# File lib/rubygems/source_index.rb, line 351
  def outdated
    outdateds = []

    latest_specs.each do |local|
      dependency = Gem::Dependency.new local.name, ">= #{local.version}"

      begin
        fetcher = Gem::SpecFetcher.fetcher
        remotes = fetcher.find_matching dependency
        remotes = remotes.map { |(name, version,_),_| version }
      rescue Gem::RemoteFetcher::FetchError => e
        raise unless fetcher.warn_legacy e do
          require 'rubygems/source_info_cache'

          specs = Gem::SourceInfoCache.search_with_source dependency, true

          remotes = specs.map { |spec,| spec.version }
        end
      end

      latest = remotes.sort.last

      outdateds << local.name if latest and local.version < latest
    end

    outdateds
  end