[swift-evolution] [Late Pitch] Deprecations, Moves, and Renames

[Tim Vermeulen]

They’re still in Swift 3. Did something go wrong, or will they simply not show up in the final Swift 3.0?

> On 10 Aug 2016, at 22:28, Dave Abrahams <dabrahams at apple.com> wrote:
> 
> 
> on Wed Aug 10 2016, Tim Vermeulen <tvermeulen-AT-me.com <http://tvermeulen-at-me.com/>> wrote:
> 
>> Some protocols of SE-0104 seem to be part of the latest Swift 3
>> snapshots (Arithmetic, FixedWidthInteger, etc) - was this a mistake
>> then, if they won’t be in Swift 3.0?
> 
> Yes, they've been pulled out of the release branch:
> https://github.com/apple/swift/pull/4112#issuecomment-238451509 <https://github.com/apple/swift/pull/4112#issuecomment-238451509>
> 
>> 
>> 
>>> on Wed Aug 10 2016, Ben Rimmington<me-AT-benrimmington.com>wrote:
>>> 
>>>>> On 10 Aug 2016, at 00:36, Dave Abrahams wrote:
>>>>> 
>>>>>> on Tue Aug 09 2016, Ben Rimmington wrote:
>>>>>> 
>>>>>>> On 9 Aug 2016, at 20:09, Dave Abrahams wrote:
>>>> 
>>>>>>> 
>>>>>>> Hi Everybody,
>>>>>>> 
>>>>>>> With another round of apologies for taking late action, we propose to
>>>>>>> make some deprecations, moves, and renames. The background for these
>>>>>>> moves is as follows:
>>>>>>> 
>>>>>>> We've always known that when Swift reached ABI stability
>>>>>>> (now slated for
>>>>>>> Swift 4), we would be committed to supporting many of the standard
>>>>>>> library's design decisions for years to come. What we only realized
>>>>>>> very recently is that, although Swift 3.0 is *not* shipping with a
>>>>>>> stable ABI, the promise that Swift 3.0 code will work with Swift 4.0
>>>>>>> code creates similar implications when it comes to certain protocols,
>>>>>>> today. Especially where these protocols show up in refinement
>>>>>>> hierarchies, we can't keep Swift 3 code working in the future without
>>>>>>> carrying them forward into future libraries.
>>>>>>> 
>>>>>>> The proposed changes are as follows:
>>>>>>> 
>>>>>>> * Move `CustomPlaygroundQuickLookable` to the
>>>>>>> PlaygroundSupport module.
>>>>>>> This component is really only useful for playgrounds, and doesn't
>>>>>>> belong in the standard library.
>>>>>> 
>>>>>> I didn't think it was possible to `import PlaygroundSupport` unless the
>>>>>> current file is within a playground. If so, how can corelibs-foundation
>>>>>> or third-party modules add `CustomPlaygroundQuickLookable`
>>>>>> conformance?
>>>>> 
>>>>> Ahhh... yeah, I didn't realize that, and we don't have time to change
>>>>> that restriction for Swift 3. It's not a problem for
>>>>> corelibs-foundation but it would be for 3rd-party libraries.
>>>>> 
>>>>> OK, Dmitri and I just figured out how we can change the home of these
>>>>> types for Swift 4 without breaking Swift 3 code (mirrors to the rescue!)
>>>>> So I'm going to withdraw this part of the proposal.
>>>> 
>>>> Will the following need to be reverted?
>>>> 
>>>> <https://github.com/apple/swift/pull/4089>
>>>> 
>>>> <https://github.com/apple/swift-xcode-playground-support/commit/aab7af4>
>>>> <https://github.com/apple/swift-xcode-playground-support/commit/865fd0c>
>>>> <https://github.com/apple/swift-xcode-playground-support/commit/ab605ef>
>>>> <https://github.com/apple/swift-xcode-playground-support/commit/4bd6575>
>>>> <https://github.com/apple/swift-xcode-playground-support/commit/acee2e1>
>>> Technically, no, because typealiases make it unnecessary, but yes, we
>>> plan to do that.
>>> 
>>>>>>> * Deprecate the Indexable protocols with a message
>>>>>>> indicating that they
>>>>>>> will be gone in Swift 4. These protocols are implementation details
>>>>>>> of the standard library designed to work around language limitations
>>>>>>> that we expect to be gone in Swift 4. There's no reason for anyone to
>>>>>>> ever touch these; users should always use a corresponding Collection
>>>>>>> protocol (e.g. instead of MutableIndexable, use MutableCollection).
>>>>>>> 
>>>>>>> * Deprecate the ExpressibleByStringInterpolation protocol with a
>>>>>>> message indicating that its design is expected to change. We know
>>>>>>> this protocol to be mis-designed
>>>>>>> (https://bugs.swift.org/browse/SR-1260) and limited
>>>>>>> (https://bugs.swift.org/browse/SR-2303), but there's no time
>>>>>>> to fix it
>>>>>>> for Swift 3. If we knew what the new design should look like, we
>>>>>>> might be able to calculate that the current API is supportable in a
>>>>>>> forward-compatible way (as we do for Comparable). Unfortunately, we
>>>>>>> do not.
>>>>>>> 
>>>>>>> * Rename Streamable to TextOutputStreamable and add a deprecated
>>>>>>> Streamable typealias for it. Now that OutputStream been renamed to
>>>>>>> TextOutputStream, we should also move Streamable out of the way.
>>>> 
>>>> In apple/swift#4131, these lines have overrun the 80 column limit:
>>>> 
>>>> <https://github.com/apple/swift/blob/f2443f4/stdlib/public/core/Mirror.swift#L843>
>>>> <https://github.com/apple/swift/blob/f2443f4/stdlib/public/core/Mirror.swift#L893>
>>>> 
>>>> <https://github.com/apple/swift/blob/f2443f4/stdlib/public/core/Print.swift#L177>
>>>> <https://github.com/apple/swift/blob/f2443f4/stdlib/public/core/Print.swift#L228>
>>>> 
>>>> TextFormatting.rst also needs `Streamable` =>`TextOutputStreamable`:
>>>> 
>>>> <https://github.com/apple/swift/blob/master/docs/TextFormatting.rst>
>>> Pull requests gratefully accepted for all of these corrections
>>> 
>>>>>>> Deprecation is being proposed instead of underscoring or renaming
>>>>>>> because it allows existing code to keep working (with warnings). At
>>>>>>> this late stage, it would be bad to actually break anything.
>>>>>> 
>>>>>> If the SE-0104 (protocol-oriented integers) proposal has been deferred,
>>>>>> should any protocols (e.g. SignedNumber) be deprecated?
>>>> 
>>>> Will the SE-0104 proposal be accepted for Swift 4.0?
>>> It is expected to be. We may even be able to get it into a Swift 3
>>> point-release (e.g. 3.1)
>>> 
>>> --
>>> Dave
>>> 
>>> 
>>> 
> 
> -- 
> -Dave

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