Use a name that better reflect the return value

actionview/lib/action_view/helpers/form_helper.rb

@@ -1226,11 +1226,11 @@ def instantiate_builder(record_name, record_object, options)
             object_name = model_name_from_record_or_class(object).param_key
           end
 
-          builder = options[:builder] || build_default_form_builder
+          builder = options[:builder] || default_form_builder_class
           builder.new(object_name, object, self, options)
         end
 
-        def build_default_form_builder
+        def default_form_builder_class
           builder = ActionView::Base.default_form_builder
           builder.respond_to?(:constantize) ? builder.constantize : builder
         end