module Unparser::AbstractType

def self.create_new_method(abstract_class)
  abstract_class.define_singleton_method(:new) do |*args, &block|
    if equal?(abstract_class)
      fail NotImplementedError, "#{self} is an abstract type"
    else
      super(*args, &block)
    end
  end
end

def self.included(descendant)
  super
  create_new_method(descendant)
  descendant.extend(AbstractMethodDeclarations)
end