diff -u b/core/includes/theme.inc b/core/includes/theme.inc
--- b/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -1066,6 +1066,7 @@
   }
 }
 
+
 /**
  * Prepares variables for inline list templates.
  *
@@ -1073,66 +1074,16 @@
  *
  * @param array $variables
  *   An associative array containing:
- *   - items: An array of items to be displayed in the list. Each item can be
- *     either a string or a render array. If #type, #theme, or #markup
- *     properties are not specified for child render arrays, they will be
- *     inherited from the parent list, allowing callers to specify larger
- *     nested lists without having to explicitly specify and repeat the
- *     render properties for all nested child lists.
- *   - separator: A string to separate list items.
+ *   - items: An array of items to be displayed in the list.
  *
  * @see https://www.drupal.org/node/1842756
  */
 function template_preprocess_inline_list(&$variables) {
-  foreach ($variables['items'] as &$item) {
-    $attributes = array();
-    // If the item value is an array, then it is a render array.
-    if (is_array($item)) {
-      // List items support attributes via the '#wrapper_attributes' property.
-      if (isset($item['#wrapper_attributes'])) {
-        $attributes = $item['#wrapper_attributes'];
-      }
-      // Determine whether there are any child elements in the item that are not
-      // fully-specified render arrays. If there are any, then the child
-      // elements present nested lists and we automatically inherit the render
-      // array properties of the current list to them.
-      foreach (Element::children($item) as $key) {
-        $child = &$item[$key];
-        // If this child element does not specify how it can be rendered, then
-        // we need to inherit the render properties of the current list.
-        if (!isset($child['#type']) && !isset($child['#theme']) && !isset($child['#markup'])) {
-          // Since inline-list.html.twig supports both strings and render arrays
-          // as items, the items of the nested list may have been specified as
-          // the child elements of the nested list, instead of #items. For
-          // convenience, we automatically move them into #items.
-          if (!isset($child['#items'])) {
-            // This is the same condition as in
-            // \Drupal\Core\Render\Element::children(), which cannot be used
-            // here, since it triggers an error on string values.
-            foreach ($child as $child_key => $child_value) {
-              if ($child_key[0] !== '#') {
-                $child['#items'][$child_key] = $child_value;
-                unset($child[$child_key]);
-              }
-            }
-          }
-          // Lastly, inherit the original theme variables of the current list.
-          $child['#theme'] = $variables['theme_hook_original'];
-        }
-      }
-    }
-
-    // Set the item's value and attributes for the template.
-    $item = array(
-      'value' => $item,
-      'attributes' => new Attribute($attributes),
-    );
-
-    // Since the separator may be user-specified, it must be sanitized.
-    $variables['separator'] = SafeString::create(Xss::filterAdmin($variables['separator']));
-  }
+  // Since the separator may be user-specified, it must be sanitized.
+  $variables['separator'] = SafeString::create(Xss::filterAdmin($variables['separator']));
 }
 
+
 /**
  * Returns HTML for an indentation div; used for drag and drop tables.
  *
diff -u b/core/modules/system/templates/inline-list.html.twig b/core/modules/system/templates/inline-list.html.twig
--- b/core/modules/system/templates/inline-list.html.twig
+++ b/core/modules/system/templates/inline-list.html.twig
@@ -4,11 +4,8 @@
  * Default theme implementation for an inline list of items.
  *
  * Available variables:
- * - items: A list of items. Each item contains:
- *   - attributes: HTML attributes to be applied to each list item.
- *   - value: The content of the list element.
+ * - items: An array of items.
  * - separator: A string to separate list items.
- * - attributes: HTML attributes to be applied to the list.
  * - empty: A message to display when there are no items. Allowed value is a
  *   string or render array.
  *
@@ -18,7 +15,7 @@
  */
 #}
 {%- for item in items -%}
-  {{ item.value }}{{ loop.last ? '' : separator }}
+  {{ item }}{{ loop.last ? '' : separator }}
 {%- else -%}
   {{- empty -}}
 {%- endfor -%}
reverted:
--- b/core/themes/classy/templates/dataset/inline-list.html.twig
+++ /dev/null
@@ -1,30 +0,0 @@
-{#
-/**
- * @file
- * Theme override for an inline list of items.
- *
- * Available variables:
- * - items: A list of items. Each item contains:
- *   - attributes: HTML attributes to be applied to each list item.
- *   - value: The content of the list element.
- * - separator: A string to separate list items.
- * - attributes: HTML attributes to be applied to the list.
- * - empty: A message to display when there are no items. Allowed value is a
- *   string or render array.
- *
- * @see template_preprocess_inline_list()
- *
- * @ingroup themeable
- */
-#}
-{%- if items or empty -%}
-  {%- if items -%}
-    <span{{ attributes }}>
-      {%- for item in items -%}
-        <span{{ item.attributes }}>{{ item.value }}</span>
-      {%- endfor -%}
-    </span>
-  {%- else -%}
-    {{- empty -}}
-  {%- endif -%}
-{%- endif %}
only in patch2:
unchanged:
--- a/core/modules/system/src/Tests/Theme/FunctionsTest.php
+++ b/core/modules/system/src/Tests/Theme/FunctionsTest.php
@@ -168,6 +168,50 @@ function testItemList() {
   }
 
   /**
+   * Tests inline-list.html.twig.
+   */
+  function testInlineList() {
+    // Verify that empty items produce no output.
+    $variables = array();
+    $expected = '';
+    $this->assertThemeOutput('inline_list', $variables, $expected, 'Empty %callback generates no output.');
+
+    // Verify that empty items produce the empty string.
+    $variables = array();
+    $variables['empty'] = 'No items found.';
+    $expected = 'No items found.';
+    $this->assertThemeOutput('inline_list', $variables, $expected, 'Empty %callback generates empty string.');
+
+    // Verify that empty text is not displayed when there are list items.
+    $variables = array();
+    $variables['empty'] = 'No items found.';
+    $variables['items'] = array('Un', 'Deux', 'Trois');
+    $expected = 'Un, Deux, Trois';
+    $this->assertThemeOutput('inline_list', $variables, $expected, '%callback does not print empty text when there are list items.');
+
+    // Verify that a non-default separator is rendered
+    $variables = array();
+    $variables['items'] = array('Un', 'Deux', 'Trois');
+    $variables['separator'] = ' and ';
+    $expected = 'Un and Deux and Trois';
+    $this->assertThemeOutput('inline_list', $variables, $expected, '%callback uses a custom separator when provided.');
+
+    // Verify that HTML separators are properly rendered
+    $variables = array();
+    $variables['items'] = array('Un', 'Deux', 'Trois');
+    $variables['separator'] = '<br />';
+    $expected = 'Un<br />Deux<br />Trois';
+    $this->assertThemeOutput('inline_list', $variables, $expected, '%callback allows HTML in user-provided separators.');
+
+    // Verify that the separator is sanitized
+    $variables = array();
+    $variables['items'] = array('Un', 'Deux', 'Trois');
+    $variables['separator'] = '<script>alert("test")</script>';
+    $expected = 'Unalert("test")Deuxalert("test")Trois';
+    $this->assertThemeOutput('inline_list', $variables, $expected, '%callback sanitizes user-provided separators.');
+  }
+
+    /**
    * Tests links.html.twig.
    */
   function testLinks() {