class ActiveModel::Validations::ConfirmationValidator

def setup!(klass)
  klass.send(:attr_reader, *attributes.map do |attribute|
    :"#{attribute}_confirmation" unless klass.method_defined?(:"#{attribute}_confirmation")
  end.compact)
  klass.send(:attr_writer, *attributes.map do |attribute|
    :"#{attribute}_confirmation" unless klass.method_defined?(:"#{attribute}_confirmation=")
  end.compact)
end