The SDK overlays have been provided in the Apple SDKs for many years, and the interface and implementation has diverged in more recent years such that trying to build the Swift version no longer works. Remove all of the dead code.
rdar://151889154
This change introduces a new compilation target platform to the Swift compiler - visionOS.
- Changes to the compiler build infrastrucuture to support building compiler-adjacent artifacts and test suites for the new target.
- Addition of the new platform kind definition.
- Support for the new platform in language constructs such as compile-time availability annotations or runtime OS version queries.
- Utilities to read out Darwin platform SDK info containing platform mapping data.
- Utilities to support re-mapping availability annotations from iOS to visionOS (e.g. 'updateIntroducedPlatformForFallback', 'updateDeprecatedPlatformForFallback', 'updateObsoletedPlatformForFallback').
- Additional tests exercising platform-specific availability handling and availability re-mapping fallback code-path.
- Changes to existing test suite to accomodate the new platform.
It shares many of the same values as OpenBSD (which both inherited from 4.4BSD),
and we wouldn't expect those to diverge due to the respective platforms'
bincompat goals.
* Not implementing POSIXError for a given platform is not a blocking
problem to getting a successful build of Swift. However, it is
part of the validation tests (albeit locked behind REQUIRES) and is
referenced when building Foundation. Implement by forklifting from
`sys/errno.h`.
* Some Foundation class implementations require some missing includes in
the platform modulemap. Add these.
Clean up a few general patterns that are now obviated by canImport
This aligns more generally with the cleanup that the Swift Package
Manager has already done in their automated XCTest-plumbing tool in
apple/swift-package-manager#1826.
In theory there could be a "fixed-layout" enum that's not exhaustive
but promises not to add any more cases with payloads, but we don't
need that distinction today.
(Note that @objc enums are still "fixed-layout" in the actual sense of
"having a compile-time known layout". There's just no special way to
spell that.)
- Add newlines where missing to match sys/errno.h error groups separation
- Prefer single-line comments to C-style comments
- Align most comments to same column
- Add comment following #endif at EOF to show what it ends
- Remove extraneous whitespace
