[swift-evolution] Warn about unused Optional.some(())

[Jordan Rose]

> On Feb 6, 2017, at 11:46, Daniel Duan <daniel at duan.org> wrote:
> 
>> 
>> On Feb 6, 2017, at 11:35 AM, Jordan Rose <jordan_rose at apple.com <mailto:jordan_rose at apple.com>> wrote:
>> 
>>> 
>>> On Feb 6, 2017, at 11:08, Daniel Duan <daniel at duan.org <mailto:daniel at duan.org>> wrote:
>>> 
>>> 
>>>> On Feb 6, 2017, at 10:58 AM, Jordan Rose <jordan_rose at apple.com <mailto:jordan_rose at apple.com>> wrote:
>>>> 
>>>> I think I see Alex's point here. Optional chaining is still intended to be a substitute for Objective-C's nil-swallowing, and therefore foo?.bar() should not warn if 'bar' has a discardable result, even though there is semantic information about whether the method was actually called. I think that of the three things under consideration here:
>>>> 
>>>> 1. foo?.bar() should not warn
>>>> 2. foo.map(baz) should warn
>>>> 3. Ternaries should be consistent with non-ternaries
>>>> 
>>> 
>>> I 100% agree with this analysis.
>>> 
>>>> #1 is the most important, at least to me. The Swift 3 change was to sacrifice #2 in favor of #3, which I'm not sure I would have done, but I wouldn't want to sacrifice #1 in favor of #2.
>>>> 
>>>> I wouldn't mind the model of the type being '@discardableResult Optional<Void>' or whatever, but I think that's probably more work than anyone wants to sign up for.
>>> 
>>> I’ll give this a go and report back. *crosses fingers*
>> 
>> I suspect this will entail making a new sugared type kind and then threading it carefully through the constraint solver (hence why I said it's probably more work than you want to take on).
>> 
> 
> I was going to write a enhanced version of TypeBase::lookThroughAllAnyOptionalTypes(). Too hacky?

Oh, to specifically handle ternaries? I hadn't thought of that. That'd be a much more targeted fix. :-)

Jordan

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