> On Apr 10, 2016, at 4:45 AM, Антон Жилин via swift-evolution
> <[email protected]> wrote:
>
> First of all, I tried to change the original proposal to add actual
> @autounwrapped attribute to Swift.
> Because "explicit is better than implicit" and consistency and so on.
>
> Its authors did not pay much attention, and so I'm going to create a separate
> proposal for that purpose.
>
> Next, implicitly unwrapped optional was designed purely for bridging to
> Objective-C (and now C).
> Notation T! that is still used in Swift code, is misleading, because it's not
> an actual type.
>
> So I also propose that T! notation is reserved for entities imported from
> Objective-C.
> Swift code, which needs that behaviour, such as delayed initialization, will
> use @autounwrapped.
> It's more clear and explicit about this being a property behaviour and not a
> type, with all consequences.
>
> What do you think?
Hi Anton,
I agree with you in theory, and this is definitely important to discuss. My
main concern is about the readability impact that this will have on the
readability of unaudited APIs. Here are two random unaudited examples, with
the rules we have today:
JSValue / Darwin:
func defineProperty(property: String!, descriptor: AnyObject!)
func strcat(_: UnsafeMutablePointer<Int8>!, _: UnsafePointer<Int8>!) ->
UnsafeMutablePointer<Int8>!
If we got rid of !, we’d end up with:
func defineProperty(property: @autounwrapped String?, descriptor:
@autounwrapped AnyObject?)
func strcat(_: @autounwrapped UnsafeMutablePointer<Int8>?, _:
@autounwrapped UnsafePointer<Int8>?) -> @autounwrapped
UnsafeMutablePointer<Int8>?
Here are some problems:
a) @autounwrapped ends up dominating the signature, since it is longer than
many type names.
b) While it is appropriate for return values and properties, it isn’t the right
attribute name for parameters. There, a better name would be “@unaudited”.
When passing a parameter, there is no behavioral difference between T! and T?
after all.
I suppose that you could argue that we should just drop annotations completely
for parameters. My concern with doing that is that it would lose the
distinction between audited APIs that accept nil and do something meaningful
with it, and those that have been unaudited.
-Chris
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