class Rake::FileTask

def out_of_date?(stamp)
  all_prerequisite_tasks.any? { |prereq|
    prereq_task = application[prereq, @scope]
    if prereq_task.instance_of?(Rake::FileTask)
      prereq_task.timestamp > stamp || @application.options.build_all
    else
      prereq_task.timestamp > stamp
    end
  }
end