diplays mentioned but not merged message on MR show page

app/helpers/merge_requests_helper.rb

@@ -59,6 +59,17 @@ module MergeRequestsHelper
     @mr_closes_issues ||= @merge_request.closes_issues
   end
 
+  def mr_issues_mentioned_but_not_closing
+    @mr_issues_mentioned_but_not_closing ||= @merge_request.issues_mentioned_but_not_closing
+  end
+
+  def mr_issues_mentioned_but_not_closing_message
+    verb = mr_issues_mentioned_but_not_closing.size > 1 ? 'are' : 'is'
+    issue_text = 'issue'.pluralize(mr_issues_mentioned_but_not_closing.size)
+
+    "The following #{issue_text} #{verb} mentioned but not being closed:"
+  end
+
   def mr_change_branches_path(merge_request)
     new_namespace_project_merge_request_path(
       @project.namespace, @project,

app/views/projects/merge_requests/widget/_open.html.haml

@@ -30,6 +30,15 @@
     - elsif @merge_request.can_be_merged? || resolved_conflicts
       = render 'projects/merge_requests/widget/open/accept'
 
+  - if mr_issues_mentioned_but_not_closing.present?
+    .mr-widget-footer
+      %span
+        %i.fa.fa-warning
+        = mr_issues_mentioned_but_not_closing_message
+        = succeed '.' do
+          != markdown issues_sentence(mr_issues_mentioned_but_not_closing), pipeline: :gfm, author: @merge_request.author
+        = mr_assign_issues_link
+
   - if mr_closes_issues.present?
     .mr-widget-footer
       %span