diff --git a/core/lib/Drupal/Component/Plugin/CategorizingPluginManagerInterface.php b/core/lib/Drupal/Component/Plugin/CategorizingPluginManagerInterface.php
index 2a3afab..01f7eaf 100644
--- a/core/lib/Drupal/Component/Plugin/CategorizingPluginManagerInterface.php
+++ b/core/lib/Drupal/Component/Plugin/CategorizingPluginManagerInterface.php
@@ -23,7 +23,7 @@ public function getCategories();
   /**
    * Gets sorted definitions.
    *
-   * @param array $definitions
+   * @param array[]|null $definitions
    *   (optional) The definitions to sort. If omitted, all definitions are used.
    *
    * @return array[]
@@ -34,13 +34,13 @@ public function getSortedDefinitions(array $definitions = NULL);
   /**
    * Gets definitions grouped by category.
    *
-   * @param array $definitions
+   * @param array[]|null $definitions
    *   (optional) The definitions to group. If omitted, all definitions are
    *   used.
    *
    * @return array[]
-   *   A nested array containing plugin definitions, keyed by category and
-   *   plugin id.
+   *   Keys are category names, and values are arrays of which the keys are
+   *   plugin IDs and the values are plugin definitions.
    */
   public function getGroupedDefinitions(array $definitions = NULL);
 
diff --git a/core/lib/Drupal/Core/Plugin/CategorizingPluginManagerTrait.php b/core/lib/Drupal/Core/Plugin/CategorizingPluginManagerTrait.php
index f6f283e..4450deb 100644
--- a/core/lib/Drupal/Core/Plugin/CategorizingPluginManagerTrait.php
+++ b/core/lib/Drupal/Core/Plugin/CategorizingPluginManagerTrait.php
@@ -69,9 +69,10 @@ protected function getModuleName($module) {
   }
 
   /**
-   * See \Drupal\Component\Plugin\CategorizingPluginManagerInterface::getCategories().
+   * Implements \Drupal\Component\Plugin\CategorizingPluginManagerInterface::getCategories().
    */
   public function getCategories() {
+    /** @var \Drupal\Core\Plugin\CategorizingPluginManagerTrait|\Drupal\Component\Plugin\PluginManagerInterface $this */
     $categories = array_unique(array_values(array_map(function ($definition) {
       return $definition['category'];
     }, $this->getDefinitions())));
@@ -80,14 +81,11 @@ public function getCategories() {
   }
 
   /**
-   * See \Drupal\Component\Plugin\CategorizingPluginManagerInterface::getSortedDefinitions().
-   *
-   * @param string $label_key
-   *   (optional) The key used for the label in plugin definitions. Defaults to
-   *   label.
+   * Implements \Drupal\Component\Plugin\CategorizingPluginManagerInterface::getSortedDefinitions().
    */
   public function getSortedDefinitions(array $definitions = NULL, $label_key = 'label') {
     // Sort the plugins first by category, then by label.
+    /** @var \Drupal\Core\Plugin\CategorizingPluginManagerTrait|\Drupal\Component\Plugin\PluginManagerInterface $this */
     $definitions = isset($definitions) ? $definitions : $this->getDefinitions();
     uasort($definitions, function ($a, $b) use ($label_key) {
       if ($a['category'] != $b['category']) {
@@ -99,9 +97,10 @@ public function getSortedDefinitions(array $definitions = NULL, $label_key = 'la
   }
 
   /**
-   * See \Drupal\Component\Plugin\CategorizingPluginManagerInterface::getGroupedDefinitions().
+   * Implements \Drupal\Component\Plugin\CategorizingPluginManagerInterface::getGroupedDefinitions().
    */
   public function getGroupedDefinitions(array $definitions = NULL) {
+    /** @var \Drupal\Core\Plugin\CategorizingPluginManagerTrait|\Drupal\Component\Plugin\PluginManagerInterface $this */
     $definitions = isset($definitions) ? $definitions : $this->getDefinitions();
     $grouped_definitions = array();
     foreach ($definitions as $id => $definition) {