[swift-evolution] Guaranteed closure execution

[Gwendal Roué]

Felix Cloutier already wrote one: https://github.com/zneak/swift-evolution/blob/master/proposals/00xx-noescape-once.md

Do you think it needs to be rewritten?

Gwendal Roué

> Le 10 avr. 2016 à 14:56, Andrew Bennett <cacoyi at gmail.com> a écrit :
> 
> Hi, not beyond this thread that I have seen. I think it's worth you summarizing this thread in a formal proposal and putting it up for discussion or submitting it as a PR :)
> 
> On Sunday, 10 April 2016, Gwendal Roué <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
> Hello all,
> 
> I was wondering if this topic had evolved in anyway since its original introduction.
> 
> @noescape(once) would still be a useful addition to the language!
> 
> Gwendal Roué
> 
> 
> 
>> Le 3 févr. 2016 à 22:21, Félix Cloutier via swift-evolution <swift-evolution at swift.org <javascript:_e(%7B%7D,'cvml','swift-evolution at swift.org');>> a écrit :
>> 
>> I updated the proposal to address some concerns. It can be found at: https://github.com/zneak/swift-evolution/blob/master/proposals/00xx-noescape-once.md <https://github.com/zneak/swift-evolution/blob/master/proposals/00xx-noescape-once.md>
>> 
>> Things that changed:
>> 
>> It now says that the closure must be called on code paths where the function throws;
>> you can have multiple @noescape(once) parameters but they can't make assumptions from one another.
>> 
>> I'm not 100% convinced that forcing a call on code paths that throw is always desirable. I've changed it because Chris's support probably means that the feature has better chances of making it, but I'm not convinced yet. If throwing allows me to return without calling the closure, I can write this:
>> 
>> do {
>> 	let foo: Int
>> 	try withLock(someLock, timeout: 0.5) {
>> 		foo = sharedThing.foo
>> 	}
>> } catch {
>> 	print("couldn't acquire lock fast enough")
>> }
>> 
>> which would be kind of messy if instead, the closure needed a parameter to tell whether the lock was acquired or not when it runs.
>> 
>> Félix
>> 
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