Issue #11953 has been updated by James Gray. This is the minimal reproduction I could come up with: ~~~ require "forwardable" require "singleton" class Surprise include Singleton class << self extend Forwardable def method_added(method) (class << self; self; end).def_delegator(:instance, method) end end define_method(:new) do |*| fail "Oops" end def self.do_something wrong_level end private def wrong_level end end Surprise.do_something ~~~ ---------------------------------------- Bug #11953: ThreadError in 2.3 on code that works on 2.2.4 https://bugs.ruby-lang.org/issues/11953#change-55975 * Author: Clayton Flesher * Status: Open * Priority: Normal * Assignee: * ruby -v: 2.3.0 * Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN ---------------------------------------- This is my first bug reporting, so I'm sorry if this isn't exactly correct format. I'll update my report accordingly if pointed in the right direction. I ran into what appears to be a bug while doing a quiz. I've included the breaking code, the test suite and the description of the quiz as attachments to this bug report. The following code works fine on Ruby 2.2.4. class Prime def self.nth(num) error(num) primes = build_primes(num) primes.last end private def build_primes(num) primes = [2] index = 3 until primes.size == num if example?(index, primes) primes << index end index += 1 end primes end def error(num) unless num > 0 raise ArgumentError end end def example?(index, primes) primes.each do |prime| if index % prime == 0 return false end end true end end It raises this error in Ruby 2.3.0 ThreadError: deadlock; recursive locking /home/clayton/.rubies/ruby-2.3.0/lib/ruby/2.3.0/singleton.rb:140:in `synchronize' /home/clayton/.rubies/ruby-2.3.0/lib/ruby/2.3.0/singleton.rb:140:in `instance' /home/clayton/.rubies/ruby-2.3.0/lib/ruby/2.3.0/singleton.rb:142:in `block in instance' /home/clayton/.rubies/ruby-2.3.0/lib/ruby/2.3.0/singleton.rb:140:in `synchronize' /home/clayton/.rubies/ruby-2.3.0/lib/ruby/2.3.0/singleton.rb:140:in `instance' /home/clayton/exercism/ruby/nth-prime/nth_prime.rb:3:in `nth' nth_prime_test.rb:28:in `test_first' If this is expected behavior, I'm sorry in advance for wasting your time. ---Files-------------------------------- nth_prime.rb (528 Bytes) nth_prime_test.rb (973 Bytes) README.md (1.27 KB) -- https://bugs.ruby-lang.org/ Unsubscribe: <mailto:ruby-core-request / ruby-lang.org?subject=unsubscribe> <http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>