* eval.c (rb_mod_using): raise an ArgumentError if cyclic using is

detected.  based on the patch by Charlie Somerville.
  [ruby-core:49092] Bug #7308

* test/ruby/test_refinement.rb: related test.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@37646 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_refinement.rb

@@ -801,4 +801,25 @@ class TestRefinement < Test::Unit::TestCase
       p c.foo
     INPUT
   end
+
+  def test_circular_using_is_not_allowed
+    a = Module.new
+    b = Module.new
+
+    assert_raise ArgumentError do
+      a.module_eval do
+        using a
+      end
+    end
+
+    b.module_eval do
+      using a
+    end
+
+    assert_raise ArgumentError do
+      a.module_eval do
+        using b
+      end
+    end
+  end
 end