[swift-evolution] [pitch] Variadic Arguments should accept Arrays

[Derrick Ho]

Rudolf, I don't believe that is a rule.

One example includes NSLog()

In which the first parameter is a format string and the second is a
variadic argument. The second one can be omitted.
On Wed, Mar 8, 2017 at 5:09 PM Rudolf Adamkovič via swift-evolution <
swift-evolution at swift.org> wrote:

> Correct me if I’m wrong but a variadic argument is guaranteed to have one
> or more elements in the array. Isn’t that the case? As an example, consider
> the following initializer:
>
>     public init(state: State, actions: Action...) {
>         // ...
>     }
>
> Here, I can count on actions to be a non-empty array. It’s
> self-documenting and type-safe. How would this work if arrays are
> (implicitly or explicitly) convertible to variadic arguments?
>
> R+
>
> On 26 Feb 2017, at 17:26, Derrick Ho via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> In swift, a variadic argument can become an array without too much effort.
>
> func foo(_ va: String...) {
>    let a: [String] = va
> }
>
> However, it seems odd to me that an array can not be converted into a
> variadic argument
>
> foo(["a", "b", "c"]) // <-error
> foo("a", "b", "c") // no error
>
> Other people have wondered about this too.
> <http://stackoverflow.com/questions/24024376/passing-an-array-to-a-function-with-variable-number-of-args-in-swift>
>
> According to this thread
> <https://devforums.apple.com/message/970958#970958> Doug Gregor says it
> is due to some type ambiguity. with Generics.
>
> If type ambiguity is the issue, Do we have the option to cast it to the
> correct type?
>
> foo(["a", "b", "c"] as String...) // <- error.  doesn't consider String...
> to be a type.
>
> What does the community think? Should we be granted some mechanism to turn
> an array into a variadic argument?
>
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