Virtus::ValueObject and Equalizer. Equalizer instances are immutable. https://github.com/dkubb/equalizer/issues/8

block_like_class_new.rb

module Virtus::ValueObject
  def self.new(super_class = Object, &block)
    result = Class.new(super_class)
    result.class_exec(&block)
    result.include(Equalizer.new(*result.attribute_set.map(&:name)))
  end
end

MyClass = Virtus::ValueObject.new do
  attribute ...
end

x = MyClass.new ...

freeze_means_done.rb

module Virtus
  module ClassMethods
    def freeze
      include Equalizer.new(*attribute_set.map(&:name))
      super
    end
  end
end

class MyClass
  include Virtus::ValueObject
  attribute ...
end
MyClass.freeze

x = MyClass.new ...

new_means_done.rb

module Virtus
  module ClassMethods
    def new(*args)
      unless @equalizer
        @equalizer = Equalizer.new(*attribute_set.map(&:name))
        include @equalizer
      end
      super
    end
  end
end

class MyClass
  include Virtus::ValueObject
  attribute ...
end

x = MyClass.new ...