    # File lib/rubygems/source_index.rb, line 299
      def outdated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