Bug #13762: Change in `#==` in Ruby 2.4?

• Status: Rejected
• Assignee: -
• Target version: -
• ruby -v: ruby 2.4.1p111 (2017-03-22 revision 58053) [x86_64-darwin16]
• Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN

[backus (John Backus)]

Given this code:

# frozen_string_literal: true

class MyProxy < BasicObject
  def initialize(target)
    @target = target
  end

  undef_method :==

  def method_missing(method_name, *args, &block)
    if target_respond_to?(method_name)
      @target.__send__(method_name, *args, &block)
    else
      ::Object
        .instance_method(method_name)
        .bind(@target)
        .call(*args, &block)
    end
  end

  private

  def target_respond_to?(method_name)
    ::Object
      .instance_method(:respond_to?)
      .bind(@target)
      .call(method_name, true)
  end
end

puts 'a' == MyProxy.new('a')
puts MyProxy.new('a') == 'a'
puts MyProxy.new('a') == MyProxy.new('a')

The output differs depending on the Ruby version:

$ chruby 2.3.4
$ ruby test.rb
true
true
true
$ chruby 2.4.1
$ ruby test.rb
false
true
false

[nobu (Nobuyoshi Nakada)]

• Description updated (diff)
• Status changed from Open to Rejected

When you write your custom method_missing, you have to write your custom respond_to_missing? too.