Minimal sample to produce "Can't modify frozen hash" when rolling back transaction

double_destroy_in_transaction_rollback.rb

gem 'activerecord', '4.2.0' # No error with 4.1.8
require 'active_record'
require 'minitest/autorun'
require 'logger'

Minitest::Test = MiniTest::Unit::TestCase unless defined?(Minitest::Test)
ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do

  create_table :stylesheets do |t|
    t.string :name
  end

  create_table :settings do |t|
    t.integer :parent_id
    t.integer :stylesheet_id
    t.string :name
  end
end


class Stylesheet < ActiveRecord::Base
  has_many :settings, -> { where(parent_id: nil) }, dependent: :destroy # No error without `dependent: :destroy`
end

class Setting < ActiveRecord::Base

  belongs_to :stylesheet

  # No error if these (unused) associations are removed
  belongs_to :parent, class_name: 'Setting', inverse_of: :children
  has_many :children, class_name: 'Setting', inverse_of: :parent
end

class BugTest < Minitest::Test

  def test_double_destroy_in_transaction

    Setting.transaction do

      stylesheet = Stylesheet.create!(name: 'sheet1')
      setting = stylesheet.settings.create!(name: 'setting1')

      # No error if only one destroy is called.
      setting.destroy
      stylesheet.destroy

      raise ActiveRecord::Rollback # Results in "Can't modify frozen hash" error
    end

  end
end