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.send { color:#77bb77; }
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.error { color:#AA0000; }</style></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div class="bloop_markdown"><p>+1 Well summarized.</p>
<p>The <code>!!</code> operator feels more like:</p>
<pre><code>func !! <T>(optional: T?, errorMessage: String) -> T {
return optional ?? fatalError(errorMessage)
}
</code></pre>
<p>Which is totally unnecessary.</p>
<p></p></div><div class="bloop_original_html"><style>body{font-family:Helvetica,Arial;font-size:13px}</style><div id="bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px; color: rgba(0,0,0,1.0); margin: 0px; line-height: auto;"><br></div> <br> <div id="bloop_sign_1498812801473484032" class="bloop_sign"><div style="font-family:helvetica,arial;font-size:13px">-- <br>Adrian Zubarev<br>Sent with Airmail</div></div> <br><p class="airmail_on">Am 30. Juni 2017 um 07:24:04, Brent Royal-Gordon via swift-evolution (<a href="mailto:swift-evolution@swift.org">swift-evolution@swift.org</a>) schrieb:</p> <blockquote type="cite" class="clean_bq"><span><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div></div><div>
<title></title>
<div>
<blockquote type="cite" class="">
<div class="">On Jun 27, 2017, at 10:16 AM, Erica Sadun 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="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">
<div class="">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 class=""><br class=""></div>
<div class=""><font face="Menlo" class="">guard !lastItem.isEmpty
else { return }</font></div>
<div class=""><font face="Menlo" class="">let lastItem = array.last
!! "Array must be non-empty"</font></div>
<div class=""><br class=""></div>
<div class="">Details here: <a href="https://gist.github.com/erica/423e4b1c63b95c4c90338cdff4939a9b" class="">https://gist.github.com/erica/423e4b1c63b95c4c90338cdff4939a9b</a></div>
<div class=""><br class=""></div>
<div class="">Thank you for your thoughtful feedback, -- E</div>
</div>
</div>
</blockquote>
<br class=""></div>
<div>Finally found a few minutes to read this thread.</div>
<div><br class=""></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 class=""></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 class=""></div>
<div>2. It allows you to control the optimization behavior by using
`fatalError`, `preconditionFailure`, or `assertionFailure` as
desired.</div>
<div><br class=""></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 class=""></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 class=""></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 class=""><br class=""></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 class=""></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>
<br class="">
<div class="">
<div class="">
<div style="font-size: 12px;" class=""><span class="Apple-style-span" style="border-collapse: separate; font-variant-ligatures: normal; font-variant-east-asian: normal; font-variant-position: normal; line-height: normal; border-spacing: 0px;">
-- </span></div>
<div style="font-size: 12px;" class=""><span class="Apple-style-span" style="border-collapse: separate; font-variant-ligatures: normal; font-variant-east-asian: normal; font-variant-position: normal; line-height: normal; border-spacing: 0px;">
Brent Royal-Gordon</span></div>
<div style="font-size: 12px;" class=""><span class="Apple-style-span" style="border-collapse: separate; font-variant-ligatures: normal; font-variant-east-asian: normal; font-variant-position: normal; line-height: normal; border-spacing: 0px;">
Architechies</span></div>
</div>
</div>
<br class="">
_______________________________________________<br>swift-evolution mailing list<br>swift-evolution@swift.org<br>https://lists.swift.org/mailman/listinfo/swift-evolution<br></div></div></span></blockquote></div><div class="bloop_markdown"><p></p></div></body></html>