<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="">I believe the scoped <font face="Menlo" class="">@discardableResult(warn|critical)</font> attribute is a nice idea for future directions, but I'm not sure it's in scope of this proposal, which, as a first small step, aims to basically invert the <font face="Menlo" class="">@warn_unused_result</font> standard.<div class=""><br class=""></div><div class="">cc Erica</div><div class=""><br class=""><div class="">
<div style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><font color="#929292" class=""><br class="Apple-interchange-newline">Pozdrawiam – Regards,</font></div><div style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><font color="#929292" class="">Adrian Kashivskyy</font></div>
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<br class=""><div><blockquote type="cite" class=""><div class="">Wiadomość napisana przez Haravikk <<a href="mailto:swift-evolution@haravikk.me" class="">swift-evolution@haravikk.me</a>> w dniu 21.03.2016, o godz. 22:28:</div><br class="Apple-interchange-newline"><div class=""><meta http-equiv="Content-Type" content="text/html charset=utf-8" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div class=""><blockquote type="cite" class=""><div class="">On 21 Mar 2016, at 20:35, Erica Sadun via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:</div><div class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class=""><div class=""><div class=""><h2 style="box-sizing: border-box; margin-bottom: 16px; line-height: 1.225; font-size: 1.75em; padding-bottom: 0.3em; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(238, 238, 238); color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; background-color: rgb(255, 255, 255); margin-top: 0px !important;" class=""><ul style="box-sizing: border-box; padding-left: 2em; margin-top: 0px; font-size: 16px; font-weight: normal; margin-bottom: 0px !important;" class=""><li style="box-sizing: border-box;" class=""><p style="box-sizing: border-box; margin-top: 16px; margin-bottom: 16px;" class="">In Swift Evolution discussions, the term <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">@discardable</code> was mildly preferred over <span style="font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; background-color: rgba(0, 0, 0, 0.0392157);" class="">@discardableResult</span>.</p></li><li style="box-sizing: border-box;" class=""><p style="box-sizing: border-box; margin-top: 16px; margin-bottom: 16px;" class="">Some community members requested a new attribute enabling exceptional imported functions to be properly annotated from Objective-C source.</p></li><li style="box-sizing: border-box;" class=""><p style="box-sizing: border-box; margin-top: 16px; margin-bottom: 16px;" class="">Dany St-Amant requested two levels of compiler response: @discardableResult(warn) for simple warnings and @discardableResult(critical) which generates an error with unused results, such as when returning allocated resources</p></li></ul></h2></div></div></div></div></div></blockquote></div><div class="">This looks good, I think that @discardableResult() makes sense until we can get @discardable on the return type itself. I think that if warn/critical is added then there should also be a corresponding “allow” or similar (which is what the default is), i.e- @discardableResult on its own implies @discardResult(allow) to issue no warnings of any kind.</div><div class=""><br class=""></div><div class="">I also like the idea of being able to add this attribute to types as well as functions, allowing the default behaviour to be changed on a per-type basis, as this would be useful for types that are specifically designed with method chaining for example (where most results are discardable as standard). While the choice of default will never satisfy everyone, this would make it easy to tweak for your own needs.</div><div class=""><br class=""></div><div class="">Allow us to do something like the following, assuming that @discardableResult(warn) is now the default:</div><div class=""><br class=""></div><div class=""><font face="Monaco" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>@discardableResult(allow)</font></div><div class=""><font face="Monaco" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>class MyChainableType {</font></div><div class=""><font face="Monaco" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>func chainableMethod() -> Self { … }</font></div><div class=""><font face="Monaco" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>func anotherChainableMethod() -> Self { … }</font></div><div class=""><font face="Monaco" class=""><br class=""></font></div><div class=""><font face="Monaco" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>@discardableResult(critical)</font></div><div class=""><font face="Monaco" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>func getResult() -> Dictionary { … }</font></div><div class=""><font face="Monaco" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>}</font></div><div class=""><br class=""></div><div class="">Of course, if we can get attributes on return types now or in future, then the function form of the attribute should be @discardable(warn) for .getResult().</div></div></div></blockquote></div><br class=""></div></body></html>