<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">Exactly, </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 reflexion behind it is: </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">- Let's understand that 0110 and other tuple SE are important for the compiler, we do not want them to rollback</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">- However we have number of regressions for generics / functional programmers</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">- Let’s solve this step by step like a typical problem</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">- Step 0 is adressing this Void tuple of size zero :</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"><span class="Apple-tab-span" style="white-space:pre"> </span>- Zero is in many problems of CS an edge case, so let’s handle this case first</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"><span class="Apple-tab-span" style="white-space:pre"> </span>- The compiler knows what Void is, and its only value (or non-value)</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"><span class="Apple-tab-span" style="white-space:pre"> </span>- It was handled historically by the compiler because of implicit side effects</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"><span class="Apple-tab-span" style="white-space:pre"> </span>- Let’s handle it explicitely with rules in current context</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"><span class="Apple-tab-span" style="white-space:pre"> </span>- one effect of the proposal is source compatibility</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"><span class="Apple-tab-span" style="white-space:pre"> </span>- but the goal is to build atop and strengthen 0110, 0066 and other tuple-related SE</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> <br> <div id="bloop_sign_1497338200319793920" 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 13 juin 2017 at 00:44:52, Xiaodi Wu (<a href="mailto:xiaodi.wu@gmail.com">xiaodi.wu@gmail.com</a>) wrote:</p> <blockquote type="cite" class="clean_bq"><span><div><div></div><div>
<title></title>
<div dir="ltr">On Mon, Jun 12, 2017 at 5:38 PM, Xiaodi Wu
<span dir="ltr"><<a href="mailto:xiaodi.wu@gmail.com" target="_blank">xiaodi.wu@gmail.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 dir="ltr">
<div>
<div class="h5">On Mon, Jun 12, 2017 at 5:25 PM, Jérémie Girault
<span dir="ltr"><<a href="mailto:jeremie.girault@gmail.com" target="_blank">jeremie.girault@gmail.com</a>></span>
wrote:<br></div>
</div>
<div class="gmail_extra">
<div class="gmail_quote">
<div>
<div class="h5">
<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_5601571053956628674m_2043415068894562036m_-5564007550782516409bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin:0px;line-height:auto">
<span><br></span></div>
<span><br></span>
<div id="m_5601571053956628674m_2043415068894562036m_-5564007550782516409bloop_sign_1497305107136064000" class="m_5601571053956628674m_2043415068894562036m_-5564007550782516409bloop_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>
<p class="m_5601571053956628674m_2043415068894562036m_-5564007550782516409airmail_on">
<span>On 12 juin 2017 at 23:56:37, Xiaodi Wu (<a href="mailto:xiaodi.wu@gmail.com" target="_blank">xiaodi.wu@gmail.com</a>) wrote:</span></p>
<div>
<blockquote type="cite" class="m_5601571053956628674m_2043415068894562036m_-5564007550782516409clean_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 4:47 PM, Jérémie
Girault<span class="m_5601571053956628674m_2043415068894562036m_-5564007550782516409Apple-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_5601571053956628674m_2043415068894562036m_-5564007550782516409Apple-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_5601571053956628674m_2043415068894562036m_-5564007550782516409m_-3578613130368345921bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgb(0,0,0);margin:0px">
- Void as arguments is pretty common when using generics, that’s a
core point of this proposal. An maybe that’s why we misunderstood
ourselves (around 0110 / 0066). This proposal addresses
arguments.</div>
<div id="m_5601571053956628674m_2043415068894562036m_-5564007550782516409m_-3578613130368345921bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgb(0,0,0);margin:0px">
- maybe it should be revised around this ? Simple example
: </div>
<div id="m_5601571053956628674m_2043415068894562036m_-5564007550782516409m_-3578613130368345921bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgb(0,0,0);margin:0px">
<br></div>
<div id="m_5601571053956628674m_2043415068894562036m_-5564007550782516409m_-3578613130368345921bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgb(0,0,0);margin:0px">
`typealias Callback<T> = (T) -> Void` ->
`Callback<Void>` will give `(Void) => Void`. </div>
<div id="m_5601571053956628674m_2043415068894562036m_-5564007550782516409m_-3578613130368345921bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgb(0,0,0);margin:0px">
<br></div>
<div id="m_5601571053956628674m_2043415068894562036m_-5564007550782516409m_-3578613130368345921bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgb(0,0,0);margin:0px">
It was acceptable before swift4 but no more. However nobody cares
about this `Void` argument and actually we know it’s value. So why
let the developer type it ?</div>
</div>
</blockquote>
<div><br></div>
<div>Ah, I see. The purpose of SE-0029...SE-0110 was to make it
possible to distinguish an argument list `(Void)` from an argument
list `()`. This does cause some verbosity where previously users
relied on implicit tuple splatting. Ideally, we would bring back
some syntactic sugar to make this more ergonomic. But, whether or
not the spelling is made more user-friendly, the point here is that
_everybody_ should care about this `Void` argument.</div>
</div>
</div>
</div>
</div>
</div>
</blockquote>
</div>
<p>It is still be typechecked and appropriate errors should be
reported to the user so _nobody_ will ignore it.</p>
<p>But with the proposal the code will be striped out of Void
arguments at compile-time. I think it's a win for the developer on
a lot of grounds. The fact that this proposal integrates with the
type-system is also important.</p>
<p>If you are not comfortable about Void being stripped, we can
also discuss alternatives: someone was suggesting me that it would
be possible to replace :</p>
<p>```</p>
<p>func foo<T, U, V>(t: T, u: U) -> V {</p>
<p> // do something with t and u</p>
<p> // return some V</p>
<p>}</p>
<p>```</p>
<p>with</p>
<p>```</p>
<p>func foo<Void, Int, String>(u: Int) -> String { let t =
()</p>
<p> // do something with t and u</p>
<p> // return some V</p>
<p>}</p>
<p>```</p>
<p>or</p>
<p>```</p>
<p>func foo<Void, Int, String>(t: Void = (), u: Int) ->
String {</p>
<p> // do something with t and u</p>
<p> // return some V</p>
<p>}</p>
<p>```</p>
<p>I don’t know what you would consider more effective or elegant
(at an implementation level) but it’s the same result for the
developper.</p>
</div>
</blockquote>
</div>
</div>
</div>
</div>
</div>
</blockquote>
<div><br></div>
<div>Ah, but I think I catch your drift with the last example. Is
this a more general point that the compiler should treat every
parameter of type Void as having an implied default value of Void?
That would be an interesting idea.</div>
<div><br></div>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">
<div class="gmail_extra">
<div class="gmail_quote">
<div>What is the goal of such changes? Is it to allow you to write
`foo()` instead of `foo(())` for a function `foo` of type `(T)
-> Void`?</div>
<div><br></div>
<div>If so, then I think what you're seeking to do is reverse
SE-0066 (as Vladimir points out), which explicits details how it's
is an intentional change to require such a spelling. I think you're
starting from the premise that this is unintended or undesirable,
when in fact it is deliberate and approved.</div>
<div><br></div>
<div>It is also, unless I'm mistaken, not the issue that was raised
initially with respect to SE-0110, which had to do with the extra
boilerplate of destructuring a tuple inside a closure, something
that was not so obvious before implementation.</div>
<div><span class=""><br></span></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>
<blockquote type="cite" class="m_5601571053956628674m_2043415068894562036m_-5564007550782516409clean_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">
<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_5601571053956628674m_2043415068894562036m_-5564007550782516409m_-3578613130368345921bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgb(0,0,0);margin:0px">
</div>
<div id="m_5601571053956628674m_2043415068894562036m_-5564007550782516409m_-3578613130368345921bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px;color:rgb(0,0,0);margin:0px">
<span class="">My point here is that `Void` should be “striped” by
“reducing” argument list signatures.</span></div>
<span class=""><span><br></span></span>
<div id="m_5601571053956628674m_2043415068894562036m_-5564007550782516409m_-3578613130368345921bloop_sign_1497302247432667904" class="m_5601571053956628674m_2043415068894562036m_-5564007550782516409m_-3578613130368345921bloop_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_5601571053956628674m_2043415068894562036m_-5564007550782516409Apple-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>
<p class="m_5601571053956628674m_2043415068894562036m_-5564007550782516409m_-3578613130368345921airmail_on">
<span>On 12 juin 2017 at 19:15:18, John McCall (<a href="mailto:rjmccall@apple.com" target="_blank">rjmccall@apple.com</a>)
wrote:</span></p>
<div>
<div class="m_5601571053956628674m_2043415068894562036m_-5564007550782516409h5">
<blockquote type="cite" class="m_5601571053956628674m_2043415068894562036m_-5564007550782516409m_-3578613130368345921clean_bq">
<div style="word-wrap:break-word">
<div><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_5601571053956628674m_2043415068894562036m_-5564007550782516409m_-3578613130368345921Apple-interchange-newline">
</span>
<div>
<div id="m_5601571053956628674m_2043415068894562036m_-5564007550782516409m_-3578613130368345921bloop_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_5601571053956628674m_2043415068894562036m_-5564007550782516409m_-3578613130368345921bloop_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_5601571053956628674m_2043415068894562036m_-5564007550782516409m_-3578613130368345921bloop_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_5601571053956628674m_2043415068894562036m_-5564007550782516409m_-3578613130368345921bloop_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_5601571053956628674m_2043415068894562036m_-5564007550782516409m_-3578613130368345921bloop_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_5601571053956628674m_2043415068894562036m_-5564007550782516409m_-3578613130368345921bloop_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_5601571053956628674m_2043415068894562036m_-5564007550782516409m_-3578613130368345921bloop_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_5601571053956628674m_2043415068894562036m_-5564007550782516409m_-3578613130368345921bloop_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><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><span><br></span></div>
<div><span>John.</span></div>
</div>
</div>
</blockquote>
</div>
</div>
</div>
</blockquote>
</div>
<br></div>
</div>
</div>
</div>
</blockquote>
<br class="m_5601571053956628674m_2043415068894562036m_-5564007550782516409Apple-interchange-newline">
</div>
</div>
</blockquote>
</div>
<br></div>
</div>
</blockquote>
</div>
<br></div>
</div>
</div></div></span></blockquote></body></html>