> 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
>>> https://lists.swift.org/mailman/listinfo/swift-evolution
>>
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