->default_value_function) {
+      $value = call_user_func($function, $entity, $this);
     }
     else {
       $value = $this->default_value;
diff --git a/core/lib/Drupal/Core/Field/FieldItemList.php b/core/lib/Drupal/Core/Field/FieldItemList.php
index 393b827..f6ae7d5 100644
--- a/core/lib/Drupal/Core/Field/FieldItemList.php
+++ b/core/lib/Drupal/Core/Field/FieldItemList.php
@@ -318,7 +318,7 @@ public function getConstraints() {
    * {@inheritdoc}
    */
   public function defaultValuesForm(array &$form, FormStateInterface $form_state) {
-    if (empty($this->getFieldDefinition()->default_value_callback)) {
+    if (empty($this->getFieldDefinition()->default_value_function)) {
       // Place the input in a separate place in the submitted values tree.
       $widget = $this->defaultValueWidget($form_state);
 
diff --git a/core/lib/Drupal/Core/Menu/LocalTaskManager.php b/core/lib/Drupal/Core/Menu/LocalTaskManager.php
index 3914d8e..4e1f675 100644
--- a/core/lib/Drupal/Core/Menu/LocalTaskManager.php
+++ b/core/lib/Drupal/Core/Menu/LocalTaskManager.php
@@ -250,7 +250,7 @@ public function getLocalTasksForRoute($route_name) {
           foreach ($children[$parent] as $plugin_id => $task_info) {
             $plugin = $this->createInstance($plugin_id);
             $this->instances[$route_name][$level][$plugin_id] = $plugin;
-            // Normally, _l() compares the href of every link with the current
+            // Normally, l() compares the href of every link with the current
             // path and sets the active class accordingly. But the parents of
             // the current local task may be on a different route in which
             // case we have to set the class manually by flagging it active.
diff --git a/core/lib/Drupal/Core/Menu/MenuLinkBase.php b/core/lib/Drupal/Core/Menu/MenuLinkBase.php
index c82bef3..b09bfa9 100644
--- a/core/lib/Drupal/Core/Menu/MenuLinkBase.php
+++ b/core/lib/Drupal/Core/Menu/MenuLinkBase.php
@@ -141,7 +141,9 @@ public function getUrlObject($title_attribute = TRUE) {
       return new Url($this->pluginDefinition['route_name'], $this->pluginDefinition['route_parameters'], $options);
     }
     else {
-      return Url::fromUri($this->pluginDefinition['url'], $options);
+      $url = Url::createFromPath($this->pluginDefinition['url']);
+      $url->setOptions($options);
+      return $url;
     }
   }
 
diff --git a/core/lib/Drupal/Core/Menu/MenuTreeStorage.php b/core/lib/Drupal/Core/Menu/MenuTreeStorage.php
index 2ed2fb0..fb75390 100644
--- a/core/lib/Drupal/Core/Menu/MenuTreeStorage.php
+++ b/core/lib/Drupal/Core/Menu/MenuTreeStorage.php
@@ -1278,7 +1278,7 @@ protected static function schemaDefinition() {
           'not null' => FALSE,
         ),
         'options' => array(
-          'description' => 'A serialized array of options to be passed to the _url() or _l() function, such as a query string or HTML attributes.',
+          'description' => 'A serialized array of options to be passed to the url() or l() function, such as a query string or HTML attributes.',
           'type' => 'blob',
           'size' => 'big',
           'not null' => FALSE,
diff --git a/core/lib/Drupal/Core/Page/DefaultHtmlFragmentRenderer.php b/core/lib/Drupal/Core/Page/DefaultHtmlFragmentRenderer.php
index 8711ee2..164f7f5 100644
--- a/core/lib/Drupal/Core/Page/DefaultHtmlFragmentRenderer.php
+++ b/core/lib/Drupal/Core/Page/DefaultHtmlFragmentRenderer.php
@@ -110,7 +110,7 @@ public function preparePage(HtmlPage $page, &$page_array) {
     foreach (drupal_get_feeds() as $feed) {
       // Force the URL to be absolute, for consistency with other <link> tags
       // output by Drupal.
-      $link = new FeedLinkElement($feed['title'], _url($feed['url'], array('absolute' => TRUE)));
+      $link = new FeedLinkElement($feed['title'], url($feed['url'], array('absolute' => TRUE)));
       $page->addLinkElement($link);
     }
 
diff --git a/core/lib/Drupal/Core/Path/AliasWhitelist.php b/core/lib/Drupal/Core/Path/AliasWhitelist.php
index 11c68f7..394dfa2 100644
--- a/core/lib/Drupal/Core/Path/AliasWhitelist.php
+++ b/core/lib/Drupal/Core/Path/AliasWhitelist.php
@@ -88,7 +88,7 @@ protected function loadMenuPathRoots() {
    */
   public function get($offset) {
     $this->lazyLoadCache();
-    // _url() may be called with paths that are not represented by menu router
+    // url() may be called with paths that are not represented by menu router
     // items such as paths that will be rewritten by hook_url_outbound_alter().
     // Therefore internally TRUE is used to indicate whitelisted paths. FALSE is
     // used to indicate paths that have already been checked but are not
diff --git a/core/lib/Drupal/Core/Path/PathValidator.php b/core/lib/Drupal/Core/Path/PathValidator.php
index e6ebf5d..1b519c7 100644
--- a/core/lib/Drupal/Core/Path/PathValidator.php
+++ b/core/lib/Drupal/Core/Path/PathValidator.php
@@ -99,7 +99,7 @@ public function getUrlIfValid($path) {
       if (empty($parsed_url['path'])) {
         return FALSE;
       }
-      return Url::fromUri($path);
+      return Url::createFromPath($path);
     }
 
     $path = ltrim($path, '/');
diff --git a/core/lib/Drupal/Core/Render/Element/Link.php b/core/lib/Drupal/Core/Render/Element/Link.php
index 474e9f5..12bddb7 100644
--- a/core/lib/Drupal/Core/Render/Element/Link.php
+++ b/core/lib/Drupal/Core/Render/Element/Link.php
@@ -7,7 +7,7 @@
 
 namespace Drupal\Core\Render\Element;
 
-use Drupal\Core\Url as UrlObject;
+use Drupal\Core\Url;
 
 /**
  * Provides a link render element.
@@ -34,21 +34,21 @@ public function getInfo() {
    * Doing so during pre_render gives modules a chance to alter the link parts.
    *
    * @param array $element
-   *   A structured array whose keys form the arguments to _l():
-   *   - #title: The link text to pass as argument to _l().
+   *   A structured array whose keys form the arguments to l():
+   *   - #title: The link text to pass as argument to l().
    *   - One of the following
    *     - #route_name and (optionally) a #route_parameters array; The route
    *       name and route parameters which will be passed into the link
    *       generator.
-   *     - #href: The system path or URL to pass as argument to _l().
-   *   - #options: (optional) An array of options to pass to _l() or the link
+   *     - #href: The system path or URL to pass as argument to l().
+   *   - #options: (optional) An array of options to pass to l() or the link
    *     generator.
    *
    * @return array
    *   The passed-in element containing a rendered link in '#markup'.
    */
   public static function preRenderLink($element) {
-    // By default, link options to pass to _l() are normally set in #options.
+    // By default, link options to pass to l() are normally set in #options.
     $element += array('#options' => array());
     // However, within the scope of renderable elements, #attributes is a valid
     // way to specify attributes, too. Take them into account, but do not override
@@ -85,11 +85,10 @@ public static function preRenderLink($element) {
 
     if (isset($element['#route_name'])) {
       $element['#route_parameters'] = empty($element['#route_parameters']) ? array() : $element['#route_parameters'];
-      $element['#markup'] = \Drupal::l($element['#title'], new UrlObject($element['#route_name'], $element['#route_parameters'], $element['#options']));
+      $element['#markup'] = \Drupal::l($element['#title'], new Url($element['#route_name'], $element['#route_parameters'], $element['#options']));
     }
     else {
-      // @todo Convert to \Drupal::l(): https://www.drupal.org/node/2347045.
-      $element['#markup'] = _l($element['#title'], $element['#href'], $element['#options']);
+      $element['#markup'] = l($element['#title'], $element['#href'], $element['#options']);
     }
     return $element;
   }
diff --git a/core/lib/Drupal/Core/Render/Element/RenderElement.php b/core/lib/Drupal/Core/Render/Element/RenderElement.php
index 38e09fc..553496c 100644
--- a/core/lib/Drupal/Core/Render/Element/RenderElement.php
+++ b/core/lib/Drupal/Core/Render/Element/RenderElement.php
@@ -248,7 +248,7 @@ public static function preRenderAjaxForm($element) {
       }
 
       // Change path to URL.
-      $settings['url'] = isset($settings['path']) ? _url($settings['path'], $settings['options']) : NULL;
+      $settings['url'] = isset($settings['path']) ? url($settings['path'], $settings['options']) : NULL;
       unset($settings['path'], $settings['options']);
 
       // Add special data to $settings['submit'] so that when this element
@@ -286,7 +286,7 @@ public static function preRenderAjaxForm($element) {
       }
       // Change progress path to a full URL.
       if (isset($settings['progress']['path'])) {
-        $settings['progress']['url'] = _url($settings['progress']['path']);
+        $settings['progress']['url'] = url($settings['progress']['path']);
         unset($settings['progress']['path']);
       }
 
diff --git a/core/lib/Drupal/Core/Routing/UrlGenerator.php b/core/lib/Drupal/Core/Routing/UrlGenerator.php
index ae41c9c..8e2522a 100644
--- a/core/lib/Drupal/Core/Routing/UrlGenerator.php
+++ b/core/lib/Drupal/Core/Routing/UrlGenerator.php
@@ -238,7 +238,7 @@ public function generateFromPath($path = NULL, $options = array()) {
       // \Drupal\Component\Utility\UrlHelper::stripDangerousProtocols() if $path
       // contains a ':' before any / ? or #. Note: we could use
       // \Drupal\Component\Utility\UrlHelper::isExternal($path) here, but that
-      // would require another function call, and performance inside _url() is
+      // would require another function call, and performance inside url() is
       // critical.
       $colonpos = strpos($path, ':');
       $options['external'] = ($colonpos !== FALSE && !preg_match('![/?#]!', substr($path, 0, $colonpos)) && UrlHelper::stripDangerousProtocols($path) == $path);
diff --git a/core/lib/Drupal/Core/Routing/UrlGeneratorInterface.php b/core/lib/Drupal/Core/Routing/UrlGeneratorInterface.php
index 06e600d..ad58aca 100644
--- a/core/lib/Drupal/Core/Routing/UrlGeneratorInterface.php
+++ b/core/lib/Drupal/Core/Routing/UrlGeneratorInterface.php
@@ -67,10 +67,10 @@
    *   - 'script': Added to the URL between the base path and the path prefix.
    *     Defaults to empty string when clean URLs are in effect, and to
    *     'index.php/' when they are not.
-   *   - 'entity_type': The entity type of the object that called _url(). Only
-   *     set if _url() is invoked by Drupal\Core\Entity\Entity::uri().
+   *   - 'entity_type': The entity type of the object that called url(). Only
+   *     set if url() is invoked by Drupal\Core\Entity\Entity::uri().
    *   - 'entity': The entity object (such as a node) for which the URL is being
-   *     generated. Only set if _url() is invoked by Drupal\Core\Entity\Entity::uri().
+   *     generated. Only set if url() is invoked by Drupal\Core\Entity\Entity::uri().
    *
    * @return
    *   A string containing a URL to the given path.
diff --git a/core/lib/Drupal/Core/Template/TwigExtension.php b/core/lib/Drupal/Core/Template/TwigExtension.php
index 632e42a..20c71e6 100644
--- a/core/lib/Drupal/Core/Template/TwigExtension.php
+++ b/core/lib/Drupal/Core/Template/TwigExtension.php
@@ -214,7 +214,7 @@ public function getLink($text, $url) {
     }
     else {
       // @todo Convert once https://www.drupal.org/node/2306901 is in
-      return _l($text, $url);
+      return l($text, $url);
     }
   }
 
diff --git a/core/lib/Drupal/Core/Theme/Registry.php b/core/lib/Drupal/Core/Theme/Registry.php
index da3122c..8c9efb3 100644
--- a/core/lib/Drupal/Core/Theme/Registry.php
+++ b/core/lib/Drupal/Core/Theme/Registry.php
@@ -401,6 +401,9 @@ protected function build() {
    * @see _theme()
    * @see hook_theme()
    * @see list_themes()
+   * @see twig_render_template()
+   *
+   * @throws \BadFunctionCallException
    */
   protected function processExtension(&$cache, $name, $type, $theme, $path) {
     $result = array();
@@ -430,12 +433,6 @@ protected function processExtension(&$cache, $name, $type, $theme, $path) {
         $result[$hook]['type'] = $type;
         $result[$hook]['theme path'] = $path;
 
-        // If function and file are omitted, default to standard naming
-        // conventions.
-        if (!isset($info['template']) && !isset($info['function'])) {
-          $result[$hook]['function'] = ($type == 'module' ? 'theme_' : $name . '_') . $hook;
-        }
-
         if (isset($cache[$hook]['includes'])) {
           $result[$hook]['includes'] = $cache[$hook]['includes'];
         }
@@ -451,20 +448,37 @@ protected function processExtension(&$cache, $name, $type, $theme, $path) {
           $result[$hook]['includes'][] = $include_file;
         }
 
+        // A template file is the default implementation for a theme hook, but
+        // if the theme hook specifies a function callback instead, check to
+        // ensure the function actually exists.
+        if (isset($info['function']) && !function_exists($info['function'])) {
+          throw new \BadFunctionCallException(sprintf(
+            'Theme hook "%s" refers to a theme function callback that does not exist: "%s"',
+            $hook,
+            $info['function']
+          ));
+        }
+        // Provide a default naming convention for 'template' based on the
+        // hook used. If the template does not exist, the theme engine used
+        // should throw an exception at runtime when attempting to include
+        // the template file.
+        elseif (!isset($info['template'])) {
+          $info['template'] = strtr($hook, '_', '-');
+          $result[$hook]['template'] = $info['template'];
+        }
+
+        // Prepend the current theming path when none is set. This is required
+        // for the default theme engine to know where the template lives.
+        if (isset($result[$hook]['template']) && !isset($info['path'])) {
+          $result[$hook]['path'] = $path . '/templates';
+        }
+
         // If the default keys are not set, use the default values registered
         // by the module.
         if (isset($cache[$hook])) {
           $result[$hook] += array_intersect_key($cache[$hook], $hook_defaults);
         }
 
-        // The following apply only to theming hooks implemented as templates.
-        if (isset($info['template'])) {
-          // Prepend the current theming path when none is set.
-          if (!isset($info['path'])) {
-            $result[$hook]['template'] = $path . '/templates/' . $info['template'];
-          }
-        }
-
         // Preprocess variables for all theming hooks, whether the hook is
         // implemented as a template or as a function. Ensure they are arrays.
         if (!isset($info['preprocess functions']) || !is_array($info['preprocess functions'])) {
diff --git a/core/lib/Drupal/Core/Url.php b/core/lib/Drupal/Core/Url.php
index a6f0220..d97f017 100644
--- a/core/lib/Drupal/Core/Url.php
+++ b/core/lib/Drupal/Core/Url.php
@@ -7,10 +7,10 @@
 
 namespace Drupal\Core;
 
+use Drupal\Component\Utility\UrlHelper;
 use Drupal\Core\DependencyInjection\DependencySerializationTrait;
 use Drupal\Core\Routing\UrlGeneratorInterface;
 use Drupal\Core\Session\AccountInterface;
-use Drupal\Core\Utility\UnroutedUrlAssemblerInterface;
 use Symfony\Cmf\Component\Routing\RouteObjectInterface;
 use Symfony\Component\HttpFoundation\Request;
 
@@ -28,13 +28,6 @@ class Url {
   protected $urlGenerator;
 
   /**
-   * The unrouted URL assembler.
-   *
-   * @var \Drupal\Core\Utility\UnroutedUrlAssemblerInterface
-   */
-  protected $urlAssembler;
-
-  /**
    * The access manager
    *
    * @var \Drupal\Core\Access\AccessManagerInterface
@@ -63,35 +56,24 @@ class Url {
   protected $options = array();
 
   /**
-   * Indicates whether this object contains an external URL.
+   * Indicates whether this URL is external.
    *
    * @var bool
    */
   protected $external = FALSE;
 
   /**
-   * Indicates whether this URL is for a URI without a Drupal route.
-   *
-   * @var bool
-   */
-  protected $unrouted = FALSE;
-
-  /**
-   * The non-route URI.
+   * The external path.
    *
-   * Only used if self::$unrouted is TRUE.
+   * Only used if self::$external is TRUE.
    *
    * @var string
    */
-  protected $uri;
+  protected $path;
 
   /**
    * Constructs a new Url object.
    *
-   * In most cases, use Url::fromRoute() or Url::fromUri() rather than
-   * constructing Url objects directly in order to avoid ambiguity and make your
-   * code more self-documenting.
-   *
    * @param string $route_name
    *   The name of the route
    * @param array $route_parameters
@@ -113,12 +95,6 @@ class Url {
    *     defined, the current scheme is used, so the user stays on HTTP or HTTPS
    *     respectively. if mixed mode sessions are permitted, TRUE enforces HTTPS
    *     and FALSE enforces HTTP.
-   *
-   * @see static::fromRoute()
-   * @see static::fromUri()
-   *
-   * @todo Update this documentation for non-routed URIs in
-   *   https://www.drupal.org/node/2346787
    */
   public function __construct($route_name, $route_parameters = array(), $options = array()) {
     $this->routeName = $route_name;
@@ -127,101 +103,44 @@ public function __construct($route_name, $route_parameters = array(), $options =
   }
 
   /**
-   * Creates a new Url object for a URL that has a Drupal route.
-   *
-   * This method is for URLs that have Drupal routes (that is, most pages
-   * generated by Drupal). For non-routed local URIs relative to the base
-   * path (like robots.txt) use Url::fromUri() with the base:// scheme.
-   *
-   * @param string $route_name
-   *   The name of the route
-   * @param array $route_parameters
-   *   (optional) An associative array of route parameter names and values.
-   * @param array $options
-   *   (optional) An associative array of additional URL options, with the
-   *   following elements:
-   *   - 'query': An array of query key/value-pairs (without any URL-encoding)
-   *     to append to the URL. Merged with the parameters array.
-   *   - 'fragment': A fragment identifier (named anchor) to append to the URL.
-   *     Do not include the leading '#' character.
-   *   - 'absolute': Defaults to FALSE. Whether to force the output to be an
-   *     absolute link (beginning with http:). Useful for links that will be
-   *     displayed outside the site, such as in an RSS feed.
-   *   - 'language': An optional language object used to look up the alias
-   *     for the URL. If $options['language'] is omitted, it defaults to the
-   *     current language for the language type LanguageInterface::TYPE_URL.
-   *   - 'https': Whether this URL should point to a secure location. If not
-   *     defined, the current scheme is used, so the user stays on HTTP or HTTPS
-   *     respectively. if mixed mode sessions are permitted, TRUE enforces HTTPS
-   *     and FALSE enforces HTTP.
-   *
-   * @return \Drupal\Core\Url
-   *   A new Url object for a routed (internal to Drupal) URL.
-   *
-   * @see static::fromUri()
-   */
-  public static function fromRoute($route_name, $route_parameters = array(), $options = array()) {
-    return new static($route_name, $route_parameters, $options);
-  }
-
-  /**
-   * Creates a new Url object for a URI that does not have a Drupal route.
-   *
-   * This method is for generating URLs for URIs that do not have Drupal
-   * routes, both external URLs and unrouted local URIs like
-   * base://robots.txt. For URLs that have Drupal routes (that is, most pages
-   * generated by Drupal), use Url::fromRoute().
+   * Returns the Url object matching a path. READ THE FOLLOWING SECURITY NOTE.
    *
-   * @param string $uri
-   *   The URI of the external resource including the scheme. For Drupal paths
-   *   that are not handled by the routing system, use base:// for the scheme.
-   * @param array $options
-   *   (optional) An associative array of additional URL options, with the
-   *   following elements:
-   *   - 'query': An array of query key/value-pairs (without any URL-encoding)
-   *     to append to the URL. Merged with the parameters array.
-   *   - 'fragment': A fragment identifier (named anchor) to append to the URL.
-   *     Do not include the leading '#' character.
-   *   - 'absolute': Defaults to FALSE. Whether to force the output to be an
-   *     absolute link (beginning with http:). Useful for links that will be
-   *     displayed outside the site, such as in an RSS feed.
-   *   - 'language': An optional language object used to look up the alias
-   *     for the URL. If $options['language'] is omitted, it defaults to the
-   *     current language for the language type LanguageInterface::TYPE_URL.
-   *   - 'https': Whether this URL should point to a secure location. If not
-   *     defined, the current scheme is used, so the user stays on HTTP or HTTPS
-   *     respectively. if mixed mode sessions are permitted, TRUE enforces HTTPS
-   *     and FALSE enforces HTTP.
+   * SECURITY NOTE: The path is not checked to be valid and accessible by the
+   * current user to allow storing and reusing Url objects by different users.
+   * The 'path.validator' service getUrlIfValid() method should be used instead
+   * of this one if validation and access check is desired. Otherwise,
+   * 'access_manager' service checkNamedRoute() method should be used on the
+   * router name and parameters stored in the Url object returned by this
+   * method.
    *
-   * @return \Drupal\Core\Url
-   *   A new Url object for an unrouted (non-Drupal) URL.
+   * @param string $path
+   *   A path (e.g. 'node/1', 'http://drupal.org').
    *
-   * @throws \InvalidArgumentException
-   *   Thrown when the passed in path has no scheme.
+   * @return static
+   *   An Url object. Warning: the object is created even if the current user
+   *   can not access the path.
    *
-   * @see static::fromRoute()
+   * @throws \Drupal\Core\Routing\MatchingRouteNotFoundException
+   *   Thrown when the path cannot be matched.
    */
-  public static function fromUri($uri, $options = array()) {
-    if (!parse_url($uri, PHP_URL_SCHEME)) {
-      throw new \InvalidArgumentException('You must use a valid URI scheme. Use base:// for a path, e.g., to a Drupal file that needs the base path. Do not use this for internal paths controlled by Drupal.');
+  public static function createFromPath($path) {
+    if (UrlHelper::isExternal($path)) {
+      $url = new static($path);
+      $url->setExternal();
+      return $url;
     }
 
-    $url = new static($uri, array(), $options);
-    $url->setUnrouted();
-
-    return $url;
+    // Special case the front page route.
+    if ($path == '<front>') {
+      return new static($path);
+    }
+    else {
+      return static::createFromRequest(Request::create("/$path"));
+    }
   }
 
   /**
-   * Returns the Url object matching a request.
-   *
-   * SECURITY NOTE: The request path is not checked to be valid and accessible
-   * by the current user to allow storing and reusing Url objects by different
-   * users. The 'path.validator' service getUrlIfValid() method should be used
-   * instead of this one if validation and access check is desired. Otherwise,
-   * 'access_manager' service checkNamedRoute() method should be used on the
-   * router name and parameters stored in the Url object returned by this
-   * method.
+   * Returns the Url object matching a request. READ THE SECURITY NOTE ON createFromPath().
    *
    * @param \Symfony\Component\HttpFoundation\Request $request
    *   A request object.
@@ -244,23 +163,23 @@ public static function createFromRequest(Request $request) {
   }
 
   /**
-   * Sets this Url to encapsulate an unrouted URI.
+   * Sets this Url to be external.
    *
    * @return $this
    */
-  protected function setUnrouted() {
-    $this->unrouted = TRUE;
-    // What was passed in as the route name is actually the URI.
-    // @todo Consider fixing this in https://www.drupal.org/node/2346787.
-    $this->uri = $this->routeName;
+  protected function setExternal() {
+    $this->external = TRUE;
+
+    // What was passed in as the route name is actually the path.
+    $this->path = $this->routeName;
+
     // Set empty route name and parameters.
     $this->routeName = NULL;
     $this->routeParameters = array();
-    // @todo Add a method for the check below in
-    // https://www.drupal.org/node/2346859.
-    if ($this->external = strpos($this->uri, 'base://') !== 0) {
-      $this->options['external'] = TRUE;
-    }
+    // Flag the path as external so the UrlGenerator does not need to check.
+    $this->options['external'] = TRUE;
+
+    return $this;
   }
 
   /**
@@ -273,24 +192,15 @@ public function isExternal() {
   }
 
   /**
-   * Indicates if this Url has a Drupal route.
-   *
-   * @return bool
-   */
-  public function isRouted() {
-    return !$this->unrouted;
-  }
-
-  /**
    * Returns the route name.
    *
    * @return string
    *
    * @throws \UnexpectedValueException.
-   *   If this is a URI with no corresponding route.
+   *   If this is an external URL with no corresponding route.
    */
   public function getRouteName() {
-    if ($this->unrouted) {
+    if ($this->isExternal()) {
       throw new \UnexpectedValueException('External URLs do not have an internal route name.');
     }
 
@@ -303,10 +213,10 @@ public function getRouteName() {
    * @return array
    *
    * @throws \UnexpectedValueException.
-   *   If this is a URI with no corresponding route.
+   *   If this is an external URL with no corresponding route.
    */
   public function getRouteParameters() {
-    if ($this->unrouted) {
+    if ($this->isExternal()) {
       throw new \UnexpectedValueException('External URLs do not have internal route parameters.');
     }
 
@@ -320,13 +230,10 @@ public function getRouteParameters() {
    *   The array of parameters.
    *
    * @return $this
-   *
-   * @throws \UnexpectedValueException.
-   *   If this is a URI with no corresponding route.
    */
   public function setRouteParameters($parameters) {
-    if ($this->unrouted) {
-      throw new \UnexpectedValueException('External URLs do not have route parameters.');
+    if ($this->isExternal()) {
+      throw new \Exception('External URLs do not have route parameters.');
     }
     $this->routeParameters = $parameters;
     return $this;
@@ -341,13 +248,10 @@ public function setRouteParameters($parameters) {
    *   The route parameter.
    *
    * @return $this
-   *
-   * @throws \UnexpectedValueException.
-   *   If this is a URI with no corresponding route.
    */
   public function setRouteParameter($key, $value) {
-    if ($this->unrouted) {
-      throw new \UnexpectedValueException('External URLs do not have route parameters.');
+    if ($this->isExternal()) {
+      throw new \Exception('External URLs do not have route parameters.');
     }
     $this->routeParameters[$key] = $value;
     return $this;
@@ -408,22 +312,22 @@ public function setOption($name, $value) {
   }
 
   /**
-   * Returns the URI of the URL.
+   * Returns the external path of the URL.
    *
-   * Only to be used if self::$unrouted is TRUE.
+   * Only to be used if self::$external is TRUE.
    *
    * @return string
-   *   A URI not connected to a route. May be an external URL.
+   *   The external path.
    *
    * @throws \UnexpectedValueException
-   *   Thrown when the URI was requested for a routed URL.
+   *   Thrown when the path was requested for an internal URL.
    */
-  public function getUri() {
-    if (!$this->unrouted) {
-      throw new \UnexpectedValueException('This URL has a Drupal route, so the canonical form is not a URI.');
+  public function getPath() {
+    if (!$this->isExternal()) {
+      throw new \UnexpectedValueException('Internal URLs do not have external paths.');
     }
 
-    return $this->uri;
+    return $this->path;
   }
 
   /**
@@ -440,11 +344,11 @@ public function setAbsolute($absolute = TRUE) {
   }
 
   /**
-   * Generates the URI for this Url object.
+   * Generates the path for this Url object.
    */
   public function toString() {
-    if ($this->unrouted) {
-      return $this->unroutedUrlAssembler()->assemble($this->getUri(), $this->getOptions());
+    if ($this->isExternal()) {
+      return $this->urlGenerator()->generateFromPath($this->getPath(), $this->getOptions());
     }
 
     return $this->urlGenerator()->generateFromRoute($this->getRouteName(), $this->getRouteParameters(), $this->getOptions());
@@ -457,10 +361,9 @@ public function toString() {
    *   An associative array containing all the properties of the route.
    */
   public function toArray() {
-    if ($this->unrouted) {
+    if ($this->isExternal()) {
       return array(
-        // @todo Change 'path' to 'href': https://www.drupal.org/node/2347025.
-        'path' => $this->getUri(),
+        'path' => $this->getPath(),
         'options' => $this->getOptions(),
       );
     }
@@ -480,9 +383,9 @@ public function toArray() {
    *   An associative array suitable for a render array.
    */
   public function toRenderArray() {
-    if ($this->unrouted) {
+    if ($this->isExternal()) {
       return array(
-        '#href' => $this->getUri(),
+        '#href' => $this->getPath(),
         '#options' => $this->getOptions(),
       );
     }
@@ -505,14 +408,14 @@ public function toRenderArray() {
    *   The internal path for this route.
    *
    * @throws \UnexpectedValueException.
-   *   If this is a URI with no corresponding system path.
+   *   If this is an external URL with no corresponding system path.
    *
    * @deprecated in Drupal 8.x-dev, will be removed before Drupal 8.0.
    *   System paths should not be used - use route names and parameters.
    */
   public function getInternalPath() {
-    if ($this->unrouted) {
-      throw new \UnexpectedValueException('Unrouted URIs do not have internal representations.');
+    if ($this->isExternal()) {
+      throw new \UnexpectedValueException('External URLs do not have internal representations.');
     }
     return $this->urlGenerator()->getPathFromRoute($this->getRouteName(), $this->getRouteParameters());
   }
@@ -570,19 +473,6 @@ protected function urlGenerator() {
   }
 
   /**
-   * Gets the unrouted URL assembler for non-Drupal URLs.
-   *
-   * @return \Drupal\Core\Utility\UnroutedUrlAssemblerInterface
-   *   The unrouted URL assembler.
-   */
-  protected function unroutedUrlAssembler() {
-    if (!$this->urlAssembler) {
-      $this->urlAssembler = \Drupal::service('unrouted_url_assembler');
-    }
-    return $this->urlAssembler;
-  }
-
-  /**
    * Sets the URL generator.
    *
    * @param \Drupal\Core\Routing\UrlGeneratorInterface
@@ -595,17 +485,4 @@ public function setUrlGenerator(UrlGeneratorInterface $url_generator) {
     return $this;
   }
 
-  /**
-   * Sets the unrouted URL assembler.
-   *
-   * @param \Drupal\Core\Utility\UnroutedUrlAssemblerInterface
-   *   The unrouted URL assembler.
-   *
-   * @return $this
-   */
-  public function setUnroutedUrlAssembler(UnroutedUrlAssemblerInterface $url_assembler) {
-    $this->urlAssembler = $url_assembler;
-    return $this;
-  }
-
 }
diff --git a/core/lib/Drupal/Core/Utility/UnroutedUrlAssembler.php b/core/lib/Drupal/Core/Utility/UnroutedUrlAssembler.php
index 52d1d13..05fb19f 100644
--- a/core/lib/Drupal/Core/Utility/UnroutedUrlAssembler.php
+++ b/core/lib/Drupal/Core/Utility/UnroutedUrlAssembler.php
@@ -56,7 +56,7 @@ public function assemble($uri, array $options = []) {
       // UrlHelper::isExternal() only returns true for safe protocols.
       return $this->buildExternalUrl($uri, $options);
     }
-    throw new \InvalidArgumentException('You must use a valid URI scheme. Use base:// for a path e.g. to a Drupal file that needs the base path.');
+    throw new \InvalidArgumentException('You must use a valid URI scheme.  Use base:// for a path e.g. to a Drupal file that needs the base path.');
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Utility/UnroutedUrlAssemblerInterface.php b/core/lib/Drupal/Core/Utility/UnroutedUrlAssemblerInterface.php
index c1caa44..cba87fe 100644
--- a/core/lib/Drupal/Core/Utility/UnroutedUrlAssemblerInterface.php
+++ b/core/lib/Drupal/Core/Utility/UnroutedUrlAssemblerInterface.php
@@ -12,24 +12,23 @@
 interface UnroutedUrlAssemblerInterface {
 
   /**
-   * Builds a domain-local or external URL from a URI.
+   * Builds a domain-local or external URL from a path or URL.
    *
    * For actual implementations the logic probably has to be split up between
-   * domain-local URIs and external URLs.
+   * domain-local and external URLs.
    *
    * @param string $uri
-   *   A local URI or an external URL being linked to, such as "base://foo"
+   *   A path on the same domain or external URL being linked to, such as "foo"
    *    or "http://example.com/foo".
    *   - If you provide a full URL, it will be considered an external URL as
    *     long as it has an allowed protocol.
-   *   - If you provide only a local URI (e.g. "base://foo"), it will be
-   *     considered a path local to Drupal, but not handled by the routing
-   *     system.  The base path (the subdirectory where the front controller
-   *     is found) will be added to the path. Additional query arguments for
-   *     local paths must be supplied in $options['query'], not part of $uri.
+   *   - If you provide only a path (e.g. "foo"), it will be
+   *     considered a URL local to the same domain. Additional query
+   *     arguments for local paths must be supplied in $options['query'], not
+   *     included in $path.
    *   - If your external URL contains a query (e.g. http://example.com/foo?a=b),
    *     then you can either URL encode the query keys and values yourself and
-   *     include them in $uri, or use $options['query'] to let this method
+   *     include them in $path, or use $options['query'] to let this method
    *     URL encode them.
    *
    * @param array $options
@@ -49,9 +48,6 @@
    *
    * @return
    *   A string containing a relative or absolute URL.
-   *
-   * @throws \InvalidArgumentException
-   *   Thrown when the passed in path has no scheme.
    */
   public function assemble($uri, array $options = array());
 
diff --git a/core/modules/aggregator/aggregator.module b/core/modules/aggregator/aggregator.module
index 5e85078..aecd844 100644
--- a/core/modules/aggregator/aggregator.module
+++ b/core/modules/aggregator/aggregator.module
@@ -26,7 +26,6 @@ function aggregator_help($route_name, RouteMatchInterface $route_match) {
       $output .= '<p>' . t('The Aggregator module is an on-site syndicator and news reader that gathers and displays fresh content from RSS-, RDF-, and Atom-based feeds made available across the web. Thousands of sites (particularly news sites and blogs) publish their latest headlines in feeds, using a number of standardized XML-based formats. For more information, see the <a href="!aggregator-module">online documentation for the Aggregator module</a>.', array('!aggregator-module' => 'https://drupal.org/documentation/modules/aggregator')) . '</p>';
       $output .= '<h3>' . t('Uses') . '</h3>';
       $output .= '<dl>';
-      // Check if the aggregator sources View is enabled.
       if ($url = $path_validator->getUrlIfValid('aggregator/sources')) {
         $output .= '<dt>' . t('Viewing feeds') . '</dt>';
         $output .= '<dd>' . t('Users view feed content in the <a href="!aggregator">main aggregator display</a>, or by <a href="!aggregator-sources">their source</a> (usually via an RSS feed reader). The most recent content in a feed can be displayed as a block through the <a href="!admin-block">Blocks administration page</a>.', array('!aggregator' => \Drupal::url('aggregator.page_last'), '!aggregator-sources' => $url->toString(), '!admin-block' => \Drupal::url('block.admin_display'))) . '</dd>';
@@ -34,7 +33,6 @@ function aggregator_help($route_name, RouteMatchInterface $route_match) {
       $output .= '<dt>' . t('Adding, editing, and deleting feeds') . '</dt>';
       $output .= '<dd>' . t('Administrators can add, edit, and delete feeds, and choose how often to check each feed for newly updated items on the <a href="!feededit">Feed aggregator administration page</a>.', array('!feededit' => \Drupal::url('aggregator.admin_overview'))) . '</dd>';
       $output .= '<dt>' . t('<abbr title="Outline Processor Markup Language">OPML</abbr> integration') . '</dt>';
-      // Check if the aggregator opml View is enabled.
       if ($url = $path_validator->getUrlIfValid('aggregator/opml')) {
         $output .= '<dd>' . t('A <a href="!aggregator-opml">machine-readable OPML file</a> of all feeds is available. OPML is an XML-based file format used to share outline-structured information such as a list of RSS feeds. Feeds can also be <a href="!import-opml">imported via an OPML file</a>.', array('!aggregator-opml' => $url->toString(), '!import-opml' => \Drupal::url('aggregator.opml_add'))) . '</dd>';
       }
diff --git a/core/modules/aggregator/src/Entity/Item.php b/core/modules/aggregator/src/Entity/Item.php
index 0cebc3b..493e4cb 100644
--- a/core/modules/aggregator/src/Entity/Item.php
+++ b/core/modules/aggregator/src/Entity/Item.php
@@ -244,7 +244,7 @@ public function getListCacheTags() {
    * Entity URI callback.
    */
   public static function buildUri(ItemInterface $item) {
-    return Url::fromUri($item->getLink());
+    return Url::createFromPath($item->getLink());
   }
 
 }
diff --git a/core/modules/aggregator/src/Tests/FeedParserTest.php b/core/modules/aggregator/src/Tests/FeedParserTest.php
index a6d44c7..2ac0a94 100644
--- a/core/modules/aggregator/src/Tests/FeedParserTest.php
+++ b/core/modules/aggregator/src/Tests/FeedParserTest.php
@@ -80,7 +80,7 @@ function testHtmlEntitiesSample() {
    */
   function testRedirectFeed() {
     // Simulate a typo in the URL to force a curl exception.
-    $invalid_url = _url('aggregator/redirect', array('absolute' => TRUE));
+    $invalid_url = url('aggregator/redirect', array('absolute' => TRUE));
     $feed = entity_create('aggregator_feed', array('url' => $invalid_url, 'title' => $this->randomMachineName()));
     $feed->save();
     $feed->refreshItems();
diff --git a/core/modules/aggregator/src/Tests/Views/IntegrationTest.php b/core/modules/aggregator/src/Tests/Views/IntegrationTest.php
index 8b6edaa..5084bdf 100644
--- a/core/modules/aggregator/src/Tests/Views/IntegrationTest.php
+++ b/core/modules/aggregator/src/Tests/Views/IntegrationTest.php
@@ -107,7 +107,7 @@ public function testAggregatorItemView() {
     // Ensure that the rendering of the linked title works as expected.
     foreach ($view->result as $row) {
       $iid = $view->field['iid']->getValue($row);
-      $expected_link = _l($items[$iid]->getTitle(), $items[$iid]->getLink(), array('absolute' => TRUE));
+      $expected_link = l($items[$iid]->getTitle(), $items[$iid]->getLink(), array('absolute' => TRUE));
       $this->assertEqual($view->field['title']->advancedRender($row), $expected_link, 'Ensure the right link is generated');
 
       $expected_author = aggregator_filter_xss($items[$iid]->getAuthor());
diff --git a/core/modules/basic_auth/src/Tests/Authentication/BasicAuthTest.php b/core/modules/basic_auth/src/Tests/Authentication/BasicAuthTest.php
index b45105b..62346a1 100644
--- a/core/modules/basic_auth/src/Tests/Authentication/BasicAuthTest.php
+++ b/core/modules/basic_auth/src/Tests/Authentication/BasicAuthTest.php
@@ -150,7 +150,7 @@ protected function basicAuthGet($path, $username, $password) {
     $out = $this->curlExec(
       array(
         CURLOPT_HTTPGET => TRUE,
-        CURLOPT_URL => _url($path, array('absolute' => TRUE)),
+        CURLOPT_URL => url($path, array('absolute' => TRUE)),
         CURLOPT_NOBODY => FALSE,
         CURLOPT_HTTPAUTH => CURLAUTH_BASIC,
         CURLOPT_USERPWD => $username . ':' . $password,
diff --git a/core/modules/book/book.module b/core/modules/book/book.module
index dc20b1d..54ddd96 100644
--- a/core/modules/book/book.module
+++ b/core/modules/book/book.module
@@ -62,6 +62,7 @@ function book_theme() {
     ),
     'book_link' => array(
       'render element' => 'element',
+      'function' => 'theme_book_link',
     ),
     'book_export_html' => array(
       'variables' => array('title' => NULL, 'contents' => NULL, 'depth' => NULL),
@@ -70,6 +71,7 @@ function book_theme() {
     'book_admin_table' => array(
       'render element' => 'form',
       'file' => 'book.admin.inc',
+      'function' => 'theme_book_admin_table',
     ),
     'book_all_books_block' => array(
       'render element' => 'book_menus',
diff --git a/core/modules/book/config/install/core.base_field_override.node.book.promote.yml b/core/modules/book/config/install/core.base_field_override.node.book.promote.yml
index 609d391..96ce2f6 100644
--- a/core/modules/book/config/install/core.base_field_override.node.book.promote.yml
+++ b/core/modules/book/config/install/core.base_field_override.node.book.promote.yml
@@ -15,6 +15,6 @@ translatable: true
 default_value:
   -
     value: 0
-default_value_callback: ''
+default_value_function: ''
 settings: {  }
 field_type: boolean
diff --git a/core/modules/datetime/src/Plugin/Field/FieldType/DateTimeFieldItemList.php b/core/modules/datetime/src/Plugin/Field/FieldType/DateTimeFieldItemList.php
index b2f2c11..aa03882 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldType/DateTimeFieldItemList.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldType/DateTimeFieldItemList.php
@@ -32,7 +32,7 @@ class DateTimeFieldItemList extends FieldItemList {
    * {@inheritdoc}
    */
   public function defaultValuesForm(array &$form, FormStateInterface $form_state) {
-    if (empty($this->getFieldDefinition()->default_value_callback)) {
+    if (empty($this->getFieldDefinition()->default_value_function)) {
       $default_value = $this->getFieldDefinition()->default_value;
 
       $element = array(
diff --git a/core/modules/dblog/src/Controller/DbLogController.php b/core/modules/dblog/src/Controller/DbLogController.php
index a11fcb8..4e7b974 100644
--- a/core/modules/dblog/src/Controller/DbLogController.php
+++ b/core/modules/dblog/src/Controller/DbLogController.php
@@ -252,11 +252,11 @@ public function eventDetails($event_id) {
         ),
         array(
           array('data' => $this->t('Location'), 'header' => TRUE),
-          _l($dblog->location, $dblog->location),
+          l($dblog->location, $dblog->location),
         ),
         array(
           array('data' => $this->t('Referrer'), 'header' => TRUE),
-          _l($dblog->referer, $dblog->referer),
+          l($dblog->referer, $dblog->referer),
         ),
         array(
           array('data' => $this->t('Message'), 'header' => TRUE),
diff --git a/core/modules/field/src/Tests/FieldAttachStorageTest.php b/core/modules/field/src/Tests/FieldAttachStorageTest.php
index e6c578f..205dd20 100644
--- a/core/modules/field/src/Tests/FieldAttachStorageTest.php
+++ b/core/modules/field/src/Tests/FieldAttachStorageTest.php
@@ -194,7 +194,7 @@ function testFieldAttachSaveEmptyDataDefaultValue() {
     $this->createFieldWithStorage('', $entity_type);
 
     // Add a default value function.
-    $this->fieldTestData->field->default_value_callback = 'field_test_default_value';
+    $this->fieldTestData->field->default_value_function = 'field_test_default_value';
     $this->fieldTestData->field->save();
 
     // Verify that fields are populated with default values.
diff --git a/core/modules/field/tests/modules/field_test_config/config/install/field.field.entity_test.entity_test.field_test_import.yml b/core/modules/field/tests/modules/field_test_config/config/install/field.field.entity_test.entity_test.field_test_import.yml
index b205693..a9ef175 100644
--- a/core/modules/field/tests/modules/field_test_config/config/install/field.field.entity_test.entity_test.field_test_import.yml
+++ b/core/modules/field/tests/modules/field_test_config/config/install/field.field.entity_test.entity_test.field_test_import.yml
@@ -7,7 +7,7 @@ label: 'Test import field'
 description: ''
 required: false
 default_value: {  }
-default_value_callback: ''
+default_value_function: ''
 settings: { }
 field_type: text
 dependencies:
diff --git a/core/modules/field/tests/modules/field_test_config/config/install/field.field.entity_test.entity_test.field_test_import_2.yml b/core/modules/field/tests/modules/field_test_config/config/install/field.field.entity_test.entity_test.field_test_import_2.yml
index ce26663..6c359e2 100644
--- a/core/modules/field/tests/modules/field_test_config/config/install/field.field.entity_test.entity_test.field_test_import_2.yml
+++ b/core/modules/field/tests/modules/field_test_config/config/install/field.field.entity_test.entity_test.field_test_import_2.yml
@@ -7,7 +7,7 @@ label: 'Test import field 2 on entity_test bundle'
 description: ''
 required: false
 default_value: {  }
-default_value_callback: ''
+default_value_function: ''
 settings: { }
 field_type: text
 dependencies:
diff --git a/core/modules/field/tests/modules/field_test_config/config/install/field.field.entity_test.test_bundle.field_test_import_2.yml b/core/modules/field/tests/modules/field_test_config/config/install/field.field.entity_test.test_bundle.field_test_import_2.yml
index 37adede..7d63acb 100644
--- a/core/modules/field/tests/modules/field_test_config/config/install/field.field.entity_test.test_bundle.field_test_import_2.yml
+++ b/core/modules/field/tests/modules/field_test_config/config/install/field.field.entity_test.test_bundle.field_test_import_2.yml
@@ -7,7 +7,7 @@ label: 'Test import field 2 on test bundle'
 description: ''
 required: false
 default_value: {  }
-default_value_callback: ''
+default_value_function: ''
 settings: { }
 field_type: text
 dependencies:
diff --git a/core/modules/field/tests/modules/field_test_config/staging/field.field.entity_test.entity_test.field_test_import_staging.yml b/core/modules/field/tests/modules/field_test_config/staging/field.field.entity_test.entity_test.field_test_import_staging.yml
index fe28921..9a088dd 100644
--- a/core/modules/field/tests/modules/field_test_config/staging/field.field.entity_test.entity_test.field_test_import_staging.yml
+++ b/core/modules/field/tests/modules/field_test_config/staging/field.field.entity_test.entity_test.field_test_import_staging.yml
@@ -8,7 +8,7 @@ label: 'Import from staging'
 description: ''
 required: '0'
 default_value: {  }
-default_value_callback: ''
+default_value_function: ''
 settings: { }
 field_type: text
 dependencies:
diff --git a/core/modules/field/tests/modules/field_test_config/staging/field.field.entity_test.test_bundle.field_test_import_staging_2.yml b/core/modules/field/tests/modules/field_test_config/staging/field.field.entity_test.test_bundle.field_test_import_staging_2.yml
index d1db2b2..cc8ccd4 100644
--- a/core/modules/field/tests/modules/field_test_config/staging/field.field.entity_test.test_bundle.field_test_import_staging_2.yml
+++ b/core/modules/field/tests/modules/field_test_config/staging/field.field.entity_test.test_bundle.field_test_import_staging_2.yml
@@ -8,7 +8,7 @@ label: 'Test import field 2 on test bundle'
 description: ''
 required: '0'
 default_value: {  }
-default_value_callback: ''
+default_value_function: ''
 settings: { }
 field_type: text
 dependencies:
diff --git a/core/modules/field/tests/modules/field_test_config/staging/field.field.entity_test.test_bundle_2.field_test_import_staging_2.yml b/core/modules/field/tests/modules/field_test_config/staging/field.field.entity_test.test_bundle_2.field_test_import_staging_2.yml
index 07953c9..f58572a 100644
--- a/core/modules/field/tests/modules/field_test_config/staging/field.field.entity_test.test_bundle_2.field_test_import_staging_2.yml
+++ b/core/modules/field/tests/modules/field_test_config/staging/field.field.entity_test.test_bundle_2.field_test_import_staging_2.yml
@@ -8,7 +8,7 @@ label: 'Test import field 2 on test bundle 2'
 description: ''
 required: '0'
 default_value: {  }
-default_value_callback: ''
+default_value_function: ''
 settings: { }
 field_type: text
 dependencies:
diff --git a/core/modules/field/tests/src/Unit/FieldConfigEntityUnitTest.php b/core/modules/field/tests/src/Unit/FieldConfigEntityUnitTest.php
index eb516d7..15e3d65 100644
--- a/core/modules/field/tests/src/Unit/FieldConfigEntityUnitTest.php
+++ b/core/modules/field/tests/src/Unit/FieldConfigEntityUnitTest.php
@@ -159,7 +159,7 @@ public function testToArray() {
       'description' => '',
       'required' => FALSE,
       'default_value' => array(),
-      'default_value_callback' => '',
+      'default_value_function' => '',
       'settings' => array(),
       'dependencies' => array(),
       'field_type' => 'test_field',
diff --git a/core/modules/field_ui/field_ui.module b/core/modules/field_ui/field_ui.module
index 5bce9dd..5721172 100644
--- a/core/modules/field_ui/field_ui.module
+++ b/core/modules/field_ui/field_ui.module
@@ -66,6 +66,7 @@ function field_ui_theme() {
   return array(
     'field_ui_table' => array(
       'render element' => 'elements',
+      'function' => 'theme_field_ui_table',
     ),
   );
 }
diff --git a/core/modules/field_ui/src/FieldUI.php b/core/modules/field_ui/src/FieldUI.php
index 7edb1c6..77ec651 100644
--- a/core/modules/field_ui/src/FieldUI.php
+++ b/core/modules/field_ui/src/FieldUI.php
@@ -51,15 +51,15 @@ public static function getNextDestination(array $destinations) {
       $next_destination += array(
         'route_parameters' => array(),
       );
-      $next_destination = Url::fromRoute($next_destination['route_name'], $next_destination['route_parameters'], $next_destination['options']);
+      $next_destination = new Url($next_destination['route_name'], $next_destination['route_parameters'], $next_destination['options']);
     }
     else {
       $options = UrlHelper::parse($next_destination);
       if ($destinations) {
         $options['query']['destinations'] = $destinations;
       }
-      // Redirect to any given path within the same domain.
-      $next_destination = Url::fromUri('base://' . $options['path']);
+      $next_destination = Url::createFromPath($options['path']);
+      $next_destination->setOptions($options);
     }
     return $next_destination;
   }
diff --git a/core/modules/file/file.module b/core/modules/file/file.module
index 55f99ac..a516836 100644
--- a/core/modules/file/file.module
+++ b/core/modules/file/file.module
@@ -1589,7 +1589,7 @@ function template_preprocess_file_link(&$variables) {
     $options['attributes']['title'] = String::checkPlain($file_entity->getFilename());
   }
 
-  $variables['link'] = _l($link_text, $url, $options);
+  $variables['link'] = l($link_text, $url, $options);
   $variables['attributes'] = array('class' => array('file'));
 }
 
diff --git a/core/modules/file/src/Tests/DownloadTest.php b/core/modules/file/src/Tests/DownloadTest.php
index ac81651..f99f327 100644
--- a/core/modules/file/src/Tests/DownloadTest.php
+++ b/core/modules/file/src/Tests/DownloadTest.php
@@ -112,8 +112,8 @@ function testFileCreateUrl() {
       '%C3%A9%C3%B8%C3%AF%D0%B2%CE%B2%E4%B8%AD%E5%9C%8B%E6%9B%B8%DB%9E';
 
     // Public files should not be served by Drupal, so their URLs should not be
-    // generated by _url(), whereas private files should be served by Drupal, so
-    // their URLs should be generated by _url(). The difference is most apparent
+    // generated by url(), whereas private files should be served by Drupal, so
+    // their URLs should be generated by url(). The difference is most apparent
     // when $script_path is not empty (i.e., when not using clean URLs).
     $clean_url_settings = array(
       'clean' => '',
diff --git a/core/modules/filter/src/Tests/FilterDefaultConfigTest.php b/core/modules/filter/src/Tests/FilterDefaultConfigTest.php
index 5af4758..79a1160 100644
--- a/core/modules/filter/src/Tests/FilterDefaultConfigTest.php
+++ b/core/modules/filter/src/Tests/FilterDefaultConfigTest.php
@@ -21,7 +21,7 @@ class FilterDefaultConfigTest extends DrupalUnitTestBase {
   protected function setUp() {
     parent::setUp();
 
-    // Drupal\filter\FilterPermissions::permissions() calls into _url() to output
+    // Drupal\filter\FilterPermissions::permissions() calls into url() to output
     // a link in the description.
     $this->installSchema('system', 'url_alias');
 
diff --git a/core/modules/forum/config/install/core.base_field_override.node.forum.promote.yml b/core/modules/forum/config/install/core.base_field_override.node.forum.promote.yml
index 3f20b64..42c7cce 100644
--- a/core/modules/forum/config/install/core.base_field_override.node.forum.promote.yml
+++ b/core/modules/forum/config/install/core.base_field_override.node.forum.promote.yml
@@ -15,6 +15,6 @@ translatable: true
 default_value:
   -
     value: 0
-default_value_callback: ''
+default_value_function: ''
 settings: {  }
 field_type: boolean
diff --git a/core/modules/forum/config/install/core.base_field_override.node.forum.title.yml b/core/modules/forum/config/install/core.base_field_override.node.forum.title.yml
index c956f34..cd1f9d3 100644
--- a/core/modules/forum/config/install/core.base_field_override.node.forum.title.yml
+++ b/core/modules/forum/config/install/core.base_field_override.node.forum.title.yml
@@ -13,6 +13,6 @@ description: 'The title of this node, always treated as non-markup plain text.'
 required: true
 translatable: true
 default_value: {  }
-default_value_callback: ''
+default_value_function: ''
 settings: {  }
 field_type: string
diff --git a/core/modules/forum/config/install/field.field.taxonomy_term.forums.forum_container.yml b/core/modules/forum/config/install/field.field.taxonomy_term.forums.forum_container.yml
index 8056915..b1c47ea 100644
--- a/core/modules/forum/config/install/field.field.taxonomy_term.forums.forum_container.yml
+++ b/core/modules/forum/config/install/field.field.taxonomy_term.forums.forum_container.yml
@@ -10,7 +10,7 @@ required: true
 default_value:
   -
     value: 0
-default_value_callback: ''
+default_value_function: ''
 settings: {  }
 field_type: boolean
 dependencies:
diff --git a/core/modules/hal/src/Tests/DenormalizeTest.php b/core/modules/hal/src/Tests/DenormalizeTest.php
index 8b5711c..761b804 100644
--- a/core/modules/hal/src/Tests/DenormalizeTest.php
+++ b/core/modules/hal/src/Tests/DenormalizeTest.php
@@ -24,7 +24,7 @@ public function testTypeHandling() {
     $data_with_valid_type = array(
       '_links' => array(
         'type' => array(
-          'href' => _url('rest/type/entity_test/entity_test', array('absolute' => TRUE)),
+          'href' => url('rest/type/entity_test/entity_test', array('absolute' => TRUE)),
         ),
       ),
     );
@@ -36,10 +36,10 @@ public function testTypeHandling() {
       '_links' => array(
         'type' => array(
           array(
-            'href' => _url('rest/types/foo', array('absolute' => TRUE)),
+            'href' => url('rest/types/foo', array('absolute' => TRUE)),
           ),
           array(
-            'href' => _url('rest/type/entity_test/entity_test', array('absolute' => TRUE)),
+            'href' => url('rest/type/entity_test/entity_test', array('absolute' => TRUE)),
           ),
         ),
       ),
@@ -51,7 +51,7 @@ public function testTypeHandling() {
     $data_with_invalid_type = array(
       '_links' => array(
         'type' => array(
-          'href' => _url('rest/types/foo', array('absolute' => TRUE)),
+          'href' => url('rest/types/foo', array('absolute' => TRUE)),
         ),
       ),
     );
@@ -84,7 +84,7 @@ public function testMarkFieldForDeletion() {
     $no_field_data = array(
       '_links' => array(
         'type' => array(
-          'href' => _url('rest/type/entity_test/entity_test', array('absolute' => TRUE)),
+          'href' => url('rest/type/entity_test/entity_test', array('absolute' => TRUE)),
         ),
       ),
     );
@@ -94,7 +94,7 @@ public function testMarkFieldForDeletion() {
     $empty_field_data = array(
       '_links' => array(
         'type' => array(
-          'href' => _url('rest/type/entity_test/entity_test', array('absolute' => TRUE)),
+          'href' => url('rest/type/entity_test/entity_test', array('absolute' => TRUE)),
         ),
       ),
       'field_test_text' => array(),
@@ -112,7 +112,7 @@ public function testBasicFieldDenormalization() {
     $data = array(
       '_links' => array(
         'type' => array(
-          'href' => _url('rest/type/entity_test/entity_test', array('absolute' => TRUE)),
+          'href' => url('rest/type/entity_test/entity_test', array('absolute' => TRUE)),
         ),
       ),
       'uuid' => array(
@@ -182,7 +182,7 @@ public function testPatchDenormailzation() {
     $data = array(
       '_links' => array(
         'type' => array(
-          'href' => _url('rest/type/entity_test/entity_test', array('absolute' => TRUE)),
+          'href' => url('rest/type/entity_test/entity_test', array('absolute' => TRUE)),
         ),
       ),
       'field_test_text' => array(
diff --git a/core/modules/hal/src/Tests/NormalizeTest.php b/core/modules/hal/src/Tests/NormalizeTest.php
index ee40c25..00d6687 100644
--- a/core/modules/hal/src/Tests/NormalizeTest.php
+++ b/core/modules/hal/src/Tests/NormalizeTest.php
@@ -59,8 +59,8 @@ public function testNormalize() {
     $entity->getTranslation('en')->set('field_test_entity_reference', array(0 => $translation_values['field_test_entity_reference']));
     $entity->save();
 
-    $type_uri = _url('rest/type/entity_test/entity_test', array('absolute' => TRUE));
-    $relation_uri = _url('rest/relation/entity_test/entity_test/field_test_entity_reference', array('absolute' => TRUE));
+    $type_uri = url('rest/type/entity_test/entity_test', array('absolute' => TRUE));
+    $relation_uri = url('rest/relation/entity_test/entity_test/field_test_entity_reference', array('absolute' => TRUE));
 
     $expected_array = array(
       '_links' => array(
diff --git a/core/modules/image/image.field.inc b/core/modules/image/image.field.inc
index 4668e26..93ac36b 100644
--- a/core/modules/image/image.field.inc
+++ b/core/modules/image/image.field.inc
@@ -86,6 +86,6 @@ function template_preprocess_image_formatter(&$variables) {
   if (isset($variables['path']['path'])) {
     $path = $variables['path']['path'];
     $options = isset($variables['path']['options']) ? $variables['path']['options'] : array();
-    $variables['url'] = _url($path, $options);
+    $variables['url'] = url($path, $options);
   }
 }
diff --git a/core/modules/image/src/Entity/ImageStyle.php b/core/modules/image/src/Entity/ImageStyle.php
index 752dc1e..0579dbc 100644
--- a/core/modules/image/src/Entity/ImageStyle.php
+++ b/core/modules/image/src/Entity/ImageStyle.php
@@ -216,12 +216,12 @@ public function buildUrl($path, $clean_urls = NULL) {
     }
 
     // If not using clean URLs, the image derivative callback is only available
-    // with the script path. If the file does not exist, use _url() to ensure
+    // with the script path. If the file does not exist, use url() to ensure
     // that it is included. Once the file exists it's fine to fall back to the
     // actual file path, this avoids bootstrapping PHP once the files are built.
     if ($clean_urls === FALSE && file_uri_scheme($uri) == 'public' && !file_exists($uri)) {
       $directory_path = file_stream_wrapper_get_instance_by_uri($uri)->getDirectoryPath();
-      return _url($directory_path . '/' . file_uri_target($uri), array('absolute' => TRUE, 'query' => $token_query));
+      return url($directory_path . '/' . file_uri_target($uri), array('absolute' => TRUE, 'query' => $token_query));
     }
 
     $file_url = file_create_url($uri);
diff --git a/core/modules/language/language.module b/core/modules/language/language.module
index 40b9bfa..7fa87b7 100644
--- a/core/modules/language/language.module
+++ b/core/modules/language/language.module
@@ -100,10 +100,12 @@ function language_theme() {
     'language_negotiation_configure_browser_form_table' => array(
       'render element' => 'form',
       'file' => 'language.admin.inc',
+      'function' => 'theme_language_negotiation_configure_browser_form_table',
     ),
     'language_content_settings_table' => array(
       'render element' => 'element',
       'file' => 'language.admin.inc',
+      'function' => 'theme_language_content_settings_table',
     ),
   );
 }
diff --git a/core/modules/language/src/LanguageNegotiatorInterface.php b/core/modules/language/src/LanguageNegotiatorInterface.php
index fa46958..c5991c2 100644
--- a/core/modules/language/src/LanguageNegotiatorInterface.php
+++ b/core/modules/language/src/LanguageNegotiatorInterface.php
@@ -25,7 +25,7 @@
  * - Content language: The language used to present content that is available
  *   in more than one language.
  * - URL language: The language associated with URLs. When generating a URL,
- *   this value will be used by _url() as a default if no explicit preference is
+ *   this value will be used by url() as a default if no explicit preference is
  *   provided.
  * Modules can define additional language types through
  * hook_language_types_info(), and alter existing language type definitions
diff --git a/core/modules/language/src/Tests/LanguageSwitchingTest.php b/core/modules/language/src/Tests/LanguageSwitchingTest.php
index dfd8d2e..9d8f7f9 100644
--- a/core/modules/language/src/Tests/LanguageSwitchingTest.php
+++ b/core/modules/language/src/Tests/LanguageSwitchingTest.php
@@ -185,7 +185,7 @@ protected function doTestLanguageLinkActiveClassAuthenticated() {
     $function_name = '#type link';
     $path = 'language_test/type-link-active-class';
 
-    // Test links generated by _l() on an English page.
+    // Test links generated by l() on an English page.
     $current_language = 'English';
     $this->drupalGet($path);
 
@@ -210,7 +210,7 @@ protected function doTestLanguageLinkActiveClassAuthenticated() {
     $this->assertIdentical($settings['path']['isFront'], FALSE, 'drupalSettings.path.isFront is set correctly to allow drupal.active-link to mark the correct links as active.');
     $this->assertIdentical($settings['path']['currentLanguage'], 'en', 'drupalSettings.path.currentLanguage is set correctly to allow drupal.active-link to mark the correct links as active.');
 
-    // Test links generated by _l() on a French page.
+    // Test links generated by l() on a French page.
     $current_language = 'French';
     $this->drupalGet('fr/language_test/type-link-active-class');
 
@@ -246,7 +246,7 @@ protected function doTestLanguageLinkActiveClassAnonymous() {
 
     $this->drupalLogout();
 
-    // Test links generated by _l() on an English page.
+    // Test links generated by l() on an English page.
     $current_language = 'English';
     $this->drupalGet('language_test/type-link-active-class');
 
@@ -265,7 +265,7 @@ protected function doTestLanguageLinkActiveClassAnonymous() {
     $links = $this->xpath('//a[@id = :id and not(contains(@class, :class))]', array(':id' => 'fr_link', ':class' => 'active'));
     $this->assertTrue(isset($links[0]), t('A link generated by :function to the current :language page with langcode :langcode is NOT marked active.', array(':function' => $function_name, ':language' => $current_language, ':langcode' => $langcode)));
 
-    // Test links generated by _l() on a French page.
+    // Test links generated by l() on a French page.
     $current_language = 'French';
     $this->drupalGet('fr/language_test/type-link-active-class');
 
diff --git a/core/modules/language/src/Tests/LanguageUILanguageNegotiationTest.php b/core/modules/language/src/Tests/LanguageUILanguageNegotiationTest.php
index b1d40c0..4753539 100644
--- a/core/modules/language/src/Tests/LanguageUILanguageNegotiationTest.php
+++ b/core/modules/language/src/Tests/LanguageUILanguageNegotiationTest.php
@@ -388,7 +388,7 @@ function testUrlLanguageFallback() {
   }
 
   /**
-   * Tests _url() when separate domains are used for multiple languages.
+   * Tests url() when separate domains are used for multiple languages.
    */
   function testLanguageDomain() {
     // Add the Italian language.
@@ -417,26 +417,26 @@ function testLanguageDomain() {
     // Test URL in another language: http://it.example.com/admin.
     // Base path gives problems on the testbot, so $correct_link is hard-coded.
     // @see UrlAlterFunctionalTest::assertUrlOutboundAlter (path.test).
-    $italian_url = _url('admin', array('language' => $languages['it'], 'script' => ''));
+    $italian_url = url('admin', array('language' => $languages['it'], 'script' => ''));
     $url_scheme = \Drupal::request()->isSecure() ? 'https://' : 'http://';
     $correct_link = $url_scheme . $link;
-    $this->assertEqual($italian_url, $correct_link, format_string('The _url() function returns the right URL (@url) in accordance with the chosen language', array('@url' => $italian_url)));
+    $this->assertEqual($italian_url, $correct_link, format_string('The url() function returns the right URL (@url) in accordance with the chosen language', array('@url' => $italian_url)));
 
     // Test HTTPS via options.
     $this->settingsSet('mixed_mode_sessions', TRUE);
     $this->rebuildContainer();
 
-    $italian_url = _url('admin', array('https' => TRUE, 'language' => $languages['it'], 'script' => ''));
+    $italian_url = url('admin', array('https' => TRUE, 'language' => $languages['it'], 'script' => ''));
     $correct_link = 'https://' . $link;
-    $this->assertTrue($italian_url == $correct_link, format_string('The _url() function returns the right HTTPS URL (via options) (@url) in accordance with the chosen language', array('@url' => $italian_url)));
+    $this->assertTrue($italian_url == $correct_link, format_string('The url() function returns the right HTTPS URL (via options) (@url) in accordance with the chosen language', array('@url' => $italian_url)));
     $this->settingsSet('mixed_mode_sessions', FALSE);
 
     // Test HTTPS via current URL scheme.
     $request = Request::create('', 'GET', array(), array(), array(), array('HTTPS' => 'on'));
     $this->container->get('request_stack')->push($request);
     $generator = $this->container->get('url_generator');
-    $italian_url = _url('admin', array('language' => $languages['it'], 'script' => ''));
+    $italian_url = url('admin', array('language' => $languages['it'], 'script' => ''));
     $correct_link = 'https://' . $link;
-    $this->assertTrue($italian_url == $correct_link, format_string('The _url() function returns the right URL (via current URL scheme) (@url) in accordance with the chosen language', array('@url' => $italian_url)));
+    $this->assertTrue($italian_url == $correct_link, format_string('The url() function returns the right URL (via current URL scheme) (@url) in accordance with the chosen language', array('@url' => $italian_url)));
   }
 }
diff --git a/core/modules/language/src/Tests/LanguageUrlRewritingTest.php b/core/modules/language/src/Tests/LanguageUrlRewritingTest.php
index ca3d935..73b54cd 100644
--- a/core/modules/language/src/Tests/LanguageUrlRewritingTest.php
+++ b/core/modules/language/src/Tests/LanguageUrlRewritingTest.php
@@ -126,7 +126,7 @@ function testDomainNameNegotiationPort() {
 
     // Create an absolute French link.
     $language = \Drupal::languageManager()->getLanguage('fr');
-    $url = _url('', array(
+    $url = url('', array(
       'absolute' => TRUE,
       'language' => $language,
     ));
@@ -135,8 +135,8 @@ function testDomainNameNegotiationPort() {
 
     $this->assertEqual($url, $expected, 'The right port is used.');
 
-    // If we set the port explicitly in _url(), it should not be overriden.
-    $url = _url('', array(
+    // If we set the port explicitly in url(), it should not be overriden.
+    $url = url('', array(
       'absolute' => TRUE,
       'language' => $language,
       'base_url' => $request->getBaseUrl() . ':90',
diff --git a/core/modules/language/tests/language_test/src/Controller/LanguageTestController.php b/core/modules/language/tests/language_test/src/Controller/LanguageTestController.php
index 2935b7d..8095270 100644
--- a/core/modules/language/tests/language_test/src/Controller/LanguageTestController.php
+++ b/core/modules/language/tests/language_test/src/Controller/LanguageTestController.php
@@ -53,7 +53,7 @@ public static function create(ContainerInterface $container) {
   /**
    * Returns links to the current page with different langcodes.
    *
-   * Using #type 'link' causes these links to be rendered with _l().
+   * Using #type 'link' causes these links to be rendered with l().
    */
   public function typeLinkActiveClass() {
     // We assume that 'en' and 'fr' have been configured.
diff --git a/core/modules/link/link.module b/core/modules/link/link.module
index 9207818..58d3059 100644
--- a/core/modules/link/link.module
+++ b/core/modules/link/link.module
@@ -69,6 +69,6 @@ function template_preprocess_link_formatter_link_separate(&$variables) {
     $variables['link'] = \Drupal::l($variables['url_title'], $variables['url']);
   }
   else {
-    $variables['link'] = _l($variables['url_title'], $variables['url']->getUri(), $variables['url']->getOptions());
+    $variables['link'] = l($variables['url_title'], $variables['url']->getPath(), $variables['url']->getOptions());
   }
 }
diff --git a/core/modules/link/src/Plugin/Field/FieldFormatter/LinkFormatter.php b/core/modules/link/src/Plugin/Field/FieldFormatter/LinkFormatter.php
index ca753f8..05caf97 100644
--- a/core/modules/link/src/Plugin/Field/FieldFormatter/LinkFormatter.php
+++ b/core/modules/link/src/Plugin/Field/FieldFormatter/LinkFormatter.php
@@ -13,7 +13,6 @@
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Url;
 use Drupal\link\LinkItemInterface;
-use Symfony\Component\HttpFoundation\Request;
 
 /**
  * Plugin implementation of the 'link' formatter.
@@ -136,7 +135,7 @@ public function viewElements(FieldItemListInterface $items) {
       // If the title field value is available, use it for the link text.
       if (empty($settings['url_only']) && !empty($item->title)) {
         // Unsanitized token replacement here because $options['html'] is FALSE
-        // by default in _l().
+        // by default in l().
         $link_title = \Drupal::token()->replace($item->title, array($entity->getEntityTypeId() => $entity), array('sanitize' => FALSE, 'clear' => TRUE));
       }
 
@@ -164,7 +163,7 @@ public function viewElements(FieldItemListInterface $items) {
           '#options' => $url->getOptions(),
         );
         if ($url->isExternal()) {
-          $element[$delta]['#href'] = $url->getUri();
+          $element[$delta]['#href'] = $url->getPath();
         }
         else {
           $element[$delta]['#route_name'] = $url->getRouteName();
@@ -207,10 +206,11 @@ protected function buildUrl(LinkItemInterface $item) {
     }
 
     if ($item->isExternal()) {
-      $url = Url::fromUri($item->url, $options);
+      $url = Url::createFromPath($item->url);
+      $url->setOptions($options);
     }
     else {
-      $url = Url::fromRoute($item->route_name, (array) $item->route_parameters, (array) $options);
+      $url = new Url($item->route_name, (array) $item->route_parameters, (array) $options);
     }
 
     return $url;
diff --git a/core/modules/link/src/Plugin/Field/FieldFormatter/LinkSeparateFormatter.php b/core/modules/link/src/Plugin/Field/FieldFormatter/LinkSeparateFormatter.php
index a32e611..40daa44 100644
--- a/core/modules/link/src/Plugin/Field/FieldFormatter/LinkSeparateFormatter.php
+++ b/core/modules/link/src/Plugin/Field/FieldFormatter/LinkSeparateFormatter.php
@@ -54,7 +54,7 @@ public function viewElements(FieldItemListInterface $items) {
       // If the link text field value is available, use it for the text.
       if (empty($settings['url_only']) && !empty($item->title)) {
         // Unsanitized token replacement here because $options['html'] is FALSE
-        // by default in _l().
+        // by default in l().
         $link_title = \Drupal::token()->replace($item->title, array($entity->getEntityTypeId() => $entity), array('sanitize' => FALSE, 'clear' => TRUE));
       }
 
diff --git a/core/modules/link/src/Tests/LinkFieldTest.php b/core/modules/link/src/Tests/LinkFieldTest.php
index 4bd30cd..a508c0c 100644
--- a/core/modules/link/src/Tests/LinkFieldTest.php
+++ b/core/modules/link/src/Tests/LinkFieldTest.php
@@ -275,7 +275,7 @@ function testLinkTitle() {
     $this->assertText(t('entity_test @id has been created.', array('@id' => $id)));
 
     $this->renderTestEntity($id);
-    $expected_link = _l($value, $value);
+    $expected_link = l($value, $value);
     $this->assertRaw($expected_link);
 
     // Verify that a link with text is rendered using the link text.
@@ -287,7 +287,7 @@ function testLinkTitle() {
     $this->assertText(t('entity_test @id has been updated.', array('@id' => $id)));
 
     $this->renderTestEntity($id);
-    $expected_link = _l($title, $value);
+    $expected_link = l($title, $value);
     $this->assertRaw($expected_link);
   }
 
@@ -354,7 +354,7 @@ function testLinkFormatter() {
     // Verify that the link is output according to the formatter settings.
     // Not using generatePermutations(), since that leads to 32 cases, which
     // would not test actual link field formatter functionality but rather
-    // _l() and options/attributes. Only 'url_plain' has a dependency on
+    // l() and options/attributes. Only 'url_plain' has a dependency on
     // 'url_only', so we have a total of ~10 cases.
     $options = array(
       'trim_length' => array(NULL, 6),
diff --git a/core/modules/locale/locale.module b/core/modules/locale/locale.module
index 40934de..7da921f 100644
--- a/core/modules/locale/locale.module
+++ b/core/modules/locale/locale.module
@@ -182,6 +182,7 @@ function locale_theme() {
     'locale_translate_edit_form_strings' => array(
       'render element' => 'form',
       'file' => 'locale.pages.inc',
+      'function' => 'theme_locale_translate_edit_form_strings',
     ),
     'locale_translation_last_check' => array(
       'variables' => array('last' => NULL),
diff --git a/core/modules/locale/src/Tests/LocaleUpdateBase.php b/core/modules/locale/src/Tests/LocaleUpdateBase.php
index 5e9b81e..772ac2a 100644
--- a/core/modules/locale/src/Tests/LocaleUpdateBase.php
+++ b/core/modules/locale/src/Tests/LocaleUpdateBase.php
@@ -53,7 +53,7 @@ protected function setUp() {
     // Update module should not go out to d.o to check for updates. We override
     // the url to the default update_test xml path. But without providing
     // a mock xml file, no update data will be found.
-    \Drupal::config('update.settings')->set('fetch.url', _url('update-test', array('absolute' => TRUE)))->save();
+    \Drupal::config('update.settings')->set('fetch.url', url('update-test', array('absolute' => TRUE)))->save();
 
     // Setup timestamps to identify old and new translation sources.
     $this->timestampOld = REQUEST_TIME - 300;
diff --git a/core/modules/menu_link_content/src/Entity/MenuLinkContent.php b/core/modules/menu_link_content/src/Entity/MenuLinkContent.php
index ec719c2..55f3489 100644
--- a/core/modules/menu_link_content/src/Entity/MenuLinkContent.php
+++ b/core/modules/menu_link_content/src/Entity/MenuLinkContent.php
@@ -107,7 +107,7 @@ public function getUrlObject() {
     else {
       $path = $this->getUrl();
       if (isset($path)) {
-        $url = Url::fromUri($path);
+        $url = Url::createFromPath($path);
       }
       else {
         $url = new Url('<front>');
@@ -334,7 +334,7 @@ public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
 
     $fields['options'] = BaseFieldDefinition::create('map')
       ->setLabel(t('Options'))
-      ->setDescription(t('A serialized array of options to be passed to the _url() or _l() function, such as a query string or HTML attributes.'))
+      ->setDescription(t('A serialized array of options to be passed to the url() or l() function, such as a query string or HTML attributes.'))
       ->setSetting('default_value', array());
 
     $fields['external'] = BaseFieldDefinition::create('boolean')
diff --git a/core/modules/menu_link_content/src/Form/MenuLinkContentForm.php b/core/modules/menu_link_content/src/Form/MenuLinkContentForm.php
index 4fb93b2..2d37566 100644
--- a/core/modules/menu_link_content/src/Form/MenuLinkContentForm.php
+++ b/core/modules/menu_link_content/src/Form/MenuLinkContentForm.php
@@ -198,7 +198,7 @@ public function extractFormValues(array &$form, FormStateInterface $form_state)
 
     if ($extracted) {
       if ($extracted->isExternal()) {
-        $new_definition['url'] = $extracted->getUri();
+        $new_definition['url'] = $extracted->getPath();
       }
       else {
         $new_definition['route_name'] = $extracted->getRouteName();
diff --git a/core/modules/menu_ui/menu_ui.module b/core/modules/menu_ui/menu_ui.module
index 148203a..cc9eb79 100644
--- a/core/modules/menu_ui/menu_ui.module
+++ b/core/modules/menu_ui/menu_ui.module
@@ -78,6 +78,7 @@ function menu_ui_theme() {
     'menu_overview_form' => array(
       'file' => 'menu_ui.admin.inc',
       'render element' => 'form',
+      'function' => 'theme_menu_overview_form',
     ),
   );
 }
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_field_instance.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_field_instance.yml
index 978fb2c..1ef6a30 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_field_instance.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_field_instance.yml
@@ -36,7 +36,7 @@ process:
       - widget_settings
       - global_settings
 
-  default_value_callback: ''
+  default_value_function: ''
   default_value:
     plugin: d6_field_instance_defaults
     source:
diff --git a/core/modules/node/node.module b/core/modules/node/node.module
index 4e3bc46..6988f1e 100644
--- a/core/modules/node/node.module
+++ b/core/modules/node/node.module
@@ -141,6 +141,7 @@ function node_theme() {
     ),
     'node_search_admin' => array(
       'render element' => 'form',
+      'function' => 'theme_node_search_admin',
     ),
     'node_add_list' => array(
       'variables' => array('content' => NULL),
diff --git a/core/modules/node/src/Entity/Node.php b/core/modules/node/src/Entity/Node.php
index b5bb8f8..b01ae1e 100644
--- a/core/modules/node/src/Entity/Node.php
+++ b/core/modules/node/src/Entity/Node.php
@@ -376,7 +376,7 @@ public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
       ->setRevisionable(TRUE)
       ->setSetting('target_type', 'user')
       ->setSetting('handler', 'default')
-      ->setDefaultValueCallback('Drupal\node\Entity\Node::getCurrentUserId')
+      ->setDefaultValueCallback(array('Drupal\node\Entity\Node', 'getCurrentUserId'))
       ->setTranslatable(TRUE)
       ->setDisplayOptions('view', array(
         'label' => 'hidden',
diff --git a/core/modules/node/src/Tests/NodeFieldOverridesTest.php b/core/modules/node/src/Tests/NodeFieldOverridesTest.php
deleted file mode 100644
index b5d13b4..0000000
--- a/core/modules/node/src/Tests/NodeFieldOverridesTest.php
+++ /dev/null
@@ -1,69 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\node\Tests\NodeFieldOverridesTest.
- */
-
-namespace Drupal\node\Tests;
-
-use Drupal\Core\Field\Entity\BaseFieldOverride;
-use Drupal\node\Entity\Node;
-use Drupal\node\Entity\NodeType;
-use Drupal\system\Tests\Entity\EntityUnitTestBase;
-
-/**
- * Tests node field overrides.
- *
- * @group node
- */
-class NodeFieldOverridesTest extends EntityUnitTestBase {
-
-  /**
-   * Current logged in user.
-   *
-   * @var \Drupal\user\UserInterface
-   */
-  protected $user;
-
-  /**
-   * Modules to enable.
-   *
-   * @var array
-   */
-  public static $modules = array('user', 'system', 'field', 'node');
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function setUp() {
-    parent::setUp();
-    $this->installEntitySchema('node');
-    $this->installConfig(array('user'));
-    $this->user = $this->createUser();
-    \Drupal::service('current_user')->setAccount($this->user);
-  }
-
-  /**
-   * Tests that field overrides work as expected.
-   */
-  public function testFieldOverrides() {
-    if (!NodeType::load('ponies')) {
-      NodeType::create(['name' => 'Ponies', 'type' => 'ponies'])->save();
-    }
-    $override = BaseFieldOverride::loadByName('node', 'ponies', 'uid');
-    if ($override) {
-      $override->delete();
-    }
-    $uid_field = \Drupal::entityManager()->getBaseFieldDefinitions('node')['uid'];
-    $config = $uid_field->getConfig('ponies');
-    $config->save();
-    $this->assertEqual($config->get('default_value_callback'), 'Drupal\node\Entity\Node::getCurrentUserId');
-    /** @var \Drupal\node\NodeInterface $node */
-    $node = Node::create(['type' => 'ponies']);
-    $owner = $node->getOwner();
-    $this->assertTrue($owner instanceof \Drupal\user\UserInterface);
-    $this->assertEqual($owner->id(), $this->user->id());
-  }
-
-}
diff --git a/core/modules/node/src/Tests/NodeTranslationUITest.php b/core/modules/node/src/Tests/NodeTranslationUITest.php
index b5fd27a..13eced4 100644
--- a/core/modules/node/src/Tests/NodeTranslationUITest.php
+++ b/core/modules/node/src/Tests/NodeTranslationUITest.php
@@ -335,7 +335,7 @@ protected function doTestTranslations($path, array $values) {
   protected function doTestAlternateHreflangLinks($path) {
     $languages = $this->container->get('language_manager')->getLanguages();
     foreach ($this->langcodes as $langcode) {
-      $urls[$langcode] = _url($path, array('absolute' => TRUE, 'language' => $languages[$langcode]));
+      $urls[$langcode] = url($path, array('absolute' => TRUE, 'language' => $languages[$langcode]));
     }
     foreach ($this->langcodes as $langcode) {
       $this->drupalGet($path, array('language' => $languages[$langcode]));
diff --git a/core/modules/node/src/Tests/NodeViewTest.php b/core/modules/node/src/Tests/NodeViewTest.php
index 426fec1..03c0035 100644
--- a/core/modules/node/src/Tests/NodeViewTest.php
+++ b/core/modules/node/src/Tests/NodeViewTest.php
@@ -24,13 +24,13 @@ public function testHtmlHeadLinks() {
     $this->drupalGet($node->getSystemPath());
 
     $result = $this->xpath('//link[@rel = "version-history"]');
-    $this->assertEqual($result[0]['href'], _url("node/{$node->id()}/revisions"));
+    $this->assertEqual($result[0]['href'], url("node/{$node->id()}/revisions"));
 
     $result = $this->xpath('//link[@rel = "edit-form"]');
-    $this->assertEqual($result[0]['href'], _url("node/{$node->id()}/edit"));
+    $this->assertEqual($result[0]['href'], url("node/{$node->id()}/edit"));
 
     $result = $this->xpath('//link[@rel = "canonical"]');
-    $this->assertEqual($result[0]['href'], _url("node/{$node->id()}"));
+    $this->assertEqual($result[0]['href'], url("node/{$node->id()}"));
   }
 
 }
diff --git a/core/modules/path/src/Controller/PathController.php b/core/modules/path/src/Controller/PathController.php
index 96dd34b..6144b67 100644
--- a/core/modules/path/src/Controller/PathController.php
+++ b/core/modules/path/src/Controller/PathController.php
@@ -73,10 +73,10 @@ public function adminOverview($keys) {
     $destination = drupal_get_destination();
     foreach ($this->aliasStorage->getAliasesForAdminListing($header, $keys) as $data) {
       $row = array();
-      $row['data']['alias'] = _l(truncate_utf8($data->alias, 50, FALSE, TRUE), $data->source, array(
+      $row['data']['alias'] = l(truncate_utf8($data->alias, 50, FALSE, TRUE), $data->source, array(
         'attributes' => array('title' => $data->alias),
       ));
-      $row['data']['source'] = _l(truncate_utf8($data->source, 50, FALSE, TRUE), $data->source, array(
+      $row['data']['source'] = l(truncate_utf8($data->source, 50, FALSE, TRUE), $data->source, array(
         'alias' => TRUE,
         'attributes' => array('title' => $data->source),
       ));
diff --git a/core/modules/path/src/Form/PathFormBase.php b/core/modules/path/src/Form/PathFormBase.php
index ecb970c..8564156 100644
--- a/core/modules/path/src/Form/PathFormBase.php
+++ b/core/modules/path/src/Form/PathFormBase.php
@@ -95,7 +95,7 @@ public function buildForm(array $form, FormStateInterface $form_state, $pid = NU
       '#maxlength' => 255,
       '#size' => 45,
       '#description' => $this->t('Specify the existing path you wish to alias. For example: node/28, forum/1, taxonomy/term/1.'),
-      '#field_prefix' => _url(NULL, array('absolute' => TRUE)),
+      '#field_prefix' => url(NULL, array('absolute' => TRUE)),
       '#required' => TRUE,
     );
     $form['alias'] = array(
@@ -105,7 +105,7 @@ public function buildForm(array $form, FormStateInterface $form_state, $pid = NU
       '#maxlength' => 255,
       '#size' => 45,
       '#description' => $this->t('Specify an alternative path by which this data can be accessed. For example, type "about" when writing an about page. Use a relative path and don\'t add a trailing slash or the URL alias won\'t work.'),
-      '#field_prefix' => _url(NULL, array('absolute' => TRUE)),
+      '#field_prefix' => url(NULL, array('absolute' => TRUE)),
       '#required' => TRUE,
     );
 
diff --git a/core/modules/path/src/Tests/PathLanguageTest.php b/core/modules/path/src/Tests/PathLanguageTest.php
index 6f1beed..d6399a0 100644
--- a/core/modules/path/src/Tests/PathLanguageTest.php
+++ b/core/modules/path/src/Tests/PathLanguageTest.php
@@ -109,7 +109,7 @@ function testAliasTranslation() {
     $this->drupalGet('fr/' . $edit['path[0][alias]']);
     $this->assertText($french_node->body->value, 'Alias for French translation works.');
 
-    // Confirm that the alias is returned by _url(). Languages are cached on
+    // Confirm that the alias is returned by url(). Languages are cached on
     // many levels, and we need to clear those caches.
     $this->container->get('language_manager')->reset();
     $languages = $this->container->get('language_manager')->getLanguages();
diff --git a/core/modules/rdf/src/Tests/Field/LinkFieldRdfaTest.php b/core/modules/rdf/src/Tests/Field/LinkFieldRdfaTest.php
index 8478bae..8c23c07 100644
--- a/core/modules/rdf/src/Tests/Field/LinkFieldRdfaTest.php
+++ b/core/modules/rdf/src/Tests/Field/LinkFieldRdfaTest.php
@@ -75,8 +75,7 @@ public function testAllFormattersInternal() {
     // Set up test values.
     $this->testValue = 'admin';
     $this->entity = entity_create('entity_test', array());
-    $this->entity->{$this->fieldName}->route_name = 'system.admin';
-    $this->entity->{$this->fieldName}->url = 'admin';
+    $this->entity->{$this->fieldName}->url = $this->testValue;
 
     // Set up the expected result.
     // AssertFormatterRdfa looks for a full path.
@@ -95,8 +94,7 @@ public function testAllFormattersFront() {
     // Set up test values.
     $this->testValue = '<front>';
     $this->entity = entity_create('entity_test', array());
-    $this->entity->{$this->fieldName}->route_name = $this->testValue;
-    $this->entity->{$this->fieldName}->url = '<front>';
+    $this->entity->{$this->fieldName}->url = $this->testValue;
 
     // Set up the expected result.
     $expected_rdf = array(
diff --git a/core/modules/responsive_image/responsive_image.module b/core/modules/responsive_image/responsive_image.module
index 8a8df92..13f3b45 100644
--- a/core/modules/responsive_image/responsive_image.module
+++ b/core/modules/responsive_image/responsive_image.module
@@ -80,6 +80,7 @@ function responsive_image_theme() {
         'attributes' => array(),
         'mapping_id' => array(),
       ),
+      'function' => 'theme_responsive_image',
     ),
     'responsive_image_formatter' => array(
       'variables' => array(
@@ -88,6 +89,7 @@ function responsive_image_theme() {
         'image_style' => NULL,
         'mapping_id' => array(),
       ),
+      'function' => 'theme_responsive_image_formatter',
     ),
     'responsive_image_source' => array(
       'variables' => array(
@@ -96,6 +98,7 @@ function responsive_image_theme() {
         'dimensions' => NULL,
         'media' => NULL,
       ),
+      'function' => 'theme_responsive_image_source',
     ),
   );
 }
@@ -147,7 +150,7 @@ function theme_responsive_image_formatter($variables) {
     $path = $variables['path']['path'];
     $options = isset($variables['path']['options']) ? $variables['path']['options'] : array();
     $options['html'] = TRUE;
-    return _l($responsive_image, $path, $options);
+    return l($responsive_image, $path, $options);
   }
 
   return drupal_render($responsive_image);
diff --git a/core/modules/rest/src/LinkManager/RelationLinkManager.php b/core/modules/rest/src/LinkManager/RelationLinkManager.php
index f5ed9fb..04ed8ee 100644
--- a/core/modules/rest/src/LinkManager/RelationLinkManager.php
+++ b/core/modules/rest/src/LinkManager/RelationLinkManager.php
@@ -44,7 +44,7 @@ public function __construct(CacheBackendInterface $cache, EntityManagerInterface
    */
   public function getRelationUri($entity_type, $bundle, $field_name) {
     // @todo Make the base path configurable.
-    return _url("rest/relation/$entity_type/$bundle/$field_name", array('absolute' => TRUE));
+    return url("rest/relation/$entity_type/$bundle/$field_name", array('absolute' => TRUE));
   }
 
   /**
diff --git a/core/modules/rest/src/LinkManager/TypeLinkManager.php b/core/modules/rest/src/LinkManager/TypeLinkManager.php
index 6c37782..fb21a5f 100644
--- a/core/modules/rest/src/LinkManager/TypeLinkManager.php
+++ b/core/modules/rest/src/LinkManager/TypeLinkManager.php
@@ -42,7 +42,7 @@ public function __construct(CacheBackendInterface $cache) {
    */
   public function getTypeUri($entity_type, $bundle) {
     // @todo Make the base path configurable.
-    return _url("rest/type/$entity_type/$bundle", array('absolute' => TRUE));
+    return url("rest/type/$entity_type/$bundle", array('absolute' => TRUE));
   }
 
   /**
diff --git a/core/modules/rest/src/Plugin/rest/resource/EntityResource.php b/core/modules/rest/src/Plugin/rest/resource/EntityResource.php
index b565cea..c39b88f 100644
--- a/core/modules/rest/src/Plugin/rest/resource/EntityResource.php
+++ b/core/modules/rest/src/Plugin/rest/resource/EntityResource.php
@@ -96,7 +96,7 @@ public function post(EntityInterface $entity = NULL) {
       $entity->save();
       $this->logger->notice('Created entity %type with ID %id.', array('%type' => $entity->getEntityTypeId(), '%id' => $entity->id()));
 
-      $url = _url(strtr($this->pluginId, ':', '/') . '/' . $entity->id(), array('absolute' => TRUE));
+      $url = url(strtr($this->pluginId, ':', '/') . '/' . $entity->id(), array('absolute' => TRUE));
       // 201 Created responses have an empty body.
       return new ResourceResponse(NULL, 201, array('Location' => $url));
     }
diff --git a/core/modules/rest/src/Tests/AuthTest.php b/core/modules/rest/src/Tests/AuthTest.php
index 230b24c..257e7f1 100644
--- a/core/modules/rest/src/Tests/AuthTest.php
+++ b/core/modules/rest/src/Tests/AuthTest.php
@@ -87,7 +87,7 @@ protected function basicAuthGet($path, $username, $password) {
     $out = $this->curlExec(
       array(
         CURLOPT_HTTPGET => TRUE,
-        CURLOPT_URL => _url($path, array('absolute' => TRUE)),
+        CURLOPT_URL => url($path, array('absolute' => TRUE)),
         CURLOPT_NOBODY => FALSE,
         CURLOPT_HTTPAUTH => CURLAUTH_BASIC,
         CURLOPT_USERPWD => $username . ':' . $password,
diff --git a/core/modules/rest/src/Tests/CsrfTest.php b/core/modules/rest/src/Tests/CsrfTest.php
index 84bf71f..9099245 100644
--- a/core/modules/rest/src/Tests/CsrfTest.php
+++ b/core/modules/rest/src/Tests/CsrfTest.php
@@ -107,7 +107,7 @@ protected function getCurlOptions() {
       CURLOPT_HTTPGET => FALSE,
       CURLOPT_POST => TRUE,
       CURLOPT_POSTFIELDS => $this->serialized,
-      CURLOPT_URL => _url('entity/' . $this->testEntityType, array('absolute' => TRUE)),
+      CURLOPT_URL => url('entity/' . $this->testEntityType, array('absolute' => TRUE)),
       CURLOPT_NOBODY => FALSE,
       CURLOPT_HTTPHEADER => array(
         "Content-Type: {$this->defaultMimeType}",
diff --git a/core/modules/rest/src/Tests/NodeTest.php b/core/modules/rest/src/Tests/NodeTest.php
index 96619b7..4cd2bc9 100644
--- a/core/modules/rest/src/Tests/NodeTest.php
+++ b/core/modules/rest/src/Tests/NodeTest.php
@@ -68,7 +68,7 @@ public function testNodes() {
     $data = array(
       '_links' => array(
         'type' => array(
-          'href' => _url('rest/type/node/resttest', array('absolute' => TRUE)),
+          'href' => url('rest/type/node/resttest', array('absolute' => TRUE)),
         ),
       ),
       'title' => array(
diff --git a/core/modules/rest/src/Tests/RESTTestBase.php b/core/modules/rest/src/Tests/RESTTestBase.php
index 32fa9c3..a2e0ffe 100644
--- a/core/modules/rest/src/Tests/RESTTestBase.php
+++ b/core/modules/rest/src/Tests/RESTTestBase.php
@@ -86,7 +86,7 @@ protected function httpRequest($url, $method, $body = NULL, $mime_type = NULL) {
         $curl_options = array(
           CURLOPT_HTTPGET => TRUE,
           CURLOPT_CUSTOMREQUEST => 'GET',
-          CURLOPT_URL => _url($url, $options),
+          CURLOPT_URL => url($url, $options),
           CURLOPT_NOBODY => FALSE,
           CURLOPT_HTTPHEADER => array('Accept: ' . $mime_type),
         );
@@ -97,7 +97,7 @@ protected function httpRequest($url, $method, $body = NULL, $mime_type = NULL) {
           CURLOPT_HTTPGET => FALSE,
           CURLOPT_POST => TRUE,
           CURLOPT_POSTFIELDS => $body,
-          CURLOPT_URL => _url($url, array('absolute' => TRUE)),
+          CURLOPT_URL => url($url, array('absolute' => TRUE)),
           CURLOPT_NOBODY => FALSE,
           CURLOPT_HTTPHEADER => array(
             'Content-Type: ' . $mime_type,
@@ -111,7 +111,7 @@ protected function httpRequest($url, $method, $body = NULL, $mime_type = NULL) {
           CURLOPT_HTTPGET => FALSE,
           CURLOPT_CUSTOMREQUEST => 'PUT',
           CURLOPT_POSTFIELDS => $body,
-          CURLOPT_URL => _url($url, array('absolute' => TRUE)),
+          CURLOPT_URL => url($url, array('absolute' => TRUE)),
           CURLOPT_NOBODY => FALSE,
           CURLOPT_HTTPHEADER => array(
             'Content-Type: ' . $mime_type,
@@ -125,7 +125,7 @@ protected function httpRequest($url, $method, $body = NULL, $mime_type = NULL) {
           CURLOPT_HTTPGET => FALSE,
           CURLOPT_CUSTOMREQUEST => 'PATCH',
           CURLOPT_POSTFIELDS => $body,
-          CURLOPT_URL => _url($url, array('absolute' => TRUE)),
+          CURLOPT_URL => url($url, array('absolute' => TRUE)),
           CURLOPT_NOBODY => FALSE,
           CURLOPT_HTTPHEADER => array(
             'Content-Type: ' . $mime_type,
@@ -138,7 +138,7 @@ protected function httpRequest($url, $method, $body = NULL, $mime_type = NULL) {
         $curl_options = array(
           CURLOPT_HTTPGET => FALSE,
           CURLOPT_CUSTOMREQUEST => 'DELETE',
-          CURLOPT_URL => _url($url, array('absolute' => TRUE)),
+          CURLOPT_URL => url($url, array('absolute' => TRUE)),
           CURLOPT_NOBODY => FALSE,
           CURLOPT_HTTPHEADER => array('X-CSRF-Token: ' . $token),
         );
diff --git a/core/modules/search/src/Tests/SearchConfigSettingsFormTest.php b/core/modules/search/src/Tests/SearchConfigSettingsFormTest.php
index e7c98c6..7a145b6 100644
--- a/core/modules/search/src/Tests/SearchConfigSettingsFormTest.php
+++ b/core/modules/search/src/Tests/SearchConfigSettingsFormTest.php
@@ -269,8 +269,8 @@ public function testMultipleSearchPages() {
     // Ensure both search pages have their tabs displayed.
     $this->drupalGet('search');
     $elements = $this->xpath('//*[contains(@class, :class)]//a', array(':class' => 'tabs primary'));
-    $this->assertIdentical((string) $elements[0]['href'], _url('search/' . $first['path']));
-    $this->assertIdentical((string) $elements[1]['href'], _url('search/' . $second['path']));
+    $this->assertIdentical((string) $elements[0]['href'], url('search/' . $first['path']));
+    $this->assertIdentical((string) $elements[1]['href'], url('search/' . $second['path']));
 
     // Switch the weight of the search pages and check the order of the tabs.
     $edit = array(
@@ -280,8 +280,8 @@ public function testMultipleSearchPages() {
     $this->drupalPostForm('admin/config/search/pages', $edit, t('Save configuration'));
     $this->drupalGet('search');
     $elements = $this->xpath('//*[contains(@class, :class)]//a', array(':class' => 'tabs primary'));
-    $this->assertIdentical((string) $elements[0]['href'], _url('search/' . $second['path']));
-    $this->assertIdentical((string) $elements[1]['href'], _url('search/' . $first['path']));
+    $this->assertIdentical((string) $elements[0]['href'], url('search/' . $second['path']));
+    $this->assertIdentical((string) $elements[1]['href'], url('search/' . $first['path']));
 
     // Check the initial state of the search pages.
     $this->drupalGet('admin/config/search/pages');
diff --git a/core/modules/search/tests/modules/search_extra_type/src/Plugin/Search/SearchExtraTypeSearch.php b/core/modules/search/tests/modules/search_extra_type/src/Plugin/Search/SearchExtraTypeSearch.php
index d1855ad..b8f7c73 100644
--- a/core/modules/search/tests/modules/search_extra_type/src/Plugin/Search/SearchExtraTypeSearch.php
+++ b/core/modules/search/tests/modules/search_extra_type/src/Plugin/Search/SearchExtraTypeSearch.php
@@ -57,7 +57,7 @@ public function execute() {
     }
     return array(
       array(
-        'link' => _url('node'),
+        'link' => url('node'),
         'type' => 'Dummy result type',
         'title' => 'Dummy title',
         'snippet' => SafeMarkup::set("Dummy search snippet to display. Keywords: {$this->keywords}\n\nConditions: " . print_r($this->searchParameters, TRUE)),
diff --git a/core/modules/serialization/src/Tests/EntityResolverTest.php b/core/modules/serialization/src/Tests/EntityResolverTest.php
index 2bf4ed9..3cf8952 100644
--- a/core/modules/serialization/src/Tests/EntityResolverTest.php
+++ b/core/modules/serialization/src/Tests/EntityResolverTest.php
@@ -58,16 +58,16 @@ function testUuidEntityResolver() {
     $entity->set('field_test_entity_reference', array(array('target_id' => 1)));
     $entity->save();
 
-    $field_uri = _url('rest/relation/entity_test_mulrev/entity_test_mulrev/field_test_entity_reference', array('absolute' => TRUE));
+    $field_uri = url('rest/relation/entity_test_mulrev/entity_test_mulrev/field_test_entity_reference', array('absolute' => TRUE));
 
     $data = array(
       '_links' => array(
         'type' => array(
-          'href' => _url('rest/type/entity_test_mulrev/entity_test_mulrev', array('absolute' => TRUE)),
+          'href' => url('rest/type/entity_test_mulrev/entity_test_mulrev', array('absolute' => TRUE)),
         ),
         $field_uri => array(
           array(
-            'href' => _url('entity/entity_test_mulrev/' . $entity->id()),
+            'href' => url('entity/entity_test_mulrev/' . $entity->id()),
           ),
         ),
       ),
@@ -75,7 +75,7 @@ function testUuidEntityResolver() {
         $field_uri => array(
           array(
             '_links' => array(
-              'self' => _url('entity/entity_test_mulrev/' . $entity->id()),
+              'self' => url('entity/entity_test_mulrev/' . $entity->id()),
             ),
             'uuid' => array(
               array(
diff --git a/core/modules/shortcut/src/Entity/Shortcut.php b/core/modules/shortcut/src/Entity/Shortcut.php
index 4bd041e..df96d6f 100644
--- a/core/modules/shortcut/src/Entity/Shortcut.php
+++ b/core/modules/shortcut/src/Entity/Shortcut.php
@@ -14,7 +14,6 @@
 use Drupal\Core\Field\BaseFieldDefinition;
 use Drupal\Core\Url;
 use Drupal\shortcut\ShortcutInterface;
-use Symfony\Component\HttpFoundation\Request;
 
 /**
  * Defines the shortcut entity class.
@@ -135,15 +134,7 @@ public static function preCreate(EntityStorageInterface $storage, array &$values
   public function preSave(EntityStorageInterface $storage) {
     parent::preSave($storage);
 
-    // @todo fix PathValidatorInterface::getUrlIfValid() so we can use it
-    //   here. The problem is that we need an exception, not a FALSE
-    //   return value. https://www.drupal.org/node/2346695
-    if ($this->path->value == '<front>') {
-      $url = new Url($this->path->value);
-    }
-    else {
-      $url = Url::createFromRequest(Request::create("/{$this->path->value}"));
-    }
+    $url = Url::createFromPath($this->path->value);
     $this->setRouteName($url->getRouteName());
     $this->setRouteParams($url->getRouteParameters());
   }
diff --git a/core/modules/simpletest/src/TestBase.php b/core/modules/simpletest/src/TestBase.php
index b8bed09..171df78 100644
--- a/core/modules/simpletest/src/TestBase.php
+++ b/core/modules/simpletest/src/TestBase.php
@@ -745,7 +745,7 @@ protected function verbose($message) {
     $verbose_filename = $this->verboseDirectory . '/' . $this->verboseClassName . '-' . $this->verboseId . '.html';
     if (file_put_contents($verbose_filename, $message, FILE_APPEND)) {
       $url = $this->verboseDirectoryUrl . '/' . $this->verboseClassName . '-' . $this->verboseId . '.html';
-      // Not using _l() to avoid invoking the theme system, so that unit tests
+      // Not using l() to avoid invoking the theme system, so that unit tests
       // can use verbose() as well.
       $url = '<a href="' . $url . '" target="_blank">Verbose message</a>';
       $this->error($url, 'User notice');
diff --git a/core/modules/simpletest/src/Tests/SimpleTestBrowserTest.php b/core/modules/simpletest/src/Tests/SimpleTestBrowserTest.php
index 869dbca..69712c3 100644
--- a/core/modules/simpletest/src/Tests/SimpleTestBrowserTest.php
+++ b/core/modules/simpletest/src/Tests/SimpleTestBrowserTest.php
@@ -77,7 +77,7 @@ public function testInternalBrowser() {
     // Not using File API; a potential error must trigger a PHP warning.
     unlink($this->siteDirectory . '/.htkey');
     global $base_url;
-    $this->drupalGet(_url($base_url . '/core/install.php', array('external' => TRUE, 'absolute' => TRUE)));
+    $this->drupalGet(url($base_url . '/core/install.php', array('external' => TRUE, 'absolute' => TRUE)));
     $this->assertResponse(403, 'Cannot access install.php.');
   }
 
diff --git a/core/modules/simpletest/src/WebTestBase.php b/core/modules/simpletest/src/WebTestBase.php
index 3c826bf..ab560b2 100644
--- a/core/modules/simpletest/src/WebTestBase.php
+++ b/core/modules/simpletest/src/WebTestBase.php
@@ -1476,7 +1476,7 @@ protected function drupalGet($path, array $options = array(), array $headers = a
    * @param string $path
    *   Path to request AJAX from.
    * @param array $options
-   *   Array of options to pass to _url().
+   *   Array of options to pass to url().
    * @param array $headers
    *   Array of headers. Eg array('Accept: application/vnd.drupal-ajax').
    *
@@ -1925,11 +1925,11 @@ protected function drupalProcessAjaxResponse($content, array $ajax_response, arr
    *
    * @see WebTestBase::getAjaxPageStatePostData()
    * @see WebTestBase::curlExec()
-   * @see _url()
+   * @see url()
    */
   protected function drupalPost($path, $accept, array $post, $options = array()) {
     return $this->curlExec(array(
-      CURLOPT_URL => _url($path, $options + array('absolute' => TRUE)),
+      CURLOPT_URL => url($path, $options + array('absolute' => TRUE)),
       CURLOPT_POST => TRUE,
       CURLOPT_POSTFIELDS => $this->serializePostValues($post),
       CURLOPT_HTTPHEADER => array(
diff --git a/core/modules/statistics/statistics.module b/core/modules/statistics/statistics.module
index 00ca78d..3c80cd8 100644
--- a/core/modules/statistics/statistics.module
+++ b/core/modules/statistics/statistics.module
@@ -39,7 +39,7 @@ function statistics_help($route_name, RouteMatchInterface $route_match) {
 function statistics_node_view(array &$build, EntityInterface $node, EntityViewDisplayInterface $display, $view_mode) {
   if (!$node->isNew() && $view_mode == 'full' && node_is_page($node) && empty($node->in_preview)) {
     $build['statistics_content_counter']['#attached']['library'][] = 'statistics/drupal.statistics';
-    $settings = array('data' => array('nid' => $node->id()), 'url' => _url(drupal_get_path('module', 'statistics') . '/statistics.php'));
+    $settings = array('data' => array('nid' => $node->id()), 'url' => url(drupal_get_path('module', 'statistics') . '/statistics.php'));
     $build['statistics_content_counter']['#attached']['js'][] = array(
       'data' => array('statistics' => $settings),
       'type' => 'setting',
diff --git a/core/modules/system/language.api.php b/core/modules/system/language.api.php
index f52e22d..3a74f82 100644
--- a/core/modules/system/language.api.php
+++ b/core/modules/system/language.api.php
@@ -95,7 +95,7 @@
  * Perform alterations on language switcher links.
  *
  * A language switcher link may need to point to a different path or use a
- * translated link text before going through _l(), which will just handle the
+ * translated link text before going through l(), which will just handle the
  * path aliases.
  *
  * @param $links
diff --git a/core/modules/system/src/Form/SiteInformationForm.php b/core/modules/system/src/Form/SiteInformationForm.php
index 7ae14cf..d8328df 100644
--- a/core/modules/system/src/Form/SiteInformationForm.php
+++ b/core/modules/system/src/Form/SiteInformationForm.php
@@ -114,7 +114,7 @@ public function buildForm(array $form, FormStateInterface $form_state) {
       '#default_value' => $front_page,
       '#size' => 40,
       '#description' => t('Optionally, specify a relative URL to display as the front page. Leave blank to display the default front page.'),
-      '#field_prefix' => _url(NULL, array('absolute' => TRUE)),
+      '#field_prefix' => url(NULL, array('absolute' => TRUE)),
     );
     $form['error_page'] = array(
       '#type' => 'details',
@@ -127,7 +127,7 @@ public function buildForm(array $form, FormStateInterface $form_state) {
       '#default_value' => $site_config->get('page.403'),
       '#size' => 40,
       '#description' => t('This page is displayed when the requested document is denied to the current user. Leave blank to display a generic "access denied" page.'),
-      '#field_prefix' => _url(NULL, array('absolute' => TRUE)),
+      '#field_prefix' => url(NULL, array('absolute' => TRUE)),
     );
     $form['error_page']['site_404'] = array(
       '#type' => 'textfield',
@@ -135,7 +135,7 @@ public function buildForm(array $form, FormStateInterface $form_state) {
       '#default_value' => $site_config->get('page.404'),
       '#size' => 40,
       '#description' => t('This page is displayed when no other content matches the requested document. Leave blank to display a generic "page not found" page.'),
-      '#field_prefix' => _url(NULL, array('absolute' => TRUE)),
+      '#field_prefix' => url(NULL, array('absolute' => TRUE)),
     );
 
     return parent::buildForm($form, $form_state);
diff --git a/core/modules/system/src/Tests/Cache/PageCacheTagsIntegrationTest.php b/core/modules/system/src/Tests/Cache/PageCacheTagsIntegrationTest.php
index 7efb671..4b4e222 100644
--- a/core/modules/system/src/Tests/Cache/PageCacheTagsIntegrationTest.php
+++ b/core/modules/system/src/Tests/Cache/PageCacheTagsIntegrationTest.php
@@ -149,7 +149,7 @@ protected function verifyPageCacheTags($path, $expected_tags) {
     sort($actual_tags);
     $this->assertEqual($this->drupalGetHeader('X-Drupal-Cache'), 'HIT');
     $this->assertIdentical($actual_tags, $expected_tags);
-    $cid_parts = array(_url($path, array('absolute' => TRUE)), 'html');
+    $cid_parts = array(url($path, array('absolute' => TRUE)), 'html');
     $cid = sha1(implode(':', $cid_parts));
     $cache_entry = \Drupal::cache('render')->get($cid);
     sort($cache_entry->tags);
diff --git a/core/modules/system/src/Tests/Cache/PageCacheTagsTestBase.php b/core/modules/system/src/Tests/Cache/PageCacheTagsTestBase.php
index e54f97b..f3a0d76 100644
--- a/core/modules/system/src/Tests/Cache/PageCacheTagsTestBase.php
+++ b/core/modules/system/src/Tests/Cache/PageCacheTagsTestBase.php
@@ -46,7 +46,7 @@ protected function verifyPageCache($path, $hit_or_miss, $tags = FALSE) {
     $this->assertEqual($this->drupalGetHeader('X-Drupal-Cache'), $hit_or_miss, $message);
 
     if ($hit_or_miss === 'HIT' && is_array($tags)) {
-      $cid_parts = array(_url($path, array('absolute' => TRUE)), 'html');
+      $cid_parts = array(url($path, array('absolute' => TRUE)), 'html');
       $cid = sha1(implode(':', $cid_parts));
       $cache_entry = \Drupal::cache('render')->get($cid);
       sort($cache_entry->tags);
diff --git a/core/modules/system/src/Tests/Common/AddFeedTest.php b/core/modules/system/src/Tests/Common/AddFeedTest.php
index a24581d..8de6090 100644
--- a/core/modules/system/src/Tests/Common/AddFeedTest.php
+++ b/core/modules/system/src/Tests/Common/AddFeedTest.php
@@ -23,11 +23,11 @@ class AddFeedTest extends WebTestBase {
   function testBasicFeedAddNoTitle() {
     $path = $this->randomMachineName(12);
     $external_url = 'http://' . $this->randomMachineName(12) . '/' . $this->randomMachineName(12);
-    $fully_qualified_local_url = _url($this->randomMachineName(12), array('absolute' => TRUE));
+    $fully_qualified_local_url = url($this->randomMachineName(12), array('absolute' => TRUE));
 
     $path_for_title = $this->randomMachineName(12);
     $external_for_title = 'http://' . $this->randomMachineName(12) . '/' . $this->randomMachineName(12);
-    $fully_qualified_for_title = _url($this->randomMachineName(12), array('absolute' => TRUE));
+    $fully_qualified_for_title = url($this->randomMachineName(12), array('absolute' => TRUE));
 
     // Possible permutations of drupal_add_feed() to test.
     // - 'input_url': the path passed to drupal_add_feed(),
@@ -35,7 +35,7 @@ function testBasicFeedAddNoTitle() {
     // - 'title' == the title of the feed as passed into drupal_add_feed().
     $urls = array(
       'path without title' => array(
-        'url' => _url($path, array('absolute' => TRUE)),
+        'url' => url($path, array('absolute' => TRUE)),
         'title' => '',
       ),
       'external URL without title' => array(
@@ -47,7 +47,7 @@ function testBasicFeedAddNoTitle() {
         'title' => '',
       ),
       'path with title' => array(
-        'url' => _url($path_for_title, array('absolute' => TRUE)),
+        'url' => url($path_for_title, array('absolute' => TRUE)),
         'title' => $this->randomMachineName(12),
       ),
       'external URL with title' => array(
diff --git a/core/modules/system/src/Tests/Common/RenderElementTypesTest.php b/core/modules/system/src/Tests/Common/RenderElementTypesTest.php
index 9757a2b..6d83838 100644
--- a/core/modules/system/src/Tests/Common/RenderElementTypesTest.php
+++ b/core/modules/system/src/Tests/Common/RenderElementTypesTest.php
@@ -147,7 +147,7 @@ function testMoreLink() {
           '#type' => 'more_link',
           '#href' => 'a/link',
         ),
-        'expected' => '//div[@class="more-link"]/a[@href="' . _url('a/link') . '" and text()="More"]',
+        'expected' => '//div[@class="more-link"]/a[@href="' . url('a/link') . '" and text()="More"]',
       ),
       array(
         'name' => "#type 'more_link' anchor tag with a route",
@@ -165,7 +165,7 @@ function testMoreLink() {
           '#href' => 'admin/content',
           '#options' => array('absolute' => TRUE),
         ),
-        'expected' => '//div[@class="more-link"]/a[@href="' . _url('admin/content', array('absolute' => TRUE)) . '" and text()="More"]',
+        'expected' => '//div[@class="more-link"]/a[@href="' . url('admin/content', array('absolute' => TRUE)) . '" and text()="More"]',
       ),
       array(
         'name' => "#type 'more_link' anchor tag to the front page",
@@ -173,7 +173,7 @@ function testMoreLink() {
           '#type' => 'more_link',
           '#href' => '<front>',
         ),
-        'expected' => '//div[@class="more-link"]/a[@href="' . _url('<front>') . '" and text()="More"]',
+        'expected' => '//div[@class="more-link"]/a[@href="' . url('<front>') . '" and text()="More"]',
       ),
     );
 
diff --git a/core/modules/system/src/Tests/Common/RenderWebTest.php b/core/modules/system/src/Tests/Common/RenderWebTest.php
index 3e58fb0..3c8725a 100644
--- a/core/modules/system/src/Tests/Common/RenderWebTest.php
+++ b/core/modules/system/src/Tests/Common/RenderWebTest.php
@@ -111,7 +111,7 @@ function testDrupalRenderFormElements() {
       ),
     );
     $this->assertRenderedElement($element, '//a[@href=:href and contains(., :title)]', array(
-      ':href' => _url($element['#href'], array('absolute' => TRUE)),
+      ':href' => url($element['#href'], array('absolute' => TRUE)),
       ':title' => $element['#title'],
     ));
 
diff --git a/core/modules/system/src/Tests/Common/UrlTest.php b/core/modules/system/src/Tests/Common/UrlTest.php
index 0097512..4edae14 100644
--- a/core/modules/system/src/Tests/Common/UrlTest.php
+++ b/core/modules/system/src/Tests/Common/UrlTest.php
@@ -12,12 +12,12 @@
 use Drupal\simpletest\WebTestBase;
 
 /**
- * Confirm that _url(),
+ * Confirm that url(),
  * \Drupal\Component\Utility\UrlHelper::filterQueryParameters(),
- * \Drupal\Component\Utility\UrlHelper::buildQuery(), and _l() work correctly
+ * \Drupal\Component\Utility\UrlHelper::buildQuery(), and l() work correctly
  * with various input.
  *
- * _url() calls \Drupal::moduleHandler()->getImplementations(),
+ * url() calls \Drupal::moduleHandler()->getImplementations(),
  * which may issue a db query, which requires
  * inheriting from a web test case rather than a unit test case.
  *
@@ -31,12 +31,12 @@ class UrlTest extends WebTestBase {
    * Confirms that invalid URLs are filtered in link generating functions.
    */
   function testLinkXSS() {
-    // Test _l().
+    // Test l().
     $text = $this->randomMachineName();
     $path = "<SCRIPT>alert('XSS')</SCRIPT>";
-    $link = _l($text, $path);
-    $sanitized_path = check_url(_url($path));
-    $this->assertTrue(strpos($link, $sanitized_path) !== FALSE, format_string('XSS attack @path was filtered by _l().', array('@path' => $path)));
+    $link = l($text, $path);
+    $sanitized_path = check_url(url($path));
+    $this->assertTrue(strpos($link, $sanitized_path) !== FALSE, format_string('XSS attack @path was filtered by l().', array('@path' => $path)));
 
     // Test #type 'link'.
     $link_array =  array(
@@ -45,7 +45,7 @@ function testLinkXSS() {
       '#href' => $path,
     );
     $type_link = drupal_render($link_array);
-    $sanitized_path = check_url(_url($path));
+    $sanitized_path = check_url(url($path));
     $this->assertTrue(strpos($type_link, $sanitized_path) !== FALSE, format_string('XSS attack @path was filtered by #theme', array('@path' => $path)));
   }
 
@@ -76,7 +76,7 @@ function testLinkAttributes() {
     $rendered = drupal_render($hreflang_override_link);
     $this->assertTrue($this->hasAttribute('hreflang', $rendered, 'foo'), format_string('hreflang attribute with value @hreflang is present on a rendered link when @hreflang is provided in the render array.', array('@hreflang' => 'foo')));
 
-    // Test the active class in links produced by _l() and #type 'link'.
+    // Test the active class in links produced by l() and #type 'link'.
     $options_no_query = array();
     $options_query = array(
       'query' => array(
@@ -95,27 +95,27 @@ function testLinkAttributes() {
     $path = 'common-test/type-link-active-class';
 
     $this->drupalGet($path, $options_no_query);
-    $links = $this->xpath('//a[@href = :href and contains(@class, :class)]', array(':href' => _url($path, $options_no_query), ':class' => 'active'));
-    $this->assertTrue(isset($links[0]), 'A link generated by _l() to the current page is marked active.');
+    $links = $this->xpath('//a[@href = :href and contains(@class, :class)]', array(':href' => url($path, $options_no_query), ':class' => 'active'));
+    $this->assertTrue(isset($links[0]), 'A link generated by l() to the current page is marked active.');
 
-    $links = $this->xpath('//a[@href = :href and not(contains(@class, :class))]', array(':href' => _url($path, $options_query), ':class' => 'active'));
-    $this->assertTrue(isset($links[0]), 'A link generated by _l() to the current page with a query string when the current page has no query string is not marked active.');
+    $links = $this->xpath('//a[@href = :href and not(contains(@class, :class))]', array(':href' => url($path, $options_query), ':class' => 'active'));
+    $this->assertTrue(isset($links[0]), 'A link generated by l() to the current page with a query string when the current page has no query string is not marked active.');
 
     $this->drupalGet($path, $options_query);
-    $links = $this->xpath('//a[@href = :href and contains(@class, :class)]', array(':href' => _url($path, $options_query), ':class' => 'active'));
-    $this->assertTrue(isset($links[0]), 'A link generated by _l() to the current page with a query string that matches the current query string is marked active.');
+    $links = $this->xpath('//a[@href = :href and contains(@class, :class)]', array(':href' => url($path, $options_query), ':class' => 'active'));
+    $this->assertTrue(isset($links[0]), 'A link generated by l() to the current page with a query string that matches the current query string is marked active.');
 
-    $links = $this->xpath('//a[@href = :href and contains(@class, :class)]', array(':href' => _url($path, $options_query_reverse), ':class' => 'active'));
-    $this->assertTrue(isset($links[0]), 'A link generated by _l() to the current page with a query string that has matching parameters to the current query string but in a different order is marked active.');
+    $links = $this->xpath('//a[@href = :href and contains(@class, :class)]', array(':href' => url($path, $options_query_reverse), ':class' => 'active'));
+    $this->assertTrue(isset($links[0]), 'A link generated by l() to the current page with a query string that has matching parameters to the current query string but in a different order is marked active.');
 
-    $links = $this->xpath('//a[@href = :href and not(contains(@class, :class))]', array(':href' => _url($path, $options_no_query), ':class' => 'active'));
-    $this->assertTrue(isset($links[0]), 'A link generated by _l() to the current page without a query string when the current page has a query string is not marked active.');
+    $links = $this->xpath('//a[@href = :href and not(contains(@class, :class))]', array(':href' => url($path, $options_no_query), ':class' => 'active'));
+    $this->assertTrue(isset($links[0]), 'A link generated by l() to the current page without a query string when the current page has a query string is not marked active.');
 
-    // Test adding a custom class in links produced by _l() and #type 'link'.
-    // Test _l().
+    // Test adding a custom class in links produced by l() and #type 'link'.
+    // Test l().
     $class_l = $this->randomMachineName();
-    $link_l = _l($this->randomMachineName(), current_path(), array('attributes' => array('class' => array($class_l))));
-    $this->assertTrue($this->hasAttribute('class', $link_l, $class_l), format_string('Custom class @class is present on link when requested by _l()', array('@class' => $class_l)));
+    $link_l = l($this->randomMachineName(), current_path(), array('attributes' => array('class' => array($class_l))));
+    $this->assertTrue($this->hasAttribute('class', $link_l, $class_l), format_string('Custom class @class is present on link when requested by l()', array('@class' => $class_l)));
 
     // Test #type.
     $class_theme = $this->randomMachineName();
@@ -137,12 +137,12 @@ function testLinkAttributes() {
    * Tests that link functions support render arrays as 'text'.
    */
   function testLinkRenderArrayText() {
-    // Build a link with _l() for reference.
-    $l = _l('foo', 'http://drupal.org');
+    // Build a link with l() for reference.
+    $l = l('foo', 'http://drupal.org');
 
-    // Test a renderable array passed to _l().
+    // Test a renderable array passed to l().
     $renderable_text = array('#markup' => 'foo');
-    $l_renderable_text = _l($renderable_text, 'http://drupal.org');
+    $l_renderable_text = l($renderable_text, 'http://drupal.org');
     $this->assertEqual($l_renderable_text, $l);
 
     // Test a themed link with plain text 'text'.
@@ -261,30 +261,30 @@ function testExternalUrls() {
 
     // Verify external URL can contain a fragment.
     $url = $test_url . '#drupal';
-    $result = _url($url);
+    $result = url($url);
     $this->assertEqual($url, $result, 'External URL with fragment works without a fragment in $options.');
 
     // Verify fragment can be overidden in an external URL.
     $url = $test_url . '#drupal';
     $fragment = $this->randomMachineName(10);
-    $result = _url($url, array('fragment' => $fragment));
+    $result = url($url, array('fragment' => $fragment));
     $this->assertEqual($test_url . '#' . $fragment, $result, 'External URL fragment is overidden with a custom fragment in $options.');
 
     // Verify external URL can contain a query string.
     $url = $test_url . '?drupal=awesome';
-    $result = _url($url);
+    $result = url($url);
     $this->assertEqual($url, $result, 'External URL with query string works without a query string in $options.');
 
     // Verify external URL can be extended with a query string.
     $url = $test_url;
     $query = array($this->randomMachineName(5) => $this->randomMachineName(5));
-    $result = _url($url, array('query' => $query));
+    $result = url($url, array('query' => $query));
     $this->assertEqual($url . '?' . http_build_query($query, '', '&'), $result, 'External URL can be extended with a query string in $options.');
 
     // Verify query string can be extended in an external URL.
     $url = $test_url . '?drupal=awesome';
     $query = array($this->randomMachineName(5) => $this->randomMachineName(5));
-    $result = _url($url, array('query' => $query));
+    $result = url($url, array('query' => $query));
     $this->assertEqual($url . '&' . http_build_query($query, '', '&'), $result, 'External URL query string can be extended with a custom query string in $options.');
   }
 }
diff --git a/core/modules/system/src/Tests/Entity/EntityTranslationTest.php b/core/modules/system/src/Tests/Entity/EntityTranslationTest.php
index efb96c7..e6b67d5 100644
--- a/core/modules/system/src/Tests/Entity/EntityTranslationTest.php
+++ b/core/modules/system/src/Tests/Entity/EntityTranslationTest.php
@@ -438,7 +438,7 @@ function testEntityTranslationAPI() {
     $entity = $this->reloadEntity($entity);
     $field_id = implode('.', array($entity->getEntityTypeId(), $entity->bundle(), $this->field_name));
     $field = $this->entityManager->getStorage('field_config')->load($field_id);
-    $field->default_value_callback = 'entity_test_field_default_value';
+    $field->default_value_function = 'entity_test_field_default_value';
     $field->save();
     $translation = $entity->addTranslation($langcode2);
     $field_storage = $translation->get($this->field_name);
diff --git a/core/modules/system/src/Tests/Form/RebuildTest.php b/core/modules/system/src/Tests/Form/RebuildTest.php
index a1d4ac2..7affa60 100644
--- a/core/modules/system/src/Tests/Form/RebuildTest.php
+++ b/core/modules/system/src/Tests/Form/RebuildTest.php
@@ -105,6 +105,6 @@ function testPreserveFormActionAfterAJAX() {
 
     // Ensure that the form's action is correct.
     $forms = $this->xpath('//form[contains(@class, "node-page-form")]');
-    $this->assert(count($forms) == 1 && $forms[0]['action'] == _url('node/add/page'), 'Re-rendered form contains the correct action value.');
+    $this->assert(count($forms) == 1 && $forms[0]['action'] == url('node/add/page'), 'Re-rendered form contains the correct action value.');
   }
 }
diff --git a/core/modules/system/src/Tests/Menu/BreadcrumbTest.php b/core/modules/system/src/Tests/Menu/BreadcrumbTest.php
index d5d7250..cf5ab1a 100644
--- a/core/modules/system/src/Tests/Menu/BreadcrumbTest.php
+++ b/core/modules/system/src/Tests/Menu/BreadcrumbTest.php
@@ -280,7 +280,7 @@ function testBreadCrumbs() {
       // other than the breadcrumb trail.
       $elements = $this->xpath('//nav[@id=:menu]/descendant::a[@href=:href]', array(
         ':menu' => 'block-bartik-tools',
-        ':href' => _url($link_path),
+        ':href' => url($link_path),
       ));
       $this->assertTrue(count($elements) == 1, "Link to {$link_path} appears only once.");
 
diff --git a/core/modules/system/src/Tests/Menu/LocalActionTest.php b/core/modules/system/src/Tests/Menu/LocalActionTest.php
index 3c02aad..bcc443b 100644
--- a/core/modules/system/src/Tests/Menu/LocalActionTest.php
+++ b/core/modules/system/src/Tests/Menu/LocalActionTest.php
@@ -48,7 +48,7 @@ protected function assertLocalAction(array $actions) {
     $index = 0;
     foreach ($actions as $href => $title) {
       $this->assertEqual((string) $elements[$index], $title);
-      $this->assertEqual($elements[$index]['href'], _url($href));
+      $this->assertEqual($elements[$index]['href'], url($href));
       $index++;
     }
   }
diff --git a/core/modules/system/src/Tests/Menu/LocalTasksTest.php b/core/modules/system/src/Tests/Menu/LocalTasksTest.php
index fc61315..957e2eb 100644
--- a/core/modules/system/src/Tests/Menu/LocalTasksTest.php
+++ b/core/modules/system/src/Tests/Menu/LocalTasksTest.php
@@ -34,7 +34,7 @@ protected function assertLocalTasks(array $hrefs, $level = 0) {
     ));
     $this->assertTrue(count($elements), 'Local tasks found.');
     foreach ($hrefs as $index => $element) {
-      $expected = _url($hrefs[$index]);
+      $expected = url($hrefs[$index]);
       $method = ($elements[$index]['href'] == $expected ? 'pass' : 'fail');
       $this->{$method}(format_string('Task @number href @value equals @expected.', array(
         '@number' => $index + 1,
diff --git a/core/modules/system/src/Tests/Menu/MenuRouterTest.php b/core/modules/system/src/Tests/Menu/MenuRouterTest.php
index 48c7500..89a6a32 100644
--- a/core/modules/system/src/Tests/Menu/MenuRouterTest.php
+++ b/core/modules/system/src/Tests/Menu/MenuRouterTest.php
@@ -70,8 +70,8 @@ protected function doTestHookMenuIntegration() {
     $this->assertLink('Local task A');
     $this->assertLink('Local task B');
     // Confirm correct local task href.
-    $this->assertLinkByHref(_url($base_path));
-    $this->assertLinkByHref(_url($base_path . '/b'));
+    $this->assertLinkByHref(url($base_path));
+    $this->assertLinkByHref(url($base_path . '/b'));
   }
 
   /**
diff --git a/core/modules/system/src/Tests/Menu/MenuTestBase.php b/core/modules/system/src/Tests/Menu/MenuTestBase.php
index 2478af3..fc896d8 100644
--- a/core/modules/system/src/Tests/Menu/MenuTestBase.php
+++ b/core/modules/system/src/Tests/Menu/MenuTestBase.php
@@ -64,7 +64,7 @@ protected function assertBreadcrumbParts($trail) {
     // this test would go into an infinite loop, so we need to check that too.
     while ($trail && !empty($parts)) {
       foreach ($trail as $path => $title) {
-        $url = _url($path);
+        $url = url($path);
         $part = array_shift($parts);
         $pass = ($pass && $part['href'] === $url && $part['text'] === String::checkPlain($title));
       }
@@ -101,7 +101,7 @@ protected function assertMenuActiveTrail($tree, $last_active) {
         $part_xpath .= 'li[contains(@class, :class)]/a[contains(@href, :href) and contains(text(), :title)]';
         $part_args = array(
           ':class' => 'active-trail',
-          ':href' => _url($link_path),
+          ':href' => url($link_path),
           ':title' => $link_title,
         );
         $xpath .= $this->buildXPathQuery($part_xpath, $part_args);
@@ -121,7 +121,7 @@ protected function assertMenuActiveTrail($tree, $last_active) {
     $args = array(
       ':class-trail' => 'active-trail',
       ':class-active' => 'active',
-      ':href' => _url($active_link_path),
+      ':href' => url($active_link_path),
       ':title' => $active_link_title,
     );
     $elements = $this->xpath($xpath, $args);
diff --git a/core/modules/system/src/Tests/Menu/MenuTranslateTest.php b/core/modules/system/src/Tests/Menu/MenuTranslateTest.php
index ea4b302..99e1401 100644
--- a/core/modules/system/src/Tests/Menu/MenuTranslateTest.php
+++ b/core/modules/system/src/Tests/Menu/MenuTranslateTest.php
@@ -40,7 +40,7 @@ public function testMenuTranslate() {
     $this->assertResponse(403);
     $elements = $this->xpath('//ul[@class=:class]/li/a[@href=:href]', array(
       ':class' => 'tabs primary',
-      ':href' => _url('foo/asdf'),
+      ':href' => url('foo/asdf'),
     ));
     $this->assertTrue(empty($elements), 'No tab linking to foo/asdf found');
     $this->assertNoLinkByHref('foo/asdf/b');
diff --git a/core/modules/system/src/Tests/Path/UrlAlterFunctionalTest.php b/core/modules/system/src/Tests/Path/UrlAlterFunctionalTest.php
index 7f64ddb..6f81d0d 100644
--- a/core/modules/system/src/Tests/Path/UrlAlterFunctionalTest.php
+++ b/core/modules/system/src/Tests/Path/UrlAlterFunctionalTest.php
@@ -87,9 +87,9 @@ function testCurrentUrlRequestedPath() {
    * Assert that an outbound path is altered to an expected value.
    *
    * @param $original
-   *   A string with the original path that is run through _url().
+   *   A string with the original path that is run through url().
    * @param $final
-   *   A string with the expected result after _url().
+   *   A string with the expected result after url().
    * @return
    *   TRUE if $original was correctly altered to $final, FALSE otherwise.
    */
@@ -107,7 +107,7 @@ protected function assertUrlOutboundAlter($original, $final) {
    * @param $original
    *   The original path before it has been altered by inbound URL processing.
    * @param $final
-   *   A string with the expected result after _url().
+   *   A string with the expected result after url().
    * @return
    *   TRUE if $original was correctly altered to $final, FALSE otherwise.
    */
diff --git a/core/modules/system/src/Tests/System/TokenReplaceUnitTest.php b/core/modules/system/src/Tests/System/TokenReplaceUnitTest.php
index eaed0a6..2152474 100644
--- a/core/modules/system/src/Tests/System/TokenReplaceUnitTest.php
+++ b/core/modules/system/src/Tests/System/TokenReplaceUnitTest.php
@@ -74,7 +74,7 @@ public function testClear() {
    * Tests the generation of all system site information tokens.
    */
   public function testSystemSiteTokenReplacement() {
-    // The use of the _url() function requires the url_alias table to exist.
+    // The use of the url() function requires the url_alias table to exist.
     $this->installSchema('system', 'url_alias');
     $url_options = array(
       'absolute' => TRUE,
diff --git a/core/modules/system/src/Tests/Theme/FunctionsTest.php b/core/modules/system/src/Tests/Theme/FunctionsTest.php
index c8d068c..c970553 100644
--- a/core/modules/system/src/Tests/Theme/FunctionsTest.php
+++ b/core/modules/system/src/Tests/Theme/FunctionsTest.php
@@ -170,7 +170,7 @@ function testItemList() {
    * Tests links.html.twig.
    */
   function testLinks() {
-    // Turn off the query for the _l() function to compare the active
+    // Turn off the query for the l() function to compare the active
     // link correctly.
     $original_query = \Drupal::request()->query->all();
     \Drupal::request()->query->replace(array());
@@ -216,9 +216,9 @@ function testLinks() {
 
     $expected_links = '';
     $expected_links .= '<ul id="somelinks">';
-    $expected_links .= '<li class="a-link"><a href="' . _url('a/link') . '">' . String::checkPlain('A <link>') . '</a></li>';
+    $expected_links .= '<li class="a-link"><a href="' . url('a/link') . '">' . String::checkPlain('A <link>') . '</a></li>';
     $expected_links .= '<li class="plain-text">' . String::checkPlain('Plain "text"') . '</li>';
-    $expected_links .= '<li class="front-page"><a href="' . _url('<front>') . '">' . String::checkPlain('Front page') . '</a></li>';
+    $expected_links .= '<li class="front-page"><a href="' . url('<front>') . '">' . String::checkPlain('Front page') . '</a></li>';
     $expected_links .= '<li class="router-test"><a href="' . \Drupal::urlGenerator()->generate('router_test.1') . '">' . String::checkPlain('Test route') . '</a></li>';
     $query = array('key' => 'value');
     $expected_links .= '<li class="query-test"><a href="' . \Drupal::urlGenerator()->generate('router_test.1', $query) . '">' . String::checkPlain('Query test route') . '</a></li>';
@@ -258,9 +258,9 @@ function testLinks() {
     );
     $expected_links = '';
     $expected_links .= '<ul id="somelinks">';
-    $expected_links .= '<li class="a-link"><a href="' . _url('a/link') . '" class="a/class">' . String::checkPlain('A <link>') . '</a></li>';
+    $expected_links .= '<li class="a-link"><a href="' . url('a/link') . '" class="a/class">' . String::checkPlain('A <link>') . '</a></li>';
     $expected_links .= '<li class="plain-text"><span class="a/class">' . String::checkPlain('Plain "text"') . '</span></li>';
-    $expected_links .= '<li class="front-page"><a href="' . _url('<front>') . '">' . String::checkPlain('Front page') . '</a></li>';
+    $expected_links .= '<li class="front-page"><a href="' . url('<front>') . '">' . String::checkPlain('Front page') . '</a></li>';
     $expected_links .= '<li class="router-test"><a href="' . \Drupal::urlGenerator()->generate('router_test.1') . '">' . String::checkPlain('Test route') . '</a></li>';
     $query = array('key' => 'value');
     $expected_links .= '<li class="query-test"><a href="' . \Drupal::urlGenerator()->generate('router_test.1', $query) . '">' . String::checkPlain('Query test route') . '</a></li>';
@@ -273,9 +273,9 @@ function testLinks() {
     $variables['set_active_class'] = TRUE;
     $expected_links = '';
     $expected_links .= '<ul id="somelinks">';
-    $expected_links .= '<li class="a-link" data-drupal-link-system-path="a/link"><a href="' . _url('a/link') . '" class="a/class" data-drupal-link-system-path="a/link">' . String::checkPlain('A <link>') . '</a></li>';
+    $expected_links .= '<li class="a-link" data-drupal-link-system-path="a/link"><a href="' . url('a/link') . '" class="a/class" data-drupal-link-system-path="a/link">' . String::checkPlain('A <link>') . '</a></li>';
     $expected_links .= '<li class="plain-text"><span class="a/class">' . String::checkPlain('Plain "text"') . '</span></li>';
-    $expected_links .= '<li class="front-page" data-drupal-link-system-path="&lt;front&gt;"><a href="' . _url('<front>') . '" data-drupal-link-system-path="&lt;front&gt;">' . String::checkPlain('Front page') . '</a></li>';
+    $expected_links .= '<li class="front-page" data-drupal-link-system-path="&lt;front&gt;"><a href="' . url('<front>') . '" data-drupal-link-system-path="&lt;front&gt;">' . String::checkPlain('Front page') . '</a></li>';
     $expected_links .= '<li class="router-test" data-drupal-link-system-path="router_test/test1"><a href="' . \Drupal::urlGenerator()->generate('router_test.1') . '" data-drupal-link-system-path="router_test/test1">' . String::checkPlain('Test route') . '</a></li>';
     $query = array('key' => 'value');
     $encoded_query = String::checkPlain(Json::encode($query));
diff --git a/core/modules/system/system.api.php b/core/modules/system/system.api.php
index f721626..aa423b0 100644
--- a/core/modules/system/system.api.php
+++ b/core/modules/system/system.api.php
@@ -371,7 +371,7 @@ function hook_page_build(&$page) {
  *     this menu item (as a result of other properties), then the menu link is
  *     always expanded, equivalent to its 'always expanded' checkbox being set
  *     in the UI.
- *   - options: (optional) An array of options to be passed to _l() when
+ *   - options: (optional) An array of options to be passed to l() when
  *     generating a link from this menu item.
  *
  * @ingroup menu
@@ -393,7 +393,7 @@ function hook_menu_links_discovered_alter(&$links) {
  * - #link: An associative array containing:
  *   - title: The localized title of the link.
  *   - href: The system path to link to.
- *   - localized_options: An array of options to pass to _l().
+ *   - localized_options: An array of options to pass to l().
  * - #weight: The link's weight compared to other links.
  * - #active: Whether the link should be marked as 'active'.
  *
@@ -495,7 +495,7 @@ function hook_local_tasks_alter(&$local_tasks) {
  * - title: The localized title of the link.
  * - route_name: The route name of the link.
  * - route_parameters: The route parameters of the link.
- * - localized_options: An array of options to pass to _url().
+ * - localized_options: An array of options to pass to url().
  * - (optional) weight: The weight of the link, which is used to sort the links.
  *
  *
@@ -981,17 +981,18 @@ function hook_help($route_name, \Drupal\Core\Routing\RouteMatchInterface $route_
  *     theme path will be used, but if the file will not be in the default
  *     path, include it here. This path should be relative to the Drupal root
  *     directory.
- *   - template: If specified, this theme implementation is a template, and
- *     this is the template file without an extension. Do not put .html.twig on
- *     this file; that extension will be added automatically by the default
- *     rendering engine (which is Twig). If 'path' above is specified, the
- *     template should also be in this path.
+ *   - template: If specified, the theme implementation is a template file, and
+ *     this is the template name. Do not add 'html.twig' on the end of the
+ *     template name. The extension will be added automatically by the default
+ *     rendering engine (which is Twig.) If 'path' is specified, 'template'
+ *     should also be specified. If neither 'template' nor 'function' are
+ *     specified, a default template name will be assumed. For example, if a
+ *     module registers the 'search_result' theme hook, 'search-result' will be
+ *     assigned as its template name.
  *   - function: If specified, this will be the function name to invoke for
- *     this implementation. If neither 'template' nor 'function' is specified,
- *     a default function name will be assumed. For example, if a module
- *     registers the 'node' theme hook, 'theme_node' will be assigned to its
- *     function. If the chameleon theme registers the node hook, it will be
- *     assigned 'chameleon_node' as its function.
+ *     this implementation. If neither 'template' nor 'function' are
+ *     specified, a default template name will be assumed. See above for more
+ *     details.
  *   - base hook: Used for _theme() suggestions only: the base theme hook name.
  *     Instead of this suggestion's implementation being used directly, the base
  *     hook will be invoked with this implementation as its first suggestion.
@@ -2683,7 +2684,7 @@ function hook_filetransfer_info_alter(&$filetransfer_info) {
  * @param array $variables
  *   An associative array of variables defining a link. The link may be either a
  *   "route link" using \Drupal\Core\Utility\LinkGenerator::link(), which is
- *   exposed as the 'link_generator' service or a link generated by _l(). If the
+ *   exposed as the 'link_generator' service or a link generated by l(). If the
  *   link is a "route link", 'route_name' will be set, otherwise 'path' will be
  *   set. The following keys can be altered:
  *   - text: The link text for the anchor tag as a translated string.
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index a44b1fe..63301a9 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -187,10 +187,12 @@ function system_theme() {
     'system_modules_details' => array(
       'render element' => 'form',
       'file' => 'system.admin.inc',
+      'function' => 'theme_system_modules_details',
     ),
     'system_modules_uninstall' => array(
       'render element' => 'form',
       'file' => 'system.admin.inc',
+      'function' => 'theme_system_modules_uninstall',
     ),
     'status_report' => array(
       'variables' => array('requirements' => NULL),
@@ -219,6 +221,7 @@ function system_theme() {
     ),
     'system_compact_link' => array(
       'variables' => array(),
+      'function' => 'theme_system_compact_link',
     ),
   ));
 }
@@ -457,7 +460,7 @@ function system_authorized_get_url(array $options = array()) {
   // Force HTTPS if available, regardless of what the caller specifies.
   $options['https'] = TRUE;
   // Prefix with $base_url so url() treats it as an external link.
-  $url = Url::fromUri('base://core/authorize.php');
+  $url = Url::createFromPath($base_url . '/core/authorize.php');
   $url_options = $url->getOptions();
   $url->setOptions($options + $url_options);
   return $url;
@@ -619,7 +622,7 @@ function system_user_login($account) {
   $config = \Drupal::config('system.date');
   // If the user has a NULL time zone, notify them to set a time zone.
   if (!$account->getTimezone() && $config->get('timezone.user.configurable') && $config->get('timezone.user.warn')) {
-    drupal_set_message(t('Configure your <a href="@user-edit">account time zone setting</a>.', array('@user-edit' => _url("user/$account->id()/edit", array('query' => drupal_get_destination(), 'fragment' => 'edit-timezone')))));
+    drupal_set_message(t('Configure your <a href="@user-edit">account time zone setting</a>.', array('@user-edit' => url("user/$account->id()/edit", array('query' => drupal_get_destination(), 'fragment' => 'edit-timezone')))));
   }
 }
 
diff --git a/core/modules/system/tests/modules/common_test/common_test.module b/core/modules/system/tests/modules/common_test/common_test.module
index bd17563..e23a842 100644
--- a/core/modules/system/tests/modules/common_test/common_test.module
+++ b/core/modules/system/tests/modules/common_test/common_test.module
@@ -123,6 +123,7 @@ function common_test_theme() {
     ),
     'common_test_empty' => array(
       'variables' => array('foo' => 'foo'),
+      'function' => 'theme_common_test_empty',
     ),
   );
 }
diff --git a/core/modules/system/tests/modules/common_test/src/Controller/CommonTestController.php b/core/modules/system/tests/modules/common_test/src/Controller/CommonTestController.php
index be4ce96..32bc04f 100644
--- a/core/modules/system/tests/modules/common_test/src/Controller/CommonTestController.php
+++ b/core/modules/system/tests/modules/common_test/src/Controller/CommonTestController.php
@@ -18,7 +18,7 @@ class CommonTestController {
   /**
    * Returns links to the current page, with and without query strings.
    *
-   * Using #type 'link' causes these links to be rendered with _l().
+   * Using #type 'link' causes these links to be rendered with l().
    */
   public function typeLinkActiveClass() {
     return array(
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestRedirectForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestRedirectForm.php
index f7c0d4a..7fc352e 100644
--- a/core/modules/system/tests/modules/form_test/src/Form/FormTestRedirectForm.php
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestRedirectForm.php
@@ -54,7 +54,7 @@ public function buildForm(array $form, FormStateInterface $form_state) {
   public function submitForm(array &$form, FormStateInterface $form_state) {
     if (!$form_state->isValueEmpty('redirection')) {
       if (!$form_state->isValueEmpty('destination')) {
-        $form_state->setRedirectUrl(Url::fromUri('base://' . $form_state->getValue('destination')));
+        $form_state->setRedirectUrl(Url::createFromPath($GLOBALS['base_url'] . '/' . $form_state->getValue('destination')));
       }
     }
     else {
diff --git a/core/modules/system/tests/modules/theme_suggestions_test/theme_suggestions_test.module b/core/modules/system/tests/modules/theme_suggestions_test/theme_suggestions_test.module
index e963c2f..974856a 100644
--- a/core/modules/system/tests/modules/theme_suggestions_test/theme_suggestions_test.module
+++ b/core/modules/system/tests/modules/theme_suggestions_test/theme_suggestions_test.module
@@ -12,6 +12,7 @@ function theme_suggestions_test_theme() {
   $items['theme_suggestions_test_include'] = array(
     'file' => 'theme_suggestions_test.inc',
     'variables' => array(),
+    'function' => 'theme_theme_suggestions_test_include',
   );
   return $items;
 }
diff --git a/core/modules/system/tests/modules/theme_test/theme_test.module b/core/modules/system/tests/modules/theme_test/theme_test.module
index dd71fb7..8616f02 100644
--- a/core/modules/system/tests/modules/theme_test/theme_test.module
+++ b/core/modules/system/tests/modules/theme_test/theme_test.module
@@ -9,6 +9,7 @@ function theme_test_theme($existing, $type, $theme, $path) {
   $items['theme_test'] = array(
     'file' => 'theme_test.inc',
     'variables' => array('foo' => ''),
+    'function' => 'theme_theme_test',
   );
   $items['theme_test_template_test'] = array(
     'template' => 'theme_test.template_test',
@@ -34,12 +35,15 @@ function theme_test_theme($existing, $type, $theme, $path) {
   );
   $items['theme_test_function_suggestions'] = array(
     'variables' => array(),
+    'function' => 'theme_theme_test_function_suggestions',
   );
   $items['theme_test_suggestions_include'] = array(
     'variables' => array(),
+    'function' => 'theme_theme_test_suggestions_include',
   );
   $items['theme_test_foo'] = array(
     'variables' => array('foo' => NULL),
+    'function' => 'theme_theme_test_foo',
   );
   $items['theme_test_render_element'] = array(
     'render element' => 'elements',
@@ -47,9 +51,11 @@ function theme_test_theme($existing, $type, $theme, $path) {
   );
   $items['theme_test_render_element_children'] = array(
     'render element' => 'element',
+    'function' => 'theme_theme_test_render_element_children',
   );
   $items['theme_test_function_template_override'] = array(
     'variables' => array(),
+    'function' => 'theme_theme_test_function_template_override',
   );
   $info['test_theme_not_existing_function'] = array(
     'function' => 'test_theme_not_existing_function',
diff --git a/core/modules/toolbar/toolbar.module b/core/modules/toolbar/toolbar.module
index 815d1cf..ff81d67 100644
--- a/core/modules/toolbar/toolbar.module
+++ b/core/modules/toolbar/toolbar.module
@@ -41,9 +41,6 @@ function toolbar_theme($existing, $type, $theme, $path) {
     'render element' => 'element',
     'template' => 'toolbar',
   );
-  $items['toolbar_item'] = array(
-    'render element' => 'element',
-  );
 
   return $items;
 }
@@ -298,7 +295,7 @@ function toolbar_menu_navigation_links(array $tree) {
     $url = $link->getUrlObject();
     if ($url->isExternal()) {
       // This is an unusual case, so just get a distinct, safe string.
-      $id = substr(Crypt::hashBase64($url->getUri()), 0, 16);
+      $id = substr(Crypt::hashBase64($url->getPath()), 0, 16);
     }
     else {
       $id = str_replace(array('.', '<', '>'), array('-', '', ''), $url->getRouteName());
diff --git a/core/modules/update/src/Form/UpdateManagerUpdate.php b/core/modules/update/src/Form/UpdateManagerUpdate.php
index 88858a6..c90247f 100644
--- a/core/modules/update/src/Form/UpdateManagerUpdate.php
+++ b/core/modules/update/src/Form/UpdateManagerUpdate.php
@@ -111,7 +111,7 @@ public function buildForm(array $form, FormStateInterface $form_state) {
       // The project name to display can vary based on the info we have.
       if (!empty($project['title'])) {
         if (!empty($project['link'])) {
-          $project_name = _l($project['title'], $project['link']);
+          $project_name = l($project['title'], $project['link']);
         }
         else {
           $project_name = String::checkPlain($project['title']);
@@ -134,7 +134,7 @@ public function buildForm(array $form, FormStateInterface $form_state) {
       }
 
       $recommended_release = $project['releases'][$project['recommended']];
-      $recommended_version = $recommended_release['version'] . ' ' . _l($this->t('(Release notes)'), $recommended_release['release_link'], array('attributes' => array('title' => $this->t('Release notes for @project_title', array('@project_title' => $project['title'])))));
+      $recommended_version = $recommended_release['version'] . ' ' . l($this->t('(Release notes)'), $recommended_release['release_link'], array('attributes' => array('title' => $this->t('Release notes for @project_title', array('@project_title' => $project['title'])))));
       if ($recommended_release['version_major'] != $project['existing_major']) {
         $recommended_version .= '<div title="Major upgrade warning" class="update-major-version-warning">' . $this->t('This update is a major version update which means that it may not be backwards compatible with your currently running version.  It is recommended that you read the release notes and proceed at your own risk.') . '</div>';
       }
diff --git a/core/modules/update/src/Tests/UpdateContribTest.php b/core/modules/update/src/Tests/UpdateContribTest.php
index 118a60e..b389c24 100644
--- a/core/modules/update/src/Tests/UpdateContribTest.php
+++ b/core/modules/update/src/Tests/UpdateContribTest.php
@@ -50,12 +50,12 @@ function testNoReleasesAvailable() {
     // Cannot use $this->standardTests() because we need to check for the
     // 'No available releases found' string.
     $this->assertRaw('<h3>' . t('Drupal core') . '</h3>');
-    $this->assertRaw(_l(t('Drupal'), 'http://example.com/project/drupal'));
+    $this->assertRaw(l(t('Drupal'), 'http://example.com/project/drupal'));
     $this->assertText(t('Up to date'));
     $this->assertRaw('<h3>' . t('Modules') . '</h3>');
     $this->assertNoText(t('Update available'));
     $this->assertText(t('No available releases found'));
-    $this->assertNoRaw(_l(t('AAA Update test'), 'http://example.com/project/aaa_update_test'));
+    $this->assertNoRaw(l(t('AAA Update test'), 'http://example.com/project/aaa_update_test'));
 
     $available = update_get_available();
     $this->assertFalse(isset($available['aaa_update_test']['fetch_status']), 'Results are cached even if no releases are available.');
@@ -86,7 +86,7 @@ function testUpdateContribBasic() {
     $this->assertText(t('Up to date'));
     $this->assertRaw('<h3>' . t('Modules') . '</h3>');
     $this->assertNoText(t('Update available'));
-    $this->assertRaw(_l(t('AAA Update test'), 'http://example.com/project/aaa_update_test'), 'Link to aaa_update_test project appears.');
+    $this->assertRaw(l(t('AAA Update test'), 'http://example.com/project/aaa_update_test'), 'Link to aaa_update_test project appears.');
   }
 
   /**
@@ -147,10 +147,10 @@ function testUpdateContribOrder() {
     $this->assertText(t('CCC Update test'));
     // We want aaa_update_test included in the ccc_update_test project, not as
     // its own project on the report.
-    $this->assertNoRaw(_l(t('AAA Update test'), 'http://example.com/project/aaa_update_test'), 'Link to aaa_update_test project does not appear.');
+    $this->assertNoRaw(l(t('AAA Update test'), 'http://example.com/project/aaa_update_test'), 'Link to aaa_update_test project does not appear.');
     // The other two should be listed as projects.
-    $this->assertRaw(_l(t('BBB Update test'), 'http://example.com/project/bbb_update_test'), 'Link to bbb_update_test project appears.');
-    $this->assertRaw(_l(t('CCC Update test'), 'http://example.com/project/ccc_update_test'), 'Link to bbb_update_test project appears.');
+    $this->assertRaw(l(t('BBB Update test'), 'http://example.com/project/bbb_update_test'), 'Link to bbb_update_test project appears.');
+    $this->assertRaw(l(t('CCC Update test'), 'http://example.com/project/ccc_update_test'), 'Link to bbb_update_test project appears.');
 
     // We want to make sure we see the BBB project before the CCC project.
     // Instead of just searching for 'BBB Update test' or something, we want
@@ -197,7 +197,7 @@ function testUpdateBaseThemeSecurityUpdate() {
     );
     $this->refreshUpdateStatus($xml_mapping);
     $this->assertText(t('Security update required!'));
-    $this->assertRaw(_l(t('Update test base theme'), 'http://example.com/project/update_test_basetheme'), 'Link to the Update test base theme project appears.');
+    $this->assertRaw(l(t('Update test base theme'), 'http://example.com/project/update_test_basetheme'), 'Link to the Update test base theme project appears.');
   }
 
   /**
@@ -247,8 +247,8 @@ function testUpdateShowDisabledThemes() {
       'update_test_subtheme' => '1_0',
       'update_test_basetheme' => '1_1-sec',
     );
-    $base_theme_project_link = _l(t('Update test base theme'), 'http://example.com/project/update_test_basetheme');
-    $sub_theme_project_link = _l(t('Update test subtheme'), 'http://example.com/project/update_test_subtheme');
+    $base_theme_project_link = l(t('Update test base theme'), 'http://example.com/project/update_test_basetheme');
+    $sub_theme_project_link = l(t('Update test subtheme'), 'http://example.com/project/update_test_subtheme');
     foreach (array(TRUE, FALSE) as $check_disabled) {
       $update_settings->set('check.disabled_extensions', $check_disabled)->save();
       $this->refreshUpdateStatus($xml_mapping);
@@ -350,9 +350,9 @@ function testUpdateBrokenFetchURL() {
     $this->assertUniqueText(t('Failed to get available update data for one project.'));
 
     // The other two should be listed as projects.
-    $this->assertRaw(_l(t('AAA Update test'), 'http://example.com/project/aaa_update_test'), 'Link to aaa_update_test project appears.');
-    $this->assertNoRaw(_l(t('BBB Update test'), 'http://example.com/project/bbb_update_test'), 'Link to bbb_update_test project does not appear.');
-    $this->assertRaw(_l(t('CCC Update test'), 'http://example.com/project/ccc_update_test'), 'Link to bbb_update_test project appears.');
+    $this->assertRaw(l(t('AAA Update test'), 'http://example.com/project/aaa_update_test'), 'Link to aaa_update_test project appears.');
+    $this->assertNoRaw(l(t('BBB Update test'), 'http://example.com/project/bbb_update_test'), 'Link to bbb_update_test project does not appear.');
+    $this->assertRaw(l(t('CCC Update test'), 'http://example.com/project/ccc_update_test'), 'Link to bbb_update_test project appears.');
   }
 
   /**
@@ -394,7 +394,7 @@ function testHookUpdateStatusAlter() {
     $this->drupalGet('admin/reports/updates');
     $this->assertRaw('<h3>' . t('Modules') . '</h3>');
     $this->assertText(t('Security update required!'));
-    $this->assertRaw(_l(t('AAA Update test'), 'http://example.com/project/aaa_update_test'), 'Link to aaa_update_test project appears.');
+    $this->assertRaw(l(t('AAA Update test'), 'http://example.com/project/aaa_update_test'), 'Link to aaa_update_test project appears.');
 
     // Visit the reports page again without the altering and make sure the
     // status is back to normal.
@@ -402,7 +402,7 @@ function testHookUpdateStatusAlter() {
     $this->drupalGet('admin/reports/updates');
     $this->assertRaw('<h3>' . t('Modules') . '</h3>');
     $this->assertNoText(t('Security update required!'));
-    $this->assertRaw(_l(t('AAA Update test'), 'http://example.com/project/aaa_update_test'), 'Link to aaa_update_test project appears.');
+    $this->assertRaw(l(t('AAA Update test'), 'http://example.com/project/aaa_update_test'), 'Link to aaa_update_test project appears.');
 
     // Turn the altering back on and visit the Update manager UI.
     $update_test_config->set('update_status', $update_status)->save();
diff --git a/core/modules/update/src/Tests/UpdateCoreTest.php b/core/modules/update/src/Tests/UpdateCoreTest.php
index 969f15c..2201cf3 100644
--- a/core/modules/update/src/Tests/UpdateCoreTest.php
+++ b/core/modules/update/src/Tests/UpdateCoreTest.php
@@ -51,9 +51,9 @@ function testNormalUpdateAvailable() {
     $this->assertNoText(t('Up to date'));
     $this->assertText(t('Update available'));
     $this->assertNoText(t('Security update required!'));
-    $this->assertRaw(_l('7.1', 'http://example.com/drupal-7-1-release'), 'Link to release appears.');
-    $this->assertRaw(_l(t('Download'), 'http://example.com/drupal-7-1.tar.gz'), 'Link to download appears.');
-    $this->assertRaw(_l(t('Release notes'), 'http://example.com/drupal-7-1-release'), 'Link to release notes appears.');
+    $this->assertRaw(l('7.1', 'http://example.com/drupal-7-1-release'), 'Link to release appears.');
+    $this->assertRaw(l(t('Download'), 'http://example.com/drupal-7-1.tar.gz'), 'Link to download appears.');
+    $this->assertRaw(l(t('Release notes'), 'http://example.com/drupal-7-1-release'), 'Link to release notes appears.');
   }
 
   /**
@@ -66,9 +66,9 @@ function testSecurityUpdateAvailable() {
     $this->assertNoText(t('Up to date'));
     $this->assertNoText(t('Update available'));
     $this->assertText(t('Security update required!'));
-    $this->assertRaw(_l('7.2', 'http://example.com/drupal-7-2-release'), 'Link to release appears.');
-    $this->assertRaw(_l(t('Download'), 'http://example.com/drupal-7-2.tar.gz'), 'Link to download appears.');
-    $this->assertRaw(_l(t('Release notes'), 'http://example.com/drupal-7-2-release'), 'Link to release notes appears.');
+    $this->assertRaw(l('7.2', 'http://example.com/drupal-7-2-release'), 'Link to release appears.');
+    $this->assertRaw(l(t('Download'), 'http://example.com/drupal-7-2.tar.gz'), 'Link to download appears.');
+    $this->assertRaw(l(t('Release notes'), 'http://example.com/drupal-7-2-release'), 'Link to release notes appears.');
   }
 
   /**
@@ -99,7 +99,7 @@ function testDatestampMismatch() {
    */
   function testModulePageRunCron() {
     $this->setSystemInfo7_0();
-    \Drupal::config('update.settings')->set('fetch.url', _url('update-test', array('absolute' => TRUE)))->save();
+    \Drupal::config('update.settings')->set('fetch.url', url('update-test', array('absolute' => TRUE)))->save();
     \Drupal::config('update_test.settings')->set('xml_map', array('drupal' => '0'))->save();
 
     $this->cronRun();
@@ -113,7 +113,7 @@ function testModulePageRunCron() {
   function testModulePageUpToDate() {
     $this->setSystemInfo7_0();
     // Instead of using refreshUpdateStatus(), set these manually.
-    \Drupal::config('update.settings')->set('fetch.url', _url('update-test', array('absolute' => TRUE)))->save();
+    \Drupal::config('update.settings')->set('fetch.url', url('update-test', array('absolute' => TRUE)))->save();
     \Drupal::config('update_test.settings')->set('xml_map', array('drupal' => '0'))->save();
 
     $this->drupalGet('admin/reports/updates');
@@ -130,7 +130,7 @@ function testModulePageUpToDate() {
   function testModulePageRegularUpdate() {
     $this->setSystemInfo7_0();
     // Instead of using refreshUpdateStatus(), set these manually.
-    \Drupal::config('update.settings')->set('fetch.url', _url('update-test', array('absolute' => TRUE)))->save();
+    \Drupal::config('update.settings')->set('fetch.url', url('update-test', array('absolute' => TRUE)))->save();
     \Drupal::config('update_test.settings')->set('xml_map', array('drupal' => '1'))->save();
 
     $this->drupalGet('admin/reports/updates');
@@ -147,7 +147,7 @@ function testModulePageRegularUpdate() {
   function testModulePageSecurityUpdate() {
     $this->setSystemInfo7_0();
     // Instead of using refreshUpdateStatus(), set these manually.
-    \Drupal::config('update.settings')->set('fetch.url', _url('update-test', array('absolute' => TRUE)))->save();
+    \Drupal::config('update.settings')->set('fetch.url', url('update-test', array('absolute' => TRUE)))->save();
     \Drupal::config('update_test.settings')->set('xml_map', array('drupal' => '2-sec'))->save();
 
     $this->drupalGet('admin/reports/updates');
@@ -219,7 +219,7 @@ function testFetchTasks() {
   function testLanguageModuleUpdate() {
     $this->setSystemInfo7_0();
     // Instead of using refreshUpdateStatus(), set these manually.
-    \Drupal::config('update.settings')->set('fetch.url', _url('update-test', array('absolute' => TRUE)))->save();
+    \Drupal::config('update.settings')->set('fetch.url', url('update-test', array('absolute' => TRUE)))->save();
     \Drupal::config('update_test.settings')->set('xml_map', array('drupal' => '1'))->save();
 
     $this->drupalGet('admin/reports/updates');
diff --git a/core/modules/update/src/Tests/UpdateTestBase.php b/core/modules/update/src/Tests/UpdateTestBase.php
index 98b768d..47a6649 100644
--- a/core/modules/update/src/Tests/UpdateTestBase.php
+++ b/core/modules/update/src/Tests/UpdateTestBase.php
@@ -43,7 +43,7 @@
   protected function refreshUpdateStatus($xml_map, $url = 'update-test') {
     // Tell the Update Manager module to fetch from the URL provided by
     // update_test module.
-    \Drupal::config('update.settings')->set('fetch.url', _url($url, array('absolute' => TRUE)))->save();
+    \Drupal::config('update.settings')->set('fetch.url', url($url, array('absolute' => TRUE)))->save();
     // Save the map for update_test_mock_page() to use.
     \Drupal::config('update_test.settings')->set('xml_map', $xml_map)->save();
     // Manually check the update status.
@@ -55,7 +55,7 @@ protected function refreshUpdateStatus($xml_map, $url = 'update-test') {
    */
   protected function standardTests() {
     $this->assertRaw('<h3>' . t('Drupal core') . '</h3>');
-    $this->assertRaw(_l(t('Drupal'), 'http://example.com/project/drupal'), 'Link to the Drupal project appears.');
+    $this->assertRaw(l(t('Drupal'), 'http://example.com/project/drupal'), 'Link to the Drupal project appears.');
     $this->assertNoText(t('No available releases found'));
   }
 }
diff --git a/core/modules/update/src/Tests/UpdateUploadTest.php b/core/modules/update/src/Tests/UpdateUploadTest.php
index fe13c08..29d0357 100644
--- a/core/modules/update/src/Tests/UpdateUploadTest.php
+++ b/core/modules/update/src/Tests/UpdateUploadTest.php
@@ -79,7 +79,7 @@ function testUpdateManagerCoreSecurityUpdateMessages() {
       ->set('system_info', $setting)
       ->set('xml_map', array('drupal' => '2-sec'))
       ->save();
-    \Drupal::config('update.settings')->set('fetch.url', _url('update-test', array('absolute' => TRUE)))->save();
+    \Drupal::config('update.settings')->set('fetch.url', url('update-test', array('absolute' => TRUE)))->save();
     // Initialize the update status.
     $this->drupalGet('admin/reports/updates');
 
diff --git a/core/modules/update/update.module b/core/modules/update/update.module
index 0619376..9b77869 100644
--- a/core/modules/update/update.module
+++ b/core/modules/update/update.module
@@ -205,11 +205,11 @@ function update_theme() {
       'file' => 'update.report.inc',
       'template' => 'update-project-status',
     ),
+    // We are using template instead of '#type' => 'table' here to keep markup
+    // out of preprocess and allow for easier changes to markup.
     'update_version' => array(
       'variables' => array('version' => NULL, 'title' => NULL, 'attributes' => array()),
       'file' => 'update.report.inc',
-      // We are using template instead of '#type' => 'table' here to keep markup
-      // out of preprocess and allow for easier changes to markup.
       'template' => 'update-version',
     ),
   );
diff --git a/core/modules/update/update.report.inc b/core/modules/update/update.report.inc
index 38c724c..9ee4dbf 100644
--- a/core/modules/update/update.report.inc
+++ b/core/modules/update/update.report.inc
@@ -6,7 +6,6 @@
  */
 
 use Drupal\Core\Template\Attribute;
-use Drupal\Core\Url;
 
 /**
  * Prepares variables for project status report templates.
@@ -136,7 +135,7 @@ function template_preprocess_update_project_status(&$variables) {
 
   // Set the project title and URL.
   $variables['title'] = (isset($project['title'])) ? $project['title'] : $project['name'];
-  $variables['url'] = (isset($project['link'])) ? Url::fromUri($project['link'])->toString() : NULL;
+  $variables['url'] = (isset($project['link'])) ? url($project['link']) : NULL;
 
   $variables['install_type'] = $project['install_type'];
   if ($project['install_type'] == 'dev' && !empty($project['datestamp'])) {
diff --git a/core/modules/user/src/Plugin/Block/UserLoginBlock.php b/core/modules/user/src/Plugin/Block/UserLoginBlock.php
index a2111cc..ed40273 100644
--- a/core/modules/user/src/Plugin/Block/UserLoginBlock.php
+++ b/core/modules/user/src/Plugin/Block/UserLoginBlock.php
@@ -41,7 +41,7 @@ public function build() {
     unset($form['pass']['#description']);
     $form['name']['#size'] = 15;
     $form['pass']['#size'] = 15;
-    $form['#action'] = _url(current_path(), array('query' => drupal_get_destination(), 'external' => FALSE));
+    $form['#action'] = url(current_path(), array('query' => drupal_get_destination(), 'external' => FALSE));
     // Build action links.
     $items = array();
     if (\Drupal::config('user.settings')->get('register') != USER_REGISTER_ADMINISTRATORS_ONLY) {
diff --git a/core/modules/user/src/Tests/UserAdminTest.php b/core/modules/user/src/Tests/UserAdminTest.php
index ae57536..3b18295 100644
--- a/core/modules/user/src/Tests/UserAdminTest.php
+++ b/core/modules/user/src/Tests/UserAdminTest.php
@@ -54,7 +54,7 @@ function testUserAdmin() {
     // Test for existence of edit link in table.
     // @todo This cannot be converted to \Drupal::l() until
     //   https://www.drupal.org/node/2345725 is resolved.
-    $link = _l(t('Edit'), "user/" . $user_a->id() . "/edit", array('query' => array('destination' => 'admin/people')));
+    $link = l(t('Edit'), "user/" . $user_a->id() . "/edit", array('query' => array('destination' => 'admin/people')));
     $this->assertRaw($link, 'Found user A edit link on admin users page');
 
     // Test exposed filter elements.
diff --git a/core/modules/user/user.module b/core/modules/user/user.module
index 82aca31..e33cd28 100644
--- a/core/modules/user/user.module
+++ b/core/modules/user/user.module
@@ -576,7 +576,6 @@ function template_preprocess_username(&$variables) {
   $variables['name'] = String::checkPlain($name);
   $variables['profile_access'] = \Drupal::currentUser()->hasPermission('access user profiles');
 
-  $external = FALSE;
   // Populate link path and attributes if appropriate.
   if ($variables['uid'] && $variables['profile_access']) {
     // We are linking to a local user.
@@ -590,19 +589,10 @@ function template_preprocess_username(&$variables) {
     $variables['attributes']['rel'] = 'nofollow';
     $variables['link_path'] = $account->homepage;
     $variables['homepage'] = $account->homepage;
-    $external = TRUE;
   }
-  // We have a link path, so we should generate a URL.
+  // We have a link path, so we should generate a link using url().
   if (isset($variables['link_path'])) {
-    if ($external) {
-      $variables['attributes']['href'] = Url::fromUri($variables['link_path'], $variables['link_options'])
-        ->toString();
-    }
-    else {
-      $variables['attributes']['href'] = Url::fromRoute('entity.user.canonical', array(
-        'user' => $variables['uid'],
-      ))->toString();
-    }
+    $variables['attributes']['href'] = url($variables['link_path'], $variables['link_options']);
   }
 }
 
diff --git a/core/modules/views/src/Form/ViewsExposedForm.php b/core/modules/views/src/Form/ViewsExposedForm.php
index a425748..ee2fa2d 100644
--- a/core/modules/views/src/Form/ViewsExposedForm.php
+++ b/core/modules/views/src/Form/ViewsExposedForm.php
@@ -114,7 +114,7 @@ public function buildForm(array $form, FormStateInterface $form_state) {
       '#id' => drupal_html_id('edit-submit-' . $view->storage->id()),
     );
 
-    $form['#action'] = _url($view->display_handler->getUrl());
+    $form['#action'] = url($view->display_handler->getUrl());
     $form['#theme'] = $view->buildThemeFunctions('views_exposed_form');
     $form['#id'] = drupal_clean_css_identifier('views_exposed_form-' . String::checkPlain($view->storage->id()) . '-' . String::checkPlain($display['id']));
     // $form['#attributes']['class'] = array('views-exposed-form');
diff --git a/core/modules/views/src/Plugin/views/display/DisplayPluginBase.php b/core/modules/views/src/Plugin/views/display/DisplayPluginBase.php
index f370bea..140f11b 100644
--- a/core/modules/views/src/Plugin/views/display/DisplayPluginBase.php
+++ b/core/modules/views/src/Plugin/views/display/DisplayPluginBase.php
@@ -2115,7 +2115,7 @@ public function renderMoreLink() {
           $url_options['query'] = $this->view->exposed_raw_input;
         }
         $theme = $this->view->buildThemeFunctions('views_more');
-        $path = check_url(_url($path, $url_options));
+        $path = check_url(url($path, $url_options));
 
         return array(
           '#theme' => $theme,
diff --git a/core/modules/views/src/Plugin/views/display/PathPluginBase.php b/core/modules/views/src/Plugin/views/display/PathPluginBase.php
index ee8370a..1fe0a35 100644
--- a/core/modules/views/src/Plugin/views/display/PathPluginBase.php
+++ b/core/modules/views/src/Plugin/views/display/PathPluginBase.php
@@ -393,7 +393,7 @@ public function buildOptionsForm(&$form, FormStateInterface $form_state) {
           '#title' => $this->t('Path'),
           '#description' => $this->t('This view will be displayed by visiting this path on your site. You may use "%" in your URL to represent values that will be used for contextual filters: For example, "node/%/feed". If needed you can even specify named route parameters like taxonomy/term/%taxonomy_term'),
           '#default_value' => $this->getOption('path'),
-          '#field_prefix' => '<span dir="ltr">' . _url(NULL, array('absolute' => TRUE)),
+          '#field_prefix' => '<span dir="ltr">' . url(NULL, array('absolute' => TRUE)),
           '#field_suffix' => '</span>&lrm;',
           '#attributes' => array('dir' => 'ltr'),
           // Account for the leading backslash.
diff --git a/core/modules/views/src/Plugin/views/field/FieldPluginBase.php b/core/modules/views/src/Plugin/views/field/FieldPluginBase.php
index a56be9b..c6f0c1e 100644
--- a/core/modules/views/src/Plugin/views/field/FieldPluginBase.php
+++ b/core/modules/views/src/Plugin/views/field/FieldPluginBase.php
@@ -13,6 +13,7 @@
 use Drupal\Component\Utility\UrlHelper;
 use Drupal\Component\Utility\Xss;
 use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Url;
 use Drupal\views\Plugin\views\HandlerBase;
 use Drupal\views\Plugin\views\display\DisplayPluginBase;
 use Drupal\views\ResultRow;
@@ -1277,14 +1278,14 @@ public function renderText($alter) {
         $more_link_path = $this->options['alter']['more_link_path'];
         $more_link_path = strip_tags(decode_entities(strtr($more_link_path, $tokens)));
 
-        // Make sure that paths which were run through _url() work as well.
+        // Make sure that paths which were run through url() work as well.
         $base_path = base_path();
         // Checks whether the path starts with the base_path.
         if (strpos($more_link_path, $base_path) === 0) {
           $more_link_path = drupal_substr($more_link_path, drupal_strlen($base_path));
         }
 
-        $more_link = _l($more_link_text, $more_link_path, array('attributes' => array('class' => array('views-more-link'))));
+        $more_link = l($more_link_text, $more_link_path, array('attributes' => array('class' => array('views-more-link'))));
 
         $suffix .= " " . $more_link;
       }
@@ -1344,7 +1345,7 @@ protected function renderAsLink($alter, $text, $tokens) {
       'absolute' => !empty($alter['absolute']) ? TRUE : FALSE,
     );
 
-    // $path will be run through check_url() by _l() so we do not need to
+    // $path will be run through check_url() by l() so we do not need to
     // sanitize it ourselves.
     $path = $alter['path'];
 
@@ -1456,7 +1457,7 @@ protected function renderAsLink($alter, $text, $tokens) {
     // parsed values.
     if (isset($alter['query'])) {
       // Convert the query to a string, perform token replacement, and then
-      // convert back to an array form for _l().
+      // convert back to an array form for l().
       $options['query'] = UrlHelper::buildQuery($alter['query']);
       $options['query'] = strtr($options['query'], $tokens);
       $query = array();
@@ -1482,7 +1483,7 @@ protected function renderAsLink($alter, $text, $tokens) {
       $options['entity_type'] = $alter['entity_type'];
     }
 
-    $value .= _l($text, $path, $options);
+    $value .= l($text, $path, $options);
 
     if (!empty($alter['suffix'])) {
       $value .= Xss::filterAdmin(strtr($alter['suffix'], $tokens));
diff --git a/core/modules/views/src/Plugin/views/field/Url.php b/core/modules/views/src/Plugin/views/field/Url.php
index 65672ef..ea82308 100644
--- a/core/modules/views/src/Plugin/views/field/Url.php
+++ b/core/modules/views/src/Plugin/views/field/Url.php
@@ -45,7 +45,7 @@ public function buildOptionsForm(&$form, FormStateInterface $form_state) {
   public function render(ResultRow $values) {
     $value = $this->getValue($values);
     if (!empty($this->options['display_as_link'])) {
-      return _l($this->sanitizeValue($value), $value, array('html' => TRUE));
+      return l($this->sanitizeValue($value), $value, array('html' => TRUE));
     }
     else {
       return $this->sanitizeValue($value, 'url');
diff --git a/core/modules/views/src/Plugin/views/row/RssFields.php b/core/modules/views/src/Plugin/views/row/RssFields.php
index 456958f..ec4830c 100644
--- a/core/modules/views/src/Plugin/views/row/RssFields.php
+++ b/core/modules/views/src/Plugin/views/row/RssFields.php
@@ -143,7 +143,7 @@ public function render($row) {
     // Create the RSS item object.
     $item = new \stdClass();
     $item->title = $this->getField($row_index, $this->options['title_field']);
-    $item->link = _url($this->getField($row_index, $this->options['link_field']), array('absolute' => TRUE));
+    $item->link = url($this->getField($row_index, $this->options['link_field']), array('absolute' => TRUE));
     $item->description = $this->getField($row_index, $this->options['description_field']);
     $item->elements = array(
       array('key' => 'pubDate', 'value' => $this->getField($row_index, $this->options['date_field'])),
@@ -157,7 +157,7 @@ public function render($row) {
     $item_guid = $this->getField($row_index, $this->options['guid_field_options']['guid_field']);
     if ($this->options['guid_field_options']['guid_field_is_permalink']) {
       $guid_is_permalink_string = 'true';
-      $item_guid = _url($item_guid, array('absolute' => TRUE));
+      $item_guid = url($item_guid, array('absolute' => TRUE));
     }
     $item->elements[] = array(
       'key' => 'guid',
diff --git a/core/modules/views/src/Plugin/views/style/Opml.php b/core/modules/views/src/Plugin/views/style/Opml.php
index ad23aae..a1a0094 100644
--- a/core/modules/views/src/Plugin/views/style/Opml.php
+++ b/core/modules/views/src/Plugin/views/style/Opml.php
@@ -41,7 +41,7 @@ public function attachTo(array &$build, $display_id, $path, $title) {
     }
     $url_options['absolute'] = TRUE;
 
-    $url = _url($this->view->getUrl(NULL, $path), $url_options);
+    $url = url($this->view->getUrl(NULL, $path), $url_options);
     if ($display->hasPath()) {
       if (empty($this->preview)) {
         $build['#attached']['drupal_add_feed'][] = array($url, $title);
diff --git a/core/modules/views/src/Plugin/views/style/Rss.php b/core/modules/views/src/Plugin/views/style/Rss.php
index c75e7d4..f812ccc 100644
--- a/core/modules/views/src/Plugin/views/style/Rss.php
+++ b/core/modules/views/src/Plugin/views/style/Rss.php
@@ -41,7 +41,7 @@ public function attachTo(array &$build, $display_id, $path, $title) {
     }
     $url_options['absolute'] = TRUE;
 
-    $url = _url($this->view->getUrl(NULL, $path), $url_options);
+    $url = url($this->view->getUrl(NULL, $path), $url_options);
     if ($display->hasPath()) {
       if (empty($this->preview)) {
         // Add a call for drupal_add_feed to the view attached data.
diff --git a/core/modules/views/src/Plugin/views/wizard/WizardPluginBase.php b/core/modules/views/src/Plugin/views/wizard/WizardPluginBase.php
index c2a23dc..1b13575 100644
--- a/core/modules/views/src/Plugin/views/wizard/WizardPluginBase.php
+++ b/core/modules/views/src/Plugin/views/wizard/WizardPluginBase.php
@@ -218,7 +218,7 @@ public function getSorts() {
   public function buildForm(array $form, FormStateInterface $form_state) {
     $style_options = Views::fetchPluginNames('style', 'normal', array($this->base_table));
     $feed_row_options = Views::fetchPluginNames('row', 'feed', array($this->base_table));
-    $path_prefix = _url(NULL, array('absolute' => TRUE));
+    $path_prefix = url(NULL, array('absolute' => TRUE));
 
     // Add filters and sorts which apply to the view as a whole.
     $this->buildFilters($form, $form_state);
diff --git a/core/modules/views/src/Tests/GlossaryTest.php b/core/modules/views/src/Tests/GlossaryTest.php
index 61fb6a3..4518aae 100644
--- a/core/modules/views/src/Tests/GlossaryTest.php
+++ b/core/modules/views/src/Tests/GlossaryTest.php
@@ -66,7 +66,7 @@ public function testGlossaryView() {
     $this->assertResponse(200);
 
     foreach ($nodes_per_char as $char => $count) {
-      $href = _url('glossary/' . $char);
+      $href = url('glossary/' . $char);
       $label = Unicode::strtoupper($char);
       // Get the summary link for a certain character. Filter by label and href
       // to ensure that both of them are correct.
diff --git a/core/modules/views/src/Tests/Handler/FieldUrlTest.php b/core/modules/views/src/Tests/Handler/FieldUrlTest.php
index 8373071..04ed05c 100644
--- a/core/modules/views/src/Tests/Handler/FieldUrlTest.php
+++ b/core/modules/views/src/Tests/Handler/FieldUrlTest.php
@@ -70,7 +70,7 @@ public function testFieldUrl() {
 
     $this->executeView($view);
 
-    $this->assertEqual(_l('John', 'John'), $view->field['name']->advancedRender($view->result[0]));
+    $this->assertEqual(l('John', 'John'), $view->field['name']->advancedRender($view->result[0]));
   }
 
 }
diff --git a/core/modules/views/src/Tests/Plugin/ExposedFormTest.php b/core/modules/views/src/Tests/Plugin/ExposedFormTest.php
index 1be2038..ecbdbc0 100644
--- a/core/modules/views/src/Tests/Plugin/ExposedFormTest.php
+++ b/core/modules/views/src/Tests/Plugin/ExposedFormTest.php
@@ -129,7 +129,7 @@ public function testExposedFormRender() {
 
     $this->assertFieldByXpath('//form/@id', $this->getExpectedExposedFormId($view), 'Expected form ID found.');
 
-    $expected_action = _url($view->display_handler->getUrl());
+    $expected_action = url($view->display_handler->getUrl());
     $this->assertFieldByXPath('//form/@action', $expected_action, 'The expected value for the action attribute was found.');
   }
 
diff --git a/core/modules/views/src/Tests/TokenReplaceTest.php b/core/modules/views/src/Tests/TokenReplaceTest.php
index 13ae1cd..bb97765 100644
--- a/core/modules/views/src/Tests/TokenReplaceTest.php
+++ b/core/modules/views/src/Tests/TokenReplaceTest.php
@@ -44,7 +44,7 @@ function testTokenReplacement() {
       '[view:description]' => 'Test view to token replacement tests.',
       '[view:id]' => 'test_tokens',
       '[view:title]' => 'Test token page',
-      '[view:url]' => _url('test_tokens', array('absolute' => TRUE)),
+      '[view:url]' => url('test_tokens', array('absolute' => TRUE)),
       '[view:total-rows]' => (string) $view->total_rows,
       '[view:base-table]' => 'views_test_data',
       '[view:base-field]' => 'id',
diff --git a/core/modules/views/src/Tests/ViewStorageTest.php b/core/modules/views/src/Tests/ViewStorageTest.php
index 7a05428..fc78a9e 100644
--- a/core/modules/views/src/Tests/ViewStorageTest.php
+++ b/core/modules/views/src/Tests/ViewStorageTest.php
@@ -185,7 +185,7 @@ protected function displayTests() {
    * Tests the display related functions like getDisplaysList().
    */
   protected function displayMethodTests() {
-    // Enable the system module so _l() can work using url_alias table.
+    // Enable the system module so l() can work using url_alias table.
     $this->installSchema('system', 'url_alias');
 
     $config['display'] = array(
diff --git a/core/modules/views/src/Tests/Wizard/BasicTest.php b/core/modules/views/src/Tests/Wizard/BasicTest.php
index 9b6e0f2..99c495c 100644
--- a/core/modules/views/src/Tests/Wizard/BasicTest.php
+++ b/core/modules/views/src/Tests/Wizard/BasicTest.php
@@ -74,7 +74,7 @@ function testViewsWizardAndListing() {
     $this->assertText($node2->label());
 
     // Check if we have the feed.
-    $this->assertLinkByHref(_url($view2['page[feed_properties][path]']));
+    $this->assertLinkByHref(url($view2['page[feed_properties][path]']));
     $this->drupalGet($view2['page[feed_properties][path]']);
     $this->assertRaw('<rss version="2.0"');
     // The feed should have the same title and nodes as the page.
@@ -88,7 +88,7 @@ function testViewsWizardAndListing() {
     $this->drupalGet('admin/structure/views');
     $this->assertText($view2['label']);
     $this->assertText($view2['description']);
-    $this->assertLinkByHref(_url($view2['page[path]']));
+    $this->assertLinkByHref(url($view2['page[path]']));
 
     // The view should not have a REST export display.
     $this->assertNoText('REST export', 'If only the page option was enabled in the wizard, the resulting view does not have a REST export display.');
@@ -123,7 +123,7 @@ function testViewsWizardAndListing() {
     $this->drupalGet('admin/structure/views');
     $this->assertText($view3['label']);
     $this->assertText($view3['description']);
-    $this->assertLinkByHref(_url($view3['page[path]']));
+    $this->assertLinkByHref(url($view3['page[path]']));
 
     // The view should not have a REST export display.
     $this->assertNoText('REST export', 'If only the page and block options were enabled in the wizard, the resulting view does not have a REST export display.');
diff --git a/core/modules/views/src/Tests/Wizard/MenuTest.php b/core/modules/views/src/Tests/Wizard/MenuTest.php
index 8c4f7b9..ba3aa42 100644
--- a/core/modules/views/src/Tests/Wizard/MenuTest.php
+++ b/core/modules/views/src/Tests/Wizard/MenuTest.php
@@ -40,7 +40,7 @@ function testMenus() {
     $this->drupalGet('');
     $this->assertResponse(200);
     $this->assertLink($view['page[link_properties][title]']);
-    $this->assertLinkByHref(_url($view['page[path]']));
+    $this->assertLinkByHref(url($view['page[path]']));
 
     // Make sure the link is associated with the main menu.
     /** @var \Drupal\Core\Menu\MenuLinkManagerInterface $menu_link_manager */
diff --git a/core/modules/views/views.module b/core/modules/views/views.module
index 84b324f..dda2b55 100644
--- a/core/modules/views/views.module
+++ b/core/modules/views/views.module
@@ -145,6 +145,7 @@ function views_theme($existing, $type, $theme, $path) {
   // Default view themes
   $hooks['views_view_field'] = $base + array(
     'variables' => array('view' => NULL, 'field' => NULL, 'row' => NULL),
+    'function' => 'theme_views_view_field',
   );
   $hooks['views_view_grouping'] = $base + array(
     'variables' => array('view' => NULL, 'grouping' => NULL, 'grouping_level' => NULL, 'rows' => NULL, 'title' => NULL),
@@ -165,9 +166,9 @@ function views_theme($existing, $type, $theme, $path) {
       if (!isset($def['theme']) || empty($def['register_theme'])) {
         continue;
       }
-      // For each theme registration we a base directory to look for the
-      // templates folder. This will be in any case the root of the given module
-      // so we always need a module definition.
+      // For each theme registration, we have a base directory to check for the
+      // templates folder. This will be relative to the root of the given module
+      // folder, so we always need a module definition.
       // @todo: watchdog or exception?
       if (!isset($def['provider']) || !$module_handler->moduleExists($def['provider'])) {
         continue;
@@ -177,35 +178,44 @@ function views_theme($existing, $type, $theme, $path) {
         'variables' => $variables[$type],
       );
 
-      // For the views module we ensure views.theme.inc is included.
-      if ($def['provider'] == 'views') {
-        $def['theme_file'] = 'views.theme.inc';
-      }
       // We always use the module directory as base dir.
       $module_dir = drupal_get_path('module', $def['provider']);
+      $hooks[$def['theme']]['path'] = $module_dir;
 
+      // For the views module we ensure views.theme.inc is included.
+      if ($def['provider'] == 'views') {
+        if (!isset($hooks[$def['theme']]['includes'])) {
+          $hooks[$def['theme']]['includes'] = array();
+        }
+        if (!in_array('views.theme.inc', $hooks[$def['theme']]['includes'])) {
+          $hooks[$def['theme']]['includes'][] = $module_dir . '/views.theme.inc';
+        }
+      }
       // The theme_file definition is always relative to the modules directory.
-      if (isset($def['theme_file'])) {
-        $hooks[$def['theme']]['path'] = $module_dir;
+      elseif (!empty($def['theme_file'])) {
         $hooks[$def['theme']]['file'] = $def['theme_file'];
       }
-      // Whenever we got a theme file, we include it directly so we can
+
+      // Whenever we have a theme file, we include it directly so we can
       // auto-detect the theme function.
       if (isset($def['theme_file'])) {
-        $include = DRUPAL_ROOT . '/' . $module_dir. '/' . $def['theme_file'];
+        $include = DRUPAL_ROOT . '/' . $module_dir . '/' . $def['theme_file'];
         if (is_file($include)) {
           require_once $include;
         }
       }
-     // If there is no theme function for the given theme definition, we assume
-     // a template file shall be used. By default this file is located in the
-     // /templates directory of the module's folder.
-     // If a module wants to define its own location it has to set
-     // register_theme of the plugin to FALSE and implement hook_theme() by
-     // itself.
+
+      // If there is no theme function for the given theme definition, it must
+      // be a template file. By default this file is located in the /templates
+      // directory of the module's folder. If a module wants to define its own
+      // location it has to set register_theme of the plugin to FALSE and
+      // implement hook_theme() by itself.
       if (!function_exists('theme_' . $def['theme'])) {
-        $hooks[$def['theme']]['path'] = $module_dir;
-        $hooks[$def['theme']]['template'] = 'templates/' . drupal_clean_css_identifier($def['theme']);
+        $hooks[$def['theme']]['path'] .= '/templates';
+        $hooks[$def['theme']]['template'] = drupal_clean_css_identifier($def['theme']);
+      }
+      else {
+        $hooks[$def['theme']]['function'] = 'theme_' . $def['theme'];
       }
     }
   }
diff --git a/core/modules/views/views.theme.inc b/core/modules/views/views.theme.inc
index 9ab4be0..81df6a1 100644
--- a/core/modules/views/views.theme.inc
+++ b/core/modules/views/views.theme.inc
@@ -306,8 +306,8 @@ function template_preprocess_views_view_summary(&$variables) {
   }
 
   $active_urls = array(
-    _url(current_path(), array('alias' => TRUE)), // force system path
-    _url(current_path()), // could be an alias
+    url(current_path(), array('alias' => TRUE)), // force system path
+    url(current_path()), // could be an alias
   );
   $active_urls = array_combine($active_urls, $active_urls);
 
@@ -331,7 +331,7 @@ function template_preprocess_views_view_summary(&$variables) {
     if (!empty($argument->options['summary_options']['base_path'])) {
       $base_path = $argument->options['summary_options']['base_path'];
     }
-    $variables['rows'][$id]->url = _url($view->getUrl($args, $base_path), $url_options);
+    $variables['rows'][$id]->url = url($view->getUrl($args, $base_path), $url_options);
     $variables['rows'][$id]->count = intval($row->{$argument->count_alias});
     if (isset($active_urls[$variables['rows'][$id]->url])) {
       $variables['rows'][$id]->attributes['class'][] = 'active';
@@ -366,9 +366,9 @@ function template_preprocess_views_view_summary_unformatted(&$variables) {
   $count = 0;
   $active_urls = array(
     // Force system path.
-    _url(current_path(), array('alias' => TRUE)),
+    url(current_path(), array('alias' => TRUE)),
     // Could be an alias.
-    _url(current_path()),
+    url(current_path()),
   );
   $active_urls = array_combine($active_urls, $active_urls);
 
@@ -395,7 +395,7 @@ function template_preprocess_views_view_summary_unformatted(&$variables) {
     if (!empty($argument->options['summary_options']['base_path'])) {
       $base_path = $argument->options['summary_options']['base_path'];
     }
-    $variables['rows'][$id]->url = _url($view->getUrl($args, $base_path), $url_options);
+    $variables['rows'][$id]->url = url($view->getUrl($args, $base_path), $url_options);
     $variables['rows'][$id]->count = intval($row->{$argument->count_alias});
     if (isset($active_urls[$variables['rows'][$id]->url])) {
       $variables['rows'][$id]->attributes['class'][] = 'active';
@@ -484,7 +484,7 @@ function template_preprocess_views_view_table(&$variables) {
           'attributes' => array('title' => $title),
           'query' => $query,
         );
-        $variables['header'][$field]['content'] = _l($label, current_path(), $link_options);
+        $variables['header'][$field]['content'] = l($label, current_path(), $link_options);
       }
 
       // Set up the header label class.
@@ -901,7 +901,7 @@ function template_preprocess_views_view_rss(&$variables) {
       $path = '';
     }
 
-    $variables['link'] = check_url(_url($path, $url_options));
+    $variables['link'] = check_url(url($path, $url_options));
   }
 
   $variables['langcode'] = String::checkPlain(\Drupal::languageManager()->getCurrentLanguage()->id);
diff --git a/core/modules/views/views.tokens.inc b/core/modules/views/views.tokens.inc
index 4160d85..f6e2539 100644
--- a/core/modules/views/views.tokens.inc
+++ b/core/modules/views/views.tokens.inc
@@ -103,7 +103,7 @@ function views_tokens($type, $tokens, array $data = array(), array $options = ar
 
         case 'url':
           if ($path = $view->getUrl()) {
-            $replacements[$original] = _url($path, $url_options);
+            $replacements[$original] = url($path, $url_options);
           }
           break;
         case 'base-table':
diff --git a/core/modules/views_ui/src/Form/Ajax/Rearrange.php b/core/modules/views_ui/src/Form/Ajax/Rearrange.php
index 42fda54..25cf3f1 100644
--- a/core/modules/views_ui/src/Form/Ajax/Rearrange.php
+++ b/core/modules/views_ui/src/Form/Ajax/Rearrange.php
@@ -124,7 +124,7 @@ public function buildForm(array $form, FormStateInterface $form_state) {
         '#id' => 'views-removed-' . $id,
         '#attributes' => array('class' => array('views-remove-checkbox')),
         '#default_value' => 0,
-        '#suffix' => _l('<span>' . $this->t('Remove') . '</span>', 'javascript:void()', array('attributes' => array('id' => 'views-remove-link-' . $id, 'class' => array('views-hidden', 'views-button-remove', 'views-remove-link'), 'alt' => $this->t('Remove this item'), 'title' => $this->t('Remove this item')), 'html' => TRUE)),
+        '#suffix' => l('<span>' . $this->t('Remove') . '</span>', 'javascript:void()', array('attributes' => array('id' => 'views-remove-link-' . $id, 'class' => array('views-hidden', 'views-button-remove', 'views-remove-link'), 'alt' => $this->t('Remove this item'), 'title' => $this->t('Remove this item')), 'html' => TRUE)),
       );
     }
 
diff --git a/core/modules/views_ui/src/Form/Ajax/ViewsFormBase.php b/core/modules/views_ui/src/Form/Ajax/ViewsFormBase.php
index 6d558cd..b9dc99d 100644
--- a/core/modules/views_ui/src/Form/Ajax/ViewsFormBase.php
+++ b/core/modules/views_ui/src/Form/Ajax/ViewsFormBase.php
@@ -149,7 +149,7 @@ public function getForm(ViewStorageInterface $view, $display_id, $js) {
       $form_state->setUserInput(array());
       $form_path = views_ui_build_form_path($form_state);
       if (!$form_state->get('ajax')) {
-        return new RedirectResponse(_url($form_path, array('absolute' => TRUE)));
+        return new RedirectResponse(url($form_path, array('absolute' => TRUE)));
       }
       $form_state->set('path', $form_path);
       $response = views_ajax_form_wrapper($form_class, $form_state);
diff --git a/core/modules/views_ui/src/Tests/DefaultViewsTest.php b/core/modules/views_ui/src/Tests/DefaultViewsTest.php
index 080d774..67a57b9 100644
--- a/core/modules/views_ui/src/Tests/DefaultViewsTest.php
+++ b/core/modules/views_ui/src/Tests/DefaultViewsTest.php
@@ -168,7 +168,7 @@ public function testPathDestination() {
 
     // Check that a dynamic path is shown as text.
     $this->assertRaw('test_route_with_suffix/%/suffix');
-    $this->assertNoLinkByHref(_url('test_route_with_suffix/%/suffix'));
+    $this->assertNoLinkByHref(url('test_route_with_suffix/%/suffix'));
   }
 
   /**
diff --git a/core/modules/views_ui/src/ViewEditForm.php b/core/modules/views_ui/src/ViewEditForm.php
index e621513..e849070 100644
--- a/core/modules/views_ui/src/ViewEditForm.php
+++ b/core/modules/views_ui/src/ViewEditForm.php
@@ -20,7 +20,6 @@
 use Drupal\Core\Url;
 use Drupal\user\TempStoreFactory;
 use Drupal\views\Views;
-use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\RequestStack;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 
@@ -323,11 +322,13 @@ public function save(array $form, FormStateInterface $form_state) {
           $query->remove('destination');
         }
       }
-      $form_state->setRedirectUrl(Url::fromUri("base://$destination"));
+      if (!UrlHelper::isExternal($destination)) {
+        $destination = $GLOBALS['base_url'] . '/' . $destination;
+      }
+      $form_state->setRedirectUrl(Url::createFromPath($destination));
     }
 
     $view->save();
-
     drupal_set_message($this->t('The view %name has been saved.', array('%name' => $view->label())));
 
     // Remove this view from cache so we can edit it properly.
diff --git a/core/modules/views_ui/src/ViewListBuilder.php b/core/modules/views_ui/src/ViewListBuilder.php
index 9d12e5a..16b5b84 100644
--- a/core/modules/views_ui/src/ViewListBuilder.php
+++ b/core/modules/views_ui/src/ViewListBuilder.php
@@ -264,7 +264,7 @@ protected function getDisplayPaths(EntityInterface $view) {
       if ($display->hasPath()) {
         $path = $display->getPath();
         if ($view->status() && strpos($path, '%') === FALSE) {
-          $all_paths[] = _l('/' . $path, $path);
+          $all_paths[] = l('/' . $path, $path);
         }
         else {
           $all_paths[] = String::checkPlain('/' . $path);
diff --git a/core/modules/views_ui/src/ViewUI.php b/core/modules/views_ui/src/ViewUI.php
index 86d535b..1068d45 100644
--- a/core/modules/views_ui/src/ViewUI.php
+++ b/core/modules/views_ui/src/ViewUI.php
@@ -693,7 +693,7 @@ public function renderPreview($display_id, $args = array()) {
               Xss::filterAdmin($this->executable->getTitle()),
             );
             if (isset($path)) {
-              $path = _l($path, $path);
+              $path = l($path, $path);
             }
             else {
               $path = t('This display has no path.');
diff --git a/core/modules/views_ui/views_ui.module b/core/modules/views_ui/views_ui.module
index 3960294..46adb0f 100644
--- a/core/modules/views_ui/views_ui.module
+++ b/core/modules/views_ui/views_ui.module
@@ -100,6 +100,7 @@ function views_ui_theme() {
     'views_ui_build_group_filter_form' => array(
       'render element' => 'form',
       'file' => 'views_ui.theme.inc',
+      'function' => 'theme_views_ui_build_group_filter_form',
     ),
 
     // On behalf of a plugin
diff --git a/core/modules/views_ui/views_ui.theme.inc b/core/modules/views_ui/views_ui.theme.inc
index 80f2f45..ce5bcd1 100644
--- a/core/modules/views_ui/views_ui.theme.inc
+++ b/core/modules/views_ui/views_ui.theme.inc
@@ -166,7 +166,7 @@ function theme_views_ui_build_group_filter_form($variables) {
       'title' => drupal_render($form['group_items'][$group_id]['title']),
       'operator' => drupal_render($form['group_items'][$group_id]['operator']),
       'value' => drupal_render($form['group_items'][$group_id]['value']),
-      'remove' => drupal_render($form['group_items'][$group_id]['remove']) . _l('<span>' . t('Remove') . '</span>', 'javascript:void()', array('attributes' => array('id' => 'views-remove-link-' . $group_id, 'class' => array('views-hidden', 'views-button-remove', 'views-groups-remove-link', 'views-remove-link'), 'alt' => t('Remove this item'), 'title' => t('Remove this item')), 'html' => true)),
+      'remove' => drupal_render($form['group_items'][$group_id]['remove']) . l('<span>' . t('Remove') . '</span>', 'javascript:void()', array('attributes' => array('id' => 'views-remove-link-' . $group_id, 'class' => array('views-hidden', 'views-button-remove', 'views-groups-remove-link', 'views-remove-link'), 'alt' => t('Remove this item'), 'title' => t('Remove this item')), 'html' => true)),
     );
     $rows[] = array('data' => $data, 'id' => 'views-row-' . $group_id, 'class' => array('draggable'));
   }
diff --git a/core/profiles/standard/config/install/core.base_field_override.node.page.promote.yml b/core/profiles/standard/config/install/core.base_field_override.node.page.promote.yml
index 1555eed..31de54b 100644
--- a/core/profiles/standard/config/install/core.base_field_override.node.page.promote.yml
+++ b/core/profiles/standard/config/install/core.base_field_override.node.page.promote.yml
@@ -15,6 +15,6 @@ translatable: true
 default_value:
   -
     value: 0
-default_value_callback: ''
+default_value_function: ''
 settings: {  }
 field_type: boolean
diff --git a/core/profiles/standard/config/install/field.field.node.article.field_image.yml b/core/profiles/standard/config/install/field.field.node.article.field_image.yml
index b4b9168..31ba638 100644
--- a/core/profiles/standard/config/install/field.field.node.article.field_image.yml
+++ b/core/profiles/standard/config/install/field.field.node.article.field_image.yml
@@ -6,7 +6,7 @@ label: Image
 description: ''
 required: false
 default_value: {  }
-default_value_callback: ''
+default_value_function: ''
 settings:
   file_directory: field/image
   file_extensions: 'png gif jpg jpeg'
diff --git a/core/profiles/standard/config/install/field.field.node.article.field_tags.yml b/core/profiles/standard/config/install/field.field.node.article.field_tags.yml
index 53acce3..0960d3f 100644
--- a/core/profiles/standard/config/install/field.field.node.article.field_tags.yml
+++ b/core/profiles/standard/config/install/field.field.node.article.field_tags.yml
@@ -7,7 +7,7 @@ label: Tags
 description: 'Enter a comma-separated list. For example: Amsterdam, Mexico City, "Cleveland, Ohio"'
 required: false
 default_value: {  }
-default_value_callback: ''
+default_value_function: ''
 settings: {  }
 status: true
 langcode: und
diff --git a/core/profiles/standard/config/install/field.field.user.user.user_picture.yml b/core/profiles/standard/config/install/field.field.user.user.user_picture.yml
index d6b31c2..a7a2ef7 100644
--- a/core/profiles/standard/config/install/field.field.user.user.user_picture.yml
+++ b/core/profiles/standard/config/install/field.field.user.user.user_picture.yml
@@ -8,7 +8,7 @@ label: Picture
 description: 'Your virtual face or picture.'
 required: false
 default_value: {  }
-default_value_callback: ''
+default_value_function: ''
 settings:
   file_extensions: 'png gif jpg jpeg'
   file_directory: pictures
diff --git a/core/tests/Drupal/Tests/Core/DrupalTest.php b/core/tests/Drupal/Tests/Core/DrupalTest.php
index f56dee2..988cf6c 100644
--- a/core/tests/Drupal/Tests/Core/DrupalTest.php
+++ b/core/tests/Drupal/Tests/Core/DrupalTest.php
@@ -250,7 +250,7 @@ public function testUrlGenerator() {
   }
 
   /**
-   * Tests the _url() method.
+   * Tests the url() method.
    *
    * @see \Drupal\Core\Routing\UrlGeneratorInterface::generateFromRoute()
    */
@@ -276,7 +276,7 @@ public function testLinkGenerator() {
   }
 
   /**
-   * Tests the _l() method.
+   * Tests the l() method.
    *
    * @see \Drupal\Core\Utility\LinkGeneratorInterface::generate()
    */
diff --git a/core/tests/Drupal/Tests/Core/Entity/BaseFieldDefinitionTest.php b/core/tests/Drupal/Tests/Core/Entity/BaseFieldDefinitionTest.php
index 17cb518..ab0ad76 100644
--- a/core/tests/Drupal/Tests/Core/Entity/BaseFieldDefinitionTest.php
+++ b/core/tests/Drupal/Tests/Core/Entity/BaseFieldDefinitionTest.php
@@ -16,7 +16,6 @@
  * Unit test for BaseFieldDefinition.
  *
  * @group Entity
- * @coversDefaultClass \Drupal\Core\Field\BaseFieldDefinition
  */
 class BaseFieldDefinitionTest extends UnitTestCase {
 
@@ -76,8 +75,6 @@ protected function setUp() {
 
   /**
    * Tests field name methods.
-   *
-   * @covers ::getName()
    */
   public function testFieldName() {
     $definition = BaseFieldDefinition::create($this->fieldType);
@@ -88,8 +85,6 @@ public function testFieldName() {
 
   /**
    * Tests field label methods.
-   *
-   * @covers ::getLabel()
    */
   public function testFieldLabel() {
     $definition = BaseFieldDefinition::create($this->fieldType);
@@ -100,8 +95,6 @@ public function testFieldLabel() {
 
   /**
    * Tests field description methods.
-   *
-   * @covers ::getDescription()
    */
   public function testFieldDescription() {
     $definition = BaseFieldDefinition::create($this->fieldType);
@@ -112,8 +105,6 @@ public function testFieldDescription() {
 
   /**
    * Tests field type methods.
-   *
-   * @covers ::getType()
    */
   public function testFieldType() {
     $definition = BaseFieldDefinition::create($this->fieldType);
@@ -122,10 +113,6 @@ public function testFieldType() {
 
   /**
    * Tests field settings methods.
-   *
-   * @covers ::getSetting()
-   * @covers ::setSetting()
-   * @covers ::getSettings()
    */
   public function testFieldSettings() {
     $definition = BaseFieldDefinition::create($this->fieldType);
@@ -139,10 +126,6 @@ public function testFieldSettings() {
 
   /**
    * Tests the initialization of default field settings.
-   *
-   * @covers ::getSetting()
-   * @covers ::setSetting()
-   * @covers ::getSettings()
    */
   public function testDefaultFieldSettings() {
     $definition = BaseFieldDefinition::create($this->fieldType);
@@ -155,9 +138,6 @@ public function testDefaultFieldSettings() {
 
   /**
    * Tests field default value.
-   *
-   * @covers ::getDefaultValue()
-   * @covers ::setDefaultValue()
    */
   public function testFieldDefaultValue() {
     $definition = BaseFieldDefinition::create($this->fieldType);
@@ -174,9 +154,6 @@ public function testFieldDefaultValue() {
 
   /**
    * Tests field translatable methods.
-   *
-   * @covers ::isTranslatable()
-   * @covers ::setTranslatable()
    */
   public function testFieldTranslatable() {
     $definition = BaseFieldDefinition::create($this->fieldType);
@@ -189,9 +166,6 @@ public function testFieldTranslatable() {
 
   /**
    * Tests field revisionable methods.
-   *
-   * @covers ::isRevisionable()
-   * @covers ::setRevisionable()
    */
   public function testFieldRevisionable() {
     $definition = BaseFieldDefinition::create($this->fieldType);
@@ -204,9 +178,6 @@ public function testFieldRevisionable() {
 
   /**
    * Tests field cardinality.
-   *
-   * @covers ::getCardinality()
-   * @covers ::setCardinality()
    */
   public function testFieldCardinality() {
     $definition = BaseFieldDefinition::create($this->fieldType);
@@ -219,9 +190,6 @@ public function testFieldCardinality() {
 
   /**
    * Tests required.
-   *
-   * @covers ::isRequired()
-   * @covers ::setRequired()
    */
   public function testFieldRequired() {
     $definition = BaseFieldDefinition::create($this->fieldType);
@@ -234,9 +202,6 @@ public function testFieldRequired() {
 
   /**
    * Tests provider.
-   *
-   * @covers ::getProvider()
-   * @covers ::setProvider()
    */
   public function testFieldProvider() {
     $definition = BaseFieldDefinition::create($this->fieldType);
@@ -247,9 +212,6 @@ public function testFieldProvider() {
 
   /**
    * Tests custom storage.
-   *
-   * @covers ::hasCustomStorage()
-   * @covers ::setCustomStorage()
    */
   public function testCustomStorage() {
     $definition = BaseFieldDefinition::create($this->fieldType);
@@ -260,51 +222,4 @@ public function testCustomStorage() {
     $this->assertFalse($definition->hasCustomStorage());
   }
 
-  /**
-   * Tests default value callbacks.
-   *
-   * @covers ::setDefaultValueCallback()
-   */
-  public function testDefaultValueCallback() {
-    $definition = BaseFieldDefinition::create($this->fieldType);
-    $callback = get_class($this) . '::mockDefaultValueCallback';
-    $definition->setDefaultValueCallback($callback);
-  }
-
-  /**
-   * Tests invalid default value callbacks.
-   *
-   * @covers ::setDefaultValueCallback()
-   * @expectedException \InvalidArgumentException
-   */
-  public function testInvalidDefaultValueCallback() {
-    $definition = BaseFieldDefinition::create($this->fieldType);
-    $definition->setDefaultValueCallback([get_class($this), 'mockDefaultValueCallback']);
-  }
-
-  /**
-   * Tests NULL default value callbacks.
-   *
-   * @covers ::setDefaultValueCallback
-   */
-  public function testNullDefaultValueCallback() {
-    $definition = BaseFieldDefinition::create($this->fieldType);
-    $definition->setDefaultValueCallback(NULL);
-  }
-
-  /**
-   * Provides a Mock base field default value callback.
-   *
-   * @param \Drupal\Core\Entity\EntityInterface $entity
-   *   Entity interface.
-   * @param \Drupal\Core\Field\FieldDefinitionInterface $definition
-   *   Field definition.
-   *
-   * @return string
-   *   Default value.
-   */
-  public static function mockDefaultValueCallback($entity, $definition) {
-    return 'a default value';
-  }
-
 }
diff --git a/core/tests/Drupal/Tests/Core/Entity/EntityUrlTest.php b/core/tests/Drupal/Tests/Core/Entity/EntityUrlTest.php
index d1e8114..4787e62 100644
--- a/core/tests/Drupal/Tests/Core/Entity/EntityUrlTest.php
+++ b/core/tests/Drupal/Tests/Core/Entity/EntityUrlTest.php
@@ -152,7 +152,7 @@ public function testUrlInfoForNewEntity() {
   }
 
   /**
-   * Tests the _url() method.
+   * Tests the url() method.
    *
    * @covers ::url()
    */
diff --git a/core/tests/Drupal/Tests/Core/ExternalUrlTest.php b/core/tests/Drupal/Tests/Core/ExternalUrlTest.php
new file mode 100644
index 0000000..57a51d4
--- /dev/null
+++ b/core/tests/Drupal/Tests/Core/ExternalUrlTest.php
@@ -0,0 +1,190 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Tests\Core\ExternalUrlTest.
+ */
+
+namespace Drupal\Tests\Core;
+
+use Drupal\Core\DependencyInjection\ContainerBuilder;
+use Drupal\Core\Url;
+use Drupal\Tests\UnitTestCase;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\Routing\Exception\ResourceNotFoundException;
+
+/**
+ * @coversDefaultClass \Drupal\Core\Url
+ * @group ExternalUrlTest
+ */
+class ExternalUrlTest extends UnitTestCase {
+
+  /**
+   * The URL generator
+   *
+   * @var \Drupal\Core\Routing\UrlGeneratorInterface|\PHPUnit_Framework_MockObject_MockObject
+   */
+  protected $urlGenerator;
+
+  /**
+   * The router.
+   *
+   * @var \Drupal\Tests\Core\Routing\TestRouterInterface|\PHPUnit_Framework_MockObject_MockObject
+   */
+  protected $router;
+
+  /**
+   * An external URL to test.
+   *
+   * @var string
+   */
+  protected $path = 'http://drupal.org';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+
+    $this->urlGenerator = $this->getMock('Drupal\Core\Routing\UrlGeneratorInterface');
+    $this->urlGenerator->expects($this->any())
+      ->method('generateFromPath')
+      ->will($this->returnArgument(0));
+
+    $this->router = $this->getMock('Drupal\Tests\Core\Routing\TestRouterInterface');
+    $container = new ContainerBuilder();
+    $container->set('router.no_access_checks', $this->router);
+    $container->set('url_generator', $this->urlGenerator);
+    \Drupal::setContainer($container);
+  }
+
+  /**
+   * Tests the createFromPath method.
+   *
+   * @covers ::createFromPath()
+   * @covers ::setExternal()
+   */
+  public function testCreateFromPath() {
+    $url = Url::createFromPath($this->path);
+    $this->assertInstanceOf('Drupal\Core\Url', $url);
+    $this->assertTrue($url->isExternal());
+    return $url;
+  }
+
+  /**
+   * Tests the createFromRequest method.
+   *
+   * @covers ::createFromRequest()
+   *
+   * @expectedException \Symfony\Component\Routing\Exception\ResourceNotFoundException
+   */
+  public function testCreateFromRequest() {
+    $request = Request::create('/test-path');
+
+    $this->router->expects($this->once())
+      ->method('matchRequest')
+      ->with($request)
+      ->will($this->throwException(new ResourceNotFoundException()));
+
+    $this->assertNull(Url::createFromRequest($request));
+  }
+
+  /**
+   * Tests the isExternal() method.
+   *
+   * @depends testCreateFromPath
+   *
+   * @covers ::isExternal()
+   */
+  public function testIsExternal(Url $url) {
+    $this->assertTrue($url->isExternal());
+  }
+
+  /**
+   * Tests the toString() method.
+   *
+   * @depends testCreateFromPath
+   *
+   * @covers ::toString()
+   */
+  public function testToString(Url $url) {
+    $this->assertSame($this->path, $url->toString());
+  }
+
+  /**
+   * Tests the toArray() method.
+   *
+   * @depends testCreateFromPath
+   *
+   * @covers ::toArray()
+   */
+  public function testToArray(Url $url) {
+    $expected = array(
+      'path' => $this->path,
+      'options' => array('external' => TRUE),
+    );
+    $this->assertSame($expected, $url->toArray());
+  }
+
+  /**
+   * Tests the getRouteName() method.
+   *
+   * @depends testCreateFromPath
+   *
+   * @expectedException \UnexpectedValueException
+   *
+   * @covers ::getRouteName()
+   */
+  public function testGetRouteName(Url $url) {
+    $url->getRouteName();
+  }
+
+  /**
+   * Tests the getRouteParameters() method.
+   *
+   * @depends testCreateFromPath
+   *
+   * @expectedException \UnexpectedValueException
+   *
+   * @covers ::getRouteParameters()
+   */
+  public function testGetRouteParameters(Url $url) {
+    $url->getRouteParameters();
+  }
+
+  /**
+   * Tests the getInternalPath() method.
+   *
+   * @depends testCreateFromPath
+   *
+   * @covers ::getInternalPath()
+   *
+   * @expectedException \Exception
+   */
+  public function testGetInternalPath(Url $url) {
+    $this->assertNull($url->getInternalPath());
+  }
+
+  /**
+   * Tests the getPath() method.
+   *
+   * @depends testCreateFromPath
+   *
+   * @covers ::getPath()
+   */
+  public function testGetPath(Url $url) {
+    $this->assertNotNull($url->getPath());
+  }
+
+  /**
+   * Tests the getOptions() method.
+   *
+   * @depends testCreateFromPath
+   *
+   * @covers ::getOptions()
+   */
+  public function testGetOptions(Url $url) {
+    $this->assertInternalType('array', $url->getOptions());
+  }
+
+}
diff --git a/core/tests/Drupal/Tests/Core/UnroutedUrlTest.php b/core/tests/Drupal/Tests/Core/UnroutedUrlTest.php
deleted file mode 100644
index 9d6ea00..0000000
--- a/core/tests/Drupal/Tests/Core/UnroutedUrlTest.php
+++ /dev/null
@@ -1,225 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\Tests\Core\UnroutedUrlTest.
- */
-
-namespace Drupal\Tests\Core;
-
-use Drupal\Core\DependencyInjection\ContainerBuilder;
-use Drupal\Core\Url;
-use Drupal\Tests\UnitTestCase;
-use Symfony\Component\HttpFoundation\Request;
-use Symfony\Component\Routing\Exception\ResourceNotFoundException;
-
-/**
- * @coversDefaultClass \Drupal\Core\Url
- * @group UrlTest
- */
-class UnroutedUrlTest extends UnitTestCase {
-
-  /**
-   * The URL assembler
-   *
-   * @var \Drupal\Core\Utility\UnroutedUrlAssemblerInterface|\PHPUnit_Framework_MockObject_MockObject
-   */
-  protected $urlAssembler;
-
-  /**
-   * The router.
-   *
-   * @var \Drupal\Tests\Core\Routing\TestRouterInterface|\PHPUnit_Framework_MockObject_MockObject
-   */
-  protected $router;
-
-  /**
-   * An unrouted, external URL to test.
-   *
-   * @var string
-   */
-  protected $unroutedExternal = 'http://drupal.org';
-
-  /**
-   * An unrouted, internal URL to test.
-   *
-   * @var string
-   */
-  protected $unroutedInternal = 'base://robots.txt';
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function setUp() {
-    parent::setUp();
-
-    $this->urlAssembler = $this->getMock('Drupal\Core\Utility\UnroutedUrlAssemblerInterface');
-    $this->urlAssembler->expects($this->any())
-      ->method('assemble')
-      ->will($this->returnArgument(0));
-
-    $this->router = $this->getMock('Drupal\Tests\Core\Routing\TestRouterInterface');
-    $container = new ContainerBuilder();
-    $container->set('router.no_access_checks', $this->router);
-    $container->set('unrouted_url_assembler', $this->urlAssembler);
-    \Drupal::setContainer($container);
-  }
-
-  /**
-   * Tests the fromUri() method.
-   *
-   * @covers ::fromUri
-   */
-  public function testFromUri() {
-    $urls = [
-      Url::fromUri($this->unroutedExternal),
-      Url::fromUri($this->unroutedInternal)
-    ];
-
-    $this->assertInstanceOf('Drupal\Core\Url', $urls[0]);
-    $this->assertTrue($urls[0]->isExternal());
-
-    $this->assertInstanceOf('Drupal\Core\Url', $urls[1]);
-    $this->assertFalse($urls[1]->isExternal());
-
-    return $urls;
-  }
-
-  /**
-   * Tests the createFromRequest method.
-   *
-   * @covers ::createFromRequest
-   *
-   * @expectedException \Symfony\Component\Routing\Exception\ResourceNotFoundException
-   */
-  public function testCreateFromRequest() {
-    $request = Request::create('/test-path');
-
-    $this->router->expects($this->once())
-      ->method('matchRequest')
-      ->with($request)
-      ->will($this->throwException(new ResourceNotFoundException()));
-
-    $this->assertNull(Url::createFromRequest($request));
-  }
-
-  /**
-   * Tests the fromUri() method with an non-scheme path.
-   *
-   * @covers ::fromUri
-   *
-   * @expectedException \InvalidArgumentException
-   */
-  public function testFromUriWithNonScheme() {
-    Url::fromUri('test');
-  }
-
-  /**
-   * Tests the isExternal() method.
-   *
-   * @depends testFromUri
-   *
-   * @covers ::isExternal
-   */
-  public function testIsExternal(array $urls) {
-    $this->assertTrue($urls[0]->isExternal());
-    $this->assertFalse($urls[1]->isExternal());
-  }
-
-  /**
-   * Tests the toString() method.
-   *
-   * @depends testFromUri
-   *
-   * @covers ::toString
-   */
-  public function testToString(array $urls) {
-    $this->assertSame($this->unroutedExternal, $urls[0]->toString());
-    $this->assertSame($this->unroutedInternal, $urls[1]->toString());
-  }
-
-  /**
-   * Tests the toArray() method.
-   *
-   * @depends testFromUri
-   *
-   * @covers ::toArray
-   */
-  public function testToArray(array $urls) {
-    $expected = array(
-      'path' => $this->unroutedExternal,
-      'options' => array('external' => TRUE),
-    );
-    $this->assertSame($expected, $urls[0]->toArray());
-
-    $expected = array(
-      'path' => $this->unroutedInternal,
-      'options' => array(),
-    );
-    $this->assertSame($expected, $urls[1]->toArray());
-  }
-
-  /**
-   * Tests the getRouteName() method.
-   *
-   * @depends testFromUri
-   *
-   * @expectedException \UnexpectedValueException
-   *
-   * @covers ::getRouteName
-   */
-  public function testGetRouteName(array $urls) {
-    $urls[0]->getRouteName();
-  }
-
-  /**
-   * Tests the getRouteParameters() method.
-   *
-   * @depends testFromUri
-   *
-   * @expectedException \UnexpectedValueException
-   *
-   * @covers ::getRouteParameters
-   */
-  public function testGetRouteParameters(array $urls) {
-    $urls[0]->getRouteParameters();
-  }
-
-  /**
-   * Tests the getInternalPath() method.
-   *
-   * @depends testFromUri
-   *
-   * @covers ::getInternalPath
-   *
-   * @expectedException \Exception
-   */
-  public function testGetInternalPath(array $urls) {
-    $this->assertNull($urls[0]->getInternalPath());
-  }
-
-  /**
-   * Tests the getPath() method.
-   *
-   * @depends testFromUri
-   *
-   * @covers ::getUri
-   */
-  public function testGetUri(array $urls) {
-    $this->assertNotNull($urls[0]->getUri());
-    $this->assertNotNull($urls[1]->getUri());
-  }
-
-  /**
-   * Tests the getOptions() method.
-   *
-   * @depends testFromUri
-   *
-   * @covers ::getOptions
-   */
-  public function testGetOptions(array $urls) {
-    $this->assertInternalType('array', $urls[0]->getOptions());
-    $this->assertInternalType('array', $urls[1]->getOptions());
-  }
-
-}
diff --git a/core/tests/Drupal/Tests/Core/UrlTest.php b/core/tests/Drupal/Tests/Core/UrlTest.php
index cf0496f..133a73c 100644
--- a/core/tests/Drupal/Tests/Core/UrlTest.php
+++ b/core/tests/Drupal/Tests/Core/UrlTest.php
@@ -73,9 +73,11 @@ protected function setUp() {
   }
 
   /**
-   * Tests creating a Url from a request.
+   * Tests the createFromPath method.
+   *
+   * @covers ::createFromPath()
    */
-  public function testUrlFromRequest() {
+  public function testCreateFromPath() {
     $this->router->expects($this->at(0))
       ->method('matchRequest')
       ->with($this->getRequestConstraint('/node'))
@@ -100,8 +102,8 @@ public function testUrlFromRequest() {
 
     $urls = array();
     foreach ($this->map as $index => $values) {
-      $path = array_pop($values);
-      $url = Url::createFromRequest(Request::create("$path"));
+      $path = trim(array_pop($values), '/');
+      $url = Url::createFromPath($path);
       $this->assertSame($values, array_values($url->toArray()));
       $urls[$index] = $url;
     }
@@ -124,19 +126,35 @@ protected function getRequestConstraint($path) {
   }
 
   /**
-   * Tests the fromRoute() method with the special <front> path.
+   * Tests the createFromPath method with the special <front> path.
    *
-   * @covers ::fromRoute
+   * @covers ::createFromPath()
    */
-  public function testFromRouteFront() {
-    $url = Url::fromRoute('<front>');
+  public function testCreateFromPathFront() {
+    $url = Url::createFromPath('<front>');
     $this->assertSame('<front>', $url->getRouteName());
   }
 
   /**
+   * Tests that an invalid path will thrown an exception.
+   *
+   * @covers ::createFromPath()
+   *
+   * @expectedException \Symfony\Component\Routing\Exception\ResourceNotFoundException
+   */
+  public function testCreateFromPathInvalid() {
+    $this->router->expects($this->once())
+      ->method('matchRequest')
+      ->with($this->getRequestConstraint('/non-existent'))
+      ->will($this->throwException(new ResourceNotFoundException()));
+
+    $this->assertNull(Url::createFromPath('non-existent'));
+  }
+
+  /**
    * Tests the createFromRequest method.
    *
-   * @covers ::createFromRequest
+   * @covers ::createFromRequest()
    */
   public function testCreateFromRequest() {
     $attributes = array(
@@ -160,11 +178,11 @@ public function testCreateFromRequest() {
   /**
    * Tests that an invalid request will thrown an exception.
    *
-   * @covers ::createFromRequest
+   * @covers ::createFromRequest()
    *
    * @expectedException \Symfony\Component\Routing\Exception\ResourceNotFoundException
    */
-  public function testUrlFromRequestInvalid() {
+  public function testCreateFromRequestInvalid() {
     $request = Request::create('/test-path');
 
     $this->router->expects($this->once())
@@ -178,9 +196,9 @@ public function testUrlFromRequestInvalid() {
   /**
    * Tests the isExternal() method.
    *
-   * @depends testUrlFromRequest
+   * @depends testCreateFromPath
    *
-   * @covers ::isExternal
+   * @covers ::isExternal()
    */
   public function testIsExternal($urls) {
     foreach ($urls as $url) {
@@ -189,31 +207,28 @@ public function testIsExternal($urls) {
   }
 
   /**
-   * Tests the getUri() method for internal URLs.
+   * Tests the getPath() method for internal URLs.
    *
-   * @param \Drupal\Core\Url[] $urls
-   *   Array of URL objects.
-   *
-   * @depends testUrlFromRequest
+   * @depends testCreateFromPath
    *
    * @expectedException \UnexpectedValueException
    *
-   * @covers ::getUri
+   * @covers ::getPath()
    */
-  public function testGetUriForInternalUrl($urls) {
+  public function testGetPathForInternalUrl($urls) {
     foreach ($urls as $url) {
-      $url->getUri();
+      $url->getPath();
     }
   }
 
   /**
-   * Tests the getUri() method for external URLs.
+   * Tests the getPath() method for external URLs.
    *
-   * @covers ::getUri
+   * @covers ::getPath
    */
-  public function testGetUriForExternalUrl() {
-    $url = Url::fromUri('http://example.com/test');
-    $this->assertEquals('http://example.com/test', $url->getUri());
+  public function testGetPathForExternalUrl() {
+    $url = Url::createFromPath('http://example.com/test');
+    $this->assertEquals('http://example.com/test', $url->getPath());
   }
 
   /**
@@ -222,9 +237,9 @@ public function testGetUriForExternalUrl() {
    * @param \Drupal\Core\Url[] $urls
    *   An array of Url objects.
    *
-   * @depends testUrlFromRequest
+   * @depends testCreateFromPath
    *
-   * @covers ::toString
+   * @covers ::toString()
    */
   public function testToString($urls) {
     foreach ($urls as $index => $url) {
@@ -239,9 +254,9 @@ public function testToString($urls) {
    * @param \Drupal\Core\Url[] $urls
    *   An array of Url objects.
    *
-   * @depends testUrlFromRequest
+   * @depends testCreateFromPath
    *
-   * @covers ::toArray
+   * @covers ::toArray()
    */
   public function testToArray($urls) {
     foreach ($urls as $index => $url) {
@@ -260,9 +275,9 @@ public function testToArray($urls) {
    * @param \Drupal\Core\Url[] $urls
    *   An array of Url objects.
    *
-   * @depends testUrlFromRequest
+   * @depends testCreateFromPath
    *
-   * @covers ::getRouteName
+   * @covers ::getRouteName()
    */
   public function testGetRouteName($urls) {
     foreach ($urls as $index => $url) {
@@ -277,7 +292,7 @@ public function testGetRouteName($urls) {
    * @expectedException \UnexpectedValueException
    */
   public function testGetRouteNameWithExternalUrl() {
-    $url = Url::fromUri('http://example.com');
+    $url = Url::createFromPath('http://example.com');
     $url->getRouteName();
   }
 
@@ -287,9 +302,9 @@ public function testGetRouteNameWithExternalUrl() {
    * @param \Drupal\Core\Url[] $urls
    *   An array of Url objects.
    *
-   * @depends testUrlFromRequest
+   * @depends testCreateFromPath
    *
-   * @covers ::getRouteParameters
+   * @covers ::getRouteParameters()
    */
   public function testGetRouteParameters($urls) {
     foreach ($urls as $index => $url) {
@@ -304,7 +319,7 @@ public function testGetRouteParameters($urls) {
    * @expectedException \UnexpectedValueException
    */
   public function testGetRouteParametersWithExternalUrl() {
-    $url = Url::fromUri('http://example.com');
+    $url = Url::createFromPath('http://example.com');
     $url->getRouteParameters();
   }
 
@@ -314,9 +329,9 @@ public function testGetRouteParametersWithExternalUrl() {
    * @param \Drupal\Core\Url[] $urls
    *   An array of Url objects.
    *
-   * @depends testUrlFromRequest
+   * @depends testCreateFromPath
    *
-   * @covers ::getOptions
+   * @covers ::getOptions()
    */
   public function testGetOptions($urls) {
     foreach ($urls as $index => $url) {
@@ -330,7 +345,8 @@ public function testGetOptions($urls) {
    * @param bool $access
    *
    * @covers ::access
-   * @covers ::accessManager
+   * @covers ::getAccessManager
+   * @covers ::setAccessManager
    * @dataProvider accessProvider
    */
   public function testAccess($access) {
diff --git a/core/tests/Drupal/Tests/Core/Utility/LinkGeneratorTest.php b/core/tests/Drupal/Tests/Core/Utility/LinkGeneratorTest.php
index 5721010..7093fbf 100644
--- a/core/tests/Drupal/Tests/Core/Utility/LinkGeneratorTest.php
+++ b/core/tests/Drupal/Tests/Core/Utility/LinkGeneratorTest.php
@@ -40,13 +40,6 @@ class LinkGeneratorTest extends UnitTestCase {
   protected $moduleHandler;
 
   /**
-   * The mocked URL Assembler service.
-   *
-   * @var \PHPUnit_Framework_MockObject_MockObject|\Drupal\Core\Utility\UnroutedUrlAssemblerInterface
-   */
-  protected $urlAssembler;
-
-  /**
    * Contains the LinkGenerator default options.
    */
   protected $defaultOptions = array(
@@ -67,7 +60,6 @@ protected function setUp() {
     $this->moduleHandler = $this->getMock('Drupal\Core\Extension\ModuleHandlerInterface');
 
     $this->linkGenerator = new LinkGenerator($this->urlGenerator, $this->moduleHandler);
-    $this->urlAssembler = $this->getMock('\Drupal\Core\Utility\UnroutedUrlAssemblerInterface');
   }
 
   /**
@@ -152,8 +144,8 @@ public function testGenerate() {
    * @covers ::generate()
    */
   public function testGenerateExternal() {
-    $this->urlAssembler->expects($this->once())
-      ->method('assemble')
+    $this->urlGenerator->expects($this->once())
+      ->method('generateFromPath')
       ->with('http://drupal.org', array('set_active_class' => TRUE, 'external' => TRUE) + $this->defaultOptions)
       ->will($this->returnArgument(0));
 
@@ -161,14 +153,8 @@ public function testGenerateExternal() {
       ->method('alter')
       ->with('link', $this->isType('array'));
 
-    $this->urlAssembler->expects($this->once())
-      ->method('assemble')
-      ->with('http://drupal.org', array('set_active_class' => TRUE, 'external' => TRUE) + $this->defaultOptions)
-      ->willReturnArgument(0);
-
-    $url = Url::fromUri('http://drupal.org');
+    $url = Url::createFromPath('http://drupal.org');
     $url->setUrlGenerator($this->urlGenerator);
-    $url->setUnroutedUrlAssembler($this->urlAssembler);
     $url->setOption('set_active_class', TRUE);
 
     $result = $this->linkGenerator->generate('Drupal', $url);
diff --git a/core/tests/Drupal/Tests/Core/Utility/UnroutedUrlAssemblerTest.php b/core/tests/Drupal/Tests/Core/Utility/UnroutedUrlAssemblerTest.php
index 03b3375..517625f 100644
--- a/core/tests/Drupal/Tests/Core/Utility/UnroutedUrlAssemblerTest.php
+++ b/core/tests/Drupal/Tests/Core/Utility/UnroutedUrlAssemblerTest.php
@@ -33,7 +33,7 @@ class UnroutedUrlAssemblerTest extends UnitTestCase {
   protected $configFactory;
 
   /**
-   * The tested unrouted URL assembler.
+   * The tested unrouted url assembler.
    *
    * @var \Drupal\Core\Utility\UnroutedUrlAssembler
    */
diff --git a/core/themes/engines/twig/twig.engine b/core/themes/engines/twig/twig.engine
index c859b65..6311ada 100644
--- a/core/themes/engines/twig/twig.engine
+++ b/core/themes/engines/twig/twig.engine
@@ -38,23 +38,28 @@ function twig_init(Extension $theme) {
  * If the Twig debug setting is enabled, HTML comments including _theme() call
  * and template file name suggestions will surround the template markup.
  *
- * @param $template_file
+ * @param string $template_file
  *   The file name of the template to render.
- * @param $variables
+ * @param array $variables
  *   A keyed array of variables that will appear in the output.
  *
- * @return
+ * @return string
  *   The output generated by the template, plus any debug information.
  */
 function twig_render_template($template_file, $variables) {
   /** @var \Twig_Environment $twig_service */
   $twig_service = \Drupal::service('twig');
-  $output = array(
-    'debug_prefix'    => '',
-    'debug_info'      => '',
-    'rendered_markup' => $twig_service->loadTemplate($template_file)->render($variables),
-    'debug_suffix'    => '',
-  );
+  try {
+    $output = array(
+      'debug_prefix'    => '',
+      'debug_info'      => '',
+      'rendered_markup' => $twig_service->loadTemplate($template_file)->render($variables),
+      'debug_suffix'    => '',
+    );
+  }
+  catch (\Twig_Error_Loader $e) {
+    drupal_set_message($e->getMessage(), 'error');
+  }
   if ($twig_service->isDebug()) {
     $output['debug_prefix'] .= "\n\n<!-- THEME DEBUG -->";
     $output['debug_prefix'] .= "\n<!-- CALL: _theme('{$variables['theme_hook_original']}') -->";