<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=""><br class=""><div><blockquote type="cite" class=""><div class="">On Nov 26, 2016, at 5:25 PM, Robert Widmann via swift-dev <<a href="mailto:swift-dev@swift.org" class="">swift-dev@swift.org</a>> wrote:</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=""><div dir="auto" style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div dir="auto" style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Hello all,<div class=""><br class=""></div><div class="">I’ve seen and been a part of a number of conversations recently where talk of planning for “resilient enums”, or even just authors that ship frameworks that will eventually offer a binary option that export enum-based APIs. The consensus seems to be that the only safe way to deal with this situation is to <i class="">always</i> cover a `switch` statement with a default, regardless of whether the totality checker thinks you’ve covered all cases. Currently, the compiler warns when this is the case, as in stdlib</div><div class=""><br class=""></div><div class=""><div style="margin: 0px; font-size: 11px; line-height: normal;" class=""><div style="font-family: Menlo; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">extension ProcessTerminationStatus {</span></div><div style="font-family: Menlo; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> var isSwiftTrap: Bool {</span></div><div style="font-family: Menlo; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> switch self {</span></div><div style="font-family: Menlo; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> case .exit(_):</span></div><div style="font-family: Menlo; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> return false</span></div><div style="font-family: Menlo; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> case .signal(let signal):</span></div><div style="font-family: Menlo; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> return CInt(signal) == SIGILL || CInt(signal) == SIGTRAP</span></div><div style="font-family: Menlo; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> default:</span></div><div style="font-family: Menlo; margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures;" class=""> </span><span style="font-variant-ligatures: no-common-ligatures" class="">// This default case is needed for standard library builds where</span></div><div style="font-family: Menlo; margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures;" class=""> </span><span style="font-variant-ligatures: no-common-ligatures" class="">// resilience is enabled</span></div><div style="font-family: Menlo; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> return false</span></div><div style="font-family: Menlo; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> }</span></div><div style="font-family: Menlo; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> }</span></div><div style="font-family: Menlo; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div><div style="font-family: Menlo; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><br class=""></span></div><div style="margin: 0px; line-height: normal;" class="">I think this warning doesn’t actually serve a purpose and I’d like to remove it, or at the very least curb it. Currently, I see three paths forward:</div><div style="margin: 0px; line-height: normal;" class=""><br class=""></div><div style="margin: 0px; line-height: normal;" class="">1) Do nothing.</div><div style="margin: 0px; line-height: normal;" class="">2) Completely remove the diagnostic</div><div style="margin: 0px; line-height: normal;" class="">3) Only emit the diagnostic when the case-tree is switching over enum(s) declared inside the current module.</div></div></div></div></div></div></div></blockquote><br class=""></div><div>Has the “resilient enum” thing been finalized, or is this kind of code just a preventative measure?</div><div><br class=""></div><div>Also, if “resilience” is a compiler flag, there's a fourth option: Disable the warning on builds that have “resilience” enabled.</div><div><br class=""></div><div>- Dave Sweeris</div></body></html>