class Sass::Selector::CommaSequence

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