update_or_replace

# File lib/rdoc/generator/ri.rb, line 187
  def update_or_replace(cls_desc)
    old_cls = nil

    if @options.merge
      rdr = RDoc::RI::Reader.new RDoc::RI::Cache.new(@options.op_dir)

      namespace = rdr.top_level_namespace
      namespace = rdr.lookup_namespace_in(cls_desc.name, namespace)
      if namespace.empty?
        $stderr.puts "You asked me to merge this source into existing "
        $stderr.puts "documentation. This file references a class or "
        $stderr.puts "module called #{cls_desc.name} which I don't"
        $stderr.puts "have existing documentation for."
        $stderr.puts
        $stderr.puts "Perhaps you need to generate its documentation first"
        exit 1
      else
        old_cls = namespace[0]
      end
    end

    prev_cls = @generated[cls_desc.full_name]

    if old_cls and not prev_cls then
      old_desc = rdr.get_class old_cls
      cls_desc.merge_in old_desc
    end

    if prev_cls then
      cls_desc.merge_in prev_cls
    end

    @generated[cls_desc.full_name] = cls_desc

    @ri_writer.remove_class cls_desc
    @ri_writer.add_class cls_desc
  end