Proposed resolution:

Add a new sentence to [futures.state] p2:

2 This associated state consists of some state information and some (possibly not yet evaluated) result, which can be a (possibly void) value or an exception. If the associated state was created by a call to async ([futures.async]) then it may also contain a deferred function or an associated thread.

Add an extra bullet to [futures.state] p3:

The result of an associated state can be set by calling:

• promise::set_value,
• promise::set_exception, or
• packaged_task::operator()., or
• a call to async ([futures.async]).

Rationale:

Solved by N3058.

[ 2010 Pittsburgh: Moved to NAD EditorialResolved. Rationale added below. ]

The current description of the associated state in [futures.state] does not allow for futures created by an async call. The description therefore needs to be extended to cover that.