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.error { color:#AA0000; }</style></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div class="bloop_markdown"><p>I believe generic protocols could be used as a shortcut for protocols with associated types.</p>
<pre><code class="swift">// Protocol with associated type
protocol Foo {
associatedtype F
func foo(_ f: F)
}
// Existential
typealias IntFoo = Any<Foo> where F == Int
struct Test : IntFoo {} // error
struct Test : Foo { func foo(_: Int) {…} }
let intFoo: IntFoo = Test() // fine
// SE-0142
protocol IntFooProtocol : Foo where F == Int {}
// Generic protocols
// Autogenerated with all associated types present in the parameter list
protocol GenericFoo<F> : Foo { … }
</code></pre>
<p>Instead of creating new protocol for a different subset of types constrained by the where clause, this approach could come really handy. </p>
<p>Does it affect stdlib and/or ABI somehow? When SE–0142 is implemented to improve the stdlib, wouldn’t that mean that more types like <code>IntFooProtocol</code> from above will spawn? </p>
<p></p></div><div class="bloop_original_html"><style>body{font-family:Helvetica,Arial;font-size:13px}</style><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_1480770382034871040" class="bloop_sign"><div style="font-family:helvetica,arial;font-size:13px">-- <br>Adrian Zubarev<br>Sent with Airmail</div></div> <br><p class="airmail_on">Am 3. Dezember 2016 um 13:47:13, Anders Ha (<a href="mailto:hello@andersio.co">hello@andersio.co</a>) schrieb:</p> <blockquote type="cite" class="clean_bq"><span><div dir="auto"><div></div><div>
<title></title>
<div>This is called generalized existentials. It is included in the
Generic Manifesto, has been discussed quite a few times with long
email chains before, and spawned the change to the
`protocol<>` syntax as kinda a precursor. It would be
surprised if Swift 4 Phase 2 doesn't have it given its
popularity.</div>
<div><br></div>
<div>Regards</div>
<div>Anders</div>
<div><br>
On 2 Dec 2016, at 20:13, Charles Srstka via swift-evolution
<<a href="mailto:swift-evolution@swift.org">swift-evolution@swift.org</a>>
wrote:<br>
<br></div>
<blockquote type="cite">
<div>
<blockquote type="cite" class="">On Dec 2, 2016, at 12:34 PM,
Adrian Zubarev via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:<br class=""></blockquote>
<div>
<blockquote type="cite" class=""><br class="Apple-interchange-newline">
<div class="">
<p style="margin: 15px 0px; -webkit-margin-before: 0px; font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: 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="">I just overlooked that the subsection about generic
protocols was inside the<span class="Apple-converted-space"> </span><strong style="-webkit-margin-before: 0px;" class="">Unlikely</strong><span class="Apple-converted-space"> </span>section.</p>
<p style="margin: 15px 0px; font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: 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="">The problem is that I need a way to refer to a function
with a specific name. Plus the connection type has to have a
specific API, like having a DispatchQueue and know the router
object if there is any (sounds like a protocol right?!). The
function reference should also keep the connection object alive
with a strong reference.<span class="Apple-converted-space"> </span></p>
<p style="margin: 15px 0px; font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: 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=""><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; -webkit-margin-before: 0px;" class="">associatedtype</code><span class="Apple-converted-space"> </span>does not solve that problem
for me.</p>
<p style="margin: 15px 0px; font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: 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="">I clearly see that generic protocols overlap
with<span class="Apple-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; -webkit-margin-before: 0px;" class="">associatedtype</code><span class="Apple-converted-space"> </span>but couldn’t we find a
compromise here? For instance like Chris Lattner introduced generic
type aliases without the ability of constants.</p>
</div>
</blockquote>
</div>
<div class="">Why don’t we just use angle brackets to specify
associated types? Protocols aren’t using them for anything anyway.
Then you could:</div>
<div class=""><br class=""></div>
<div class="">if let someSequence as? Sequence<Iterator.Element
== Int> { // do something }</div>
<div class=""><br class=""></div>
<div class="">which would form a nice parallel to the syntax for
casting things to generic types.</div>
<div class=""><br class=""></div>
<div class="">Charles</div>
<div class=""><br class=""></div>
</div>
</blockquote>
<blockquote type="cite">
<div>
<span>_______________________________________________</span><br>
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</div>
</blockquote>
</div></div></span></blockquote></div><div class="bloop_markdown"><p></p></div></body></html>