withoutActuallyEscaping and withCheckedContinuation do not work well together #84135
Description
Description
When using withoutActuallyEscaping together with withCheckedContinuation in the following codes, I still occasionally get the runtime error “closure argument was escaped in withoutActuallyEscaping block“. I have also tried using a ClosureHolder in order to use unowned capture in the closure, but unfortunately, the same error still occurs.
This error does not always happen and is easier to be triggered when the run function in the following codes multiple times in parallel.
Reproduction
func run<R: Sendable>(_ block: @Sendable () -> R) async -> R {
return await withoutActuallyEscaping(block) { localBlock in
return await withCheckedContinuation { continuation in
DispatchQueue.global().async {
continuation.resume(returning: localBlock())
}
}
}
}
await withTaskGroup { group in
for i in 0 ..< 500 {
group.addTask {
await run {
print(i)
}
}
}
}The version with ClosureHolder
final class ClosureHolder<R>: Sendable {
let closure: (@Sendable () -> R)
init(closure: @Sendable @escaping () -> R) {
self.closure = closure
}
}
func run<R: Sendable>(_ block: @Sendable () -> R) async -> R {
return await withoutActuallyEscaping(block) { localBlock in
let holder = ClosureHolder(closure: localBlock)
return await withCheckedContinuation { [unowned holder] continuation in
DispatchQueue.global().async { [unowned holder] in
continuation.resume(returning: holder.closure())
}
}
}
}Expected behavior
with the withCheckedContinuation function, the localBlock closure should not escape the withoutActuallyEscaping function call and should not trigger the "closure argument was escaped in withoutActuallyEscaping block" error
Environment
Apple Swift version 6.2-dev (LLVM f1be75e3e69fdf9, Swift f15d600)
Target: arm64-apple-macosx26.0
Build config: +assertions
Additional information
No response