I tried to reduce as much as possible (maybe too much, we'll see...) an issue which is blocking our work on std::bind. Note, the problem disappears if I simplify the testcase further to not use variadic templates while keeping the rest unchanged.

Jason, can you help us?

//////////////////

template<typename... _Elements>
  class tuple;

template<typename _Arg>
  class _Mu;

template<typename _Signature>
  struct _Bind;

template<typename _Functor, typename... _Bound_args>
  class _Bind<_Functor(_Bound_args...)>
  {
    template<typename... _Args, typename
	     = decltype(_Functor()(_Mu<_Bound_args>()(_Bound_args(),
						      tuple<_Args...>())...) )>
      void __call() { }
  };

template<typename _Functor, typename _Arg>
  _Bind<_Functor(_Arg)>
  bind(_Functor, _Arg) { }

struct State
{
  bool ready() { return true; }

  void f()
  {
    bind(&State::ready, this);
  }
};