https://github.com/rails/rails/pull/10990

rails-10990.rb

gem 'rails', '3.2.13'
require 'active_record'

puts "Active Record #{ActiveRecord::VERSION::STRING}"

ActiveRecord::Base.establish_connection(
  adapter: 'sqlite3',
  database: ':memory:'
)

ActiveRecord::Schema.define do
  create_table :users, force: true do |t|
    t.string :name
  end
  create_table :logins, force: true do |t|
    t.integer :user_id
    t.boolean :active
  end
end

class Login < ActiveRecord::Base
  belongs_to :user

  scope :active, -> { where(active: true) }
end

class User < ActiveRecord::Base
  has_many :logins do
    def announce
      puts "#{proxy_association.owner.name} has #{count} logins"
    end
  end
end

user = User.create!(name: 'Bob')
user.logins.announce
user.logins.active.announce