Issue #19711 has been updated by dpepper (Daniel Pepper). Looks like https://github.com/rails/rails/blob/main/activesupport/test/deprecation_test... calls `.new` on the Deprecation Singleton a bunch of places. This behavior _should_ not be possible on a singleton, however `.new` is explicitly marked as public in InstanceDelegator. ```ruby module ActiveSupport class Deprecation include Singleton include InstanceDelegator # <== ``` ```ruby module ActiveSupport class Deprecation module InstanceDelegator # :nodoc: def self.included(base) ... base.public_class_method :new # <== makes otherwise private method public again end ``` https://github.com/rails/rails/blob/main/activesupport/lib/active_support/de... Essentially, this is what's happening: ```ruby klass = Class.new do include Singleton public_class_method :new end Class.new(klass).new # <== used to work but explodes after the change ``` The Singleton PR inadvertently changed `.new` to be marked private in both included and inherited (priorly just the when included), hence `.new` was made private, public, then unexpectedly private again. I agree with ioquatix in wondering why `.new` is called on a singleton, but happy to scope down the Singleton change to avoid changing behavior until we want to do that explicitly. ---------------------------------------- Bug #19711: NoMethodError "private method `new' called for class" since bebd05fb51ea65bc57344b67100748200f8311eb https://bugs.ruby-lang.org/issues/19711#change-103406 * Author: yahonda (Yasuo Honda) * Status: Open * Priority: Normal * ruby -v: ruby 3.3.0dev (2023-06-03T00:35:18Z master bebd05fb51) [x86_64-linux] * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN ---------------------------------------- Rails CI against ruby3.3.0dev has been failing https://buildkite.com/rails/rails/builds/96929#0188841c-cf1f-46d6-b48b-f510a... According to git bisect, this change has been triggered via bebd05fb51ea65bc57344b67100748200f8311eb ### Steps to reproduce (that may not be minimum though) ``` $ gem install activesupport $irb require 'active_support/deprecation' klass = Class.new(ActiveSupport::Deprecation) deprecator = klass.new ``` ### Expected behavior It should successfully work as the previous commit does. ``` $ ruby -v ruby 3.3.0dev (2023-06-02T21:16:52Z master 4e26ae3cb9) [x86_64-linux] $ gem install activesupport Successfully installed activesupport-7.0.5 Parsing documentation for activesupport-7.0.5 Done installing documentation for activesupport after 1 seconds 1 gem installed $ irb irb(main):001:0> require 'active_support/deprecation' => true irb(main):002:0> klass = Class.new(ActiveSupport::Deprecation) => #<Class:0x00007f683e01a5b0> irb(main):003:0> deprecator = klass.new => #<#<Class:0x00007f683e01a5b0>:0x00007f683e2207b0 ... irb(main):004:0> ``` ### Actual behavior It gets "(irb):5:in `<main>': private method `new' called for class #<Class:0x00007fbd57dd9b10> (NoMethodError)" ``` $ ruby -v ruby 3.3.0dev (2023-06-03T00:35:18Z master bebd05fb51) [x86_64-linux] $ gem install activesupport Successfully installed activesupport-7.0.5 Parsing documentation for activesupport-7.0.5 Done installing documentation for activesupport after 1 seconds 1 gem installed $ irb irb(main):001:0> require 'active_support/deprecation' => true irb(main):002:0> klass = Class.new(ActiveSupport::Deprecation) irb(main):003:0> deprecator = klass.new (irb):3:in `<main>': private method `new' called for class #<Class:0x00007f7e13282bc8> (NoMethodError) from <internal:kernel>:187:in `loop' from /home/yahonda/.rbenv/versions/trunk/lib/ruby/gems/3.3.0+0/gems/irb-1.7.0/exe/irb:9:in `<top (required)>' from /home/yahonda/.rbenv/versions/trunk/bin/irb:25:in `load' from /home/yahonda/.rbenv/versions/trunk/bin/irb:25:in `<main>' irb(main):004:0> irb(main):003:0> require 'active_support/deprecation' => true irb(main):004:0> klass = Class.new(ActiveSupport::Deprecation) => #<Class:0x00007fbd57dd9b10> irb(main):005:0> deprecator = klass.new (irb):5:in `<main>': private method `new' called for class #<Class:0x00007fbd57dd9b10> (NoMethodError) from <internal:kernel>:187:in `loop' from /home/yahonda/.rbenv/versions/trunk/lib/ruby/gems/3.3.0+0/gems/irb-1.7.0/exe/irb:9:in `<top (required)>' from /home/yahonda/.rbenv/versions/trunk/bin/irb:25:in `load' from /home/yahonda/.rbenv/versions/trunk/bin/irb:25:in `<main>' irb(main):006:0> -- https://bugs.ruby-lang.org/