I don't think this issue arises if you use the rule that functional closure
arguments (returning values) shouldn't trail:
func f(arr : [Int]?) {
guard let x = arr?.map({ $0+1 }) else { // compiles
preconditionFailure()
}
}
That said, this seems like a positive tweak and I have no problem with its
adoption.
-- E
> On Mar 23, 2016, at 3:52 AM, Brent Royal-Gordon via swift-evolution
> <[email protected]> wrote:
>
>> The solution is simple: allow trailing closures in guard bodies. This would
>> allow this silly example to compile correctly:
>>
>> func f(arr : [Int]?) {
>> guard let x = arr?.map {$0+1} else {
>> preconditionFailure()
>> }
>>
>> // ...
>> }
>
> This sounds perfectly reasonable.
>
>> Alternatives considered
>>
>> There are three primary alternatives: do nothing, expand the scope of ‘if'
>> and ‘while’ conditions as well, and significantly change the syntax of guard.
>
> A fourth alternative would be to change the syntaxes of `if` and `while` (and
> probably `for` and `switch`) to also have a keyword in this position.
>
> if expr then { code }
> while expr do { code }
> for elem in expr do { code }
> switch expr among { code }
>
> I'm not going to say I advocate for this option, but it *would* clearly mark
> the end of the condition so that trailing closures could be brought to all of
> these statements, so it seemed worth mentioning.
>
> --
> Brent Royal-Gordon
> Architechies
>
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