From 25d956e8a144dc9cdb826f494ed18b7992eb88f8 Mon Sep 17 00:00:00 2001
From: Jeremy Evans <code@jeremyevans.net>
Date: Mon, 10 Jun 2019 15:47:56 -0700
Subject: [PATCH] Fix SystemStackError when calling a method in an unused
 refinement

Fixes [Bug #15720]
---
 test/ruby/test_refinement.rb | 32 ++++++++++++++++++++++++++++++++
 vm_insnhelper.c              |  5 ++++-
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/test/ruby/test_refinement.rb b/test/ruby/test_refinement.rb
index 7d47a52982..c7233f4f37 100644
--- a/test/ruby/test_refinement.rb
+++ b/test/ruby/test_refinement.rb
@@ -2242,6 +2242,38 @@ def foo
     INPUT
   end
 
+  def test_refining_module_repeatedly
+    bug15720 = '[ruby-core:91916] [Bug #15720]'
+    assert_in_out_err([], <<-INPUT, ["ok"], [], bug15720)
+      module M1
+        refine Kernel do
+          def foo
+            'foo called!'
+          end
+        end
+      end
+
+      module M2
+        refine Kernel do
+          def bar
+            'bar called!'
+          end
+        end
+      end
+
+      using M1
+
+      foo
+
+      begin
+        bar
+      rescue NameError
+      end
+
+      puts "ok"
+    INPUT
+  end
+
   def test_super_from_refined_module
     a = EnvUtil.labeled_module("A") do
       def foo;"[A#{super}]";end
diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index 523ac71f42..93b1ebfe7a 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -2635,7 +2635,10 @@ vm_call_method_each_type(rb_execution_context_t *ec, rb_control_frame_t *cfp, st
 		    goto no_refinement_dispatch;
 		}
 	    }
-	    cc->me = ref_me;
+            if (cc->me->def->type != VM_METHOD_TYPE_REFINED ||
+                 cc->me->def != ref_me->def) {
+                 cc->me = ref_me;
+            }
 	    if (ref_me->def->type != VM_METHOD_TYPE_REFINED) {
 		return vm_call_method(ec, cfp, calling, ci, cc);
 	    }
-- 
2.21.0