# File lib/bundler/definition.rb, line 197
    def index
      @index ||= Index.build do |idx|
        dependency_names = @dependencies.dup || []
        dependency_names.map! {|d| d.name }

        @sources.each do |s|
          if s.is_a?(Bundler::Source::Rubygems)
            s.dependency_names = dependency_names.uniq
            idx.add_source s.specs
          else
            source_index = s.specs
            dependency_names += source_index.unmet_dependency_names
            idx.add_source source_index
          end
        end
      end
    end