<div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">On Fri, Jun 30, 2017 at 7:24 AM, Brent Royal-Gordon via swift-evolution <span dir="ltr"><<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word"><div><div class="h5"><div><blockquote type="cite"><div>On Jun 27, 2017, at 10:16 AM, Erica Sadun via swift-evolution <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>> wrote:</div><br class="m_-7157450599931287639Apple-interchange-newline"><div><div style="word-wrap:break-word"><div>Using an operator to provide feedback on the context of a failed unwrap has become a commonly implemented approach in the Swift developer Community. What are your thoughts about adopting this widely-used operator into the standard library?</div><div><br></div><div><font face="Menlo">guard !lastItem.isEmpty else { return }</font></div><div><font face="Menlo">let lastItem = array.last !! "Array must be non-empty"</font></div><div><br></div><div>Details here: <a href="https://gist.github.com/erica/423e4b1c63b95c4c90338cdff4939a9b" target="_blank">https://gist.github.com/<wbr>erica/<wbr>423e4b1c63b95c4c90338cdff4939a<wbr>9b</a></div><div><br></div><div>Thank you for your thoughtful feedback, -- E</div></div></div></blockquote><br></div></div></div><div>Finally found a few minutes to read this thread.</div><div><br></div><div>I'm a big fan of the `Never`-based approach. (I was before, but I am more so now.) Here are the points I can see in its favor:</div><div><br></div><div>1. It is extremely clear about what's happening—`!!` is another random operator to learn, but `fatalError(_:)` or `preconditionFailure(_:)` are fairly self-explanatory, and `??` is something you might already be using.</div><div><br></div><div>2. It allows you to control the optimization behavior by using `fatalError`, `preconditionFailure`, or `assertionFailure` as desired.</div><div><br></div><div>3. If we later change `throw` from being a statement to being a `Never`-returning expression, you could use `throw` on the right-hand side of `??`.</div><div><br></div><div>4. It supports other `Never`-returning operations, like `abort()` or `exit(_:)` or your custom `usage()` function, on the right side of `??`.</div><div><br></div><div><div>5. It supports file-and-line error reporting without having to add any new features; `!!` could not do this because an operator can't have extra, defaulted parameters to carry the file and line.</div><div><br></div></div><div>6. It harmonizes with the eventual idea of making `Never` a universal bottom type, but we don't actually have to implement that today, because we can just overload `??` for now.</div><div><br></div><div>Against these advantages, the only one I can see for `!!` is that it is terse. Terseness is good, especially for a feature which is competing with the single-character postfix `!` operator, but I can't help but be drawn to the flexibility and power of `??` with a `Never` expression on the right-hand side.</div></div></blockquote></div><div><br></div><div>+1 to everything.</div><div><br></div><div>If terseness is the only clear advantage of a new operator that is meant to be used sparsely, it's clear to me that the ?? Never form is better for the Swift community as a whole.</div><div><br></div>--<br><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr" style="font-size:12.8px"><div style="font-size:12.8px"></div></div></div></div></div></div></div></div></div></div></div></div></div></div>
</div><div class="gmail_extra">Víctor Pimentel</div></div>