diff --git a/core/modules/menu_link/lib/Drupal/menu_link/MenuTree.php b/core/modules/menu_link/lib/Drupal/menu_link/MenuTree.php
index bc62399..8605a33 100644
--- a/core/modules/menu_link/lib/Drupal/menu_link/MenuTree.php
+++ b/core/modules/menu_link/lib/Drupal/menu_link/MenuTree.php
@@ -87,7 +87,7 @@ class MenuTree implements MenuTreeInterface {
   protected $menuOutput;
 
   /**
-   * Stores the menu menu tree keyed by a cache ID.
+   * Stores the menu tree used by the doBuildTree method, keyed by a cache ID.
    *
    * This cache ID is built using the $menu_name, the current language and
    * some parameters passed into an entity query.
@@ -97,6 +97,9 @@ class MenuTree implements MenuTreeInterface {
   /**
    * Stores the full menu tree data keyed by a cache ID.
    *
+   * This variable distinct from static::$menuTree by having also items without
+   * access by the current user.
+   *
    * This cache ID is built with the menu name, a passed in root link ID, the
    * current language as well as the maximum depth.
    *
@@ -157,7 +160,7 @@ public function buildAllData($menu_name, $link = NULL, $max_depth = NULL) {
     if (!isset($this->menuFullTrees[$cid])) {
       // If the static variable doesn't have the data, check {cache_menu}.
       $cache = $this->cache->get($cid);
-      if ($cache && isset($cache->data)) {
+      if ($cache && $cache->data) {
         // If the cache entry exists, it contains the parameters for
         // menu_build_tree().
         $tree_parameters = $cache->data;
@@ -233,7 +236,7 @@ public function buildPageData($menu_name, $max_depth = NULL, $only_active_trail
       if (!isset($this->menuPageTrees[$cid])) {
         // If the static variable doesn't have the data, check {cache_menu}.
         $cache = $this->cache->get($cid);
-        if ($cache && isset($cache->data)) {
+        if ($cache && $cache->data) {
           // If the cache entry exists, it contains the parameters for
           // menu_build_tree().
           $tree_parameters = $cache->data;
@@ -442,7 +445,7 @@ protected function doBuildTree($menu_name, array $parameters = array()) {
     // If we do not have this tree in the static cache, check {cache_menu}.
     if (!isset($this->menuTree[$tree_cid])) {
       $cache = $this->cache->get($tree_cid);
-      if ($cache && isset($cache->data)) {
+      if ($cache && $cache->data) {
         $this->menuFullTrees[$tree_cid] = $cache->data;
       }
     }
diff --git a/core/modules/menu_link/lib/Drupal/menu_link/MenuTreeInterface.php b/core/modules/menu_link/lib/Drupal/menu_link/MenuTreeInterface.php
index 0393e11..dd0b50e 100644
--- a/core/modules/menu_link/lib/Drupal/menu_link/MenuTreeInterface.php
+++ b/core/modules/menu_link/lib/Drupal/menu_link/MenuTreeInterface.php
@@ -34,8 +34,8 @@ public function renderTree($tree);
    * This path will also affect the breadcrumbs under some circumstances.
    * Breadcrumbs are built using the preferred link returned by
    * menu_link_get_preferred(). If the preferred link is inside one of the menus
-   * specified in calls to menu_tree_set_path(), the preferred link will be
-   * overridden by the corresponding path returned by menu_tree_get_path().
+   * specified in calls to static::setPath(), the preferred link will be
+   * overridden by the corresponding path returned by static::getPath().
    *
    * Setting this path does not affect the main content; for that use
    * menu_set_active_item() instead.