Now that `SwiftStdlib 6.3` maps to real versions for Apple's operating systems
(https://github.com/swiftlang/swift/pull/87510), checks like
```
if #available(StdlibDeploymentTarget 6.3, *) { ... }
```
inside the implementation of the stdlib are no longer necessary to satisfy the
availability checker and instead cause warnings to be emitted. Remove the now
superfluous checks.
This is a reattempt of https://github.com/swiftlang/swift/pull/87744. The
previous attempt was reverted because it turned out that there were some
configurations (outside of Swift CI) in which the stdlib was built with an
unnecessarily low deployment target. That has now been corrected, unblocking
this fix.
Functions like withUnsafeBufferPointer are, by themselves, safe to
call. It's only the operations on the unsafe pointers passed into the
closure that are the safety issue.
This was the intent spelled out in SE-0458 but was not fully realized
in the library.
Fixes rdar://174519372.
Carefully overhaul our word breaking implementation to follow the recommendations of Unicode Annex #29. Start exposing the core primitives (as well as `String`-level interfaces), so that folks can prototype proper API for these concepts.
- Fix `_wordIndex(after:)` to always advance forward. It now requires its input index to be on a word boundary. Remove the `@_spi` attribute, exposing it as a (hidden, but) public entry point.
- The old SPIs `_wordIndex(before:)` and `_nearestWordIndex(atOrBelow:)` were irredemably broken; follow the Unicode recommendation for implementing random-access text segmentation and replace them both with a new public `_wordIndex(somewhereAtOrBefore:)` entry pont.
- Expose handcrafted low-level state machines for detecting word boundaries (_WordRecognizer`, `_RandomAccessWordRecognizer`), following the design of `_CharacterRecognizer`.
- Add tests to reliably validate that the two state machine flavors always produce consistent results.
rdar://155482680
* Implement String.WordView
* Add isWordAligned bit
* Hide WordView for now (also separate Index type)
add bidirectional conformance
Fix tests
* Address comments from Karoy and Michael
* Remove word view, use index methods
* Address Karoy's comments
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Allan Shortlidge
Doug Gregor
Andrew Trick
Karoy Lorentey
Alejandro Alonso
David Smith