<div dir="ltr">On Sun, Jun 11, 2017 at 10:34 AM, Gor Gyolchanyan <span dir="ltr"><<a href="mailto:gor@gyolchanyan.com" target="_blank">gor@gyolchanyan.com</a>></span> wrote:<br><div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word;line-break:after-white-space"><div>I just didn't want to use the commonly proposed `factory` word, because it implies a specific semantic tied to the factory method pattern.</div><div>I gave it another thought and I'm thinking maybe we can forego the annotation and have the compiler deduce it automatically.</div><div>There are only two places where an indirect initializer can exist:</div><div>* Protocol extensions, returning a conforming type.</div><div>* Classes, returning an instance.</div><div>It doesn't make sense to have this on value types, since they do not have subtypes of any kind.</div><div>Indirect initializers are very unambiguous in protocol extensions, because the only other way of implementing an initializer in a protocol extension is via delegating initialization, so the indirect-ness of the initializer can be statically determined by whether or not there is a delegating initializer involved.</div><div>If the initializer in a protocol extension has a delegating initialization on any execution path, then returning an instance is disallowed and vice versa. This will ensure strict separation of initializer types for the compiler to generate code for.</div><div>If a failable initializer in a protocol extension unconditionally returns `nil`, then no initialization takes place anyway, so it doesn't matter, which one the compiler chooses.</div><div>In classes this is a bit difficult, because besides delegating initializers, they also can initialize the members directly.</div><div>So, in addition to the distinguishing rule for the protocol extensions, classes will also check whether any member is assigned to on any execution path.</div><div><br></div><div>What do you think?</div></div></blockquote><div><br></div><div>Keywords aren't just for the compiler; they're for the human reader too! If you believe the use of your proposed feature in protocol extensions is unambiguous to humans as well as compilers, then IMO it makes sense not to require another keyword in that place. I haven't thought deeply about whether that would be the case.</div><div><br></div><div>Clearly, you're saying that this is a more complicated situation with classes; I think it makes sense for you to consider requiring a keyword there. There is precedent for keywords modifying `init` to be required for classes but not for value types (e.g., `convenience`).</div><div><br></div><div>Regardless of whether a keyword is required or not, your feature needs a name. And here again, I think it is puzzling that you are calling them "indirect initializers" when there is already another meaning for "indirect" in Swift. Distinct concepts should have distinct names.</div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word;line-break:after-white-space"><div><div class="h5"><div><blockquote type="cite"><div>On Jun 11, 2017, at 5:53 PM, Xiaodi Wu <<a href="mailto:xiaodi.wu@gmail.com" target="_blank">xiaodi.wu@gmail.com</a>> wrote:</div><br class="m_-8889396346234607067Apple-interchange-newline"><div><div dir="ltr">On Sun, Jun 11, 2017 at 8:49 AM, Gor Gyolchanyan <span dir="ltr"><<a href="mailto:gor@gyolchanyan.com" target="_blank">gor@gyolchanyan.com</a>></span> wrote:<br><div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word;line-break:after-white-space">Can you recall the reasons why the removal of access modifiers on extensions was rejected?</div></blockquote><div><br></div><div>It was an unassailable reason, really: people found this shorthand useful and wanted to continue to use it--it is the only way to specify that multiple members are public without explicitly labeling each one. The core team agreed it was useful.</div><div><br></div><div>My takeaway from the whole episode (I was greatly in favor of removing this shorthand, as it's highly inconsistent with all other access modifier rules) is that in general, since the bar for new syntax is so high, if a shorthand made it into the language (and especially if it's kind of an inconsistent shorthand) the general presumption must be that it is highly desired.</div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word;line-break:after-white-space"><div>Also, do you think `indirect init` is confusing inside an `indirect enum`?</div></div></blockquote><div><br></div><div>I do. These are unrelated definitions of "indirect," and I'm puzzled why you'd actively choose to run into issues with the same word meaning two things when you could choose another word.</div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word;line-break:after-white-space"><div><div><div class="m_-8889396346234607067m_241785386340440994h5"><div><blockquote type="cite"><div>On Jun 11, 2017, at 4:40 PM, Xiaodi Wu <<a href="mailto:xiaodi.wu@gmail.com" target="_blank">xiaodi.wu@gmail.com</a>> wrote:</div><br class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484Apple-interchange-newline"><div><div>Removal of access modifiers on extensions has been proposed, reviewed, and rejected, so that’s that.</div><div><br></div><div>In general, Swift uses distinct keywords for distinct concepts, unlike Rust which likes to reuse keywords in clever ways; if you’re finding that things are getting confusing with one word meaning two things, that shouldn’t be an invitation to rip out existing syntax but is probably a good sign you shouldn’t be repurposing that keyword.</div><div><br></div><div><br><div class="gmail_quote"><div>On Sun, Jun 11, 2017 at 03:28 Adrian Zubarev via swift-evolution <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>> wrote:<br></div><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 class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178bloop_markdown"><p>Yeah, well I messed up my proposal from last year about removing the access modifier on extensions and wish now I wasn’t that confused back than and made it right.</p><p>The <code>indirect</code> keyword is literally the same story. The docs only says that this is only a shortcut.</p>
<blockquote><p>„To enable indirection for all the cases of an enumeration, mark the entire enumeration with the indirect modifier—this is convenient when the enumeration contains many cases that would each need to be marked with the indirect modifier.“</p>
</blockquote><p>If you really wish to reuse that keyword here we might need to remove such shortcuts from the language (indirect enum, access modifier on extensions, anything else?).</p><div><br class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484webkit-block-placeholder"></div></div><div class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178bloop_original_html"></div></div><div style="word-wrap:break-word"><div class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178bloop_original_html"><div id="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;margin:0px"><br></div> <br> <div id="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178bloop_sign_1497168891326406912" class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178bloop_sign"><div style="font-family:helvetica,arial;font-size:13px">-- <br>Adrian Zubarev<br>Sent with Airmail</div></div> <br></div></div><div style="word-wrap:break-word"><div class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178bloop_original_html"><p class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178airmail_on">Am 11. Juni 2017 um 10:12:38, Gor Gyolchanyan (<a href="mailto:gor@gyolchanyan.com" target="_blank">gor@gyolchanyan.com</a>) schrieb:</p> <blockquote type="cite" class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178clean_bq"><span><div style="word-wrap:break-word;line-break:after-white-space"><div></div><div>
I always wondered, why is `indirect` allowed on the `enum` itself?
Wouldn't it make more sense to apply it to individual cases that
recursively refer to the `enum`?
<div>This question also applies to access modifiers on
extensions. So, what is it supposed to do? Change the default
access modifier from `internal` to whatever I specify? That's just
confusing, reduces readability and the syntactic gain is marginal
at best.</div>
<div>If the `indirect` confusion becomes real, I'd suggest
getting rid of `indirect enum` and using `indirect case`
instead.<br>
<div><br>
<blockquote type="cite">
<div>On Jun 11, 2017, at 11:05 AM, Adrian Zubarev via
swift-evolution <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>> wrote:</div>
<br class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178Apple-interchange-newline">
<div>
<div class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178bloop_markdown" style="font-family:Helvetica,Arial;font-size:13px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(254,254,254)"><p style="margin:15px 0px">
The proposal is looking good to me. :) It will also enable easy
support for custom views using XIBs in iOS development without
unnecessary view nesting.</p><p style="margin:15px 0px">For instance the function
from this example<span class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178Apple-converted-space"> </span><a href="https://stackoverflow.com/a/43123783/4572536" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">https://stackoverflow.<wbr>com/a/43123783/4572536</a><span class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178Apple-converted-space"> </span>could be used directly inside
an<span class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178Apple-converted-space"> </span><code style="font-family:Menlo,Consolas,'Liberation Mono',Courier,monospace;font-size:10pt;border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;background-color:rgb(248,248,248);color:inherit;border:1px solid rgb(234,234,234);margin:0px 2px;padding:0px 5px;word-break:normal;word-wrap:normal">init</code>:</p>
<pre style="margin:15px 0px;font-family:Menlo,Consolas,'Liberation Mono',Courier,monospace;font-size:10pt;border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;background-color:rgb(248,248,248);color:inherit;border:1px solid rgb(204,204,204);overflow:auto;padding:4px 8px;word-break:normal;word-wrap:normal"><code style="font-family:Menlo,Consolas,'Liberation Mono',Courier,monospace;font-size:10pt;border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;background-color:rgb(248,248,248);color:inherit;border:0px;margin:0px;padding:0px;word-break:normal;word-wrap:normal">class MyView : UIView {
indirect init() {
return MyView.instantiateFromXib()
// Or after SR-0068
return Self.instantiateFromXib()
}
}
</code></pre><p style="margin:15px 0px">There is still one little
thing that bothers me, it might be a little bit confusing to have
two different meanings of<span class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178Apple-converted-space"> </span><code style="font-family:Menlo,Consolas,'Liberation Mono',Courier,monospace;font-size:10pt;border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;background-color:rgb(248,248,248);color:inherit;border:1px solid rgb(234,234,234);margin:0px 2px;padding:0px 5px;word-break:normal;word-wrap:normal">indirect</code><span class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178Apple-converted-space"> </span>on enums.</p>
<pre style="margin:15px 0px;font-family:Menlo,Consolas,'Liberation Mono',Courier,monospace;font-size:10pt;border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;background-color:rgb(248,248,248);color:inherit;border:1px solid rgb(204,204,204);overflow:auto;padding:4px 8px;word-break:normal;word-wrap:normal"><code class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178swift" style="font-family:Menlo,Consolas,'Liberation Mono',Courier,monospace;font-size:10pt;border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;background-color:rgb(248,248,248);color:inherit;border:0px;margin:0px;padding:0px;word-break:normal;word-wrap:normal">indirect enum ArithmeticExpression {
case number(Int)
case addition(ArithmeticExpression, ArithmeticExpression)
case multiplication(ArithmeticExpre<wbr>ssion, ArithmeticExpression)
// This might makes no sense, but it would still be possible after
// this proposal.
indirect init(other: ArithmeticExpression) {
return other
}
// Furthermore if the keyboard is applied to the enum
// directly all other `indirect` uses are inferred.
// Will this be implicitly `indirect` because of the previous fact?
init() { … }
}
</code></pre>
<div style="margin:15px 0px"><br class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178webkit-block-placeholder"></div>
</div>
<div class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178bloop_original_html" style="font-family:Helvetica,Arial;font-size:13px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(254,254,254)">
<div id="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;margin:0px"><br></div>
<br>
<div id="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178bloop_sign_1497167373101756160" class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178bloop_sign">
<div style="font-family:helvetica,arial;font-size:13px">-- <br>
Adrian Zubarev<br>
Sent with Airmail</div>
</div>
<br><p class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178airmail_on" style="margin:15px 0px">Am 11. Juni 2017 um
00:38:56, Riley Testut via swift-evolution (<a href="mailto:swift-evolution@swift.org" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">swift-evolution@swift.org</a>) schrieb:</p>
<blockquote type="cite" class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178clean_bq" style="margin:15px 0px">
<div style="word-wrap:break-word;line-break:after-white-space">
<div></div>
<div>
<div><span style="margin-top:0px;margin-bottom:0px">Awesome! Updated my proposal to include what I believed to
be the relevant portions of your indirect initializer idea. Let me
know if there’s anything I missed or should change :-)</span></div>
<div><span style="margin-top:0px;margin-bottom:0px"><br></span></div>
<div><span style="margin-top:0px;margin-bottom:0px"><a href="https://github.com/rileytestut/swift-evolution/blob/master/proposals/NNNN-factory-initializers.md" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">
https://github.com/rileytestut<wbr>/swift-evolution/blob/master/p<wbr>roposals/NNNN-factory-initiali<wbr>zers.md</a></span></div>
<span style="margin-top:0px;margin-bottom:0px"><br></span>
<div>
<blockquote type="cite" style="margin:15px 0px">
<div style="margin-top:0px"><span style="margin-top:0px;margin-bottom:0px">On Jun 10, 2017, at
12:43 PM, Gor Gyolchanyan <<a href="mailto:gor@gyolchanyan.com" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">gor@gyolchanyan.com</a>>
wrote:</span></div>
<span style="margin-top:0px;margin-bottom:0px"><br class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178Apple-interchange-newline"></span>
<div style="margin-bottom:0px">
<div style="word-wrap:break-word;line-break:after-white-space">
<div><span style="margin-top:0px;margin-bottom:0px">Hi, Riley!</span></div>
<div><span style="margin-top:0px;margin-bottom:0px"><br></span></div>
<span style="margin-top:0px;margin-bottom:0px">I think
that's a great idea! We can merge the second part of my proposal
(the `indirect init`) into your one and refine and consolidate the
prerequisite proposal (about returning from `init` and possibly
in-place member initializers) and bunch them up into a proposal
cluster (the way swift coders did).</span>
<div><span style="margin-top:0px;margin-bottom:0px">Feel free to tear out any chunks from my proposal, while I
think about a more in-depth rationale about revamping
initialization syntax. 🙂<br></span>
<div><span style="margin-top:0px;margin-bottom:0px"><br></span>
<blockquote type="cite" style="margin:15px 0px">
<div style="margin-top:0px"><span style="margin-top:0px;margin-bottom:0px">On Jun 10, 2017, at
8:36 PM, Riley Testut <<a href="mailto:rileytestut@gmail.com" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">rileytestut@gmail.com</a>>
wrote:</span></div>
<span style="margin-top:0px;margin-bottom:0px"><br class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178Apple-interchange-newline"></span>
<div style="margin-bottom:0px">
<div style="word-wrap:break-word;line-break:after-white-space">
<span style="margin-top:0px;margin-bottom:0px">Hi Gor
👋</span>
<div><span style="margin-top:0px;margin-bottom:0px"><br></span></div>
<div><span style="margin-top:0px;margin-bottom:0px">I’m very much in fan of a unified initialization syntax. I
submitted my own proposal for factory initializers a while back,
but since it wasn’t a focus of Swift 3 or 4 I haven’t followed up
on it recently. In the time since last working on it, I came to my
own conclusion that rather than focusing on factory initialization,
the overall initialization process should be simplified, which I’m
glad to see someone else has realized as well :-)</span></div>
<div><span style="margin-top:0px;margin-bottom:0px"><br></span></div>
<div><span style="margin-top:0px;margin-bottom:0px">Here’s my proposal for reference:<span class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178Apple-converted-space"> </span><a href="https://github.com/apple/swift-evolution/pull/247/commits/58b5a93b322aae998eb40574dee15fe54323de2e" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">https://github.com/<wbr>apple/swift-evolution/pull/247<wbr>/commits/58b5a93b322aae998eb40<wbr>574dee15fe54323de2e</a><span class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178Apple-converted-space"> </span>Originally
I used the “factory” keyword, but I think your “indirect” keyword
may be a better fit (since it has precedent in the language and is
not limited to “just” being about factory initialization). To
divide your proposal up into smaller pieces for review, maybe we
could update my proposal to use your indirect keyword, and then
start a separate topic/proposal for the remaining aspects of your
proposal? I agree that splitting it into smaller chunks may be
better for the process.</span></div>
<div><br></div>
<div>Let me know what you think!</div>
<div><br></div>
<div>Riley</div>
<div><br></div>
<div><br>
<div>
<blockquote type="cite" style="margin:15px 0px">
<div style="margin-top:0px">On Jun 10, 2017, at 3:33 AM,
Gor Gyolchanyan via swift-evolution <<a href="mailto:swift-evolution@swift.org" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">swift-evolution@swift.org</a>>
wrote:</div>
<br class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178Apple-interchange-newline">
<div style="margin-bottom:0px">
<div style="word-wrap:break-word;line-break:after-white-space">
<div>
<blockquote type="cite" style="margin:15px 0px">
<div style="margin-top:0px;margin-bottom:0px">
<div class="gmail_extra">
<div class="gmail_quote">
<div><br></div>
<div>This is a very interesting read.</div>
<div><br></div>
</div>
</div>
</div>
</blockquote>
</div>
<div>Thanks you! I tried to make it as clear and detailed
as possible. 🙂 </div>
<div><br></div>
<div>
<blockquote type="cite" style="margin:15px 0px">
<div style="margin-top:0px;margin-bottom:0px">
<div class="gmail_extra">
<div class="gmail_quote">
<div><br></div>
<div>We did not discuss the 'indirect' idea at all on this
list. Did you come up with it just now? In any case, my suggestion
as to moving forward would be this:</div>
<div><br></div>
</div>
</div>
</div>
</blockquote>
</div>
I was writing the proposal and was just about to write `factory
init`, when it occurred to me: enums already have a keyword that
does something very similar. It seemed to me that an initializer
that doesn't initialize the instance in-place, but returns a
completely separate instance from somewhere else, is kinda
"indirectly" initializing the instance. Plus, the already
established keyword and its semantic would reduce the learning
curve for this new feature and separate it from a single specific
use case (the "factory method" pattern).
<div>
<div><br></div>
<div>
<blockquote type="cite" style="margin:15px 0px">
<div style="margin-top:0px;margin-bottom:0px">
<div class="gmail_extra">
<div class="gmail_quote">
<div><br></div>
<div>- Do you feel that both halves of your draft
(expanding `return` in initializers, and `indirect` initializers)
should absolutely be one proposal, or can they be separated?</div>
<div><br></div>
</div>
</div>
</div>
</blockquote>
<div>I think the `return` can be easily implemented first,
while opening up an opportunity to later implement `indirect init`.
The reason why I unified them was that the `return` idea on its own
has very limited merit and could the thought of as a low-priority
cosmetic enhancement. I wouldn't want it to be viewed that way
because the primary purpose of that idea is to enable `indirect
init` (which Cocoa and Cocoa Touch developers would be very happy
about). </div>
<div><br></div>
<div>
<blockquote type="cite" style="margin:15px 0px">
<div style="margin-top:0px;margin-bottom:0px">
<div class="gmail_extra">
<div class="gmail_quote">
<div><br></div>
<div>a) If they can be separated because each half has
individual merit, then these ideas may be more likely to succeed as
separate proposals, as each can be critiqued fully and judged
independently as digestible units.</div>
</div>
</div>
</div>
</blockquote>
<div>
<div>
<div class="gmail_extra">
<div class="gmail_quote">
<div>
<div>
<div>
<blockquote type="cite" style="margin:15px 0px">
<div style="margin-top:0px;margin-bottom:0px">
<div class="gmail_extra">
<div class="gmail_quote">
<div><br></div>
</div>
</div>
</div>
</blockquote>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
<div>Very good point. The challenge is to correctly
separate them, without losing context in their respective proposals
and without bleeding the proposals into each other.</div>
<div><br></div>
<div><br></div>
<div>
<blockquote type="cite" style="margin:15px 0px">
<div style="margin-top:0px;margin-bottom:0px">
<div class="gmail_extra">
<div class="gmail_quote">
<div><br></div>
</div>
</div>
</div>
</blockquote>
</div>
<div>
<blockquote type="cite" style="margin:15px 0px">
<div style="margin-top:0px;margin-bottom:0px">
<div class="gmail_extra">
<div class="gmail_quote">
<div>b) If you intend to tackle all your ideas all at
once, that's going to be a much bigger change--in terms of review
effort, likely bikeshedding, and implementation effort. It'll
probably be best to solicit initial feedback on this list first
about `indirect` initializers, even if just to familiarize the
community with the idea, before launching into a pitch of the whole
proposal.</div>
<div><br></div>
</div>
</div>
</div>
</blockquote>
</div>
<div>I'd never send a pull request to swift-evolution
without thoroughly discussing it here. I just though, if I'm going
to write a whole proposal with examples and motivation, it would be
easier to demonstrate it and discuss in with the community If I
just went ahead and wrote the whole thing and sent the link. This
way it would be clearer to the reader and the discussed changes
would be accurately reflected by the commits I'd make to my
proposal.</div>
<div><br></div>
<div>Original Message</div>
<div><br></div>
<blockquote type="cite" style="margin:15px 0px">
<div style="margin-top:0px">On Jun 10, 2017, at 2:38 AM,
Daryle Walker via swift-evolution <<a href="mailto:swift-evolution@swift.org" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">swift-evolution@swift.org</a>>
wrote:</div>
<br class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178Apple-interchange-newline">
<div style="margin-bottom:0px">
<div>On Fri, Jun 9, 2017 at 5:32 PM, Gor
Gyolchanyan<span class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178Apple-converted-space"> </span><span><<a href="mailto:gor@gyolchanyan.com" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">gor@gyolchanyan.c<wbr>om</a>></span><span class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178Apple-converted-space"> </span>wrote:<br>
<div class="gmail_extra">
<div class="gmail_quote">
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex">
<div style="margin-top:0px;margin-bottom:0px;word-wrap:break-word;line-break:after-white-space">
<div>Forked swift-evolution, created a draft
proposal:</div>
<div><br></div>
<a href="https://github.com/technogen-gg/swift-evolution/blob/master/proposals/NNNN-uniform-initialization.md" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">https://github.com/technogen-g<wbr>g/swift-evolution/blob/master/<wbr>proposals/NNNN-uniform-initial<wbr>ization.md</a>
<div><br></div>
<div>This is my first proposal, so I might have missed
something or composed it wrong, so please feel free to comment,
fork and send pull requests. 🙂
<div>
<div class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178h5">
<div>
<blockquote type="cite" style="margin:15px 0px">
<div style="margin-top:0px;margin-bottom:0px"></div>
</blockquote>
</div>
</div>
</div>
</div>
</div>
</blockquote>
<div><br></div>
<div>This is a very interesting read. We did not discuss
the 'indirect' idea at all on this list. Did you come up with it
just now? In any case, my suggestion as to moving forward would be
this:</div>
<div><br></div>
<div>- Do you feel that both halves of your draft
(expanding `return` in initializers, and `indirect` initializers)
should absolutely be one proposal, or can they be separated?</div>
<div><br></div>
<div>a) If they can be separated because each half has
individual merit, then these ideas may be more likely to succeed as
separate proposals, as each can be critiqued fully and judged
independently as digestible units.</div>
<div><br></div>
<div>b) If you intend to tackle all your ideas all at
once, that's going to be a much bigger change--in terms of review
effort, likely bikeshedding, and implementation effort. It'll
probably be best to solicit initial feedback on this list first
about `indirect` initializers, even if just to familiarize the
community with the idea, before launching into a pitch of the whole
proposal.</div>
<div><br></div>
<div><br></div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex">
<div style="margin-top:0px;margin-bottom:0px;word-wrap:break-word;line-break:after-white-space">
<div>
<div>
<div class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178h5">
<div>
<blockquote type="cite" style="margin:15px 0px">
<div style="margin-top:0px">On Jun 9, 2017, at 3:24 PM,
Xiaodi Wu <<a href="mailto:xiaodi.wu@gmail.com" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">xiaodi.wu@gmail.com</a>>
wrote:</div>
<br class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178m_-7329774452902408180Apple-interchange-newline">
<div style="margin-bottom:0px">Cool. I have reservations
about idea #3, but we can tackle that another day. (Real life
things beckon.) But suffice it to say that I now really, really
like your idea #2.<br>
<div class="gmail_quote">
<div>On Fri, Jun 9, 2017 at 08:06 Gor
Gyolchanyan <<a href="mailto:gor@gyolchanyan.com" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">gor@gyolchanyan.com</a>>
wrote:<br></div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex">
<div style="margin-top:0px;word-wrap:break-word;line-break:after-white-space">
You know, come to think of it, I totally agree, and here's why:
<div>A normal initializer (if #2 is accepted) would
*conceptually* have the signature:</div>
<div><br></div>
<div>mutating func `init`(...) -> Self</div>
<div><br></div>
<div>Which would mean that both `self` and the returned
result are non-optional.</div>
<div>A failable initializer could then have the
signature:</div>
<div><br></div>
<div>mutating func `init`() -> Self?</div>
<div><br></div>
<div>Which would make the returned result optional, but
leave `self` non-optional.</div>
<div>This would make `return nil` less out-of-place, like
you said, while still leaving `self` as a set-exactly-once `inout
Self`.</div>
<div>A factory initializer would then have the
signature:</div>
<div><br></div>
<div>static func `init`(...) -> Self</div>
<div><br></div>
<div>or in case of a failable factory initializer:</div>
<div><br></div>
<div>static func `init`(...) -> Self?</div>
<div><br></div>
<div>Which would still make sense with the now legal
`return ...` syntax, while adding the restriction of not having any
`self` at all.</div>
<div>So, annotating the initializer with the keyword
`factory` would cause it to change the signature as well as remove
any compiler assumptions about the dynamic type of the returned
instance.</div>
<div><br></div>
<div>In addition, idea #3 would be available for more
deterministic in-place initialization.</div>
</div>
<div style="margin-bottom:0px;word-wrap:break-word;line-break:after-white-space">
<div>
<div><br>
<blockquote type="cite" style="margin:15px 0px">
<div style="margin-top:0px">On Jun 9, 2017, at 2:47 PM,
Xiaodi Wu <<a href="mailto:xiaodi.wu@gmail.com" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">xiaodi.wu@gmail.com</a>>
wrote:</div>
<br class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178m_-7329774452902408180m_-1696318748622386158Apple-interchange-newline">
<div style="margin-bottom:0px">
<div>
<div>
<div class="gmail_quote">
<div>On Fri, Jun 9, 2017 at 07:33 Gor Gyolchanyan
<<a href="mailto:gor@gyolchanyan.com" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">gor@gyolchanyan.com</a>>
wrote:<br></div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex">
<div style="margin-top:0px;margin-bottom:0px;word-wrap:break-word;line-break:after-white-space">
So far, we've discussed two ways of interpreting `self = nil`, both
of which have a sensible solution, in my opinion:
<div><br></div>
<div>1. It's a special rule like you said, which can be
seen as counter-intuitive, but recall that `return nil` is just as
much of a special rule and is also largely counter-intuitive.</div>
</div>
</blockquote>
<div><br></div>
</div>
</div>
</div>
<div>
<div>
<div class="gmail_quote">
<div>`return nil` is “special,” but it doesn’t conflict
with any other syntax because the initializer notionally has no
return value. Personally, I have always disliked `return nil` in
failable initializers for that reason, but I couldn’t come up with
a better alternative.</div>
<div><br></div>
<div>Your proposed idea to allow returning any value is
interesting because, in the case of a failable initializer, `return
nil` continues to have the same meaning if we consider the return
value of the initializer to be of type `Self?`. For that reason, I
think your idea #2 is quite clever, and it would go a long way in
making `return nil` a lot less odd. It also increases the
expressivity of initializers because it allows one to set the value
of self and also return in one statement, clearly demonstrating the
intention that no other code in the initializer should be run
before returning.</div>
<div><br></div>
<div>For all of those reasons, I think idea #2 is a
winning idea.</div>
</div>
</div>
</div>
<div>
<div>
<div class="gmail_quote">
<div><br></div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex">
<div style="margin-top:0px;margin-bottom:0px;word-wrap:break-word;line-break:after-white-space">
<div>The benefit of `self = nil` is that it's much more in
line with initialization semantics, it provides more uniform syntax
and it's a bit less restrictive.<br>
<div><br></div>
<div>2. It's an `inout Self!`, like Greg said, which can
be seen as more cumbersome. Implicitly unwrapped optionals are a
bit difficult, but this "variation" of it is much more restrictive
then the normal ones, because unlike normal implicitly unwrapped
optionals, this one cannot be accessed after being assigned nil
(and it also cannot be indirectly assigned `nil`, because escaping
`self` is not allowed before full initialization), so there is only
one possible place it can be set to nil and that's directly in the
initializer. This means that `self` can be safely treated as `inout
Self` before being set to nil (and after being set to nil, it
doesn't matter any more because you aren't allowed to access it,
due to not being fully initialized).</div>
</div>
</div>
</blockquote>
<div><br></div>
<div>I have to say, I don’t like either of these
explanations at all. I think having a “special” IUO is a difficult
sell; it is just conceptually too complicated, and I don’t agree
that it gains you much.</div>
<div><br></div>
<div>By your own admission, `self = nil` is wonky, and
making the language wonkier because it currently has a parallel
wonky feature in `return nil` seems like the wrong way to go. In
addition, there’s nothing gained here that cannot be done with a
defer statement; of course, defer statements might not be very
elegant, but it would certainly be less wonky than inventing a new
variation on an IUO to allow assignment of nil to self... For those
reasons, I conclude that I’m not excited about your idea #1.</div>
<div><br></div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex">
<div style="margin-top:0px;word-wrap:break-word;line-break:after-white-space">
<div>
<div></div>
<div>Overall, I'd go with #2 because it involves much less
confusing magic and the restrictions of `self as inout Self!` are
imposed by already existing and well-understood initialization
logic, so the provided guarantees don't really come at the cost of
much clarity.</div>
</div>
</div>
<div style="margin-bottom:0px;word-wrap:break-word;line-break:after-white-space">
<div>
<div><br>
<blockquote type="cite" style="margin:15px 0px">
<div style="margin-top:0px">On Jun 9, 2017, at 2:23 PM,
Xiaodi Wu <<a href="mailto:xiaodi.wu@gmail.com" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">xiaodi.wu@gmail.com</a>>
wrote:</div>
<br class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178m_-7329774452902408180m_-1696318748622386158m_-1836007598760388288m_758143498405985784Apple-interchange-newline">
<div style="margin-bottom:0px">
<div><br>
<div class="gmail_quote">
<div>On Fri, Jun 9, 2017 at 07:12 Gor Gyolchanyan
<<a href="mailto:gor@gyolchanyan.com" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">gor@gyolchanyan.com</a>>
wrote:<br></div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex">
<div style="margin-top:0px;word-wrap:break-word;line-break:after-white-space">
I think a good approach would be to have `self = nil` only mean
`the initializer is going to fail` because if your type is
ExpressibleByNilLiteral, it means that the `nil` of your type
already carries the same meaning as if your type was not
ExpressibleByNilLiteral and was an optional instead, so having a
failable initializer doesn't really make sense in that case (since
you could've initialized `self` to its own `nil` in case of
failure). Still, some valid use cases may exist, so the natural
(and quite intuitive) way to circumvent this would be to call
`self.init(nilLiteral: ())` directly.</div>
<div style="margin-bottom:0px;word-wrap:break-word;line-break:after-white-space">
<div>
<div>
<div></div>
</div>
</div>
</div>
</blockquote>
<div><br></div>
<div>So you would create a special rule that `self = nil`
means a different thing in an initializer than it does in a
function? Essentially, then, you’re creating your own variation on
an implicitly unwrapped optional, where `self` is of type `inout
Self?` for assignment in initializers only but not for any other
purpose. Implicitly unwrapped optionals are hard to reason about,
and having a variation on it would be even harder to understand. I
don’t think this is a workable design.</div>
<div><br></div>
<div>It might be possible to have `self` be of type `inout
Self?`; however, I do think Greg is right that it would create more
boilerplate than the current situation.</div>
<div><br></div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex">
<div style="margin-top:0px;margin-bottom:0px;word-wrap:break-word;line-break:after-white-space">
<div>
<div>
<div>
<blockquote type="cite" style="margin:15px 0px">
<div style="margin-top:0px">On Jun 9, 2017, at 2:07 PM,
Xiaodi Wu <<a href="mailto:xiaodi.wu@gmail.com" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">xiaodi.wu@gmail.com</a>>
wrote:</div>
<br class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178m_-7329774452902408180m_-1696318748622386158m_-1836007598760388288m_758143498405985784m_8163076293838887182Apple-interchange-newline">
<div style="margin-bottom:0px">
<div style="font-family:DejaVuSans;font-size:14px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
<br class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178m_-7329774452902408180m_-1696318748622386158m_-1836007598760388288m_758143498405985784m_8163076293838887182Apple-interchange-newline">
On Fri, Jun 9, 2017 at 06:56 Gor Gyolchanyan <<a href="mailto:gor@gyolchanyan.com" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">gor@gyolchanyan.com</a>>
wrote:<br></div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;font-family:DejaVuSans;font-size:14px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex">
<div style="margin-top:0px;margin-bottom:0px;word-wrap:break-word;line-break:after-white-space">
<div>The type of `self` could remain `inout Self` inside
the failable initializer. The ability to assign nil would be a
compiler magic (much like `return nil` is compiler magic) that is
meant to introduce uniformity to the initialization logic.</div>
<br>
<div>The idea is to define all different ways
initialization can take place and expand them to be used uniformly
on both `self` and all its members, as well as remove the ways that
do not make sense for their purpose.</div>
<div><br></div>
<div>Currently, there are 3 ways of initializing self as a
whole:</div>
<div>1. delegating initializer</div>
<div>2. assigning to self</div>
<div>3. returning nil</div>
<div>
<div><br></div>
<div>#1: The delegating initializer is pretty much perfect
at this point, in my opinion, so no changes there.</div>
<div><br></div>
<div>#2: The only exception in assigning to self is the
`nil` inside failable initializers.</div>
<div><br></div>
<div>#3: The only thing that can be returned from an
initializer is `nil`, which is compiler magic, so we can thing of
it as a misnomer (because we aren't really **returning**
anything).</div>
<div><br></div>
<div>If, for a second, we forget about potential factory
initializers, returning anything from an initializer doesn't make
much sense, because an initializer is conceptually meant to bring
an existing object in memory to a type-specific valid state. This
semantic was very explicitly in Objective-C with `[[MyType alloc]
init]`. Especially since even syntactically, the initializer does
not specify any return type, the idea of returning from an
initializer is counter-intuitive both syntactically and
semantically.</div>
<div><br></div>
<div>The actual *behavior* of `return nil` is very
sensible, so the behavior, I imagine `self = nil`, would largely
mean the same (except not needed to return immediately and allowing
non-self-accessing code to be executed before return). Being able
to assign `nil` to a non-optional (ExpressibleByNilLiteral doesn't
count) may feel a bit wonky,</div>
</div>
</div>
</blockquote>
<div style="font-family:DejaVuSans;font-size:14px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
<br></div>
<div style="font-family:DejaVuSans;font-size:14px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
What happens when Self is ExpressibleByNilLiteral and you want to
initialize self to nil? That is what `self = nil` means if `self`
is of type `inout Self`. If `self` is of type `inout Self` and Self
is not ExpressibleByNilLiteral, then it must be an error to assign
nil to self. Anything else does not make sense, unless `self` is of
type `inout Self?`.</div>
<div style="font-family:DejaVuSans;font-size:14px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
<br></div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;font-family:DejaVuSans;font-size:14px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex">
<div style="margin-top:0px;word-wrap:break-word;line-break:after-white-space">
<div>
<div>but not as wonky as returning nil from something that
is meant to initialize an object in-place and doesn't look like it
should return anything.</div>
<div><br></div>
<div># Factory Initializers</div>
<div><br></div>
<div>In case of factory initializers, the much discussed
`factory init` syntax could completely flip this logic, but making
the initializer essentially a static function that returns an
object. In this case the initializer could be made to specify the
return type (that is the supertype of all possible factory-created
objects) and assigning to self would be forbidden because there is
not self yet:</div>
<div><br></div>
<div>extension MyProtocol {</div>
<div><br></div>
<div>public factory init(weCool: Bool) -> MyProtocol
{</div>
<div>self = MyImpl() // error: cannot assign to `self` in
a factory initializer</div>
<div>self.init(...) // error: cannot make a delegating
initializer call in a factory initializer</div>
<div>if weCool {</div>
<div>return MyCoolImpl()</div>
<div>} else {</div>
<div>return MyUncoolImpl()</div>
<div>}</div>
<div>}</div>
<div><br></div>
<div>}</div>
<div><br></div>
<div># In-place Member Initializers</div>
<div><br></div>
<div>In addition, member initialization currently is only
possible with #2 (as in `self.member = value`), which could be
extended in a non-factory initializer to be initializable in-place
like this:</div>
<div><br></div>
<div>self.member.init(...)</div>
<div><br></div>
<div>This would compliment the delegating initialization
syntax, while giving a more reliable performance guarantee that
this member will not be copy-initialized.</div>
</div>
</div>
<div style="margin-bottom:0px;word-wrap:break-word;line-break:after-white-space">
<div>
<div><br>
<blockquote type="cite" style="margin:15px 0px">
<div style="margin-top:0px">On Jun 9, 2017, at 1:32 PM,
Xiaodi Wu <<a href="mailto:xiaodi.wu@gmail.com" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">xiaodi.wu@gmail.com</a>>
wrote:</div>
<br class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178m_-7329774452902408180m_-1696318748622386158m_-1836007598760388288m_758143498405985784m_8163076293838887182m_-8492261585337030922Apple-interchange-newline">
<div style="margin-bottom:0px">If `self` is not of type
`inout Self?`, then what is the type of `self` such that you may
assign it a value of `nil`?<br>
<br>
It certainly cannot be of type `inout Self`, unless `Self` conforms
to `ExpressibleByNilLiteral`, in which case you are able to assign
`self = nil` an unlimited number of times–but that has a totally
different meaning.<br>
<br>
Could `self` be of type `inout Self!`? Now that implicitly
unwrapped optionals are no longer their own type, I’m not sure
that’s possible. But even if it were, that seems unintuitive and
potentially error-prone.<br>
<br>
So I think Greg is quite right that, to enable this feature, `self`
would have to be of type `inout Self?`–which is intriguing but
potentially more boilerplatey than the status quo.<br>
<div class="gmail_quote">
<div>On Fri, Jun 9, 2017 at 05:24 Gor Gyolchanyan via
swift-evolution <<a href="mailto:swift-evolution@swift.org" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">swift-evolution@swift.org</a>>
wrote:<br></div>
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<div style="margin-top:0px;word-wrap:break-word;line-break:after-white-space">
Good point, but not necessarily.<br>
<div>Since you cannot access `self` before it being fully
initialized and since `self` can only be initialized once, this
would mean that after `self = nil`, you won't be allowed to access
`self` in your initializer at all.You'll be able to do any
potential, cleanup though.</div>
<div>Also, since there can be only one `self = nil`,
there's no reason to treat `self` as `inout Self?`, because the
only place it can be `nil` is the place it cannot be accessed any
more.</div>
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<div><br>
<div><br>
<blockquote type="cite" style="margin:15px 0px">
<div style="margin-top:0px">On Jun 9, 2017, at 7:45 AM,
Greg Parker <<a href="mailto:gparker@apple.com" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">gparker@apple.com</a>>
wrote:</div>
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<div style="word-wrap:break-word;line-break:after-white-space"><br>
<div>
<blockquote type="cite" style="margin:15px 0px">
<div style="margin-top:0px">On Jun 8, 2017, at 5:09 AM,
Gor Gyolchanyan via swift-evolution <<a href="mailto:swift-evolution@swift.org" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">swift-evolution@swift.org</a>>
wrote:</div>
<div style="margin-bottom:0px">
<div><br>
1. Arbitrary `self` Assignments In Intializers<br>
<br>
The first ideas is to allow `self = nil` inside failable
initializers (essentially making `self` look like `inout Self?`
instead of `inout Self` with magical `return nil`), so that all
initializers uniformly can be written in `self = ...` form for
clarity and convenience purposes. This should, theoretically, be
nothing but a `defer { return nil }` type of rewrite, so I don't
see any major difficulties implementing this. This is especially
useful for failable-initializing enums where the main switch simply
assigns to self in all cases and the rest of the initializer does
some post-processing.<br></div>
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<div>I don't see how to avoid source incompatibility and
uglification of failable initializer implementations here. Allowing
`self = nil` inside a failable initializer would require `self` to
be an optional. That in turn would require every use of `self` in
the initializer to be nil-checked or forced. I don't think that
loss everywhere outweighs the gain of `self = nil` in some
places.</div>
</div>
<br>
<div><br></div>
<div>-- </div>
<div>Greg Parker <span class="m_-8889396346234607067m_241785386340440994m_-5415623279022033484m_1338021824996647178m_-7329774452902408180m_-1696318748622386158m_-1836007598760388288m_758143498405985784m_8163076293838887182Apple-converted-space"> </span><a href="mailto:gparker@apple.com" style="color:rgb(65,131,196);background-color:inherit;text-decoration:none" target="_blank">gparker@apple.com</a>
Runtime Wrangler</div>
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