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, 4 insertions, 9 deletions

diff --git a/activerecord/test/cases/persistence_test.rb b/activerecord/test/cases/persistence_test.rb
index 7f5d0d66d3..9127101433 100644
--- a/activerecord/test/cases/persistence_test.rb
+++ b/activerecord/test/cases/persistence_test.rb
@@ -250,11 +250,9 @@ class PersistenceTest < ActiveRecord::TestCase
   end
 
   def test_create_columns_not_equal_attributes
-    topic = Topic.allocate.init_with(
-      'raw_attributes' => {
-        'title'          => 'Another New Topic',
-        'does_not_exist' => 'test'
-      }
+    topic = Topic.instantiate(
+      'title'          => 'Another New Topic',
+      'does_not_exist' => 'test'
     )
     assert_nothing_raised { topic.save }
   end
@@ -300,10 +298,7 @@ class PersistenceTest < ActiveRecord::TestCase
     topic.title = "Still another topic"
     topic.save
 
-    topic_reloaded = Topic.allocate
-    topic_reloaded.init_with(
-      'raw_attributes' => topic.attributes.merge('does_not_exist' => 'test')
-    )
+    topic_reloaded = Topic.instantiate(topic.attributes.merge('does_not_exist' => 'test'))
     topic_reloaded.title = 'A New Topic'
     assert_nothing_raised { topic_reloaded.save }
   end