Don't remove key-value from the subject hash we might want to use it again.

lib/cancan/rule.rb

@@ -123,7 +123,7 @@ module CanCan
     end
 
     def nested_subject_matches_conditions?(subject_hash)
-      parent, child = subject_hash.shift
+      parent, child = subject_hash.first
       matches_conditions_hash?(parent, @conditions[parent.class.name.downcase.to_sym] || {})
     end
 

spec/cancan/ability_spec.rb

@@ -298,6 +298,14 @@ describe CanCan::Ability do
     @ability.can?(:read, 123 => Range).should be_true
   end
   
+  it "passing a hash of subjects with multiple definitions should check permissions correctly" do
+    @ability.can :read, Range, :string => {:length => 4}
+    @ability.can [:create, :read], Range, :string => {:upcase => 'FOO'}
+    @ability.can?(:read, "foo" => Range).should be_true
+    @ability.can?(:read, "foobar" => Range).should be_false
+    @ability.can?(:read, 1234 => Range).should be_true
+  end  
+  
   it "should allow to check ability on Hash-like object" do
     class Container < Hash; end
     @ability.can :read, Container