assign_deprecated_shortcuts

# File actionpack/lib/action_controller/base.rb, line 1074
      def assign_deprecated_shortcuts(request, response)
        DEPRECATED_INSTANCE_VARIABLES.each do |method|
          var = "@#{method}"
          if instance_variables.include?(var)
            value = instance_variable_get(var)
            unless ActiveSupport::Deprecation::DeprecatedInstanceVariableProxy === value
              raise "Deprecating #{var}, but it's already set to #{value.inspect}! Use the #{method}= writer method instead of setting #{var} directly."
            end
          end
          instance_variable_set var, ActiveSupport::Deprecation::DeprecatedInstanceVariableProxy.new(self, method)
        end
      end