[swift-evolution] Extending declaration scope to condition for `repeat { } while ()`

[Braeden Profile]

Great point; an infinite loop syntax would make a lot of sense.  It seems good for it to have its own syntax, considering you must have a `break` or `return` to escape it.  `while true { }` provides the same functionality, though it seems a bit less direct in its purpose than `repeat {  }` could.

> On Jul 18, 2016, at 4:16 PM, Haravikk <swift-evolution at haravikk.me> wrote:
> 
> 
>> On 18 Jul 2016, at 21:32, Sean Heber via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> I’ve wanted this myself, too, so I’m generally +1, although I’ve also wondered if maybe this syntax should be changed somehow. I’ve not put a lot of thought into it, and this perhaps has come up before, but I sort of wonder.. would it make more sense to get rid of the trailing “while” entirely?
>> 
>> Here’s what I’m thinking:
>> 
>> This repeats forever - infinite loop:
>> 
>> repeat {}
>> 
>> And to get out of the infinite loop, you’d just use an if or guard the same way you might in any other loop in some cases:
>> 
>> repeat {
>>  let success = doSomething()
>>  guard success else { break }
>> }
>> 
>> We could potentially even warn if you use a repeat {} without there being a break inside the body somewhere.
>> 
>> This way, we eliminate a special syntactical form (repeat/while has always felt weird in every brace-based language I’ve used) and just piggyback on the existing break/continue/guard/if mechanisms that are already there and common. Then we also don’t need to have a special “weird” rule where the scope of variables change magically for repeat/while.
>> 
>> l8r
>> Sean
> 
> That's a very interesting alternative, especially with a warning when there's no break (or return), and it would be clearer about the scope. Actually now I think about it, the repeat/while is a little odd in Swift since the while condition doesn't require parenthesis, which is great for a regular while or if condition because the braces give it structure, but that's not quite the case with the repeat/while.
> 
> I'm fine either way, but this should be explored as well; guard in particular goes well this style of repeat syntax. More interestingly though is that this would actually allow us to write while loops as:
> 
> 	repeat {
> 		guard someCondition() else { break }
> 		doSomething()
> 	}
> 
> while would essentially just become a shorthand.

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