This seems to be https://bugs.swift.org/browse/SR-1856, which is resolved in
Swift 4.1.
Martin
> Am 12.01.2018 um 07:49 schrieb Kelvin Ma via swift-dev <swift-dev@swift.org>:
>
> it happens when the n is a literal
>
> let a:[Int] = [1, 2, 3]
> let f:(Int) -> Int = { $0 + 5 }
>
> print(a.prefix(5).map(f))
>
>
> ab.swift:4:7: error: ambiguous use of 'prefix'
> print(a.prefix(5).map(f))
> ^
> Swift.Collection:85:17: note: found this candidate
> public func prefix(_ maxLength: Int) -> Self.SubSequence
> ^
> Swift.Sequence:81:17: note: found this candidate
> public func prefix(_ maxLength: Int) -> AnySequence<Self.Element>
>
>
> On Thu, Jan 11, 2018 at 11:30 PM, Ben Cohen <ben_co...@apple.com> wrote:
> Hi Kelvin,
>
> Can you give a bit more detail on the type of the sequence, and which
> compiler version you’re seeing this on?
>
> I can’t reproduce this with a recent Xcode or a recent master toolchain with
> this code:
>
> let sequence = 0..<10
> let n = 5
> let f = { $0*2 }
>
> sequence.prefix(n).map(f)
>
> Thanks
> Ben
>
>> On Jan 11, 2018, at 19:11, Kelvin Ma via swift-dev <swift-dev@swift.org>
>> wrote:
>>
>> when I write sequence.prefix(n).map(f) the compiler complains that .prefix
>> is ambiguous. If I replace it with [..<n] it works fine. Why is this
>> happening? I found SR-1856 which looks like a similar issue but it’s marked
>> fixed.
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>
>
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