It was difficult to preserve the existing, buggy behavior of availability
attribute inference with respect to attributes specifying availability for
non-platform-specific domains. Instead, this change improves attribute merging
by tracking every domain independently, and only merging attributes from the
same domain.
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.
The "#if compiler(>=5.3) && $AsyncAwait" checks were necessary for
staging in concurrency in Swift 5.5. At this point, it's safe to assume
that any compiler that tries to read a generated Swift interface file will
support concurrency, so we can stop emitting these guards.
The macCatalyst platform availability of a declaration may be inferred from the
iOS platform availability of that declaration in the absence of an explicit
macCatalyst availability attribute. This means that when inheriting macCatalyst
platform availability, the explict iOS availability of an inner ancestor should
take precedence over explicit macCatalyst availability of an outer ancestor.
The algorithm that computes inferred availability attributes for synthesized
declarations was treating macCatalyst and iOS as independent platforms, though,
sometimes yielding inapproparite macCatalyst availability.
Resolves rdar://107766644
In https://github.com/apple/swift/pull/63898 conformance requirement
typechecking was relaxed to allow unavailable decls to witness conformance
requirements as long as the conforming nominal was also unavailable. However,
only nominals that were directly marked unavailable were accepted. Nominals
that are declared in unavailable scopes should also be allowed to have
unavailable wintesses.
Resolves rdar://107052715
It turns out that we must allow declarations with `introduced:` availability
nested inside of other declarations that are `unavailable` in order to
influence weak linking. Stop diagnosing declarations as being more available
than their unavailable containers and revert some changes to availability
inference that were designed to avoid creating these nestings but caused
regressions for declarations marked `@_spi_available.`
Reverts parts of https://github.com/apple/swift/pull/64310,
https://github.com/apple/swift/pull/64015, and
https://github.com/apple/swift/pull/62900.
Previously, when creating availability attributes for synthesized declarations
we would identify some set of reference declarations that the synthesized
declaration should be as-available-as. The availability attributes of the
reference declarations would then be merged together to create the attributes
for the synthesized declaration. The problem with this approach is that the
reference declarations themselves may implicitly inherit availability from their
enclosing scopes, so the resulting merged attributes could be incomplete. The
fix is to walk though the enclosing scopes of the reference declarations,
merging the availability attributes found at each level.
Additionally, the merging algorithm that produces inferred availability
attributes failed to deal with conflicts between platform specific and platform
agnostic availability. Now the merging algorithm notices when platform agnostic
availability should take precedence and avoids generating conflicting platform
specific attributes.
Resolves rdar://106575142
When synthesizing a declaration and inferring its availability, the synthesized attribute should factor in unavailability of the parent declarations. This recently regressed with https://github.com/apple/swift/pull/63361. However, the previous implementation did not produce correct results, either, because the logic for merging availability attributes produced a non-sensical result when both `unavailable` and `introduced:` availability attributes were merged. For example, this was the result for the synthesized `unownedExecutor` property of an actor when the actor was marked unavailable:
```
@available(macOS, unavailable)
actor A {
// Incorrectly synthesized availability for `unownedExecutor` which results from merging
// the unavailability of the parent and the availability of the UnownedSerialExecutor type.
@available(macOS, unavailable, introduced: macOS 10.15)
@_semantics("defaultActor") nonisolated final var unownedExecutor: UnownedSerialExecutor { get }
}
```
This is fixed by omitting all version components from the synthesized attribute when the overall attribute kind is "unavailable".
Additionally, I discovered that the `concurrency_availability.swift` test case was no longer testing what it intended to test. The conformances to `Actor` for each `actor` in the test were no longer being synthesized and therefore `unownedExecutor` was not being synthesized. That was fixed by importing the `_Concurrency` module directly, which seems to be necessary because of the `-parse-stdlib` flag in the test.
Resolves rdar://106055566
