SE-0296: async/await

[Douglas_Gregor]

@adamkemp

I feel like that example is more of an example of "code not to put in an async function period".

I said it was contrived ;)

@adamkemp

@David_Catmull

To me that implies that any subsequent statement that would exit scope and trigger that defer would have to be called with await .

Oh please no...that would be terrible UX. I believe conceptually a developer does not need to know that a try/throw/return statement might be a suspension point because the actual suspension point is in the defer block itself. The try/throw/return statement is control flow, and thus it results in jumping to some other place. That other place may happen to suspend, but that happens after the normal control flow.

I agree that I wouldn't want this to force us to have await return, await try, await throw, etc.

@adamkemp

But I still think await in defer can work, and I still think there's not quite a strong enough reason (that I've seen) that it shouldn't work.

There's no technical reason that I can see, either. There are use cases (e.g., closing a file handle), and the reasons I can come up to not allow it---somewhat less-obvious potential suspension points (although there's still clearly an await in the source within the defer) and asymmetry with throw (which is banned in defer for legitimate reasons)---aren't very strong.

So let's chalk this up to "we should remove this restriction unless more arguments come up in favor of keeping it."

Doug