<html><head><style>body{font-family:Helvetica,Arial;font-size:13px}</style></head><body style="word-wrap:break-word"><div id="bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin:0px;line-height:auto">As I said, the goal is to make propositions for rules which would solves inconsistencies, but it’s needed on multiple levels :</div><div id="bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin:0px;line-height:auto">- tuples of cardinality 0</div><div id="bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin:0px;line-height:auto">- tuples of cardinality 1</div><div id="bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin:0px;line-height:auto">- tuples of cardinality n > 1</div><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><div id="bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin:0px;line-height:auto">This proposition effectively addresses the first one and not the others. </div><div id="bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin:0px;line-height:auto">The goal is improve consistency step by step with simple rules.</div><div id="bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin:0px;line-height:auto">Having this clear set of rules would resolve a lot of issues, and having a tuple-Void type is actually legacy and confusing in swift4 where arguments have changed a lot at the moment.</div> <br> <div id="bloop_sign_1497298961277890816" class="bloop_sign"><div style="font-family:helvetica,arial;font-size:13px">—</div><div><font face="Helvetica" size="1">very short reply expected - <a href="http://vsre.info">vsre.info</a></font></div><div style="font-family:helvetica,arial;font-size:13px">Jérémie Girault<br></div></div> <br><p class="airmail_on">On 12 juin 2017 at 22:17:31, Jens Persson (<a href="mailto:jens@bitcycle.com">jens@bitcycle.com</a>) wrote:</p> <blockquote type="cite" class="clean_bq"><span><div><div></div><div>
<title></title>
<div dir="ltr">I think this proposal would be complicating rather
than simplifying the type system, it would be adding a special
rule.
<div>And it is not a step towards resolving the many
parentheses-related inconsistencies that still remain.</div>
<div><br>
<div>Here is an example of one such remaining inconsistency, it's
still in (latest dev snapshot) Swift 4, so this is the behavior of
both Swift 3(.2) and 4:</div>
<div>
<div>func foo() -> Void {}</div>
<div>func foo(_: Void) -> Void {} // This is OK</div>
<div>func bar(fn: () -> Void) {}</div>
<div>func bar(fn: (_: Void) -> Void) {} // ERR: Invalid
redecl.</div>
</div>
<div><br></div>
<div>I think the least surprising behavior here would be no error,
rather than two.</div>
<div>The current behavior with one error is very surprising.</div>
</div>
<div><br></div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Mon, Jun 12, 2017 at 10:09 PM, Xiaodi
Wu via swift-evolution <span dir="ltr"><<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr"><span class="">On Mon, Jun 12, 2017 at 3:04 PM,
Jérémie Girault <span dir="ltr"><<a href="mailto:jeremie.girault@gmail.com" target="_blank">jeremie.girault@gmail.com</a>></span>
wrote:<br></span>
<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">
<div id="m_4485791670783688197m_1903000068028871225bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin:0px;line-height:auto">
<span class="">Exactly, that means that your implementation of the
tuple splatting operator is out of the type system.</span></div>
<div id="m_4485791670783688197m_1903000068028871225bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin:0px;line-height:auto">
<span class="">Can you expose it’s signature ?</span></div>
<div id="m_4485791670783688197m_1903000068028871225bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin:0px;line-height:auto">
<span class=""><br></span></div>
<div id="m_4485791670783688197m_1903000068028871225bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin:0px;line-height:auto">
<span class="">If you want the operator to be “compiler-magic” it’s
possible. </span></div>
</div>
</blockquote>
<div><span class=""><br></span></div>
<div>Yes, it requires compiler support.</div>
<div>
<div class="h5">
<div> </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 id="m_4485791670783688197m_1903000068028871225bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin:0px;line-height:auto">
This proposal is an alternate solution.</div>
<div id="m_4485791670783688197m_1903000068028871225bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin:0px;line-height:auto">
<br></div>
<div id="m_4485791670783688197m_1903000068028871225bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin:0px;line-height:auto">
My point is that updating Void according to this proposal
would </div>
<div id="m_4485791670783688197m_1903000068028871225bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin:0px;line-height:auto">
- preserve the type system in a better way</div>
<div id="m_4485791670783688197m_1903000068028871225bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin:0px;line-height:auto">
- have better source compatibility (in time for swift 4
release, were we probably won’t see tuple splatting)</div>
<div id="m_4485791670783688197m_1903000068028871225bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin:0px;line-height:auto">
- also keep the elegant original syntax of swift instead of
stacking parenthesis</div>
<div id="m_4485791670783688197m_1903000068028871225bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin:0px;line-height:auto">
<br></div>
<div id="m_4485791670783688197m_1903000068028871225bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin:0px;line-height:auto">
The impact for code writers would be minimized on time for swift 4
release</div>
<div id="m_4485791670783688197m_1903000068028871225bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin:0px;line-height:auto">
<br></div>
<div id="m_4485791670783688197m_1903000068028871225bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin:0px;line-height:auto">
As for return values: this proposition does not intend to change
the how return value of Void functions works.</div>
<span><br></span>
<div id="m_4485791670783688197m_1903000068028871225bloop_sign_1497297412491527168" class="m_4485791670783688197m_1903000068028871225bloop_sign">
<div style="font-family:helvetica,arial;font-size:13px">
<span>—</span></div>
<div><span><font face="Helvetica" size="1">very short reply
expected - <a href="http://vsre.info" target="_blank">vsre.info</a></font></span></div>
<div style="font-family:helvetica,arial;font-size:13px">
<span>Jérémie Girault<br></span></div>
</div>
<span><br></span>
<div>
<div class="m_4485791670783688197h5">
<p class="m_4485791670783688197m_1903000068028871225airmail_on">On
12 juin 2017 at 21:45:08, Xiaodi Wu (<a href="mailto:xiaodi.wu@gmail.com" target="_blank">xiaodi.wu@gmail.com</a>) wrote:</p>
<div>
<blockquote type="cite" class="m_4485791670783688197m_1903000068028871225clean_bq" 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">
<div>
<div>
<div dir="ltr"><span>On Mon, Jun 12, 2017 at 2:32 PM, Jérémie
Girault<span class="m_4485791670783688197m_1903000068028871225Apple-converted-space"> </span><span dir="ltr"><<a href="mailto:jeremie.girault@gmail.com" target="_blank">jeremie.girault@gmail<wbr>.com</a>></span><span class="m_4485791670783688197m_1903000068028871225Apple-converted-space"> </span>wrote:<br>
</span>
<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="word-wrap:break-word">
<div id="m_4485791670783688197m_1903000068028871225m_-3005406717236171156bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgb(0,0,0);margin:0px">
@xiaodi </div>
<div id="m_4485791670783688197m_1903000068028871225m_-3005406717236171156bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgb(0,0,0);margin:0px">
I disagree on many points, for example what is the type of x when
we type `let x = *Void` ?</div>
</div>
</blockquote>
<div><br></div>
<div>That would not be a legal statement. Exploding a tuple is an
operation that only makes sense inside an argument list. Likewise
`let x = &Void` will not compile.</div>
<div> </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="word-wrap:break-word">
<div id="m_4485791670783688197m_1903000068028871225m_-3005406717236171156bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgb(0,0,0);margin:0px">
This is the essence of the problem and this proposition wants to
solve this.</div>
<div id="m_4485791670783688197m_1903000068028871225m_-3005406717236171156bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgb(0,0,0);margin:0px">
<br></div>
<div id="m_4485791670783688197m_1903000068028871225m_-3005406717236171156bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgb(0,0,0);margin:0px">
The regression is due to both reason combined : typealias Void = ()
AND SE-0110</div>
<div id="m_4485791670783688197m_1903000068028871225m_-3005406717236171156bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgb(0,0,0);margin:0px">
<br></div>
<div id="m_4485791670783688197m_1903000068028871225m_-3005406717236171156bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgb(0,0,0);margin:0px">
My proposition is to change the meaning of Void from () to
“something else” that is type-compatible with SE-0110 (and
splatting in the future).</div>
</div>
</blockquote>
<div><br></div>
<div>I'm not sure I understand your motivation. Void is just a
typealias. If tomorrow Void meant something else, all functions
must still return (), and there is still no implicit tuple
splatting.</div>
</div>
</div>
</div>
</div>
</div>
</blockquote>
</div>
<p><br></p>
<div>
<blockquote type="cite" class="m_4485791670783688197m_1903000068028871225clean_bq" 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">
<div>
<div>
<div dir="ltr">
<div class="gmail_extra">
<div class="gmail_quote">
<div><span><br class="m_4485791670783688197m_1903000068028871225Apple-interchange-newline">
</span></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="word-wrap:break-word">
<div id="m_4485791670783688197m_1903000068028871225m_-3005406717236171156bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgb(0,0,0);margin:0px">
</div>
<div id="m_4485791670783688197m_1903000068028871225m_-3005406717236171156bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgb(0,0,0);margin:0px">
<span>If you want an example of the changes needed to migrate to
swift4, just look at the 42 files of handling parenthesis PR of
RxSwift needed for swift4 upgrade : <a href="https://github.com/ReactiveX/RxSwift/pull/1282/files" target="_blank">https://github.com/ReactiveX<wbr>/RxSwift/pull/1282/files</a></span></div>
</div>
</blockquote>
<div><span><br></span></div>
<div><span>Indeed, that's the result of SE-0110; these parentheses
are needed because there is no implicit tuple splatting. They would
be required even if `Void` did not exist in the language at
all.</span></div>
<div><span> </span></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="word-wrap:break-word"><span><span><br></span></span>
<div id="m_4485791670783688197m_1903000068028871225m_-3005406717236171156bloop_sign_1497295426021404928" class="m_4485791670783688197m_1903000068028871225m_-3005406717236171156bloop_sign">
<div style="font-family:helvetica,arial;font-size:13px">
<span>—</span></div>
<div><span><font face="Helvetica" size="1">very short reply
expected -<span class="m_4485791670783688197m_1903000068028871225Apple-converted-space"> </span><a href="http://vsre.info" target="_blank">vsre.info</a></font></span></div>
<div style="font-family:helvetica,arial;font-size:13px">
<span>Jérémie Girault<br></span></div>
</div>
<span><br></span>
<div>
<div class="m_4485791670783688197m_1903000068028871225h5">
<p class="m_4485791670783688197m_1903000068028871225m_-3005406717236171156airmail_on">
On 12 juin 2017 at 21:18:06, Xiaodi Wu (<a href="mailto:xiaodi.wu@gmail.com" target="_blank">xiaodi.wu@gmail.com</a>) wrote:</p>
<blockquote type="cite" class="m_4485791670783688197m_1903000068028871225m_-3005406717236171156clean_bq">
<div>
<div>
<div dir="ltr"><span>On Mon, Jun 12, 2017 at 2:05 PM, David
Hart<span class="m_4485791670783688197m_1903000068028871225Apple-converted-space"> </span><span dir="ltr"><<a href="mailto:david@hartbit.com" target="_blank">david@hartbit.com</a>></span><span class="m_4485791670783688197m_1903000068028871225Apple-converted-space"> </span>wrote<wbr>:<br>
</span>
<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="word-wrap:break-word"><br>
<div>
<blockquote type="cite">
<div><span>On 12 Jun 2017, at 19:25, Xiaodi Wu via swift-evolution
<<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>> wrote:</span></div>
<span><br class="m_4485791670783688197m_1903000068028871225m_-3005406717236171156m_-2753128709184820463Apple-interchange-newline">
</span>
<div>
<div><span>Unfortunately, I think this proposal appears to be
mistaken as to this key premise: Void was never (IIUC) meant to
model the absence of arguments; it is a type with one possible
value.<br>
<br>
If I recall, a number of conversations have been raised about Void
being a typealias of (), and the definitive response has been that
this falls into the ship-has-sailed category of out-of-scope
changes.<br>
<br>
More generally, the recent spate of complaints about regressions to
a particular coding style have to do with loss of implicit tuple
splatting, the cure for which is a proper implementation of tuple
splatting, not poking holes into settled parts of the type
system.</span></div>
</div>
</blockquote>
<div><span><br></span></div>
<div>But you can’t deny that SE-0110 has also caused regressions in
the use of Void as generic argument because Void is modelled as the
empty tuple.</div>
</div>
</div>
</blockquote>
<div><br></div>
<div>I'm not sure I understand this statement. Void is a synonym
for the empty tuple, and that hasn't ever changed, so it can't be
the root cause of any regressions.</div>
<div> </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="word-wrap:break-word">
<div>
<div>And tuple splatting will not fix those regressions.</div>
</div>
</div>
</blockquote>
<div><br></div>
<div>How come? If `*` is the splat operator, then it would be legal
to call a function `foo` that takes no arguments with `foo(*Void)`;
if implicit tuple splatting returns in fully implemented form, then
it would be legal to call it once again with `foo(Void)`.</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="word-wrap:break-word">
<div>
<div>And contrary to what some people might think, this is not an
“edge-case”. Most useful monads modelled with generics have good
reasons to use Void:</div>
<div><br></div>
<div><b>The Result<T> monad:</b><span class="m_4485791670783688197m_1903000068028871225Apple-converted-space"> </span>Result<Void>
represents the result of an operation with no return value</div>
<div><b>The Promise<T> monad:</b><span class="m_4485791670783688197m_1903000068028871225Apple-converted-space"> </span>Promise<Void>
represents the result of an asynchronous operation with no return
value</div>
<div><b>The Observable<T> monad (in functional reactive
programming):</b><span class="m_4485791670783688197m_1903000068028871225Apple-converted-space"> </span>Observable<Void>
represents a stream of events with no values</div>
<div><br></div>
<div>I use all three monads in my code and I’ve had to modify a lot
of code when migrating to Swift 4 beta1 because of Void.</div>
</div>
</div>
</blockquote>
<div><br></div>
<div>Can you give examples of the modifications needed during
migration? From here, I can only see that the reason any code needs
modification is the complete removal of implicit tuple splatting.
Nothing has changed about Void being a synonym for the empty tuple;
even if you rename Void, functions will still return () by some
other name, and unless there is tuple splatting in some form, the
migration you performed is inevitable.</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="word-wrap:break-word">
<div>
<blockquote type="cite">
<div>
<div>
<div class="gmail_quote">
<div><span>On Mon, Jun 12, 2017 at 12:15 John McCall via
swift-evolution <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>
wrote:<br></span></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="word-wrap:break-word"><span><br></span>
<div>
<blockquote type="cite">
<div><span>On Jun 12, 2017, at 4:48 AM, Jérémie Girault via
swift-evolution <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>>
wrote:</span></div>
<span><br class="m_4485791670783688197m_1903000068028871225m_-3005406717236171156m_-2753128709184820463m_7884169765734884326m_-2000047954192297274Apple-interchange-newline">
</span>
<div>
<div id="m_4485791670783688197m_1903000068028871225m_-3005406717236171156m_-2753128709184820463m_7884169765734884326m_-2000047954192297274bloop_customfont" 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;margin:0px">
<span>Hi here,</span></div>
<div id="m_4485791670783688197m_1903000068028871225m_-3005406717236171156m_-2753128709184820463m_7884169765734884326m_-2000047954192297274bloop_customfont" 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;margin:0px">
<span><br></span></div>
<div id="m_4485791670783688197m_1903000068028871225m_-3005406717236171156m_-2753128709184820463m_7884169765734884326m_-2000047954192297274bloop_customfont" 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;margin:0px">
<span>As I tested swift4 in xcode9b1 I noticed a lot of regressions
about tuples usage.</span></div>
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<span><br></span></div>
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<span>After documenting myself about the changes which happened, I
thought that they could be improved. Instead of fighting these
propositions (which make sense), I wanted create a few proposal
which would improve these recent changes with a few simple
rules.</span></div>
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<span><br></span></div>
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<span>My propositions are based on the recent decisions and in the
continuation of SE-0110. The first one is about Void.</span></div>
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<span>Void is historically defined as the type of the empty tuple.
The reason of this is that arguments were initially considered as
tuple.</span></div>
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<div><span>The dominant consideration here was always return types,
not parameters. I'm not sure there was ever much point in
writing Void in a parameter list, but whatever reasons there were
surely vanished with SE-0066.</span></div>
<div><span><br></span></div>
<div><span>Note that 'void' in C was originally exclusively a
return type. ANSI gave it a new purpose it with void*, but
the meaning is totally unrelated.</span></div>
</div>
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<div><span><br></span></div>
<div><span>John.</span></div>
</div>
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