<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="">IMO, this is the best way to approach it.</div><br class=""><div class="">
<span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: 'Lucida Grande'; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; ">Félix</span>
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<br class=""><div><blockquote type="cite" class=""><div class="">Le 3 janv. 2016 à 22:54:17, Jack Lawrence via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> a écrit :</div><br class="Apple-interchange-newline"><div class=""><span style="font-family: LucidaGrande; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: 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; float: none; display: inline !important;" class="">You could also use type inference on the return type:</span><div class="" style="font-family: LucidaGrande; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: 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;"><br class=""></div><div class="" style="font-family: LucidaGrande; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: 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;"><div class="" style="margin: 0px; line-height: normal; font-family: 'Andale Mono'; color: rgb(41, 249, 20); background-color: rgb(0, 0, 0);"><span class="" style="color: rgb(14, 118, 5);"> 1><span class="Apple-converted-space"> </span></span><span class="">func returnsNil<T>(errCode: Int) -> T? { </span></div><div class="" style="margin: 0px; line-height: normal; font-family: 'Andale Mono'; color: rgb(41, 249, 20); background-color: rgb(0, 0, 0);"><span class="" style="color: rgb(14, 118, 5);"> 2.<span class="Apple-converted-space"> </span></span><span class=""> print(errCode) </span></div><div class="" style="margin: 0px; line-height: normal; font-family: 'Andale Mono'; color: rgb(41, 249, 20); background-color: rgb(0, 0, 0);"><span class="" style="color: rgb(14, 118, 5);"> 3.<span class="Apple-converted-space"> </span></span><span class=""> return nil </span></div><div class="" style="margin: 0px; line-height: normal; font-family: 'Andale Mono'; color: rgb(14, 118, 5); background-color: rgb(0, 0, 0);"><span class=""> 4.<span class="Apple-converted-space"> </span></span><span class="" style="color: rgb(41, 249, 20);">} </span></div><div class="" style="margin: 0px; line-height: normal; font-family: 'Andale Mono'; color: rgb(41, 249, 20); background-color: rgb(0, 0, 0);"><span class="" style="color: rgb(14, 118, 5);"> 5><span class="Apple-converted-space"> </span></span><span class="">func returnsAnOptional() -> Int? { </span></div><div class="" style="margin: 0px; line-height: normal; font-family: 'Andale Mono'; color: rgb(41, 249, 20); background-color: rgb(0, 0, 0);"><span class="" style="color: rgb(14, 118, 5);"> 6.<span class="Apple-converted-space"> </span></span><span class=""> return returnsNil(5) </span></div><div class="" style="margin: 0px; line-height: normal; font-family: 'Andale Mono'; color: rgb(41, 249, 20); background-color: rgb(0, 0, 0);"><span class="" style="color: rgb(14, 118, 5);"> 7.<span class="Apple-converted-space"> </span></span><span class="">} </span></div></div><div class="" style="font-family: LucidaGrande; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: 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;"><span class=""><br class=""></span></div><div class="" style="font-family: LucidaGrande; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: 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;"><br class=""><div class=""><blockquote type="cite" class=""><div class="">On Jan 3, 2016, at 7:51 PM, Jeff Kelley 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=""><span class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: 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; float: none; display: inline !important;">Just spit-balling here, but couldn’t you do this with a generic extension on Optional?</span><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: 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;"><br class=""></div><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: 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;"><font face="Menlo" class=""><blockquote type="cite" class="">extension Optional {<br class=""> func returnsNil(errorCode: Int) -> Wrapped? {<br class=""> logError(errorCode)<br class=""> return nil<br class=""> }<br class="">}</blockquote></font></div><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: 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;"><br class=""></div><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: 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;"><br class=""><div class=""><div class="" style="font-family: Helvetica; font-style: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div class="" style="font-family: Helvetica; font-style: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div class="" style="font-family: Helvetica; font-style: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><span class="Apple-style-span" style="border-collapse: separate; line-height: normal; border-spacing: 0px;"><div class="" style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div class="">Jeff Kelley</div><div class=""><br class=""></div><div class=""><a href="mailto:SlaunchaMan@gmail.com" class="">SlaunchaMan@gmail.com</a> | <a href="https://twitter.com/SlaunchaMan" class="">@SlaunchaMan</a> | <a href="http://jeffkelley.org/" class="">jeffkelley.org</a></div></div></span></div></div></div></div><br class=""><div class=""><blockquote type="cite" class=""><div class="">On Jan 3, 2016, at 10:43 PM, Andrew Duncan 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=""><div class="">It should be possible to declare a function that returns only nil, and have its return type be substitutable for any function that returns and Optional. This is something like having a bottom type but not really. What I mean is:<br class=""><br class="">func returnsNil(errCode:Int) -> nil {<br class=""> logError(errCode) // A side-effect. Not FP, sosumi.<br class=""> return nil<br class="">}<br class=""><br class="">func returnAOptional() -> A? {<br class=""> // Bla bla. We discover an error so we decide to bail and return nil.<br class=""> return returnsNil(errCode) // Would be legal.<br class="">}<br class="">func returnsBOptional() -> B? {<br class=""> // Bla bla. We discover an error so we decide to bail and return nil.<br class=""> return returnsNil(errCode) // Would also be legal.<br class="">}<br class=""><br class="">I seek a return type that conforms to any Optional -- I think that implies it *must* (or correct me here) be nil.<br class=""><br class="">Now perhaps this is already possible with wizardry from the Next Level. (There always is one.)</div></div></blockquote></div></div><img src="https://u2002410.ct.sendgrid.net/wf/open?upn=fPHCHxM8OEqkFI0LoY8YMuXDKRTx6ILsXcJMmyHEOCKbc6d9BprJEbjnGcEtdSMoRSL0gEtFrbu-2FXnG2WNe1BtmSoMmW6DN6-2BBnsygh16ih3LO-2BiI5BdE52wdBXq1liyuPOHbHVLa1VxirNAyWDb4hLYaVI2H7xBw0GDU72TTXQzzgrptI8NRV6DdDDXSrYJBhXps5WDVTQorWn9QLjrriI7ErXRhPzhBtqfbubqzd0-3D" alt="" width="1" height="1" border="0" class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: 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; height: 1px !important; width: 1px !important; border-width: 0px !important; margin: 0px !important; padding: 0px !important;"><span class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: 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; float: none; display: inline !important;"><span class="Apple-converted-space"> </span></span><span class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: 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; float: none; display: inline !important;">_______________________________________________</span><br class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: 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;"><span class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: 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; float: none; display: inline !important;">swift-evolution mailing list</span><br class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: 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;"><a href="mailto:swift-evolution@swift.org" class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: 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;">swift-evolution@swift.org</a><br class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: 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;"><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: 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;">https://lists.swift.org/mailman/listinfo/swift-evolution</a></div></blockquote></div><br class=""></div><img src="https://u2002410.ct.sendgrid.net/wf/open?upn=iRI3beHTe3UxYAHTlV3lA38zIPfHMhyuRzgTmGKV6k7-2F8T-2F-2FVF-2BeXnDs6jRZyBj0rB1BU3i0uQGAH9Li5S9ermODWFuKdbu7HeHdgC-2FFaF4347OBpqDzN3qjaKXMHkp-2Bk-2F8NxfRTk-2BPbeiCnTdCUGBJypRLnvzPfgTMupr7qTR0l9LxO84seuMMHX0QtPQNFo-2FKnop8akHCQRkbHoGzrd7C2xuHwHgvdENid3SAGrq4-3D" alt="" width="1" height="1" border="0" style="font-family: LucidaGrande; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: 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; height: 1px !important; width: 1px !important; border-width: 0px !important; margin: 0px !important; padding: 0px !important;" class=""><span style="font-family: LucidaGrande; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: 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; float: none; display: inline !important;" class=""><span class="Apple-converted-space"> </span>_______________________________________________</span><br style="font-family: LucidaGrande; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: 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=""><span style="font-family: LucidaGrande; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: 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; float: none; display: inline !important;" class="">swift-evolution mailing list</span><br style="font-family: LucidaGrande; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: 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=""><a href="mailto:swift-evolution@swift.org" style="font-family: LucidaGrande; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: 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="">swift-evolution@swift.org</a><br style="font-family: LucidaGrande; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: 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=""><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" style="font-family: LucidaGrande; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: 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="">https://lists.swift.org/mailman/listinfo/swift-evolution</a></div></blockquote></div><br class=""></body></html>