module Dry::Core::ClassAttributes

def defines(*args, type: Object)
  mod = Module.new do
    args.each do |name|
      define_method(name) do |value = Undefined|
        ivar = "@#{name}"
        if value == Undefined
          if instance_variable_defined?(ivar)
            instance_variable_get(ivar)
          else
            nil
          end
        else
          raise InvalidClassAttributeValue.new(name, value) unless type === value
          instance_variable_set(ivar, value)
        end
      end
    end
    define_method(:inherited) do |klass|
      args.each { |name| klass.public_send(name, send(name)) }
      super(klass)
    end
  end
  extend(mod)
end