vm_method.c: resolve refined method to undef

* vm_method.c (rb_undef): resolve the method entry which refines a
  prepended method entry.  [ruby-core:78944] [Bug #13096]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57362 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_refinement.rb

@@ -1474,6 +1474,25 @@ class TestRefinement < Test::Unit::TestCase
     INPUT
   end
 
+  def test_undef_prepended_method
+    bug13096 = '[ruby-core:78944] [Bug #13096]'
+    klass = EnvUtil.labeled_class("X") do
+      def foo; end
+    end
+    klass.prepend(Module.new)
+    ext = EnvUtil.labeled_module("Ext") do
+      refine klass do
+        def foo
+        end
+      end
+    end
+    assert_nothing_raised(NameError, bug13096) do
+      klass.class_eval do
+        undef :foo
+      end
+    end
+  end
+
   def test_call_refined_method_in_duplicate_module
     bug10885 = '[ruby-dev:48878]'
     assert_in_out_err([], <<-INPUT, [], [], bug10885)

vm_method.c

@@ -1171,7 +1171,7 @@ rb_attr(VALUE klass, ID id, int read, int write, int ex)
 void
 rb_undef(VALUE klass, ID id)
 {
-    rb_method_entry_t *me;
+    const rb_method_entry_t *me;
 
     if (NIL_P(klass)) {
 	rb_raise(rb_eTypeError, "no class to undef method");
@@ -1182,6 +1182,9 @@ rb_undef(VALUE klass, ID id)
     }
 
     me = search_method(klass, id, 0);
+    if (me && me->def->type == VM_METHOD_TYPE_REFINED) {
+	me = rb_resolve_refined_method(Qnil, me);
+    }
 
     if (UNDEFINED_METHOD_ENTRY_P(me) ||
 	UNDEFINED_REFINED_METHOD_P(me->def)) {