Introduce an Attribute object to handle the type casting dance

There's a lot more that can be moved to these, but this felt like a good
place to introduce the object. Plans are:

- Remove all knowledge of type casting from the columns, beyond a
  reference to the cast_type
- Move type_cast_for_database to these objects
- Potentially make them mutable, introduce a state machine, and have
  dirty checking handled here as well
- Move `attribute`, `decorate_attribute`, and anything else that
  modifies types to mess with this object, not the columns hash
- Introduce a collection object to manage these, reduce allocations, and
  not require serializing the types

1 files changed, 0 insertions, 6 deletions

diff --git a/activerecord/test/cases/serialized_attribute_test.rb b/activerecord/test/cases/serialized_attribute_test.rb
index 7d1c240638..82df0a5f08 100644
--- a/activerecord/test/cases/serialized_attribute_test.rb
+++ b/activerecord/test/cases/serialized_attribute_test.rb
@@ -36,12 +36,6 @@ class SerializedAttributeTest < ActiveRecord::TestCase
     assert_equal(myobj, topic.content)
   end
 
-  def test_serialized_attribute_init_with
-    topic = Topic.allocate
-    topic.init_with('raw_attributes' => { 'content' => '--- foo' })
-    assert_equal 'foo', topic.content
-  end
-
   def test_serialized_attribute_in_base_class
     Topic.serialize("content", Hash)