<=>

# File lib/rubygems/source.rb, line 53
  def <=>(other)
    case other
    when Gem::Source::Installed,
         Gem::Source::Local,
         Gem::Source::Lock,
         Gem::Source::SpecificFile,
         Gem::Source::Git,
         Gem::Source::Vendor then
      -1
    when Gem::Source then
      if !@uri
        return 0 unless other.uri
        return 1
      end

      return -1 if !other.uri

      # Returning 1 here ensures that when sorting a list of sources, the
      # original ordering of sources supplied by the user is preserved.
      return 1 unless @uri.to_s == other.uri.to_s

      0
    else
      nil
    end
  end