Merge pull request #4220 from bensie/singleton-class-master

Further simplify singleton_class checking in class_attribute

activesupport/lib/active_support/core_ext/class/attribute.rb

@@ -81,21 +81,13 @@ def self.#{name}=(val)
             define_method(:#{name}) { val }
           end
 
-          if singleton_class?
-            class_eval do
-              remove_possible_method(:#{name})
-              def #{name}
-                defined?(@#{name}) ? @#{name} : singleton_class.#{name}
-              end
-            end
-          end
           val
         end
 
         if instance_reader
           remove_possible_method :#{name}
           def #{name}
-            defined?(@#{name}) ? @#{name} : self.class.#{name}
+            defined?(@#{name}) ? @#{name} : singleton_class.#{name}
           end
 
           def #{name}?
@@ -107,9 +99,4 @@ def #{name}?
       attr_writer name if instance_writer
     end
   end
-
-  private
-  def singleton_class?
-    !name || '' == name
-  end
 end