> On Nov 7, 2017, at 3:34 PM, Kevin Ballard via swift-evolution
> <swift-evolution@swift.org> wrote:
>
> On Tue, Nov 7, 2017, at 03:23 PM, John McCall via swift-evolution wrote:
>> https://github.com/apple/swift-evolution/blob/master/proposals/0187-introduce-filtermap.md
>>
>> <https://github.com/apple/swift-evolution/blob/master/proposals/0187-introduce-filtermap.md>
>>
>> • What is your evaluation of the proposal?
>
> This proposal is going to cause an insane amount of code churn. The proposal
> suggests this overload of flatMap is used "in certain circumstances", but in
> my experience it's more like 99% of all flatMaps on sequences are to deal
> with optionals, not to flatten nested sequences.
>
>> • Is the problem being addressed significant enough to warrant a change to
>> Swift?
>
> I don't think so. It's a fairly minor issue, one that really only affects new
> Swift programmers anyway rather than all users, and it will cause far too
> much code churn to be worthwhile.
>
> I'd much rather see a proposal to add a new @available type, something like
> 'warning’,
Please write one, seriously!
> that lets you attach an arbitrary warning message to a call (which you can
> kind of do with 'deprecated' except that makes the warning message claim the
> API is deprecated). With that sort of thing we could then declare
>
> extension Sequence {
> @available(*, warning: "Use map instead")
> func flatMap<U>(_ f: (Element) -> U) -> [U] {
> return map(f)
> }
> }
FWIW: This was attempted in the past, and had to be reverted for the reason
other than «deprecated» being a confusing message.
https://github.com/apple/swift/pull/9390
<https://github.com/apple/swift/pull/9390>
>
> And now if someone writes flatMap in a way that invokes optional hoisting,
> it'll match this overload instead and warn them.
>
>> • How much effort did you put into your review? A glance, a quick reading,
>> or an in-depth study?
>
> A quick reading, and a couple of minutes testing overload behavior with
> availability attributes (to confirm that we can't simply use 'unavailable'
> for this).
>
> -Kevin Ballard
>
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