> On 31 Jan 2017, at 07:23, Daniel Duan via swift-evolution
> <swift-evolution@swift.org> wrote:
>
> I guess I missed that discussion. This "feature" does more harm than good
> IMHO.
Indeed. I find this behavior very surprising and goes against Swift's
safe-by-default and explicitness philosophy.
I'd argue removing it.
>> On Jan 30, 2017, at 10:16 PM, Charlie Monroe via swift-evolution
>> <swift-evolution@swift.org> wrote:
>>
>>
>>> On Jan 31, 2017, at 1:03 AM, Matthew Johnson via swift-evolution
>>> <swift-evolution@swift.org> wrote:
>>>
>>>
>>>
>>> Sent from my iPad
>>>
>>>> On Jan 30, 2017, at 5:25 PM, Slava Pestov via swift-evolution
>>>> <swift-evolution@swift.org> wrote:
>>>>
>>>>
>>>>> On Jan 30, 2017, at 2:58 PM, Daniel Duan via swift-evolution
>>>>> <swift-evolution@swift.org> wrote:
>>>>>
>>>>> Hi all,
>>>>>
>>>>> Right now, expressions that evaluates to Optional<()>,
>>>>> Optional<Optional<()>>… gets special treatment when it’s unused. For
>>>>> example:
>>>>>
>>>>> func f(s: String) {}
>>>>> let s: String = “”
>>>>> s.map(f) // no warning here, even tho the resulting type is
>>>>> `Optional<()>` and unused.
>>>>>
>>>>> func g() throws {}
>>>>> try? g() // no warnings here neither.
>>>>>
>>>>> This is convenient, but encourages composing map/filter/reduce, etc with
>>>>> side-effect-ful functions, which we have found a few cases of in our
>>>>> production code recently. Granted, these cases could’ve been caught with
>>>>> more careful code reviews. But we wouldn’t have missed them if this
>>>>> “feature” didn’t exist.
>>>>>
>>>>> I think we should remove the special treatment so that code in the
>>>>> example above would generate a warning about `()?` being unused. Users
>>>>> can silence it manually by assigning the result to `_`.
>>>>>
>>>>> OTOH, this would undermine the convenience of `try?` when the throwing
>>>>> function don’t return anything.
>>>>
>>>> IMHO, using ‘try?’ to ignore an error result, instead of just turning it
>>>> into an optional, is an anti-pattern, and forcing users to write ‘_ = try?
>>>> foo()’ might not be so bad…
>>>
>>> +1
>>
>> Isn't this how it was in Swift 2.x and the first versions of 3.0? I believe
>> this was changed only recently - which I personally found as good news. In
>> some cases you simply do not care about the error result since it has no
>> impact if the call fails and typing "_ =" seemed like boilerplate...
>>
>> If I recall correctly, this was discussed here on the list and changed to
>> the current behavior.
>>
>>
>>>
>>>>
>>>>>
>>>>> What do y’all think?
>>>>>
>>>>> Daniel Duan
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>>>>> swift-evolution@swift.org
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>>>>
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