merge revision(s) 96c5a4be7b0d72502001734770af0f4a735c544c: [Backport #19894]

	Fix memory leak in complemented method entries

	[Bug #19894]

	When a copy of a complemented method entry is created, there are two
	issues:

	1. IMEMO_FL_USER3 is not copied, so the complemented status is not
	   copied over.
	2. In rb_method_entry_clone we increment both alias_count and
	   complemented_count. However, when we free the method entry in
	   rb_method_definition_release, we only decrement one of the two
	   counters, resulting in the rb_method_definition_t being leaked.

	Co-authored-by: Adam Hess <adamhess1991@gmail.com>
	---
	 method.h                 |  5 +++--
	 test/ruby/test_module.rb | 29 +++++++++++++++++++++++++++++
	 vm_method.c              |  8 +++++---
	 3 files changed, 37 insertions(+), 5 deletions(-)

1 files changed, 29 insertions, 0 deletions

diff --git a/test/ruby/test_module.rb b/test/ruby/test_module.rb
index 54985f0f87..9d9b7243d2 100644
--- a/test/ruby/test_module.rb
+++ b/test/ruby/test_module.rb
@@ -3289,6 +3289,35 @@ class TestModule < Test::Unit::TestCase
     CODE
   end
 
+  def test_complemented_method_entry_memory_leak
+    # [Bug #19894]
+    assert_no_memory_leak([], <<~PREP, <<~CODE, rss: true)
+      code = proc do
+        $c = Class.new do
+          def foo; end
+        end
+
+        $m = Module.new do
+          refine $c do
+            def foo; end
+          end
+        end
+
+        Class.new do
+          using $m
+
+          def initialize
+            o = $c.new
+            o.method(:foo).unbind
+          end
+        end.new
+      end
+      1_000.times(&code)
+    PREP
+      100_000.times(&code)
+    CODE
+  end
+
   private
 
   def assert_top_method_is_private(method)