column will use coder to typecase value when it is available

activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb

@@ -72,6 +72,8 @@ def klass
       # Casts value (which is a String) to an appropriate instance.
       def type_cast(value)
         return nil if value.nil?
+        return coder.load(value) if encoded?
+
         klass = self.class
 
         case type

activerecord/test/cases/column_definition_test.rb

@@ -24,6 +24,12 @@ def test_encoded?
         assert column.encoded?
       end
 
+      def test_type_case_coded_column
+        column = Column.new("title", nil, "varchar(20)")
+        column.coder = YAML
+        assert_equal "hello", column.type_cast("--- hello")
+      end
+
       # Avoid column definitions in create table statements like:
       # `title` varchar(255) DEFAULT NULL
       def test_should_not_include_default_clause_when_default_is_null