<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 Feb 1, 2017, at 4:09 PM, Douglas Gregor 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-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 Feb 1, 2017, at 3:13 PM, David Hart <<a href="mailto:david@hartbit.com" class="">david@hartbit.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;">Second question inline:</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 class=""><br class=""><br class="">Sent from my iPhone</div>On 1 Feb 2017, at 23:09, David Hart <<a href="mailto:david@hartbit.com" class="">david@hartbit.com</a>> wrote:<br class=""><br class=""></div><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;"><div class="">I did consider it, but didn’t want to put too much on your plate for Swift 4. But if you’re mentioning it, I’ll go ahead and add it to the second version of the proposal.<div class=""><br class=""></div><div class="">By the way, what you is your point of view about the discussions we’ve had concerning the positioning of the class constraint?</div><div class=""><br class=""></div><div class="">David.</div><div class=""><br class=""><div class=""><blockquote type="cite" class=""><div class="">On 1 Feb 2017, at 22:58, Douglas Gregor <<a href="mailto:dgregor@apple.com" class="">dgregor@apple.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="" applecontenteditable="true" style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><br class=""><div class=""><blockquote type="cite" class=""><div class="">On Jan 29, 2017, at 8:39 AM, David Hart <<a href="mailto:david@hartbit.com" class="">david@hartbit.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="" style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">Hello,<div class=""><br class=""></div><div class="">As promised, I wrote the first draft of a proposal to add class requirements to the existential syntax. Please let me know what you think.</div><div class=""><br class=""></div><div class=""><a href="https://github.com/hartbit/swift-evolution/blob/subclass-existentials/proposals/XXXX-subclass-existentials.md" class="">https://github.com/hartbit/swift-evolution/blob/subclass-existentials/proposals/XXXX-subclass-existentials.md</a></div></div></div></blockquote><div class=""><br class=""></div><div class="">This looks good! I’m looking forward to the second draft, but I have one question.</div><div class=""><br class=""></div><div class="">Did you consider the generalized “class” constraint? IIRC, this was in Austin’s larger proposal, and it allowed for (e.g.)</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>typealias CustomStringConvertibleClass = class & CustomStringConvertible // class that conforms to CustomStringConvertible</div><div class=""><br class=""></div><div class="">and potentially a wonderful cleanup where AnyObject ceases to be a weird special protocol and instead becomes</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>typealias AnyObject = Any & class</div><div class=""><br class=""></div></div></div></div></blockquote></div></div></div></blockquote><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;">Austin's proposal defines it as:</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;"><span class="pl-k" style="background-color: rgba(255, 255, 255, 0); box-sizing: border-box;"><br class=""></span></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;"><span class="pl-k" style="background-color: rgba(255, 255, 255, 0); box-sizing: border-box;">typealias</span><span class="" style="background-color: rgba(255, 255, 255, 0);"><span class="Apple-converted-space"> </span></span><span class="pl-en" style="background-color: rgba(255, 255, 255, 0); box-sizing: border-box;">AnyObject</span><span class="" style="background-color: rgba(255, 255, 255, 0);"><span class="Apple-converted-space"> </span></span><span class="pl-k" style="background-color: rgba(255, 255, 255, 0); box-sizing: border-box;">=</span><span class="" style="background-color: rgba(255, 255, 255, 0);"><span class="Apple-converted-space"> </span>class</span></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;"><span class="" style="background-color: rgba(255, 255, 255, 0);"><br class=""></span></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;"><span class="" style="background-color: rgba(255, 255, 255, 0);">Is Any necessary?</span></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="">Nah, it should be okay to just have “class” there.</div></div></blockquote><div><br class=""></div>This would mean ‘class’ can appear anywhere we expect to parse a type, or would we have a special grammar rule for the RHS of a typealias?</div><div><br class=""></div><div>Slava</div><div><br class=""></div><div><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=""><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=""><span class="Apple-tab-span" style="white-space: pre;"> </span>- Doug</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><span style="font-family: Helvetica; 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