This effectively reverts 6823744779
The blanket removal of isolation in default-value expressions had
unintented consequences for important workflows. It's still
a problem that needs to be addressed, but we need to be more precise
about the problematic situations.
There were some tests that relied on the top-level code not being an
asynchronous context to emit certain error messages. Now that it is,
those tests weren't emitting the expected error message.
In other cases, the issue was that they were trying to initialize a
global variable and weren't really using top-level code as top-level
code, so adding `-parse-as-library` was sufficient for the testing
purposes.
To fix the objc_async test, parsing as a library was nearly sufficient.
Unfortunately, the little `if #available` trick that I was using stopped
working since it relied on being in top-level code. So that we emit the
unavailableFromAsync error message, I had to set the availability on
everything correctly because we can't just disable availability
checking.
Any test using swift version 6 will only work on asserts builds of the
compiler to avoid seeing:
```
<unknown>:0: error: invalid value '6' in '-swift-version 6'
<unknown>:0: note: valid arguments to '-swift-version' are '4', '4.2', '5'
```
It's possible to create an impossible set of constraints for
instance-member stored properties of a type. For example:
@MainActor func getStatus() -> Int { /* ... */ }
@PIDActor func genPID() -> ProcessID { /* ... */ }
class Process {
@MainActor var status: Int = getStatus()
@PIDActor var pid: ProcessID = genPID()
init() {} // Problem: what is the isolation of this init?
}
We cannot satisfy the isolation of the initilizing expressions,
which demand that genStatus and genPID are run with isolation
from a non-async designated initializer, which is not possible.
This patch changes the isolation for those initializer expressions
for instance members, saying that the isolation is unspecified.
fixes rdar://84225474
The first attempt to do this was in
https://github.com/apple/swift/pull/40652
But, I implemented that as a hard source break, since the isolation
was changed in a way that an error diagnostic would be emitted.
This commit reimplements the change more gently, as a warning for
Swift 5 users.
