[swift-evolution] Revisiting SE-0110

[Tony Parker]

> On May 24, 2017, at 12:51 PM, Pavel Yaskevich <pavel.yaskevich at gmail.com> wrote:
> 
> Hi Tony,
> 
> On Wed, May 24, 2017 at 12:37 PM, Jose Cheyo Jimenez via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
> The way I interpreted SE-110 is that it was suppose to address anonymous arguments. 
> 
> Instead of using $0.0, $0.1, One needs to use $0, $1 when there are multiple arguments. 
> 
> I was not aware of any implications for explicitly named parameters. 
> 
> Perhaps the issue is with the signature of forEach. Does it need to be a nested tuple?
> 
> public func forEach(_ body: ((key: Key, value: Value)) throws -> Void) rethrows
> 
> Jose is right about this one, since the signature of forEach is a tuple nested into paren it means that `forEach` expects a single argument
> of a tuple type instead of two arguments, such "tuple argument destructuring" was supported by Swift 3 but after SE-0110 no longer is
> because type-checker is preserving top level parens in parameters/arguments. 
> 
> Best Regards, Pavel.

Well, frankly, I don’t think we should ship with such a glaring usability regression.

What’s the mitigation plan? Perhaps we should wholesale revert it until we have time to reconsider the fallout?

- Tony

>  
> 
> 
>> On May 24, 2017, at 12:12 PM, Tony Parker via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> Hi everyone,
>> 
>> We received a pull request in swift-corelibs-foundation which is apparently in response to a language change for SE-0110.
>> 
>> It turns this perfectly reasonable code:
>> 
>> -        self.forEach { (keyItem, valueItem) in
>> 
>> into this:
>> 
>> 
>> +        self.forEach { (arg) in
>> +            let (keyItem, valueItem) = arg
>> 
>> Is that really the design pattern we want to encourage? What was wrong with the previous code?
>> 
>> (https://github.com/apple/swift-corelibs-foundation/pull/995/files <https://github.com/apple/swift-corelibs-foundation/pull/995/files>)
>> 
>> - Tony
>> 
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> 
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