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[changelog] SE-0311 Task Local Values #38282

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Jul 7, 2021
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[changelog] SE-0311 Task Local Values #38282

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[changelog] SE-0311 Task Local Values
ktoso Jul 7, 2021
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Update CHANGELOG.md
ktoso Jul 7, 2021
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37 changes: 37 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,42 @@ _**Note:** This is in reverse chronological order, so newer entries are added to
Swift 5.5
---------

* [SE-0311][]:

Task local values can be defined using the new `@TaskLocal` property wrapper.
Such values are carried implicitly by the task in which the binding was made,
as well as any child-tasks, and unstructured task created from the tasks context.

```swift
struct TraceID {
@TaskLocal
static var current: TraceID?
}

func printTraceID() {
if let traceID = TraceID.current {
print("\(traceID)")
} else {
print("nil")
}
}

func run() async {
printTraceID() // prints: nil
TraceID.$current.withValue("1234-5678") {
printTraceID() // prints: 1234-5678
inner() // prints: 1234-5678
}
printTraceID() // prints: nil
}

func inner() {
// if called from a context in which the task-local value
// was bound, it will print it (or 'nil' otherwise)
printTraceID()
}
```

* [SE-0316][]:

A type can be defined as a global actor. Global actors extend the notion
Expand Down Expand Up @@ -8562,6 +8598,7 @@ Swift 1.0
[SE-0300]: <https://github.com/apple/swift-evolution/blob/main/proposals/0300-continuation.md>
[SE-0306]: <https://github.com/apple/swift-evolution/blob/main/proposals/0306-actors.md>
[SE-0310]: <https://github.com/apple/swift-evolution/blob/main/proposals/0310-effectful-readonly-properties.md>
[SE-0311]: <https://github.com/apple/swift-evolution/blob/main/proposals/0311-task-locals.md>
[SE-0313]: <https://github.com/apple/swift-evolution/blob/main/proposals/0313-actor-isolation-control.md>
[SE-0316]: <https://github.com/apple/swift-evolution/blob/main/proposals/0316-global-actors.md>

Expand Down