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

Michael Ilseman milseman at apple.com
Tue Aug 9 19:21:47 CDT 2016

> On Aug 9, 2016, at 1:01 PM, Charles Srstka via swift-evolution <swift-evolution at swift.org> wrote:
>> On Aug 9, 2016, at 2:09 PM, Dave Abrahams via swift-evolution <swift-evolution at swift.org> 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.
>> * 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.
>> 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.
> Is the team taking suggestions on APIs to be deprecated, renamed and/or modified? I’ve been noticing quite a few translated ObjC APIs that don’t quite seem to fit the Swift paradigm lately.

Please file radars for these against the offending frameworks. You can additionally discuss them on swift-dev or swift-users, but definitely file those radars!

> Charles
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