Handle any default column class when deduplicating

Author: Aidan Haran

lib/active_record/connection_adapters/sqlserver_column.rb

@@ -30,13 +30,15 @@ def case_sensitive?
 
       private
 
-      # Handle when the default value is a boolean. Boolean's do not respond to the method `:-@`. Method now
-      # checks whether the default value is already frozen and if so it uses that, otherwise it calls `:-@` to
-      # freeze it.
+      # Change to Rails implementation that handles when the `default` object does not respond to the `:-@` method
+      # call. Examples of classes that do not respond to `:-@` are `TrueClass`, `FalseClass` and `Date`.
+      #
+      # The `default` object for other database adapters is always a String. This isn't the case for the SQL Server
+      # adapter.
       def deduplicated
         @name = -name
         @sql_type_metadata = sql_type_metadata.deduplicate if sql_type_metadata
-        @default = (default.frozen? ? default : -default) if default
+        @default = (default.respond_to?(:-@) ? -default : default.dup.freeze) if default
         @default_function = -default_function if default_function
         @collation = -collation if collation
         @comment = -comment if comment