[swift-evolution] [Draft] Abolish IUO type

[Chris Willmore]

> 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

— Chris Willmore