On May 16, 2016, at 10:09 AM, Joe Groff via swift-users <swift-users@swift.org>
wrote:
>
>> 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.
FWIW, master produces the error:
test.swift:2:27: error: cannot subscript a value of type '[Int]' with an index
of type 'CountableRange<Int>'
var x : [Int] = a[0..<n]
^
test.swift:2:27: note: overloads for 'subscript' exist with these partially
matching parameter lists: (Int), (Range<Int>), (Range<Self.Index>),
(ClosedRange<Self.Index>), (CountableClosedRange<Self.Index>)
var x : [Int] = a[0..<n]
^
-Chris
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