Based on feedback in PR https://github.com/swiftlang/swift/pull/69460, enabling indexing for synthesized decls because they are usable by users and make sense to appear in the indexstore.
Sets `synthesized` on some additional decls:
- derived `hashInto(...)`
- Objc properties and methods derived from Objc protocols
https://github.com/apple/swift/issues/67446
`visitBinaryExpr` wasn't handling `UnresolvedDeclRefExpr` nodes, which the
synthesized `==` implementation uses to compare fields/payloads. Also fixed
the test that wasn't catching it since it also left out the operators.
The `_diagnoseUnavailableCodeReached()` function was introduced in the Swift
5.9 standard library and employs `@backDeployed` to support compilation of
binaries that target OS releases aligned with earlier Swift releases.
Unfortunately, though, this backdeployment strategy doesn't work well for some
unusual build environments. Specifically, in some configurations code may be
built with a compiler from a recent Swift toolchain and then linked against the
dylibs in an older toolchain. When linking against the older dylibs, the
`_diagnoseUnavailableCodeReached()` function does not exist but the
`@backDeployed` thunks emitted into the binary reference that function and
therefore linking fails.
The idea of building with one toolchain and then linking to the dylibs in a
different, older toolchain is extremely dubious. However, it exists and for now
we need to support it. This PR introduces an alternative
`_diagnoseUnavailableCodeReached()` function that is annotated with
`@_alwaysEmitIntoClient`. Calls to the AEIC variant are now emitted by the
compiler when the deployment target is before Swift 5.9.
Once these unusual build environments upgrade and start linking against a Swift
5.9 toolchain or later we can revert all of this.
Resolves rdar://119046537
When deriving the `hash(into:)` and `==` witnesses for `Hashable`/`Equatable`
enums, call `_diagnoseUnavailableCodeReached()` in the case bodies for
unavailable enum elements. This is needed because the previously derived code
would operate on the values associated with unavailable enum elements, which is
illegal if the types of those associated values are also unavailable (these
case bodies would have failed typechecking had they been hand-written). The new
structure also more explicitly documents that reaching these cases is
unexpected, since unavailable enum elements should not be instantiated at run
time.
