[swift-evolution] Revisiting SE-0110

[Pavel Yaskevich]

On Wed, May 24, 2017 at 12:57 PM, Tony Parker <anthony.parker at apple.com>
wrote:

>
>
> 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> 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?
>

There is a migrator support, and I've made a couple of diagnostic
improvements for it, that produce fix-its which are exactly
what you see in the aforementioned PR. Otherwise, I'd defer to Slava, who
was implementor of SE-0110.



>
> - Tony
>
>
>
>>
>>
>> On May 24, 2017, at 12:12 PM, Tony Parker via swift-evolution <
>> 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)
>>
>> - Tony
>>
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>>
>>
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>
>
>
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