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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><code>typealias AnyObject = …</code> is nice to have, but how about if we fully drop the <code>class</code> constraint-keyword and generalize <code>AnyObject</code> instead?</p>
<p>In the future we might want to add <code>AnyValue</code> with value (semantics) constraint, would that mean that we’d need another keyword there like <code>value</code>?</p>
<p>The former is similar to the debate we had last year about <code>Any</code> vs. <code>Any<…></code>, where we decided to go with a magical <code>Any</code>.</p>
<p>Speaking of the future directions:</p>
<ul>
<li><p>Now that we’re no longer supporting the idea of <code>Any<…></code> syntax and any type prefixed with <code>Any</code> seems to be special for its particular usage, could we safely bring the empty <code>Any</code> protocol back (is this somehow ABI related?)?</p></li>
<li><p>One day after this proposal is accepted, implemented and released, we probably will talk about the <code>where</code> clause for existentials. But since a lot of the existentials will have the form <code>typealias Abc = …</code>, this talk will also include the ability to constrain generic typealiases.</p></li>
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<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_1486019368635563008" 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 2. Februar 2017 um 05:52:41, Douglas Gregor 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 dir="auto"><div></div><div>
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Sent from my iPhone</div>
<div><br>
On Feb 1, 2017, at 8:46 PM, Slava Pestov <<a href="mailto:spestov@apple.com">spestov@apple.com</a>> wrote:<br>
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<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>
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<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>
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Second question inline:</div>
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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="">
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<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>
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<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>
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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>
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<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="">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="">typealias AnyObject = Any & class</div>
<div class=""><br class=""></div>
</div>
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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>
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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>
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<div>This is sorta why I'm nervous about it and suggested the "Any
& class" thing. In theory any type can in an expression,
so</div>
<div><br></div>
<div> class.self </div>
<div><br></div>
<div>Would be a valid expression.</div>
<div><br></div>
<div>I don't think it's actually ambiguous, but it feels... odd.
And can mess with parser recovery. </div>
<div><br></div>
<div> - Doug</div>
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<div>Slava</div>
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<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="">- 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>
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