[embedded] Use async main in the test

Author: kubamracek

stdlib/public/Concurrency/CMakeLists.txt

@@ -210,7 +210,9 @@ if(SWIFT_SHOULD_BUILD_EMBEDDED_STDLIB)
       # TODO: Only a handful of Swift Concurrency .swift sources, for now.
       Task.swift
       AsyncLet.swift
+      Executor.swift
       Errors.swift
+      PartialAsyncTask.swift
 
       SWIFT_COMPILE_FLAGS
         -Xcc -D__MACH__ -Xcc -D__APPLE__ -Xcc -ffreestanding -enable-experimental-feature Embedded

stdlib/public/Concurrency/PartialAsyncTask.swift

@@ -97,6 +97,7 @@ public struct UnownedJob: Sendable {
 }
 
 @available(SwiftStdlib 5.9, *)
+@_unavailableInEmbedded
 extension UnownedJob: CustomStringConvertible {
   @available(SwiftStdlib 5.9, *)
   public var description: String {
@@ -147,6 +148,7 @@ public struct Job: Sendable {
 
   // TODO: move only types cannot conform to protocols, so we can't conform to CustomStringConvertible;
   //       we can still offer a description to be called explicitly though.
+  @_unavailableInEmbedded
   public var description: String {
     let id = _getJobTaskId(UnownedJob(context: self.context))
     /// Tasks are always assigned an unique ID, however some jobs may not have it set,
@@ -215,6 +217,7 @@ public struct ExecutorJob: Sendable {
 
   // TODO: move only types cannot conform to protocols, so we can't conform to CustomStringConvertible;
   //       we can still offer a description to be called explicitly though.
+  @_unavailableInEmbedded
   public var description: String {
     let id = _getJobTaskId(UnownedJob(context: self.context))
     /// Tasks are always assigned an unique ID, however some jobs may not have it set,

stdlib/public/Concurrency/Task.cpp

@@ -1601,7 +1601,6 @@ static void swift_task_asyncMainDrainQueueImpl() {
   swift_task_donateThreadToGlobalExecutorUntil([](void *context) {
     return *reinterpret_cast<bool*>(context);
   }, &Finished);
-  exit(0);
 #elif !SWIFT_CONCURRENCY_ENABLE_DISPATCH
   // FIXME: consider implementing a concurrent global main queue for
   // these environments?

test/embedded/concurrency-simple.swift

@@ -23,32 +23,24 @@ public func test() async -> Int {
   return v
 }
 
-@_silgen_name("swift_task_asyncMainDrainQueue")
-func _asyncMainDrainQueue() -> Never
-
 @main
 struct Main {
-  static func main() {
+  static func main() async {
     print("main")
     // CHECK: main
-
-    Task {
+    let t = Task {
       print("task")
       let x = await test()
       print(x == 42 ? "42" : "???")
     }
-    print("drain")
-    // CHECK-NEXT: drain
-
-    _asyncMainDrainQueue()
+    print("after task")
+    await t.value
+    // CHECK-NEXT: after task
     // CHECK-NEXT: task
     // CHECK-NEXT: test
     // CHECK-NEXT: await
     // CHECK-NEXT: return 42
     // CHECK-NEXT: return
     // CHECK-NEXT: 42
-
-    print("done")
-    // CHECK-NOT: done
   }
 }