    # File lib/yard/handlers/ruby/mixin_handler.rb, line 23
      def process_mixin(mixin)
        raise YARD::Parser::UndocumentableError unless mixin.ref?
        raise YARD::Parser::UndocumentableError if mixin.first.type == :ident

        case obj = Proxy.new(namespace, mixin.source)
        when Proxy
          obj.type = :module
        when ConstantObject # If a constant is included, use its value as the real object
          obj = Proxy.new(namespace, obj.value)
        end

        namespace.mixins(scope).unshift(obj) unless namespace.mixins(scope).include?(obj)
      end