Missed singleton_class

activesupport/lib/active_support/core_ext/object/singleton_class.rb

@@ -0,0 +1,13 @@
+class Object
+  # Returns the object's singleton class.
+  def singleton_class
+    class << self
+      self
+    end
+  end unless respond_to?(:singleton_class)
+
+  # class_eval on an object acts like singleton_class_eval.
+  def class_eval(*args, &block)
+    singleton_class.class_eval(*args, &block)
+  end
+end