From f3c77bd480834f2835fe6fef5c0475336248dbde Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Mon, 17 Jan 2022 01:56:31 +0900
Subject: Fix the placeholder subclass entry skipping [Bug #18489]

---
 test/ruby/test_module.rb | 9 +++++++++
 1 file changed, 9 insertions(+)

(limited to 'test/ruby')

diff --git a/test/ruby/test_module.rb b/test/ruby/test_module.rb
index 0a6959c5e6..e744121718 100644
--- a/test/ruby/test_module.rb
+++ b/test/ruby/test_module.rb
@@ -475,6 +475,15 @@ class TestModule < Test::Unit::TestCase
     assert_not_include(mod.ancestor_list, BasicObject)
   end
 
+  def test_module_collected_extended_object
+    m1 = labeled_module("m1")
+    m2 = labeled_module("m2")
+    Object.new.extend(m1)
+    GC.start
+    m1.include(m2)
+    assert_equal([m1, m2], m1.ancestors)
+  end
+
   def test_dup
     OtherSetup.call
 
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