# File lib/optparse.rb, line 1062
  def make_switch(opts, block = nil)
    short, long, nolong, style, pattern, conv, not_pattern, not_conv, not_style = [], [], []
    ldesc, sdesc, desc, arg = [], [], []
    default_style = Switch::NoArgument
    default_pattern = nil
    klass = nil
    o = nil
    n, q, a = nil

    opts.each do |o|
      # argument class
      next if search(:atype, o) do |pat, c|
        klass = notwice(o, klass, 'type')
        if not_style and not_style != Switch::NoArgument
          not_pattern, not_conv = pat, c
        else
          default_pattern, conv = pat, c
        end
      end

      # directly specified pattern(any object possible to match)
      if !(String === o) and o.respond_to?(:match)
        pattern = notwice(o, pattern, 'pattern')
        conv = (pattern.method(:convert).to_proc if pattern.respond_to?(:convert))
        next
      end

      # anything others
      case o
      when Proc, Method
        block = notwice(o, block, 'block')
      when Array, Hash
        case pattern
        when CompletingHash
        when nil
          pattern = CompletingHash.new
          conv = (pattern.method(:convert).to_proc if pattern.respond_to?(:convert))
        else
          raise ArgumentError, "argument pattern given twice"
        end
        o.each {|(o, *v)| pattern[o] = v.fetch(0) {o}}
      when Module
        raise ArgumentError, "unsupported argument type: #{o}"
      when *ArgumentStyle.keys
        style = notwice(ArgumentStyle[o], style, 'style')
      when /^--no-([^\[\]=\s]*)(.+)?/
        q, a = $1, $2
        o = notwice(a ? Object : TrueClass, klass, 'type')
        not_pattern, not_conv = search(:atype, o) unless not_style
        not_style = (not_style || default_style).guess(arg = a) if a
        default_style = Switch::NoArgument
        default_pattern, conv = search(:atype, FalseClass) unless default_pattern
        ldesc << "--no-#{q}"
        long << 'no-' + (q = q.downcase)
        nolong << q
      when /^--\[no-\]([^\[\]=\s]*)(.+)?/
        q, a = $1, $2
        o = notwice(a ? Object : TrueClass, klass, 'type')
        if a
          default_style = default_style.guess(arg = a)
          default_pattern, conv = search(:atype, o) unless default_pattern
        end
        ldesc << "--[no-]#{q}"
        long << (o = q.downcase)
        not_pattern, not_conv = search(:atype, FalseClass) unless not_style
        not_style = Switch::NoArgument
        nolong << 'no-' + o
      when /^--([^\[\]=\s]*)(.+)?/
        q, a = $1, $2
        if a
          o = notwice(NilClass, klass, 'type')
          default_style = default_style.guess(arg = a)
          default_pattern, conv = search(:atype, o) unless default_pattern
        end
        ldesc << "--#{q}"
        long << (o = q.downcase)
      when /^-(\[\^?\]?(?:[^\\\]]|\\.)*\])(.+)?/
        q, a = $1, $2
        o = notwice(Object, klass, 'type')
        if a
          default_style = default_style.guess(arg = a)
          default_pattern, conv = search(:atype, o) unless default_pattern
        end
        sdesc << "-#{q}"
        short << Regexp.new(q)
      when /^-(.)(.+)?/
        q, a = $1, $2
        if a
          o = notwice(NilClass, klass, 'type')
          default_style = default_style.guess(arg = a)
          default_pattern, conv = search(:atype, o) unless default_pattern
        end
        sdesc << "-#{q}"
        short << q
      when /^=/
        style = notwice(default_style.guess(arg = o), style, 'style')
        default_pattern, conv = search(:atype, Object) unless default_pattern
      else
        desc.push(o)
      end
    end

    default_pattern, conv = search(:atype, default_style.pattern) unless default_pattern
    if !(short.empty? and long.empty?)
      s = (style || default_style).new(pattern || default_pattern,
                                       conv, sdesc, ldesc, arg, desc, block)
    elsif !block
      raise ArgumentError, "no switch given" if style or pattern
      s = desc
    else
      short << pattern
      s = (style || default_style).new(pattern,
                                       conv, nil, nil, arg, desc, block)
    end
    return s, short, long,
      (not_style.new(not_pattern, not_conv, sdesc, ldesc, nil, desc, block) if not_style),
      nolong
  end