[swift-evolution] [Proposal] Set literal and Set type syntax

[David Waite]

Keep in mind Array<T> cannot currently be stored in a Set (it will bridge to NSArray if the contained elements are compatible, which then supports Hashable.)

The non-labelled initializer expects a formed SequenceType.

If you want to use varargs, you can use Set(arrayLiteral:[1], [2], [3]) - so no removal of the array literal convertible conformance needed, it does what you want already

-DW
 
> On Jan 19, 2016, at 6:56 PM, Howard Lovatt via swift-evolution <swift-evolution at swift.org> wrote:
> 
> The horse has probably bolted on this one, but in general array literals can be confusing when used for anything other than an array. A compromise position might be to remove the array literal `init` from `Set` and replace it with a var arg `init`. It would break code, but not that much since `Set` is new and a migration tool could find it easily. This gives:
> 
>     let sI = Set(1) // Set of Int
>     let sAI = Set([1]) // Set of array of Int
> 
> On Wednesday, 20 January 2016, Greg Parker <gparker at apple.com <mailto:gparker at apple.com>> wrote:
> 
>> On Jan 18, 2016, at 2:55 PM, Howard Lovatt via swift-evolution <swift-evolution at swift.org <>> wrote:
>> 
>>> On Tuesday, 19 January 2016, Jack Lawrence <jackl at apple.com <>> wrote:
>>> 
>>>> On Jan 18, 2016, at 2:50 PM, Liam Butler-Lawrence via swift-evolution <swift-evolution at swift.org <>> wrote:
>>>> 
>>>> Set("a", "b", "c”) doesn’t compile. It currently has to be  Set(arrayLiteral: "a", "b", "c”). That said, I’d be satisfied with removing the external parameter name “arrayLiteral”. Not only is it unnecessary, but it’s confusing too: variadic parameters are not the same as an Array.
>>> 
>>> init(arrayLiteral:) is there to satisfy ArrayLiteralConvertible. Set([“a”, “b”, “c”]) works just fine.
>> 
> 
>> Sure, but you could add another overload without the label.
> 
> 
> Only if you break existing code. Consider this expression:
> 
>     Set(["a", "b"])
> 
> Is this
> 1. a Set<String> with two elements "a" and "b"
> 2. a Set<Array<String>> with one element ["a", "b"]
> 
> Currently it means #1. You could change it to mean #2, but that breaks existing code that expects #1. You could try to overload the no-name initializer, but that will be confusing to humans in some cases.
> 
> 
> -- 
> Greg Parker     gparker at apple.com <>     Runtime Wrangler
> 
> 
> 
> 
> -- 
>   -- Howard.
> 
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