diff -u b/core/includes/theme.inc b/core/includes/theme.inc
--- b/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -21,6 +21,7 @@
 use Drupal\Core\Theme\ThemeSettings;
 use Drupal\Component\Utility\NestedArray;
 use Drupal\Core\Render\Element;
+use Zend\Stdlib\ArrayUtils;
 
 /**
  * @defgroup content_flags Content markers
@@ -2315,11 +2316,9 @@
  *   - elements: An associative array containing properties of the region.
  */
 function template_preprocess_region(&$variables) {
-  $elements = $variables['elements'];
-
   // Create the $content variable that templates expect.
-  $variables['content'] = $elements['#children'];
-  $variables['region'] = $elements['#region'];
+  $variables['content'] = $variables['elements']['#children'];
+  $variables['region'] = $variables['elements']['#region'];
 
   $variables['attributes']['class'][] = 'region';
   $variables['attributes']['class'][] = drupal_html_class('region-' . $variables['region']);
@@ -2338,30 +2337,6 @@
  *   - content_attributes: A string containing the attributes for the content's
  *     div.
  */
-
-/**
- * @todo this should probably be in another place
- * but gets the job done & merge the arrays for field attributes
- */
-function mergeAttributes($array) {
-  $mergedAttributes = array();
-  foreach(func_get_args() as $argument) {
-    foreach($argument as $key => $value) {
-      if (!isset($mergedAttributes[$key]) ) {
-        $mergedAttributes[$key] = array();
-      }
-      if (is_array($value)) {
-        foreach($value as $innerValue) {
-          $mergedAttributes[$key][] = $innerValue;
-        }
-      } else {
-        $mergedAttributes[$key][] = $value;
-      }
-    }
-  }
-  return $mergedAttributes;
-}
-
 function template_preprocess_field(&$variables, $hook) {
   $element = $variables['element'];
 
@@ -2384,15 +2359,24 @@
     $delta++;
   }
 
-  // Are there multiple field items.
-  if ( isset($element['#items']) && is_object($element['#items']) ){
-    $variables['multiple'] = $element['#items']->getFieldDefinition()->isMultiple();
+  // Add default CSS classes. Since there can be many fields rendered on a page,
+  // save some overhead by calling strtr() directly instead of
+  // drupal_html_class().
+  $variables['entity_type_css'] = strtr($element['#entity_type'], '_', '-');
+  $variables['field_name_css'] = strtr($element['#field_name'], '_', '-');
+  $variables['field_type_css'] = strtr($element['#field_type'], '_', '-');
+  $variables['attributes']['class'] = array(
+    'field',
+    'field-' . $variables['entity_type_css'] . '--' . $variables['field_name_css'],
+    'field-name-' . $variables['field_name_css'],
+    'field-type-' . $variables['field_type_css'],
+    'field-label-' . $element['#label_display'],
+  );
+  // Add a "clearfix" class to the wrapper since we float the label and the
+  // field items in field.module.css if the label is inline.
+  if ($element['#label_display'] == 'inline') {
+    $variables['attributes']['class'][] = 'clearfix';
   }
-  // Add default CSS class names. Since there can be many fields rendered on a
-  // page, save some overhead by calling strtr()
-  $variables['field_name'] = strtr($element['#field_name'], '_', '-');
-  $variables['field_type'] = strtr($element['#field_type'], '_', '-');
-  $variables['field_label'] = strtr($element['#label_display'], '_', '-');
 
   static $default_attributes;
   if (!isset($default_attributes)) {
@@ -2413,9 +2397,11 @@
  *   - elements: An associative array containing properties of the region.
  */
 function template_preprocess_region(&$variables) {
+  $elements = $variables['elements'];
+
   // Create the $content variable that templates expect.
-  $variables['content'] = $variables['elements']['#children'];
-  $variables['region'] = $variables['elements']['#region'];
+  $variables['content'] = $elements['#children'];
+  $variables['region'] = $elements['#region'];
 
   $variables['attributes']['class'][] = 'region';
   $variables['attributes']['class'][] = drupal_html_class('region-' . $variables['region']);
@@ -2456,24 +2442,15 @@
     $delta++;
   }
 
-  // Add default CSS classes. Since there can be many fields rendered on a page,
-  // save some overhead by calling strtr() directly instead of
-  // drupal_html_class().
-  $variables['entity_type_css'] = strtr($element['#entity_type'], '_', '-');
-  $variables['field_name_css'] = strtr($element['#field_name'], '_', '-');
-  $variables['field_type_css'] = strtr($element['#field_type'], '_', '-');
-  $variables['attributes']['class'] = array(
-    'field',
-    'field-' . $variables['entity_type_css'] . '--' . $variables['field_name_css'],
-    'field-name-' . $variables['field_name_css'],
-    'field-type-' . $variables['field_type_css'],
-    'field-label-' . $element['#label_display'],
-  );
-  // Add a "clearfix" class to the wrapper since we float the label and the
-  // field items in field.module.css if the label is inline.
-  if ($element['#label_display'] == 'inline') {
-    $variables['attributes']['class'][] = 'clearfix';
+  // Are there multiple field items.
+  if ( isset($element['#items']) && is_object($element['#items']) ){
+    $variables['multiple'] = $element['#items']->getFieldDefinition()->isMultiple();
   }
+  // Add default CSS class names. Since there can be many fields rendered on a
+  // page, save some overhead by calling strtr()
+  $variables['field_name'] = strtr($element['#field_name'], '_', '-');
+  $variables['field_type'] = strtr($element['#field_type'], '_', '-');
+  $variables['field_label'] = strtr($element['#label_display'], '_', '-');
 
   static $default_attributes;
   if (!isset($default_attributes)) {
@@ -2502,26 +2479,25 @@
   }
 
   //@todo this is dummy data for testing merging of the attributes remove when merge works.
-  // $variables['attributes']['class'] = 'test-attribute-merge-1';
-  // $variables['content_attributes']['class'] ='test-attribute-merge-2';
-
-  // $variables['content_attributes']['role'] = 'content_attributes-role';
-  // $variables['attributes']['role'] = 'attributes-role';
-  // $variables['title_attributes']['role'] = 'title-attributes-role';
-  // $variables['item_attributes']['0']['role'] = 'item-attributes-role';
-
+  $variables['attributes']['class'] = 'test-attribute-merge-1';
+  $variables['content_attributes']['class'] ='test-attribute-merge-1';
+  $variables['content_attributes']['role'] = 'content_attributes-role';
+  $variables['attributes']['role'] = 'attributes-role';
+  $variables['title_attributes']['role'] = 'title-attributes-role';
+  $variables['item_attributes']['0']['role'] = 'item-attributes-role';
 
-  // Merge the attributes when its a multiple fields with hidden label
+  //@todo: merge attributes for fields
   if ($element['#label_display'] == 'hidden' && $variables['multiple']) {
-     $variables['attributes'] = mergeAttributes ($variables['attributes'], $variables['content_attributes']);
+    //@todo: merge $variables['attributes'] and  $variables['content_attributes']
+    // $variables['attributes'] = NestedArray::mergeDeep($variables['attributes']->storage(), $variables['content_attributes']->storage());
   }
-  // Merge the attributes when its a single field with a label
   if ($element['#label_display'] != 'hidden' && !$variables['multiple']) {
-     $variables['content_attributes'] = mergeAttributes ($variables['content_attributes'], $variables['item_attributes']['0']);
+    //@todo: merge  $variables['item_attributes'][0] and $variables['content_attributes']
+    //$variables['content_attributes'] = NestedArray::mergeDeep($variables['content_attributes']->storage(), $variables['item_attributes']['0']->storage());
   }
-  // Merge the attributes when its a single field with hidden label
   if ($element['#label_display'] == 'hidden' && !$variables['multiple']) {
-     $variables['attributes'] =  mergeAttributes ($variables['attributes'], $variables['content_attributes'], $variables['item_attributes']['0']);
+    //@todo: merge $variables['attributes'], $variables['item_attributes'][0] &  $variables['content_attributes']
+    // $variables['attributes'] = NestedArray::mergeDeep($variables['attributes']->storage(), $variables['content_attributes']->storage(), $variables['item_attributes']['0']->storage());
   }
 
 }
diff -u b/core/modules/system/templates/field.html.twig b/core/modules/system/templates/field.html.twig
--- b/core/modules/system/templates/field.html.twig
+++ b/core/modules/system/templates/field.html.twig
@@ -54,10 +54,10 @@
   </div>
 #}
   <div class="{{ classes }}"{{ attributes|without('class') }}>
-    <div class="field__label{{ title_attributes.class }}"{{ title_attributes|without('class') }}>{{ label }}:</div>
-    <div class="field__items {{ content_attributes.class }}"{{ content_attributes|without('class') }}>
+    <div class="field__label"{{ title_attributes }}>{{ label }}:</div>
+    <div class="field__items"{{ content_attributes }}>
       {% for delta, item in items %}
-        <div class="field__item{{ item_attributes[delta].class }}"{{ item_attributes[delta]|without('class') }}>{{ item }}</div>
+        <div class="field__item"{{ item_attributes[delta] }}>{{ item }}</div>
       {% endfor %}
     </div>
   </div>
@@ -72,9 +72,9 @@
   </div>
   attributes are merged  with  content_attributes
 #}
-  <div class="{{ classes }} field__items"{{ attributes|without('class') }}>
+  <div class="{{ classes }} field__items"{{ attributes }}>
     {% for delta, item in items %}
-      <div class="field__item{{ item_attributes[delta].class }}"{{ item_attributes[delta]|without('class') }}>{{ item }}</div>
+      <div class="field__item"{{ item_attributes[delta] }}>{{ item }}</div>
     {% endfor %}
   </div>
 
@@ -88,9 +88,9 @@
   content_attributes are merged with item_attributes
 #}
   <div class="{{ classes }}"{{ attributes|without('class') }}>
-    <div class="field__label{{ title_attributes.class}}"{{ title_attributes|without('class') }}>{{ label }}:</div>
+    <div class="field__label"{{ title_attributes }}>{{ label }}:</div>
     {% for delta, item in items %}
-      <div class="field__item{{ content_attributes.class }}"{{ content_attributes|without('class') }}>{{ item }}</div>
+      <div class="field__item"{{ content_attributes }}>{{ item }}</div>
     {% endfor %}
   </div>