SE-0304: Structured Concurrency

[xAlien95 (Stefano De Carolis)]

@ktoso

I would like to propose:

  public static func withGroup<ChildTaskResult, GroupResult>(
    childResult: ChildTaskResult.Type,
    returning returnType: GroupResult.Type = GroupResult.self,
    body: (inout Task.Group<ChildTaskResult>) async throws -> GroupResult
  ) async rethrows -> GroupResult {

or even more fluently:

  public static func withGroup<ChildTaskResult, GroupResult>(
    aggregating: ChildTaskResult.Type, // or collecting?
    returning returnType: GroupResult.Type = GroupResult.self,
    body: (inout Task.Group<ChildTaskResult>) async throws -> GroupResult
  ) async rethrows -> GroupResult

If there's room for API naming changes I would propose:

static func withGroup<Element, GroupResult>(
  of: Element.Type,
  returning returnType: GroupResult.Type = GroupResult.self,
  body: (inout Task.Group<Element>) async throws -> GroupResult
) async rethrows -> GroupResult { ... }

Task.Group<TaskResult> conforms to AsyncSequence and TaskResult is its Element type. "A task group of Ints" as an async sequence of Ints.

await Task.withGroup(of: Int.self) { group in
  await group.add { 1 }

  for try await int in group { ... }
}