class Shoulda::Matchers::ActiveModel::ValidateUniquenessOfMatcher

def validate_after_scope_change?
  if @options[:scopes].blank?
    true
  else
    @options[:scopes].all? do |scope|
      previous_value = existing.send(scope)
      # Assume the scope is a foreign key if the field is nil
      previous_value ||= correct_type_for_column(@subject.class.columns_hash[scope.to_s])
      next_value = if previous_value.respond_to?(:next)
        previous_value.next
      else
        previous_value.to_s.next
      end
      @subject.send("#{scope}=", next_value)
      if allows_value_of(existing_value, @expected_message)
        @subject.send("#{scope}=", previous_value)
        @failure_message_for_should_not <<
          " (with different value of #{scope})"
        true
      else
        @failure_message_for_should << " (with different value of #{scope})"
        false
      end
    end
  end
end