[swift-evolution] [Proposal] Scoped resources (like C# using statement)

[Kevin Wooten]

> On Dec 30, 2015, at 4:23 PM, Matthew Johnson via swift-evolution <swift-evolution at swift.org> wrote:
> 
> 
>> On Dec 30, 2015, at 5:19 PM, Kevin Ballard via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> On Wed, Dec 30, 2015, at 03:12 PM, Kevin Wooten via swift-evolution wrote:
>>>>>  
>>>>> Another possibility I've thought of is defining `defer { val }` to guarantee that val remains alive until the defer fires on scope exit. That might let us leave `defer` as the one "guarantee something happens exactly at scope exit" language construct.
>>>  
>>> What about this…
>>>  
>>> defer let val = grabOrCreateSomething() {
>>>   return;
>>> }
>>>  
>>> Seems natural once you learn guard.
>>  
>> Natural? I have no idea what you're expecting that expression to actually do. What is a "defer let”?
> 
> I think the idea is that a local variable declared with a `defer` modifier has its lifetime extended until the scope exits.  It is a slightly more compact version of what Joe suggested.  But I agree that it has potential for confusion - it reads like it is deferring the initialization of `val` until the scope exits which would be rather pointless.
> 

Given our discussion that’s definitely the gist of it, but I do stand corrected.  I guess I meant the syntax felt “familiar” to guard, but I'd agree upon reflection it doesn’t read well.

> I do like the idea of making the extended lifetime part of the local variable declaration but I’m not sure about how this specific syntax reads.
> 
>>  
>> -Kevin
>>  
>> 
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