[region-isolation] Ensure that if a var is captured by reference in a closure that we do not allow for later accesses to sendableFields #70171
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… of a non-Sendable typed var and the var is captured in a closure If the var is captured in a closure before it is transferred, it is not safe to access the Sendable field since we may race on accessing the field with an assignment to the field in another concurrency domain. rdar://115124361
…t require T to conform to PointerLikeTypeTraits. This allows one to place types like PointerIntPair and value types that wrap a pointer into the pointer set. I am making this change before I use this data structure in TransferNonSendable and using ARC to validate that I haven't broken anything.
…truction, track all of them.
Previously I avoided doing this since the only problem would be that in a case
where we had two transfer instructions that were in an if-else block, we would
just emit an error for one:
```swift
if boolValue {
transfer(x)
} else {
transfer(x) // Only emit error for this transfer!
}
useValue(x)
```
Now that we are tracking at the transfer point if any element in the transfer
was captured in a closure, this becomes an actual semantic issue since if we
track the transfer instruction that isn't reachable from the closure capture, we
will not become more pessimistic:
```swift
if boolValue {
closure = { useInOut(&x) }
transfer(x)
} else {
transfer(x)
}
// Since we grab from the else block, sendableField is allowed to be accessed
// since we do not track that x was captured by reference in a closure.
x.sendableField
useValue(x)
```
To be truly safe, we need to emit both errors.
rdar://119048779
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This PR contains two different commits and a utility commit:
rdar://119048779
rdar://115124361