# File lib/nanoc/extra/checking/checks/stale.rb, line 7
    def run
      require 'set'

      item_rep_paths = Set.new(@site.items.collect { |i| i.reps }.flatten.collect { |r| r.raw_path })

      self.output_filenames.each do |f|
        next if self.pruner.filename_excluded?(f)
        if !item_rep_paths.include?(f)
          self.add_issue(
            "file without matching item",
            :subject  => f)
        end
      end
    end