Merge pull request #40616 from DougGregor/concurrency-sendable-frozen-types

Author: DougGregor

stdlib/public/Concurrency/Executor.swift

@@ -46,7 +46,7 @@ public protocol SerialExecutor: Executor {
 /// actor.
 @available(SwiftStdlib 5.1, *)
 @frozen
-public struct UnownedSerialExecutor {
+public struct UnownedSerialExecutor: Sendable {
   #if compiler(>=5.5) && $BuiltinExecutor
   @usableFromInline
   internal var executor: Builtin.Executor

stdlib/public/Concurrency/Task.swift

@@ -762,6 +762,10 @@ public struct UnsafeCurrentTask {
   }
 }
 
+@available(SwiftStdlib 5.1, *)
+@available(*, unavailable)
+extension UnsafeCurrentTask: Sendable { }
+
 @available(SwiftStdlib 5.1, *)
 extension UnsafeCurrentTask: Hashable {
   public func hash(into hasher: inout Hasher) {

stdlib/public/Concurrency/TaskGroup.swift

@@ -394,6 +394,10 @@ public struct TaskGroup<ChildTaskResult: Sendable> {
   }
 }
 
+@available(SwiftStdlib 5.1, *)
+@available(*, unavailable)
+extension TaskGroup: Sendable { }
+
 // Implementation note:
 // We are unable to just™ abstract over Failure == Error / Never because of the
 // complicated relationship between `group.spawn` which dictates if `group.next`
@@ -694,6 +698,10 @@ public struct ThrowingTaskGroup<ChildTaskResult: Sendable, Failure: Error> {
   }
 }
 
+@available(SwiftStdlib 5.1, *)
+@available(*, unavailable)
+extension ThrowingTaskGroup: Sendable { }
+
 /// ==== TaskGroup: AsyncSequence ----------------------------------------------
 
 @available(SwiftStdlib 5.1, *)