This is due to SE-0110:
https://github.com/apple/swift-evolution/blob/master/proposals/0110-distingish-single-tuple-arg.md
but see the additional commentary:
https://lists.swift.org/pipermail/swift-evolution-announce/2017-June/000386.html
For now you can rewrite it as:
```
let filenamelength = bytes
.enumerated()
.map {
let (index, element) = $0
return Int(Double(element) * pow(256,Double(index))) }
.reduce(0, +)
```
- Daniel
> On Jun 29, 2017, at 8:08 PM, CK TUNG via swift-users <swift-users@swift.org>
> wrote:
>
> I have the following code snippet that compile OK in swift 3
>
> bytes = Array(UnsafeBufferPointer(....))
> let filenamelength = bytes[(i+28)..<(i+28+2)]
> .enumerated()
> .map { (index, element) in return Int(Double(element) *
> pow(256,Double(index))) }
> .reduce(0, +)
>
> I have the following code snippet that compile OK in swift 3
> In Swift 4 (Xcode beta1) it compiled with error something like "... too
> complex"
> Now in Swift 4 Xocde beta2 the error is tuple parameter element does not
> support destructing
> what has been changed in swift 4 ?
>
> Please help how to solve it ?
>
> Thanks
>
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