don't set default scope for discriminator's root model

lib/dm-core/model.rb

@@ -548,7 +548,7 @@ def load(records, query)
             record = record.dup
             field_map.each { |property, field| record[property] = record.delete(field) if record.key?(field) }
 
-            model     = discriminator && (klass = record[discriminator]) && discriminator.typecast(klass) || self
+            model     = discriminator && discriminator.typecast(record[discriminator]) || self
             model_key = model.key(repository_name)
 
             resource = if model_key.valid?(key_values = record.values_at(*model_key))

lib/dm-core/types/discriminator.rb

@@ -13,8 +13,6 @@ def self.bind(property)
         model           = property.model
         property_name   = property.name
 
-        model.default_scope(repository_name).update(property_name => model.descendants)
-
         model.class_eval <<-RUBY, __FILE__, __LINE__ + 1
           extend Chainable
 

spec/public/types/discriminator_spec.rb

@@ -3,18 +3,12 @@
 describe DataMapper::Types::Discriminator do
   before :all do
     module ::Blog
-      class NewDiscriminator < DataMapper::Types::Discriminator
-        primitive Class
-        default   lambda { |resource, property| resource.model }
-        required  true
-      end
-
       class Article
         include DataMapper::Resource
 
         property :id,    Serial
         property :title, String, :required => true
-        property :type,  NewDiscriminator
+        property :type,  Discriminator
       end
 
       class Announcement < Article; end
@@ -89,8 +83,8 @@ class Release < Announcement; end
   end
 
   describe 'Model#default_scope' do
-    it 'should set the default scope for the grandparent model' do
-      @article_model.default_scope[:type].should equal(@article_model.descendants)
+    it "shouldn't set the default scope for root model if you want all descendants anyway" do
+      @article_model.default_scope[:type].should be_nil
     end
 
     it 'should set the default scope for the parent model' do