Rails has_one关系eager_load与多态通过多态（或周围）？

Question

我想实现以下目标：

class Document < ActiveRecord::Base
    has_one :number, as: numberable, through: typeable #<- This relation is the thing I want to have but doesn't work like this (and many other ways I tried)
    belongs_to :typeable, polymorphic: true
end

# Example Document Type
class Order < ActiveRecord::Base
    has_one :number, as: :numberable
    has_one :document, as: :typeable
end

# Number
class DocumentTypeNumber < ActiveRecord::Base
  belongs_to :numberable, polymorphic: true
end  

由于typeable和numberable将包含相等的记录，我可以在numberable.id = typeable.id和numberable.type = typeable.type 上执行左连接。但是我无法使用rails has_one关系（我想我试图将其滥用到很难）这样工作。所以我的问题是，用上面的数据模型实现以下的最佳方法是什么：

Document.eager_load(:number)
Document.find(1).number
# Or:
Document.eager_load(typeable: { :number })
Document.find(1).typeable.number

这里以图形方式..