include_in_memory? should check against @target list in case of new records. [#6257 state:resolved]

activerecord/lib/active_record/associations/association_collection.rb

@@ -518,10 +518,10 @@ def fetch_first_or_last_using_find?(args)
 
         def include_in_memory?(record)
           if @reflection.is_a?(ActiveRecord::Reflection::ThroughReflection)
-            @owner.send(proxy_reflection.through_reflection.name).any? do |source|
+            @owner.send(proxy_reflection.through_reflection.name).any? { |source|
               target = source.send(proxy_reflection.source_reflection.name)
               target.respond_to?(:include?) ? target.include?(record) : target == record
-            end
+            } || @target.include?(record)
           else
             @target.include?(record)
           end

activerecord/test/cases/associations/has_many_through_associations_test.rb

@@ -32,6 +32,13 @@ def setup
     Reader.create :person_id => 0, :post_id => 0
   end
 
+  def test_include?
+    person = Person.new
+    post = Post.new
+    person.posts << post
+    assert person.posts.include?(post)
+  end
+
   def test_associate_existing
     assert_queries(2) { posts(:thinking); people(:david) }