Datamapper DataMapper

Brought up in IRC today, this is more of an annoyance than a bug. Duck typing isn't possible with properties of subclasses in single-table-inheritance...

class Order
  include DataMapper::Resource
  property :type, Discriminator
end

class Debit < Order
  property :refunded, Boolean
end

# This works fine:
Debit.all.each |d|
  puts d.refunded
end

# This should be possible but will fail:
Order.all.each |o|
  puts o.refunded if o.type == Debit
end

A workaround is to declare all properties on the superclass, but this is an annoyance. Subclasses should be able to have properties independent of their parents.