module ActionMailer::AdvAttrAccessor

def adv_attr_accessor(name, deprecation=nil)
  ivar = "@#{name}"
  deprecation ||= "Please pass :#{name} as hash key to mail() instead"
  class_eval <<-ACCESSORS, __FILE__, __LINE__ + 1
    def #{name}=(value)
      ActiveSupport::Deprecation.warn "#{name}= is deprecated. #{deprecation}"
      #{ivar} = value
    end
    def #{name}(*args)
      raise ArgumentError, "expected 0 or 1 parameters" unless args.length <= 1
      if args.empty?
        ActiveSupport::Deprecation.warn "#{name}() is deprecated and will be removed in future versions."
        #{ivar} if instance_variable_names.include?(#{ivar.inspect})
      else
        ActiveSupport::Deprecation.warn "#{name}(value) is deprecated. #{deprecation}"
        #{ivar} = args.first
      end
    end
  ACCESSORS
  self.protected_instance_variables << ivar if self.respond_to?(:protected_instance_variables)
end