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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>Hmmmm, currently I’m inserting some changes and tweaks into your last gist update.</p>
<blockquote>
<p>Metatypes are still in the language; it turned out that they <em>must</em> remain in the language</p>
</blockquote>
<p><code>Type<T></code> wraps around metatypes and will provide better maintenance if ever needed, because metatype instantiation will be sealed to <code>Type<T>.metatype</code> or <code>typeInstance.metatype</code>. </p>
<blockquote>
<p>The new primary <code>Type<T></code> struct duplicates semantics and interface of metatypes.</p>
</blockquote>
<p>True, but properties of a <code>Type<T></code> instance work with a ‘dynamic’ metatype, which can be up- and downcased. However static properties are used for quick access and do only with the fixed metatype for <code>T</code>.</p>
<blockquote>
<p>But it cannot get extensive native support, so it uses <code>init?(casting:)</code> instead of <code>as</code> cast, <code>is(_:)</code> method instead of <code>is</code>, etc.</p>
</blockquote>
<p>I believe this is not a huge problem. I’m sure dynamic casts can be teched to work with with <code>Type<T></code> instances. This can be purely additional and added after Swift 3.</p>
<pre><code class="swift">class A {}
class B: A {}
// In Swift 3
let typeB: Type<B> = B.self
let typeA: Type<A>? = Type<A>(casting: typeB)
let anotherTypeA: Type<A> = Type<A>(casting: typeB)!
// Post Swift 3 - Easy migration and removing `init?(casting:)`
let typeA: Type<A>? = typeB as? Type<A>
let anotherTypeA: Type<A> = typeB as! Type<A>
</code></pre>
<p>Same for for <code>is</code>:</p>
<pre><code class="swift">let typeB: Type<B> = B.self
typeB.`is`(A.self) // true
// Post Swift 3 - Easy migration and removing `func `is`(_:) -> Bool`
// Here the `is` cast extract `A` from `Type<A>` and checks the
// metatype inside of `typeB` if it's compatible with `A`
typeB is Type<A> // true
</code></pre>
<p>The <code>as</code> dynamic cast needs additional teaching post Swift 3 without any regrets.
<code>Type<T></code> would be a special case for dynamic casts.</p>
<blockquote>
<p><code>Type<T></code> does not add new possibilities right now, although the proposal promises to add reflection to <code>Type<T></code> in the future.</p>
</blockquote>
<p>This is my personal opinion, but we’d move SE–0101 into a better place tied side by side to the (dynamic) metatype. <code>MemoryLayout</code> doesn’t provide an instance of itself, it’s purely static.</p>
<p>An instance of <code>Type<T></code> can be casted and we still can get nicely all the needed information and do not need to extract the dynamic metatype.</p>
<pre><code class="swift">let typeB: Type<B> = B.self
let typeA: Type<A>? = Type<A>(casting: typeB)
let anotherTypeA: Type<A> = Type<A>(casting: typeB)!
typeB.size
typeA?.size
anotherTypeA.size
</code></pre>
<blockquote>
<p><code>Mirror</code> already does reflection. It wraps <code>Any.Type</code> statically, which is a simpler and more suitable model for reflection.</p>
</blockquote>
<p>I can’t argue on that one. The only thing that I know and have a strong feeling about is that <code>Any.Type</code> is broken. There should be <code>AnyMetatype</code> and current <code>Any.Type</code> should be the metatype for <code>Any</code> returned from the current <code>Any.self</code>. The bug is mentioned in our proposal.</p>
<p>We should move reflection to <strong>possible</strong> future direction.</p>
<blockquote>
<p>Rename metatypes <code>T.Type</code> to <code>Type<T></code></p>
</blockquote>
<p>I don’t like <code>.Type</code> the way it is right now. <code>T.Metatype</code> makes more sense, which would implies (MHO) it should be called <code>Metatype<T></code>. This is coved in our proposal.</p>
<blockquote>
<p>Rename <code>T.self</code> to <code>T</code></p>
</blockquote>
<p>It’s not about renaming here. SE–0090 aims to drop <code>.self</code> completely. Okay we could go the same way like I already mentioned in some previous examples:</p>
<pre><code class="swift">// Only renaming `T.Type` into `Metatype<T>`
let const1: Metatype<T> = T
let const2: T = T()
let const3: T = T.init()
let const4: SomeOtherType = T.staticMember
// My vision
let const1: Type<T> = T
let const2: T = T()
let const3: T = T.init()
let const4: SomeOtherType = T.staticMember
</code></pre>
<p>I asked the community if’s possible to make current <code>T.Type</code> conform to <code>Hashable</code> protocol. The response was positive, because this would be really handy. </p>
<p>Such a change would need more compiler magic or an internal protocol which I believe isn’t the best way to solve this. There I come up with the idea wrapping the metatype into a type called <code>Type<T></code> and make the <em>public</em> <code>T.self</code> notation construct an instance of <code>Type<T></code> instead.</p>
<blockquote>
<p>Allow <code>Type<Type<T>></code></p>
</blockquote>
<p>Already possible with our current <code>Type<T></code>.</p>
<blockquote>
<p><strong>Extend <code>Mirror</code></strong> for Swift 4 </p>
</blockquote>
<p>Maybe, but I would still tackle the proposal for <code>Type<T></code>. Maybe we’ll find a solution which will suit everyone.</p>
<p>PS:</p>
<ul>
<li>I’m updating your last gist and preparing two refactored up (possible) implementation.</li>
<li>I’ll need a few hours, because I’m not that fast. :)</li>
<li>Stay patient.</li>
</ul>
<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_1468660071891723008" class="bloop_sign"><div style="font-family:helvetica,arial;font-size:13px">-- <br>Adrian Zubarev<br>Sent with Airmail</div></div></div><div class="bloop_markdown"><p></p></div></body></html>