<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="">Ah, that’s a neat idea! Not sure it’s an improvement though to have a magic type that changes how the compiler treats your method, rather than a rather explicit *attribute* on the method…</div><br class=""><div class="">
<div class="">— Radek</div>
</div>
<br class=""><div><blockquote type="cite" class=""><div class="">On 25 Feb 2016, at 23:12, Joe Groff 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 style="font-family: Helvetica; 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=""><blockquote type="cite" class=""><div class=""><br class="Apple-interchange-newline">On Feb 25, 2016, at 1:44 PM, Jacob Bandes-Storch 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 dir="ltr" class=""><div class="">Premise: there are multiple ways of describing control-/data-flow when a function is called:</div><div class=""><br class=""></div><div class=""><font face="arial, helvetica, sans-serif" class=""> func x()<span class="Apple-converted-space"> </span><b class="">-> T</b><span class="Apple-converted-space"> </span> // x returns a value, of type T, to the caller</font></div><div class=""><font face="arial, helvetica, sans-serif" class=""> func x()<span class="Apple-converted-space"> </span><b class="">throws</b><span class="Apple-converted-space"> </span> // x may throw an error to the caller</font></div><font face="arial, helvetica, sans-serif" class=""> func x()<span class="Apple-converted-space"> </span><b class="">throws -> T</b><span class="Apple-converted-space"> </span> // x may throw an error, and also return a value</font><div class=""><font face="arial, helvetica, sans-serif" class=""> func x(...)<span class="Apple-converted-space"> </span><b class="">rethrows</b> ... // if a closure argument can throw an error, x may also throw</font><div class=""><font face="arial, helvetica, sans-serif" class=""> <span class="Apple-converted-space"> </span><b class="">@noreturn</b><span class="Apple-converted-space"> </span>func x() // x never returns to the caller</font></div><div class=""><br class=""></div><div class="">"noreturn" is currently spelled as an attribute, but like "throws" / "rethrows" / "-> T", it's really describing how control flow works.</div><div class=""><br class=""></div><div class="">IMO this calls for consistency: whatever happens "after" the function is called should appear "after" the parameter list.</div><div class=""><br class=""></div><div class=""><font face="arial, helvetica, sans-serif" class=""> func x()<span class="Apple-converted-space"> </span><b class="">noreturn</b><span class="Apple-converted-space"> </span>{</font></div><div class=""><font face="arial, helvetica, sans-serif" class=""> ...</font></div><div class=""><font face="arial, helvetica, sans-serif" class=""> }</font></div><div class=""><br class=""></div><div class=""><br class=""></div>Thoughts?<br clear="all" class=""></div></div></div></blockquote><br class=""></div><div style="font-family: Helvetica; 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="">We really don't even need a special syntactic form or attribute for 'no return' at all. We could provide a standard unconstructible type:</div><div style="font-family: Helvetica; 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=""><br class=""></div><blockquote class="" style="font-family: Helvetica; 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; margin: 0px 0px 0px 40px; border: none; padding: 0px;"><div class="">public /*closed*/ enum NoReturn {}</div><div class=""><br class=""></div></blockquote><span style="font-family: Helvetica; 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="">and it would be impossible for a function that returns NoReturn to return normally.</span><div class="" style="font-family: Helvetica; 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: Helvetica; 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;">-Joe<br class=""><br class=""></div><span style="font-family: Helvetica; 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><br style="font-family: Helvetica; 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: Helvetica; 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: Helvetica; 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: Helvetica; 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: Helvetica; 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: Helvetica; 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>