You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: mkmf.rb
    path of file: ./repos/jruby/lib/ruby/stdlib
    
    the code of the file until where you have to start completion: # -*- coding: us-ascii -*-
# frozen-string-literal: false
# module to create Makefile for extension modules
# invoke like: ruby -r mkmf extconf.rb

require 'rbconfig'
require 'fileutils'
require 'shellwords'

# :stopdoc:
class String
  # Wraps a string in escaped quotes if it contains whitespace.
  def quote
    /\s/ =~ 
    
  def depend_rules(depend)
    suffixes = []
    depout = []
    cont = implicit = nil
    impconv = proc do
      each_compile_rules {|rule| depout << (rule % implicit[0]) << implicit[1]}
      implicit = nil
    end
    ruleconv = proc do |line|
      if implicit
        if /\A\t/ =~ line
          implicit[1] << line
          next
        else
          impconv[]
        end
      end