Proposed resolution:

1. Change [futures.task]/2, class template packaged_task synopsis as indicated:

   template<class R, class... ArgTypes>
   class packaged_task<R(ArgTypes...)> {
   public:
     typedef R result_type;
     [..]
     explicit operator bool valid() const;
     [..]
   };
   

2. Change [futures.task] before p. 15 as indicated:

   explicit operator bool valid() const;
   

   15 Returns: true only if *this has an associated asynchronous state.

   16 Throws: nothing.

[ Resolved in Batavia by accepting n3194. ]

[ 2010-11-02 Daniel translates proposed wording changes into a proper proposed resolution and verified that no other places implicitly take advantage of packaged_task conversion to bool. ]

[ Resolution proposed by ballot comment: ]

Replaced the name packaged_task::operator bool() with packaged_task::valid() in the synopsis ([futures.task]/2) and the member function specification (before [futures.task.members]/15).

Addresses US-201

packaged_task provides operator bool() to check whether an object has an associated asynchronous state. The various future types provide a member function valid() that does the same thing. The names of these members should be the same.