join_scopes

# File activerecord/lib/active_record/reflection.rb, line 1273
      def join_scopes(table, predicate_builder = nil, klass = self.klass, record = nil) # :nodoc:
        scopes = super
        unless @previous_reflection.through_reflection?
          scopes += @previous_reflection.join_scopes(table, predicate_builder, klass, record)
        end
        scopes << build_scope(table, predicate_builder, klass).instance_exec(record, &source_type_scope)
      end