implement simple rethrowing logic, however body throw always wins

Author: ktoso

include/swift/Runtime/Concurrency.h

@@ -307,7 +307,8 @@ bool swift_taskGroup_isDiscardingResults(TaskGroup *group);
 /// \code
 /// func swift_taskGroup_waitAll(
 ///     waitingTask: Builtin.NativeObject, // current task
-///     group: Builtin.RawPointer
+///     group: Builtin.RawPointer,
+///     bodyError: Swift.Error?
 /// ) async throws
 /// \endcode
   SWIFT_EXPORT_FROM(swift_Concurrency)
@@ -316,6 +317,7 @@ bool swift_taskGroup_isDiscardingResults(TaskGroup *group);
       OpaqueValue *resultPointer,
       SWIFT_ASYNC_CONTEXT AsyncContext *callerContext,
       TaskGroup *group,
+      SwiftError *bodyError,
       ThrowingTaskFutureWaitContinuationFunction *resumeFn,
       AsyncContext *callContext);
 

stdlib/public/CompatibilityOverride/CompatibilityOverrideConcurrency.def

@@ -326,9 +326,10 @@ OVERRIDE_TASK_GROUP(taskGroup_waitAll, void,
                     (OpaqueValue *resultPointer,
                         SWIFT_ASYNC_CONTEXT AsyncContext *callerContext,
                         TaskGroup *_group,
+                        SwiftError *bodyError,
                         ThrowingTaskFutureWaitContinuationFunction *resumeFn,
                         AsyncContext *callContext),
-                    (resultPointer, callerContext, _group,
+                    (resultPointer, callerContext, _group, bodyError,
                         resumeFn, callContext))
 
 OVERRIDE_TASK_LOCAL(task_reportIllegalTaskLocalBindingWithinWithTaskGroup, void,

stdlib/public/Concurrency/DiscardingTaskGroup.swift

@@ -154,7 +154,7 @@ public struct DiscardingTaskGroup {
   /// - Throws: The first error that was encountered by this group.
   @usableFromInline
   internal mutating func awaitAllRemainingTasks() async throws {
-    let _: Void? = try await _taskGroupWaitAll(group: _group)
+    let _: Void? = try await _taskGroupWaitAll(group: _group, bodyError: nil)
   }
 
   @_alwaysEmitIntoClient
@@ -393,12 +393,12 @@ public func withThrowingDiscardingTaskGroup<GroupResult>(
   } catch {
     group.cancelAll()
 
-    try await group.awaitAllRemainingTasks()
+    try await group.awaitAllRemainingTasks(bodyError: error)
 
     throw error
   }
 
-  try await group.awaitAllRemainingTasks()
+  try await group.awaitAllRemainingTasks(bodyError: nil)
 
   return result
   #else
@@ -466,8 +466,8 @@ public struct ThrowingDiscardingTaskGroup<Failure: Error> {
 
   /// Await all the remaining tasks on this group.
   @usableFromInline
-  internal mutating func awaitAllRemainingTasks() async throws {
-    let _: Void? = try await _taskGroupWaitAll(group: _group)
+  internal mutating func awaitAllRemainingTasks(bodyError: Error?) async throws {
+    let _: Void? = try await _taskGroupWaitAll(group: _group, bodyError: bodyError)
   }
 
 #if SWIFT_STDLIB_TASK_TO_THREAD_MODEL_CONCURRENCY
@@ -549,7 +549,8 @@ extension ThrowingDiscardingTaskGroup: Sendable { }
 @discardableResult
 @_silgen_name("swift_taskGroup_waitAll")
 func _taskGroupWaitAll<T>(
-    group: Builtin.RawPointer
+    group: Builtin.RawPointer,
+    bodyError: Error?
 ) async throws -> T?
 
 @available(SwiftStdlib 5.8, *) // FIXME: remove