<html><head><style>body{font-family:Helvetica,Arial;font-size:13px}</style></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div id="bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px; color: rgba(0,0,0,1.0); margin: 0px; line-height: auto;">Oh, it could be so, I’m just not aware of it. I’ve tried Swift version 2.2-dev (LLVM 46be9ff861, Clang 4deb154edc, Swift 778f82939c) with</div><div id="bloop_customfont" style="margin: 0px;"><div id="bloop_customfont" style="margin: 0px;"><br></div><div id="bloop_customfont" style="margin: 0px;">extension Array where Element == Double { </div><div id="bloop_customfont" style="margin: 0px;"> func foo() -> String { </div><div id="bloop_customfont" style="margin: 0px;"> return "hello doubles!" </div><div id="bloop_customfont" style="margin: 0px;"> } </div><div id="bloop_customfont" style="margin: 0px;">}</div><div id="bloop_customfont" style="margin: 0px;"><br></div><div id="bloop_customfont" style="margin: 0px;">and got</div><div id="bloop_customfont" style="margin: 0px;"><br></div><div id="bloop_customfont" style="margin: 0px;">repl.swift:1:31: error: same-type requirement makes generic parameter 'Element' non-generic</div><div id="bloop_customfont" style="margin: 0px;">extension Array where Element == Double {</div><div id="bloop_customfont" style="margin: 0px;"> ^</div><div id="bloop_customfont" style="margin: 0px;"><br></div><div id="bloop_customfont" style="margin: 0px;">Could you please point to docs / example / reference?</div><div id="bloop_customfont" style="margin: 0px;"><br></div><div id="bloop_customfont" style="margin: 0px;">All the best,</div><div id="bloop_customfont" style="margin: 0px;">Krzysztof</div></div> <br> <div id="bloop_sign_1449492596071899904" class="bloop_sign"></div> <br><p class="airmail_on">On 7 December 2015 at 13:34:51, Davide De Franceschi via swift-evolution (<a href="mailto:swift-evolution@swift.org">swift-evolution@swift.org</a>) wrote:</p> <blockquote type="cite" class="clean_bq"><span><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div></div><div>
<title></title>
I thought constraining an extension to a single type (#1) was
already in 2.2?
<div class="">I've seen it in a SPM example and also someone
confirmed to me that it compiled</div>
<div class=""><br class=""></div>
<div class="">It went like</div>
<div class="">extension Array where Element == Double { // add
stuff }</div>
<div class=""><br class="">
<div>
<blockquote type="cite" class="">
<div class="">On 7 Dec 2015, at 12:14, Krzysztof Siejkowski via
swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:</div>
<br class="Apple-interchange-newline">
<div class="">
<div id="bloop_customfont" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; margin: 0px;" class="">Concerning extension constraining, it’s already doable
with:</div>
<div id="bloop_customfont" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; margin: 0px;" class=""><br class=""></div>
<div id="bloop_customfont" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; margin: 0px;" class="">```</div>
<div id="bloop_customfont" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; margin: 0px;" class="">
<div id="bloop_customfont" style="margin: 0px;" class="">protocol
DoubleProtocol {}</div>
<div id="bloop_customfont" style="margin: 0px;" class=""><br class=""></div>
<div id="bloop_customfont" style="margin: 0px;" class="">extension
Double : DoubleProtocol {}</div>
<div id="bloop_customfont" style="margin: 0px;" class=""><br class=""></div>
<div id="bloop_customfont" style="margin: 0px;" class="">extension
Array where Element : DoubleProtocol {</div>
<div id="bloop_customfont" style="margin: 0px;" class="">
func onlyForDoubles() -> String {</div>
<div id="bloop_customfont" style="margin: 0px;" class="">
return "hello doubles!"</div>
<div id="bloop_customfont" style="margin: 0px;" class="">
}</div>
<div id="bloop_customfont" style="margin: 0px;" class="">}</div>
<div id="bloop_customfont" style="margin: 0px;" class=""><br class=""></div>
<div id="bloop_customfont" style="margin: 0px;" class="">
[1.2].onlyForDoubles() // „hello doubles!”</div>
<div id="bloop_customfont" style="margin: 0px;" class="">
["a"].onlyForDoubles() // error: type of expression is ambiguous
without more context</div>
<div id="bloop_customfont" style="margin: 0px;" class="">```</div>
<div id="bloop_customfont" style="margin: 0px;" class=""><br class=""></div>
<div id="bloop_customfont" style="margin: 0px;" class="">However, I
personally like the idea of making a syntactic sugar for that
case.</div>
<div id="bloop_customfont" style="margin: 0px;" class=""><br class=""></div>
<div id="bloop_customfont" style="margin: 0px;" class="">All the
best,</div>
<div id="bloop_customfont" style="margin: 0px;" class="">
Krzysztof</div>
</div>
<br style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<div id="bloop_sign_1449489930156427776" class="bloop_sign" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">
</div>
<br style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<p class="airmail_on" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">
On 7 December 2015 at 13:01:11, Krzysztof Siejkowski (<a href="mailto:krzysztof@siejkowski.net" class="">krzysztof@siejkowski.net</a>) wrote:</p>
<blockquote type="cite" class="clean_bq" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">
<div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">
<div class=""></div>
<div class="">
<div id="bloop_customfont" style="font-family: Helvetica, Arial; font-size: 13px; margin: 0px;" class=""><span class="">Concerning generic typealiases, the topic
is already being discussed in „Generic `typealias`s”
thread: <a href="https://lists.swift.org/pipermail/swift-evolution/2015-December/000132.html" class="">https://lists.swift.org/pipermail/swift-evolution/2015-December/000132.html</a>.
The core Swift team approves:</span></div>
<div id="bloop_sign_1449489099373719808" class="bloop_sign">
<div id="bloop_customfont" style="margin: 0px;" class="">
<span class=""><br class=""></span></div>
<div id="bloop_customfont" style="margin: 0px;" class="">
<span class="">> <span style="white-space: pre-wrap;" class="">Yes, this is definitely something that I (at least) would
like to see. Patches welcome :-)</span></span></div>
<div id="bloop_customfont" style="margin: 0px;" class="">> Chris
(Lattner)</div>
<div id="bloop_customfont" style="margin: 0px;" class=""><br class=""></div>
<div id="bloop_customfont" style="margin: 0px;" class="">All the
best,</div>
<div class="">Krzysztof</div>
<div class=""><br class=""></div>
</div>
<p class="airmail_on">On 7 December 2015 at 12:41:05, Tuur Anton
via swift-evolution (<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>) wrote:</p>
<blockquote type="cite" class="clean_bq">
<div class="">
<div class="">
<div class=""><span class="">Can you please add these features in
Swift 3?</span></div>
<div class=""><span class=""><br class=""></span></div>
<div class=""><span class="">1. The ability to do
this:</span></div>
<div class=""><span class="">extension Array<Double>
{</span></div>
<div class=""><span class=""> //extend arrays of
doubles</span></div>
<div class=""><span class="">}</span></div>
<div class=""><span class=""><br class=""></span></div>
<div class=""><span class="">2. Generic typealiases:</span></div>
<div class=""><span class="">struct Foo<T,V> {</span></div>
<div class=""><span class=""> let t: T</span></div>
<div class=""><span class=""> let v: V</span></div>
<div class=""><span class="">}</span></div>
<div class=""><span class="">typealias IntFoo<V> =
Foo<Int,V> //Error in Swift 2.1</span></div>
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