<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 May 4, 2016, at 10:15 AM, Jordan Rose <<a href="mailto:jordan_rose@apple.com" class="">jordan_rose@apple.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: 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 May 4, 2016, at 10:07, Andrew Trick <<a href="mailto:atrick@apple.com" class="">atrick@apple.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: 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;"><blockquote type="cite" class=""><div class=""><br class="Apple-interchange-newline">On May 4, 2016, at 9:40 AM, Jordan Rose <<a href="mailto:jordan_rose@apple.com" class="">jordan_rose@apple.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: 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;"><blockquote type="cite" class=""><div class=""><br class="Apple-interchange-newline">On May 4, 2016, at 09:18, 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=""><blockquote type="cite" class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: 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="Apple-interchange-newline">On May 3, 2016, at 9:39 PM, Andrew Trick via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:<br class=""><br class=""><br class=""><blockquote type="cite" class="">On May 3, 2016, at 8:56 PM, Chris Lattner <<a href="mailto:clattner@apple.com" class="">clattner@apple.com</a>> wrote:<br class=""><br class="">Hello Swift community,<br class=""><br class="">The review of "SE-0076: Add overrides taking an UnsafePointer source to non-destructive copying methods on UnsafeMutablePointer" begins now and runs through May 9. The proposal is available here:<br class=""><br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><a href="https://github.com/apple/swift-evolution/blob/master/proposals/0076-copying-to-unsafe-mutable-pointer-with-unsafe-pointer-source.md" class="">https://github.com/apple/swift-evolution/blob/master/proposals/0076-copying-to-unsafe-mutable-pointer-with-unsafe-pointer-source.md</a><br class=""><br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>* What is your evaluation of the proposal?<br class=""></blockquote><br class="">The new methods are needed, but they don’t need to be overloads. I have no idea why the argument type was originally declared Mutable.<br class=""><br class="">func assignBackwardFrom(source: UnsafePointer<Pointee>, count: Int<br class="">)<br class=""><br class="">func assignFrom(source: UnsafePointer<Pointee>, count: Int<br class="">)<br class=""><br class="">func initializeFrom(source: UnsafePointer<Pointee>, count: Int)<br class=""><br class="">FWIW: I made precisely this change a while back on an experimental branch while experimenting with UnsafePointer conversion. I don’t see a problem with it.<br class=""><br class="">Implicit argument conversion from UnsafeMutablePointer<Pointee> to UnsafePointer<Pointee> is normal and extremely obvious.<br class=""></blockquote><br class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: 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-variant-caps: 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;">Yeah, Andy's approach seems cleaner than overloading.</span></div></blockquote><br class=""></div><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: 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;">:-( …but it’s an implicit conversion. Which we’re trying to expunge from the language. (Sort of.)</div></div></blockquote><br class=""></div><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: 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;">I’ve heard exactly the opposite argument recently. Namely that explicit UnsafePointer construction indicates an “unsafe” cast (I personally don’t agree with that argument though).</div><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: 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-caps: 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;">Tangential: Which of our current implicit conversions are considered bad? I can’t think of a good alternative, particularly for String/Array to UnsafePointer.</div></div></blockquote><br class=""></div><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: 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="">String/Array to UnsafePointer can't be safely expressed in the language right now without the lifetime-extending wrapper closure, so I feel less bad about those. Inout-to-pointer conversions don't feel implicit because of the '&'.</div><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: 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><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: 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="">For other conversions, the remaining implicit value-to-reference bridging conversion is up for review, and we've talked about tightening up when implicit optional wrapping can occur. IUOs are out of the type system, which is probably as far as they'll go. I think subclass-to-superclass and covariant function pointer conversions are likely to stay as is, though.</div><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: 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><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: 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="">I think converting initialization from UnsafeMutablePointer<T> to UnsafePointer<T> is always safe, but all the other initializers may need to grow a label (under our rules). That doesn't mean there should be an implicit conversion for it, as convenient as it may be.</div></div></blockquote><div><br class=""></div><div>That’s good to hear. I completely agree that unsafe conversions need to grow a label.</div><div><br class=""></div><div>Although I still somewhat prefer implicit Mutable to Immutable conversions not only because it is so convenient but because programmers will expect that behavior. It feels to me like we are mimicking a type qualifier. AFAIK it doesn’t introduce implementation complexity or strange corner cases.</div><div><br class=""></div><div>-Andy</div><br class=""><blockquote type="cite" class=""><div class=""><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: 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="">(The counter-movement is people who want implicit conversions from smaller to larger integer and floating-point types, so the tide may shift here.)</div><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: 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><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: 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="">Jordan</div></div></blockquote></div><br class=""></body></html>