<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"><span class=""><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">Exactly, that means that your implementation of the tuple splatting operator is out of the type system.</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">Can you expose it’s signature ?</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">If you want the operator to be “compiler-magic” it’s possible. </div></div></blockquote><div><br></div></span><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> <div id="m_4485791670783688197m_1903000068028871225bloop_sign_1497297412491527168" class="m_4485791670783688197m_1903000068028871225bloop_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" target="_blank">vsre.info</a></font></div><div style="font-family:helvetica,arial;font-size:13px">Jérémie Girault<br></div></div> <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"><span><div><div></div><div><div dir="ltr">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><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></span></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"><span><div><div><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><div><br class="m_4485791670783688197m_1903000068028871225Apple-interchange-newline"> </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">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></div></div></blockquote><div><br></div><div>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.</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"><span><br></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><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>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><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>My propositions are based on the recent decisions and in the continuation of SE-0110. The first one is about Void.</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>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></div></blockquote><span><br></span></div></div><div style="word-wrap:break-word"><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><div style="word-wrap:break-word"><div><span><br></span></div><div><span>John.</span></div></div><span>______________________________<wbr>_________________<br>swift-evolution mailing list<br><a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailma<wbr>n/listinfo/swift-evolution</a><br></span></blockquote></div></div><span>______________________________<wbr>_________________<br>swift-evolution mailing list<br><a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" target="_blank">https://lists.swift.org/mailma<wbr>n/listinfo/swift-evolution</a><br></span></div></blockquote></div><br></div></blockquote></div><br></div></div></div></div></blockquote></div></div></div></blockquote></div><br></div></div></div></div></span></blockquote><br class="m_4485791670783688197m_1903000068028871225Apple-interchange-newline"></div></div></div></div>
</blockquote></div></div></div><br></div></div>
<br>______________________________<wbr>_________________<br>
swift-evolution mailing list<br>
<a href="mailto:swift-evolution@swift.org">swift-evolution@swift.org</a><br>
<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/<wbr>mailman/listinfo/swift-<wbr>evolution</a><br>
<br></blockquote></div><br></div>