Stop trying to be clever about when to define attribute methods.

There is no meaningful performance penalty in defining attribute
methods, since it only happens once.

There is also no reason *not* to define them, since they get thrown in
an included module, so they will not 'overwrite' anything. In fact, this
is desirable, since it allows us to call super.

activerecord/lib/active_record/attribute_methods.rb

@@ -38,21 +38,12 @@ def undefine_attribute_methods(*args)
         end
       end
 
-      # Checks whether the method is defined in the model or any of its subclasses
-      # that also derive from Active Record. Raises DangerousAttributeError if the
-      # method is defined by Active Record though.
       def instance_method_already_implemented?(method_name)
         if dangerous_attribute_method?(method_name)
           raise DangerousAttributeError, "#{method_name} is defined by ActiveRecord"
         end
 
-        method_name = method_name.to_s
-        index = ancestors.index(ActiveRecord::Base) || ancestors.length
-        @_defined_class_methods         ||= ancestors.first(index).map { |m|
-          m.instance_methods(false) | m.private_instance_methods(false)
-        }.flatten.map {|m| m.to_s }.to_set
-
-        @_defined_class_methods.include?(method_name) || generated_attribute_methods.method_defined?(method_name)
+        super
       end
 
       # A method name is 'dangerous' if it is already defined by Active Record, but

activerecord/test/cases/attribute_methods_test.rb

@@ -431,30 +431,6 @@ def test_typecast_attribute_from_select_to_true
     assert topic.is_test?
   end
 
-  def test_kernel_methods_not_implemented_in_activerecord
-    %w(test name display y).each do |method|
-      assert !ActiveRecord::Base.instance_method_already_implemented?(method), "##{method} is defined"
-    end
-  end
-
-  def test_defined_kernel_methods_implemented_in_model
-    %w(test name display y).each do |method|
-      klass = Class.new ActiveRecord::Base
-      klass.class_eval "def #{method}() 'defined #{method}' end"
-      assert klass.instance_method_already_implemented?(method), "##{method} is not defined"
-    end
-  end
-
-  def test_defined_kernel_methods_implemented_in_model_abstract_subclass
-    %w(test name display y).each do |method|
-      abstract = Class.new ActiveRecord::Base
-      abstract.class_eval "def #{method}() 'defined #{method}' end"
-      abstract.abstract_class = true
-      klass = Class.new abstract
-      assert klass.instance_method_already_implemented?(method), "##{method} is not defined"
-    end
-  end
-
   def test_raises_dangerous_attribute_error_when_defining_activerecord_method_in_model
     %w(save create_or_update).each do |method|
       klass = Class.new ActiveRecord::Base