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: definitions.rb
    path of file: ./repos/opal/lib/opal/nodes
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

require 'opal/nodes/base'

module Opal
  module Nodes
    class UndefNode < Base
      handle :undef

      children :value

      def compile
        children.each do |child|
          line "Opal.udef(#{scope.self}, '$' + ", expr(child), ');'
        end
      end
    end

    class AliasNode < Base
      handle :alias

      c
    
      def compile
        # We only need to check one type, because parser otherwise denies invalid expressions
        case new_name.type
        when :gvar # This is a gvar alias: alias $a $b
          helper :alias_gvar
          new_name_str = new_name.children.first.to_s[1..-1].inspect
          old_name_str = old_name.children.first.to_s[1..-1].inspect
          push '$alias_gvar(', new_name_str, ', ', old_name_str, ')'
        when :dsym, :sym # This is a method alias: alias a b
          helper :alias
          compiler.record_method_call old_name.children.last if old_name.type == :sym

          push "$alias(#{scope.self}, ", expr(new_name), ', ', expr(old_name), ')'
        else # Nothing else is available, but just in case, drop an error
          error "Opal doesn't know yet how to alias with #{new_name.type}"
        end
      end