swift

c04eb7c4 - [Concurrency] Downgrade errors when isolated member is referenced from a preconcurrency context

[Concurrency] Downgrade errors when isolated member is referenced from a preconcurrency context Such references used to be downgraded until Swift 6 but since the context is `@preconcurrency` it should be possible for API authors to introduce concurrency annotations such as `@Sendable` without breaking clients even when they are compiled in Swift 6 mode. Resolves: rdar://157061896 (cherry picked from commit 5ee673f358c9dd7dbbfe58f02bc78af60e0377b8)