<div dir="ltr"><div class="markdown-here-wrapper" style=""><p style="margin:0px 0px 1.2em!important">I have to agree with Tino Heth, our aim is to add something basic at first. Although we’d better make sure that we will be able to add other wanted features in the future.</p>
<p style="margin:0px 0px 1.2em!important">How about this plan?</p>
<ol style="margin:1.2em 0px;padding-left:2em">
<li style="margin:0.5em 0px">Generic protocols without associated types</li>
<li style="margin:0.5em 0px">Basic conflict resolution using “dot” syntax</li>
<li style="margin:0.5em 0px">Generic protocols with associated types (depends on (2))</li>
<li style="margin:0.5em 0px">Specialization of non-generic protocols with associated types (+work on existential notation)</li>
</ol>
<p style="margin:0px 0px 1.2em!important">Some inline reply follows.</p>
<p style="margin:0px 0px 1.2em!important"></p><div class="markdown-here-exclude"><p></p><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="word-wrap:break-word"><div class="gmail-m_6932992864106346999gmail-m_7779821207004609716bloop_markdown">
<p>While trying to find the talk about overlapping protocol members from different protocols I spotted your proposal: <a href="https://github.com/Anton3/swift-evolution/blob/generic-protocols/proposals/NNNN-generic-protocols.md" target="_blank">https://github.com/Anton3/swif<wbr>t-evolution/blob/generic-proto<wbr>cols/proposals/NNNN-generic-<wbr>protocols.md</a></p></div></div></blockquote><p></p></div><p style="margin:0px 0px 1.2em!important"></p>
<p style="margin:0px 0px 1.2em!important">This is quite an old listing. Thanks for reminding!</p>
<p style="margin:0px 0px 1.2em!important"></p><div class="markdown-here-exclude"><p></p><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="word-wrap:break-word"><div class="gmail-m_6932992864106346999gmail-m_7779821207004609716bloop_markdown">
<p>Here is the evolution-thread: <a href="https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20160919/027122.html" target="_blank">https://lists.swift.org/piperm<wbr>ail/swift-evolution/Week-of-<wbr>Mon–20160919/027122.html</a></p>
<p>The suggestion there was to prefix everything with the corresponding protocol when there is a collision.</p>
<pre><code class="gmail-m_6932992864106346999gmail-m_7779821207004609716swift">struct Test : Foo<Int>, Foo<String> {
init(_ value: Foo<Int>.Value) { … } // or better: init(_ value: Int)
init(_ value: Foo<String>.Value) { … } // init(_ value: String)
// assume both had the function `foo()`
func Foo<Int>.foo() { … }
func Foo<String>.foo() { … }
}</code></pre></div></div></blockquote><p></p></div><p style="margin:0px 0px 1.2em!important"></p>
<p style="margin:0px 0px 1.2em!important">That’s a working solution. It doesn’t scale very much, if we try to apply it to protocol inheritance (conformance) hierarchies, but we shouldn’t care for now.</p>
<p style="margin:0px 0px 1.2em!important"></p><div class="markdown-here-exclude"><p></p><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="word-wrap:break-word"><div class="gmail-m_6932992864106346999gmail-m_7779821207004609716bloop_markdown"><pre>Is there really a need for true generic protocols? I’m still fascinated by the idea how a generic and constrained <code>typealias</code><span style="font-family:arial,sans-serif"> could create this new ‘pseudo’ generic protocol.</span></pre></div></div></blockquote><p></p></div><p style="margin:0px 0px 1.2em!important"></p>
<p style="margin:0px 0px 1.2em!important">I agree that ideally, existing protocols should be intact. If so, then we should consider “the original protocol with associated types” and “explicitly specialized protocol” as two different protocols:</p>
<pre style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;font-size:1em;line-height:1.2em;margin:1.2em 0px"><code class="hljs language-swift" style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);background-color:rgb(248,248,248);border-radius:3px;display:inline;white-space:pre;overflow:auto;border-radius:3px;border:1px solid rgb(204,204,204);padding:0.5em 0.7em;display:block!important;display:block;overflow-x:auto;padding:0.5em;color:rgb(51,51,51);background:rgb(248,248,248)"><span class="hljs-class"><span class="hljs-keyword" style="color:rgb(51,51,51);font-weight:bold">protocol</span> <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold;color:rgb(68,85,136);font-weight:bold">Constructible</span> </span>{
associatedtype <span class="hljs-type" style="color:rgb(68,85,136);font-weight:bold">Value</span>
<span class="hljs-func"><span class="hljs-keyword" style="color:rgb(51,51,51);font-weight:bold">func</span> <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">foo</span><span class="hljs-params">()</span>
}
<span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">struct</span> <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">MyStruct</span> : <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">Constructible</span> </span>{
<span class="hljs-keyword" style="color:rgb(51,51,51);font-weight:bold">typealias</span> <span class="hljs-type" style="color:rgb(68,85,136);font-weight:bold">Value</span> = <span class="hljs-type" style="color:rgb(68,85,136);font-weight:bold">Int</span>
<span class="hljs-func"><span class="hljs-keyword" style="color:rgb(51,51,51);font-weight:bold">func</span> <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">foo</span><span class="hljs-params">()</span> </span>{ }
}
<span class="hljs-class"><span class="hljs-keyword" style="color:rgb(51,51,51);font-weight:bold">extension</span> <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold;color:rgb(68,85,136);font-weight:bold">MyStruct</span> : <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold;color:rgb(68,85,136);font-weight:bold">Constructible</span><<span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold;color:rgb(68,85,136);font-weight:bold">String</span>> </span>{ <span class="hljs-comment" style="color:rgb(153,153,136);font-style:italic">// or Constructible<Value: String>, or whatever</span>
<span class="hljs-keyword" style="color:rgb(51,51,51);font-weight:bold">typealias</span> <span class="hljs-type" style="color:rgb(68,85,136);font-weight:bold">Constructible</span><<span class="hljs-type" style="color:rgb(68,85,136);font-weight:bold">String</span>>.<span class="hljs-type" style="color:rgb(68,85,136);font-weight:bold">Value</span> = <span class="hljs-type" style="color:rgb(68,85,136);font-weight:bold">String</span>
<span class="hljs-func"><span class="hljs-keyword" style="color:rgb(51,51,51);font-weight:bold">func</span> <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">Constructible</span><span class="hljs-generics"><String></span>.<span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">foo</span><span class="hljs-params">()</span> </span>{ }
}
<span class="hljs-type" style="color:rgb(68,85,136);font-weight:bold">MyStruct</span>.<span class="hljs-type" style="color:rgb(68,85,136);font-weight:bold">Value</span> <span class="hljs-comment" style="color:rgb(153,153,136);font-style:italic">// Int</span>
<span class="hljs-type" style="color:rgb(68,85,136);font-weight:bold">MyStruct</span>.<span class="hljs-type" style="color:rgb(68,85,136);font-weight:bold">Constructible</span><<span class="hljs-type" style="color:rgb(68,85,136);font-weight:bold">String</span>>.<span class="hljs-type" style="color:rgb(68,85,136);font-weight:bold">Value</span> <span class="hljs-comment" style="color:rgb(153,153,136);font-style:italic">// String</span>
<span class="hljs-func"><span class="hljs-keyword" style="color:rgb(51,51,51);font-weight:bold">func</span> <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">bar</span><span class="hljs-generics"><T: Constructible></span><span class="hljs-params">(t: T)</span> // <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">can</span> <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">call</span> <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">with</span> <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">MyStruct</span>
<span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">func</span> <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">bar</span><span class="hljs-generics"><T: Constructible<Int></span>><span class="hljs-params">(t: T)</span> // <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">can</span> <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">NOT</span> <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">call</span> <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">with</span> <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">MyStruct</span>
<span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">func</span> <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">bar</span><span class="hljs-generics"><T: Constructible<String></span>><span class="hljs-params">(t: T)</span> // <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">can</span> <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">call</span> <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">with</span> <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold">MyStruct</span></span>
</code></pre>
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