rails/rails — pull request #12132 by kennyj (2013-09-04 16:22:21+00:00)
Title: ActiveRecord::Base#attributes return HashWithIndifferentAccess instance instead of Hash instance.

In current behavior, ActiveRecord::Base#attributes return Hash instance.

But instance[] / instance[]= support not only string key but also symbol key.
And other many api support string / symbol key.

I think ActiveRecord::Base#attributes also return HWIA instance to support string / symbol keys.