build_scope

# File activerecord/lib/active_record/associations/preloader/association.rb, line 133
          def build_scope
            scope = klass.scope_for_association

            if reflection.type
              scope.where!(reflection.type => model.base_class.sti_name)
            end

            scope.merge!(reflection_scope)
            scope.merge!(preload_scope) if preload_scope != NULL_RELATION
            scope
          end