[swift-evolution] Guaranteed closure execution

[Chris Lattner]

On Jan 31, 2016, at 9:54 AM, Dany St-Amant via swift-evolution <swift-evolution at swift.org> wrote:
>>> it is not required to be executed on a code path that throws;
>> 
>> 
>> It may need to be clarified into "must" or "must not", but I can't think about very good examples supporting either case right now.
>> 
> 
> What is the implication of this @noescape(once) closure not being call on throws when the caller use try? variation?

The compiler needs a guarantee one way or the other (that the closure is called or that it is not called), because it needs to know whether to clean up values initialized by the closure.

-Chris