[swift-evolution] [Concurrency] async/await + actors

Zach Waldowski zach at waldowski.me
Thu Aug 17 23:11:46 CDT 2017

On Thu, Aug 17, 2017, at 10:04 PM, Chris Lattner via swift-evolution wrote:> That said, I don’t feel like I have enough data to have a strong
> opinion on it.  The missing link for me is exactly how pervasive the
> non-throwing cocoa completion handlers are.  If it turns out that
> people would have to confront "async(nonthrowing)” in practice (as
> opposed to being an obscure corner that the compiler implementers have
> to care about) then it is probably the wrong design.
It may be helpful to look at data points outside of Cocoa. We use a
Future framework that distinguishes between plain old `Future<T>` and
`Future<Result<T>>`. In a back-of-the-hand calculation, about 10% of our
futures don’t use  Result. It’s rarer, but it is useful; it aligns well
with the Error manifesto’s notion of a domain failures.
I think I’m overall in favor of an implicitly throwing model, though.
Not only is it cleaner, but it’ll simplify all sorts of abstractions.
f.ex: In our use of this framework, collecting up errors or
cancellations for an array of tasks is a perennial problem. `Future<T?>`
(and similarly `async -> T?`) can be plenty useful, but I’m not sure
they pull their weight enough to deserve occupying the best syntax.
(Huge, huge +1 to the whole shebang, though. Let’s just do this!!!)

  Zachary Waldowski
  zach at waldowski.me

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