<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">Bringing up a possible edge case:</div><div class=""><br class=""></div><div class="">func foo() {</div><div class=""> while(…) {</div><div class=""> guard x > 0</div><div class=""> }</div><div class="">}</div><div class=""><br class=""></div><div class="">if guard defaulted to return even inside a while (as was suggested), this might be counterintuitive.</div><br class=""><div><blockquote type="cite" class=""><div class="">On Dec 16, 2015, at 5:06 PM, Etan Kissling via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class="">
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Also +1 on default return, -1 on default continue / break, and -1 for removing braces
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<div class="">Instead of VoidLiteralConvertible, one could extend on the idea with something that is not specifically tailored to nil, like</div>
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<div class="">func foo(x: Int) -> Int = 5 {</div>
<div class=""> guard x < 10 // Would return default 5 for x >= 10</div>
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</div>
<div class=""> if x > 5 {</div>
<div class=""> return // Would return default 5</div>
<div class=""> }</div>
<div class=""> return x</div>
<div class="">}</div>
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<div class="">Etan</div>
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<div class="">On 16 Dec 2015, at 19:39, Ian Ynda-Hummel via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:</div>
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<div class="">I am also +1 for implicit return, but -1 on continue/break for the reasons already stated.</div>
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I'm -1 for removing braces for one-liners. I think maintaining braces around blocks helps distinguish them from expressions. For example,
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<div class=""><span class="s1" style="line-height: 1.5;"> guard</span><span class="s2" style="line-height: 1.5;"><span class="Apple-converted-space"> </span>x < 1</span><span class="s3" style="line-height: 1.5;">0</span><span class="s2" style="line-height: 1.5;"><span class="Apple-converted-space"> </span></span><span class="s1" style="line-height: 1.5;">else</span><span class="s2" style="line-height: 1.5;"><span class="Apple-converted-space"> </span></span><span class="s1" style="line-height: 1.5;">return</span><br class="">
</div>
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</span></div>
<div class=""><span class="s1" style="line-height: 1.5;">would catch me off guard (pardon the pun).</span></div>
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<div class="">I think I'm -1 on VoidLiteralConvertible, but I'm somewhat undecided. I think that separating the return value from the actual return point could lead to a lot of confusion, and would subsequently also make it easy to accidentally return the default
value when you didn't intend to as the compiler wouldn't complain about a missing return value. I don't think I have totally convinced myself that the latter is a non-trivial problem, but I thought it was worth mentioning.</div>
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<div dir="ltr" class="">On Wed, Dec 16, 2015 at 11:59 AM ilya via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:<br class="">
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<div style="white-space: pre-wrap;" class="">Actually I thought about VoidLiteralConvertible some more and now I think if we include it the only nontrivial case in the standard library case should be Optional.Nonel. Empty arrays and dictionaries are different
from nothing, so it's best to always return them explicitly. <br class="">
<br class="">
Oh, and it would help with default values, e.g.<br class="">
<br class="">
var something:Something?<br class="">
// where does the default value come from? VoidLiteralConvertible! <br class="">
<br class="">
I want all default values for String in this scope be "none":<br class="">
<br class="">
private extension String: VoidLiteralConvertible { ... return "None" ... }</div>
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<div dir="ltr" class="">On Wed, Dec 16, 2015 at 10:49 ilya <<a href="mailto:ilya.nikokoshev@gmail.com" target="_blank" class="">ilya.nikokoshev@gmail.com</a>> wrote:<br class="">
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<div style="white-space: pre-wrap;" class="">+1 on default return <br class="">
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-1 on default continue or break, this is ambiguous. <br class="">
Even inside switch it's not clear if guard should break or return, so let's not make people guess. .
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Also can we stop requiring braces for simple one-liners: <br class="">
<br class="">
guard x<10 else return 5<br class="">
<br class="">
As for default return values, we could create a VoidLiteralConvertible, so that default return automatically becomes return nil or return [] in an Optional or Array context respectively. As a bonus, it will be technically possible to override this behavior
inside a specific function scope. <br class="">
</div>
<div style="white-space: pre-wrap;" class=""><br class="">
> swift would provide a warning that the guard statement needs an else block<br class="">
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<div style="white-space: pre-wrap;" class="">In this specific case the compiler basically has to guess, so an error seems more appropriate.
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Ilya. </div>
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<div dir="ltr" class="">On Wed, Dec 16, 2015 at 02:53 Vester Gottfried via swift-evolution <<a href="mailto:swift-evolution@swift.org" target="_blank" class="">swift-evolution@swift.org</a>> wrote:<br class="">
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<div dir="ltr" class=""><font face="monospace, monospace" class="">I find myself writing the same else blocks for guard statements over and over again, so it might be reasonable to think about a default behaviour.<br class="">
<br class="">
In a current project I found 217 guard statements from which 183 have repetitive else clauses<br class="">
<br class="">
From which:<br class="">
131 end with "else { return nil }"<br class="">
44 "else { return }"<br class="">
6 "else { continue }"<br class="">
2 "else { break }"<br class="">
<br class="">
My proposal would be to make the else block optional and define a default behaviour.<br class="">
<br class="">
For example:<br class="">
<br class="">
func foo(x: Int) {<br class="">
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<span class="Apple-converted-space"> </span> </div>
guard x < 10<br class="">
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<span class="Apple-converted-space"> </span> </div>
...<br class="">
}<br class="">
<br class="">
swift would implicitly add "else { return }"<br class="">
<br class="">
--<br class="">
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func foo(x: Int) -> Int? {<br class="">
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<span class="Apple-converted-space"> </span> </div>
guard x < 10<br class="">
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<span class="Apple-converted-space"> </span> </div>
...<br class="">
}<br class="">
<br class="">
swift would implicitly add "else { return nil }"<br class="">
<br class="">
--<br class="">
<br class="">
for i in 0..<10 {<br class="">
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<span class="Apple-converted-space"> </span> </div>
guard i%2 == 0<br class="">
}<br class="">
<br class="">
swift would implicitly add "else { continue }"<br class="">
<br class="">
--<br class="">
<br class="">
switch {<br class="">
case a :<br class="">
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<span class="Apple-converted-space"> </span> </div>
guard x != y<br class="">
case b :</font>
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<div class="gmail_default" style="font-family: monospace, monospace; display: inline;">
<span class="Apple-converted-space"> </span> ...</div>
<br class="">
}<br class="">
<br class="">
swift would implicitly add "else { break }"<br class="">
<br class="">
--<br class="">
<br class="">
func foo(x: Int) -> Int {<br class="">
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<span class="Apple-converted-space"> </span> </div>
guard x < 10<br class="">
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<span class="Apple-converted-space"> </span> </div>
...<br class="">
}<br class="">
<br class="">
swift would provide a warning that the guard statement needs an else block<br class="">
<br class="">
--<br class="">
<br class="">
Possible advantages<br class="">
- Less code
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<span class="Apple-converted-space"> </span>to write</div>
<br class="">
- visually cleaner<br class="">
-
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</div>
In code with multiple guard statements
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you
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would not have to repeat the else block<br class="">
<br class="">
<br class="">
Possible Disadvantages<br class="">
- Different behaviour in different contexts (func/return, for/continue, switch/break, …) needs to be learned and understood<br class="">
- programmers might forget that guard + else {} is an option</font><br class="">
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