module Regexp::Syntax

def fallback_version_class(version)
  sorted_versions = (specified_versions + [version])
                    .sort_by { |name| comparable_version(name) }
  return if (version_index = sorted_versions.index(version)) < 1
  next_lower_version = sorted_versions[version_index - 1]
  inherit_from_version(next_lower_version, version)
end