# File lib/sass/selector/comma_sequence.rb, line 23
      def resolve_parent_refs(super_cseq)
        if super_cseq.nil?
          if @members.any? do |sel|
              sel.members.any? do |sel_or_op|
                sel_or_op.is_a?(SimpleSequence) && sel_or_op.members.any? {|ssel| ssel.is_a?(Parent)}
              end
            end
            raise Sass::SyntaxError.new("Base-level rules cannot contain the parent-selector-referencing character '&'.")
          end
          return self
        end

        CommaSequence.new(
          super_cseq.members.map do |super_seq|
            @members.map {|seq| seq.resolve_parent_refs(super_seq)}
          end.flatten)
      end