> On May 15, 2016, at 5:31 AM, Neil Faiman via swift-users
> <swift-users@swift.org> wrote:
>
> This function seems simple enough:
>
>
> func foo(a: [Int], n: Int) {
> var x : [Int] = a[0..<n]
> }
>
> But it doesn’t compile.
>
> error: ambiguous subscript with base type '[Int]' and index type
> 'Range<Int>'
> var x : [Int] = a[0..<n]
> ~^~~~~~~
> Swift.Array:100:12: note: found this candidate
> public subscript (subRange: Range<Int>) -> ArraySlice<Element> { get set }
> ^
> Swift.MutableCollectionType:3:12: note: found this candidate
> public subscript (bounds: Range<Self.Index>) -> MutableSlice<Self> { get
> set }
> ^
> Swift.CollectionType:2:12: note: found this candidate
> public subscript (bounds: Range<Self.Index>) -> Slice<Self> { get }
> ^
>
> The oddity is that if I change the assignment to this
>
> var y : [Int] = Array(a[0..<n])
>
> then the compiler is happy.
>
> Shouldn’t it be able to do any necessary type inference from the fact that
> the expression is in a context where an array is required?
The error message is misleading (if you have time, we'd appreciate a bug
report!). What's really going on is that a[0..<n] produces an ArraySlice<T>,
not an Array<T>, in order to share memory with the underlying array. The type
doesn't match in your assignment. If `x` is just temporary, I'd recommend
leaving the type annotation out, since `var x = a[0..<n]` should just work.
-Joe
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