1 files changed, 6 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb
index 0771f26218..33fd8afee2 100755
--- a/activerecord/lib/active_record/associations.rb
+++ b/activerecord/lib/active_record/associations.rb
@@ -655,6 +655,12 @@ module ActiveRecord
       #              :conditions => 'discounts > #{payments_count}'
       #   belongs_to :attachable, :polymorphic => true
       def belongs_to(association_id, options = {})
+        if options.include?(:class_name) && !options.include?(:foreign_key)
+          ::ActiveSupport::Deprecation.warn(
+          "The inferred foreign_key name will change in Rails 2.0 to use the association name instead of its class name when they differ.  When using :class_name in belongs_to, use the :foreign_key option to explicitly set the key name to avoid problems in the transition.",
+          caller)
+        end
+        
         reflection = create_belongs_to_reflection(association_id, options)
         
         if reflection.options[:polymorphic]