Problem combining single table inheritance and a has_many relation

Hi all!

I think I've found a bug that occurs when combining single table inheritance with a has_many relation.

My models look something like this:

class Content < ActiveRecord::Base
  inheritance_column = 'inheritance_type'
  
  has_many :children, :class_name => 'Content', :foreign_key => 'parent_id'
end

class Page < Content
end

class Section < Content
end

When I have the following data in my database, for example:

{ id => 1, parent_id => nil, inheritance_type => 'Page' }

{ id => 2, parent_id => 1, inheritance_type => 'Section' }

{ id => 3, parent_id => 1, inheritance_type => 'Section' }

Page.find(:all)

Will return one page object and two section objects

Page.find(1).children

Will return two content objects while I'd expect it to return two section objects