Issue #2723961 by jo.st, rajeshwari10, andrewmacpherson: Broken aria-labelledby ID reference in menu block and breadcrumb templates

core/modules/system/templates/block--system-menu-block.html.twig

@@ -40,7 +40,7 @@
     {% set title_attributes = title_attributes.addClass('visually-hidden') %}
   {% endif %}
   {{ title_prefix }}
-  <h2{{ title_attributes }}>{{ configuration.label }}</h2>
+  <h2{{ title_attributes.setAttribute('id', heading_id) }}>{{ configuration.label }}</h2>
   {{ title_suffix }}
 
   {# Menu. #}

core/modules/system/templates/breadcrumb.html.twig

@@ -11,7 +11,7 @@
 #}
 {% if breadcrumb %}
   <nav role="navigation" aria-labelledby="system-breadcrumb">
-    <h2 class="visually-hidden">{{ 'Breadcrumb'|t }}</h2>
+    <h2 id="system-breadcrumb" class="visually-hidden">{{ 'Breadcrumb'|t }}</h2>
     <ol>
     {% for item in breadcrumb %}
       <li>

core/themes/stable/templates/block/block--system-menu-block.html.twig

@@ -38,7 +38,7 @@
     {% set title_attributes = title_attributes.addClass('visually-hidden') %}
   {% endif %}
   {{ title_prefix }}
-  <h2{{ title_attributes }}>{{ configuration.label }}</h2>
+  <h2{{ title_attributes.setAttribute('id', heading_id) }}>{{ configuration.label }}</h2>
   {{ title_suffix }}
 
   {# Menu. #}

core/themes/stable/templates/navigation/breadcrumb.html.twig

@@ -9,7 +9,7 @@
 #}
 {% if breadcrumb %}
   <nav role="navigation" aria-labelledby="system-breadcrumb">
-    <h2 class="visually-hidden">{{ 'Breadcrumb'|t }}</h2>
+    <h2 id="system-breadcrumb" class="visually-hidden">{{ 'Breadcrumb'|t }}</h2>
     <ol>
     {% for item in breadcrumb %}
       <li>