module RSpec::Core::Extensions::InstanceEvalWithArgs

def instance_eval_with_args(*args, &block)
  return instance_exec(*args, &block) if respond_to?(:instance_exec)
  # If there are no args and the block doesn't expect any, there's no
  # need to fake instance_exec with our hack below.
  # Notes:
  #   * lambda { }.arity # => -1
  #   * lambda { || }.arity # => 0
  #   * lambda { |*a| }.arity # -1
  return instance_eval(&block) if block.arity < 1 && args.size.zero?
  singleton_class = (class << self; self; end)
  begin
    orig_critical, Thread.critical = Thread.critical, true
    n = 0
    n += 1 while respond_to?(method_name="__instance_exec#{n}")
    singleton_class.module_eval{ define_method(method_name, &block) }
  ensure
    Thread.critical = orig_critical
  end
  begin
    return send(method_name, *args)
  ensure
    singleton_class.module_eval{ remove_method(method_name) } rescue nil
  end
end