<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">Joshua,</div><div class=""><br class=""></div><div class="">Could you please peek at the latest version here: <a href="https://gist.github.com/erica/29c1a7fb7f49324d572f" class="">https://gist.github.com/erica/29c1a7fb7f49324d572f</a> Also, the [Further Discussion] Naming Attributes thread has subsumed this one.</div><div class=""><br class=""></div><div class="">Thanks, -- Erica</div><div class=""><br class=""></div><br class=""><div><blockquote type="cite" class=""><div class="">On Feb 24, 2016, at 5:26 PM, Joshua Kopin 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 class="markdown"><p dir="auto" class="">+1</p><p dir="auto" class="">Jacob, I think your proposal is on point. Although I know this is probably outside the scope of what Erica would like to propose, I think it's important to point out that the custom attributes you called out arguably are so different semantically from the other attributes that they deserve their own syntactic treatment. Since the following analysis might affect the naming discussion, I'll put this out there now and see how it lands.</p><p dir="auto" class="">It seems to me that there are two broad categories of attributes, each of which wants its own level of syntactic optimization:</p>
<ul class="">
<li class=""><p dir="auto" class="">General Swift Attributes - use should be optimized</p>
<ul class="">
<li class="">Semantic Modifiers
<ul class="">
<li class=""><strong class="">@autoclosure</strong> / <strong class="">@autoclosure(escaping)</strong> - modifies expression semantics at call site</li>
<li class=""><strong class="">@convention(</strong>...<strong class="">)</strong> - modifies declared function's calling convention</li>
<li class=""><strong class="">@testable</strong> - modifies declaration's visibility</li>
<li class=""><strong class="">@noescape</strong> - modifies closure capture semantics, closure declaration syntax, escape analysis</li>
<li class=""><strong class="">@noreturn</strong> - modifies control flow analysis</li>
<li class=""><strong class="">@objc</strong> / <strong class="">@objc(</strong>...<strong class="">)</strong> / <strong class="">@nonobjc</strong> - modifies calling convention, class synthesis</li>
<li class=""><strong class="">@NSCopying</strong> - modifies property storage and semantics</li>
</ul></li>
<li class="">Warning and Error Generation Modifiers
<ul class="">
<li class=""><strong class="">@available(</strong><expression in the availability DSL><strong class="">)</strong></li>
<li class=""><strong class="">@warn_unused_result</strong></li>
<li class=""><strong class="">@warn_unused_result(message=</strong>...<strong class="">)</strong></li>
<li class=""><strong class="">@warn_unused_result(mutable_variant=</strong>...<strong class="">)</strong></li>
</ul></li>
</ul></li>
<li class=""><p dir="auto" class="">Specific Attributes - use should not be optimized</p>
<ul class="">
<li class="">Semantic Modifiers
<ul class="">
<li class=""><strong class="">@UIApplicationMain</strong> / <strong class="">@NSApplicationMain</strong> - specific to UIKit/AppKit</li>
<li class=""><strong class="">@NSManaged</strong> - specific to CoreData</li>
</ul></li>
<li class="">Xcode Semantic Modifiers
<ul class="">
<li class=""><strong class="">@IBAction</strong></li>
<li class=""><strong class="">@IBDesignable</strong></li>
<li class=""><strong class="">@IBInspectable</strong></li>
<li class=""><strong class="">@IBOutlet</strong></li>
</ul></li>
</ul></li>
</ul><p dir="auto" class="">(To be fair, @objc, @nonobjc, and @NSCopying are all tied to the Objective-C runtime and/or Foundation pretty closely and could arguably be considered framework-specific.)</p><p dir="auto" class="">As a first stab, how about something along the lines of the following?</p>
<ul class="">
<li class=""><p dir="auto" class="">General Swift Attributes</p>
<ul class="">
<li class="">Semantic Modifiers
<ul class="">
<li class=""><strong class="">@autoclosure</strong> / <strong class="">@autoclosure(escaping)</strong></li>
<li class=""><strong class="">@convention(</strong>...<strong class="">)</strong></li>
<li class=""><strong class="">@testable</strong></li>
<li class=""><strong class="">@noescape</strong></li>
<li class=""><strong class="">@noreturn</strong></li>
<li class=""><strong class="">@objc</strong> / <strong class="">@objc(</strong>...<strong class="">)</strong> / <strong class="">@nonbjc</strong></li>
<li class=""><strong class="">@copy</strong></li>
</ul></li>
<li class="">Warning and Error Generation Modifiers
<ul class="">
<li class=""><strong class="">@available(</strong><expression in the availability DSL><strong class="">)</strong></li>
<li class=""><strong class="">@warning(</strong><expression in a new warning DSL><strong class="">)</strong>
<ul class="">
<li class=""><strong class="">@warning(unusedResult)</strong></li>
<li class=""><strong class="">@warning(unusedResult, message=</strong>...<strong class="">)</strong></li>
<li class=""><strong class="">@warning(unusedResult, mutableVariant=</strong>...<strong class="">)</strong></li>
</ul></li>
</ul></li>
</ul></li>
<li class=""><p dir="auto" class="">Specific Attributes (syntax subject to bikeshedding)</p>
<ul class="">
<li class=""><strong class="">@modifyingCustomSemanticAttribute(</strong><expression in semantic attribute modifier DSL><strong class="">)</strong>
<ul class="">
<li class=""><strong class="">@modifyingCustomSemanticAttribute(Cocoa, applicationMain)</strong></li>
<li class=""><strong class="">@modifyingCustomSemanticAttribute(CoreData, managed)</strong></li>
<li class=""><strong class="">@modifyingCustomSemanticAttribute(InterfaceBuilder, action)</strong></li>
<li class=""><strong class="">@modifyingCustomSemanticAttribute(InterfaceBuilder, designable)</strong></li>
<li class=""><strong class="">@modifyingCustomSemanticAttribute(InterfaceBuilder, inspectable)</strong></li>
<li class=""><strong class="">@modifyingCustomSemanticAttribute(InterfaceBuilder, outlet)</strong></li>
</ul></li>
</ul></li>
</ul><p dir="auto" class="">On 17 Feb 2016, at 23:29, Jacob Bandes-Storch via swift-evolution wrote:</p>
<blockquote class=""><p dir="auto" class="">Arguably, these are all framework/IDE-specific functionality, a.k.a.<br class="">
"custom attributes", which should have an entirely different syntax.</p><p dir="auto" class="">On Wed, Feb 17, 2016 at 9:43 PM, Erica Sadun via swift-evolution <<br class="">
<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:</p>
<blockquote class=""><p dir="auto" class="">How would you re-design the existing upper camel attributes then?</p><p dir="auto" class="">They are: @UIApplicationMain, @NSManaged, @NSCopying, @NSApplicationMain,<br class="">
@IBAction, @IBDesignable, @IBInspectable, and @IBOutlet</p><p dir="auto" class="">-- E</p>
<blockquote class=""><p dir="auto" class="">On Feb 17, 2016, at 10:29 PM, Brent Royal-Gordon <a href="mailto:brent@architechies.com" class="">brent@architechies.com</a></p>
</blockquote><p dir="auto" class="">wrote:</p>
<blockquote class="">
<blockquote class=""><p dir="auto" class="">@Autoclosure // was @autoclosure<br class="">
@Available // was @available<br class="">
@ObjC // was @objc<br class="">
@NoEscape // was @noescape<br class="">
@NonObjC // was @nonobjc<br class="">
@NoReturn // was @noreturn<br class="">
@Testable // was @testable<br class="">
@WarnUnusedResult // was @warn-unused-result<br class="">
@Convention // was @convention<br class="">
@NoReturn // was @noreturn</p><p dir="auto" class="">In the revised design, the following example for Swift 2.2</p><p dir="auto" class="">@warn_unused_result(mutable_variant="sortInPlace")<br class="">
public func sort() -> [Self.Generator.Element]</p><p dir="auto" class="">becomes</p><p dir="auto" class="">@WarnUnusedResult(mutableVariant: "sortInPlace")<br class="">
public func sort() -> [Self.Generator.Element]</p>
</blockquote><p dir="auto" class="">Wow, I'm surprised by how much I hate this. Currently, all Swift</p>
</blockquote><p dir="auto" class="">keywords are entirely lowercase (ignoring things like <code class="">Type</code>, <code class="">Protocol</code>,<br class="">
and <code class="">dynamicType</code> which come after a dot). I think I've learned to<br class="">
half-ignore things that look like that, but capitalizing suddenly pulls the<br class="">
spotlight onto these keywords. I'm just not a fan.</p>
<blockquote class=""><p dir="auto" class="">I think we're better off renaming or redesigning <code class="">warn_unused_result</code> so</p>
</blockquote><p dir="auto" class="">that it's readable when it's all-lowercase with no underscores. Some ideas:</p>
<blockquote class="">
<pre class=""><code class=""> @onlyreturns func sorted() -> [Self.Generator.Element]
func sorted() -> @important [Self.Generator.Element]
</code></pre><p dir="auto" class="">Alternatively, we could reverse the semantic and make all all non-Void</p>
</blockquote><p dir="auto" class="">functions warn unless they have an attribute saying not to.</p>
<blockquote class="">
<pre class=""><code class=""> @ignoreresult mutating func updateValue(value: Value, forKey key:
</code></pre>
</blockquote><p dir="auto" class="">Key) -> Value?</p>
<blockquote class="">
<pre class=""><code class=""> mutating func updateValue(value: Value, forKey key: Key) ->
</code></pre>
</blockquote><p dir="auto" class="">@ignorable Value?</p>
<blockquote class="">
<pre class=""><code class=""> mutating func updateValue(value: Value, forKey key: Key) ->
</code></pre>
</blockquote><p dir="auto" class="">@convenience Value?</p>
<blockquote class=""><p dir="auto" class="">If we do that, we'll likely still want to be able to annotate</p>
</blockquote><p dir="auto" class="">non-mutating methods with their mutating variants (well, unless we think<br class="">
the compiler can guess based on the API Guidelines.)</p>
<blockquote class="">
<pre class=""><code class=""> @variant(mutating: "sort") func sorted() ->
</code></pre>
</blockquote><p dir="auto" class="">[Self.Generator.Element]</p>
<blockquote class="">
<pre class=""><code class=""> @alternative(mutating: "sort") func sorted() ->
</code></pre>
</blockquote><p dir="auto" class="">[Self.Generator.Element]</p>
<blockquote class=""><p dir="auto" class="">That opens the possibility of using <code class="">@variant(nonmutating:)</code> on mutating</p>
</blockquote><p dir="auto" class="">functions, too.</p>
<blockquote class=""><p dir="auto" class="">--<br class="">
Brent Royal-Gordon<br class="">
Architechies</p>
</blockquote>
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</blockquote>
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