On the proliferation of try (and, soon, await)

[gwendal.roue (Gwendal Roué)]

@David_Catmull

A task created with async let is run concurrently, which I take to mean executed on a different thread, though the proposal doesn't seem to say that explicitly so I'm a little confused.

The actual scheduling of tasks is delegated to an executor: https://github.com/DougGregor/swift-evolution/blob/structured-concurrency/proposals/nnnn-structured-concurrency.md#executors

So the actual flavor of concurrency will depend on both the async method, and the executor. The phrasing prefers "concurrency" over "parallelism", for multiple reasons:

• As a consumer of an async methods with the await keyword (or async let), the language wants you to think about concurrency more than parallelism or threads (lexicon). For example, an async method is allowed to execute and return synchronously. An async method is allowed to schedule some little jobs on the main RunLoop (think I/O). An async method is allowed to spawn a new thread, or use libDispatch, or use other facilities provided by the new Task and Actor apis.
• async/await are more fundamental than Structured concurrency and Actors, which will, I guess, answer your questions with more details.
• I expect that "don't mismatch DispatchQueue.async with Swift's async" will soon become a mantra, and a key step in the discovery of the new concurrency features.