class ActionDispatch::Routing::PolymorphicRoutes::HelperMethodBuilder

def polymorphic_mapping(target, record)
  if record.respond_to?(:to_model)
    target._routes.polymorphic_mappings[record.to_model.model_name.name]
  else
    target._routes.polymorphic_mappings[record.class.name]
  end
end