<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div>This has been answered in various forms in the thread. Short answer: yes.</div><div><br>On Feb 2, 2017, at 2:05 AM, Adrian Zubarev <<a href="mailto:adrian.zubarev@devandartist.com">adrian.zubarev@devandartist.com</a>> wrote:<br><br></div><blockquote type="cite"><div><style>
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.error { color:#AA0000; }</style><div class="bloop_markdown"><p>Is that correct that this proposal will add some sort of overloading enum cases by different labels?</p>
<pre><code class="swift">enum Foo {
case foo(a: Int)
case foo(a: Int, b: Int)
}
</code></pre>
<p>Is <code>Foo</code> a valid enum after this proposal?</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_1486029767109051904" 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 19. Januar 2017 um 19:37:50, Daniel Duan via swift-evolution (<a href="mailto:swift-evolution@swift.org">swift-evolution@swift.org</a>) schrieb:</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>
Hi all,
<div class=""><br class=""></div>
<div class="">Here’s a short proposal for fixing an inconsistency
in Swift’s enum. Please share you feedback :)</div>
<div class=""><br class=""></div>
<div class="">(Updating/rendered version: <a href="https://github.com/dduan/swift-evolution/blob/compound-names-for-enum-cases/proposals/NNNN-Compound-Names-For-Enum-Cases.md" class="">https://github.com/dduan/swift-evolution/blob/compound-names-for-enum-cases/proposals/NNNN-Compound-Names-For-Enum-Cases.md</a>)</div>
<div class=""><br class=""></div>
<div class=""><br class=""></div>
<div class="">
<div class="">## Introduction</div>
<div class=""><br class=""></div>
<div class="">Argument labels are part of its function's
declaration name. An enum case</div>
<div class="">declares a function that can be used to construct
enum values. For cases with</div>
<div class="">associated values, their labels should be part of the
constructor name, similar</div>
<div class="">to "normal" function and methods. In Swift 3,
however, this is not true. This</div>
<div class="">proposal aim to change that.</div>
<div class=""><br class=""></div>
<div class="">## Motivation</div>
<div class=""><br class=""></div>
<div class="">After SE-0111, Swift function's fully qualified name
consists of its base name</div>
<div class="">and all argument labels. As a example, one can invoke
a function with its</div>
<div class="">fully name:</div>
<div class=""><br class=""></div>
<div class="">```swift</div>
<div class="">func f(x: Int, y: Int) {}</div>
<div class=""><br class=""></div>
<div class="">f(x: y:)(0, 0) // Okay, this is equivalent to f(x: 0,
y: 0)</div>
<div class="">```</div>
<div class=""><br class=""></div>
<div class="">This, however, is not true when enum cases with
associated value were</div>
<div class="">constructed:</div>
<div class=""><br class=""></div>
<div class="">```swift</div>
<div class="">enum Foo {</div>
<div class=""> case bar(x: Int, y: Int)</div>
<div class="">}</div>
<div class=""><br class=""></div>
<div class="">Foo.bar(x: y:)(0, 0) // Does not compile as of Swift
3</div>
<div class="">```</div>
<div class=""><br class=""></div>
<div class="">Here, the declared name for the case is `foo`; it has
a tuple with two labeled</div>
<div class="">fields as its associated value. `x` and `y` aren't
part of the case name. This</div>
<div class="">inconsistency may surprise some users.</div>
<div class=""><br class=""></div>
<div class="">Using tuple to implement associated value also limits
us from certain layout</div>
<div class="">optimizations as each payload need to be a tuple
first, as opposed to simply be</div>
<div class="">unique to the enum.</div>
<div class=""><br class=""></div>
<div class="">## Proposed solution</div>
<div class=""><br class=""></div>
<div class="">Include labels in enum case's declaration name. In
the last example, `bar`'s</div>
<div class="">full name would become `bar(x:y:)`, `x` and `y` will
no longer be labels in a</div>
<div class="">tuple. The compiler may also stop using tuple to
represent associated values.</div>
<div class=""><br class=""></div>
<div class="">## Detailed design</div>
<div class=""><br class=""></div>
<div class="">When labels are present in enum cases, they are now
part of case's declared name</div>
<div class="">instead of being labels for fields in a tuple. In
details, when constructing an</div>
<div class="">enum value with the case name, label names must
either be supplied in the</div>
<div class="">argument list it self, or as part of the full
name.</div>
<div class=""><br class=""></div>
<div class="">```swift</div>
<div class="">Foo.bar(x: 0, y: 0) // Okay, the Swift 3 way.</div>
<div class="">Foo.bar(x: y:)(0, 0) // Equivalent to the previous
line.</div>
<div class="">Foo.bar(x: y:)(x: 0, y: 0) // This would be an error,
however.</div>
<div class="">```</div>
<div class=""><br class=""></div>
<div class="">Note that since the labels aren't part of a tuple,
they no longer participate in</div>
<div class="">type checking, similar to functions:</div>
<div class=""><br class=""></div>
<div class="">```swift</div>
<div class="">let f = Foo.bar // f has type (Int, Int) ->
Foo</div>
<div class="">f(0, 0) // Okay!</div>
<div class="">f(x: 0, y: 0) // Won't compile.</div>
<div class="">```</div>
<div class=""><br class=""></div>
<div class="">## Source compatibility</div>
<div class=""><br class=""></div>
<div class="">Since type-checking rules on labeled tuple is
stricter than that on function</div>
<div class="">argument labels, existing enum value construction by
case name remain valid.</div>
<div class="">This change is source compatible with Swift 3.</div>
<div class=""><br class=""></div>
<div class="">## Effect on ABI stability and resilience</div>
<div class=""><br class=""></div>
<div class="">This change introduces compound names for enum cases,
which affects their</div>
<div class="">declaration's name mangling.</div>
<div class=""><br class=""></div>
<div class="">The compiler may also choose to change enum payload's
representation from tuple.</div>
<div class="">This may open up more space for improving enum's
memory layout.</div>
<div class=""><br class=""></div>
<div class="">## Alternatives considered</div>
<div class=""><br class=""></div>
<div class="">Keep current behaviors, which means we live with the
inconsistency.</div>
</div>
<div class=""><br class=""></div>
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