[swift-evolution] [Draft] Abolish IUO type

[Chris Willmore]

> On Mar 17, 2016, at 2:19 PM, Joe Groff <jgroff at apple.com> wrote:
> 
>> 
>> On Mar 17, 2016, at 1:38 PM, Chris Willmore via swift-evolution <swift-evolution at swift.org> wrote:
>> 
>>> On Mar 17, 2016, at 6:53 AM, Brent Royal-Gordon <brent at architechies.com> wrote:
>>> 
>>>> 1. We have to add @implicitly_unwrapped attribute to the proposal. I hate implied "attributes", available only to compiler. The wording needs to be reformulated in terms of this attribute
>>> 
>>> Agree.
>>> 
>>>> 2. We need to encourage using the attribute instead of `!`.
>>>> 3. In the future, `!` can be removed entirely and leave only the attribute. But not for now
>>> 
>>> Disagree. As I mentioned earlier in the thread, IUOs are going to become less common on Apple platforms, but they are here to stay in Swift as a whole.
>> 
>> I agree with this.
>>> 
>>>> In order to do this, I suggest finding a concise name for it. Like @IUO, but possibly more readable
>>> 
>>> I do agree that we should look for a shorter, better name. I suggest `@autounwrap`, by analogy with `@autoclosure`. Both features insert invisible syntax at usage sites to make an expression of one type appear to be an expression of a different type.
>>> 
>>> (Actually, I think that `@autoclosure` is a great analogy for this feature in many respects.)
>> 
>> The similarity to @autoclosure is a good observation.
>> 
>> It sounds like an explicit attribute name may be a necessary part of this proposal rather than a thought for the future. So far we’ve heard:
>> 
>> @implicitly_unwrapped
>> @iuo
>> @autounwrap
> 
> I'm not sure this is a great idea yet. Punishing IUOs with verbose syntax may feel good, but runs the danger of making projected Swift interfaces from unaudited C and Objective-C APIs too noisy to read. Our current syntax was motivated by a strong desire to ensure that Swift interfaces remain readable, even for foreign APIs that haven't been annotated with Swift interop in mind yet.

I don’t think that Brent and I are suggesting that attribute syntax for IUOs should be mandatory or even recommended, merely that it should exist. That way we can talk about the feature in terms of the underlying attribute-based representation without it being some hidden, exclusively compiler-internal thing.
— Chris Willmore
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20160317/158c21d9/attachment.html>