# File lib/bundler/dsl.rb, line 80
    def gem(name, *args)
      options = args.last.is_a?(Hash) ? args.pop.dup : {}
      version = args || [">= 0"]

      normalize_options(name, version, options)

      dep = Dependency.new(name, version, options)

      # if there's already a dependency with this name we try to prefer one
      if current = @dependencies.find {|d| d.name == dep.name }
        if current.requirement != dep.requirement
          if current.type == :development
            @dependencies.delete current
          elsif dep.type == :development
            return
          else
            raise GemfileError, "You cannot specify the same gem twice with different version requirements.\n" \
                            "You specified: #{current.name} (#{current.requirement}) and #{dep.name} (#{dep.requirement})"
          end

        else
          Bundler.ui.warn "Your Gemfile lists the gem #{current.name} (#{current.requirement}) more than once.\n" \
                          "You should probably keep only one of them.\n" \
                          "While it's not a problem now, it could cause errors if you change the version of just one of them later."
        end

        if current.source != dep.source
          if current.type == :development
            @dependencies.delete current
          elsif dep.type == :development
            return
          else
            raise GemfileError, "You cannot specify the same gem twice coming from different sources.\n" \
                            "You specified that #{dep.name} (#{dep.requirement}) should come from " \
                            "#{current.source || "an unspecified source"} and #{dep.source}\n"
          end
        end
      end

      @dependencies << dep
    end