Stream: wg-async-foundations

Topic: meeting 2020.01.21


tmandry (Jan 21 2020 at 18:01, on Zulip):

@WG-async-foundations meeting time

Florian Gilcher (Jan 21 2020 at 18:01, on Zulip):

:wave:

tmandry (Jan 21 2020 at 18:02, on Zulip):

ok, let's start with triage

tmandry (Jan 21 2020 at 18:02, on Zulip):

Uncategorized issues

tmandry (Jan 21 2020 at 18:02, on Zulip):

only one today

tmandry (Jan 21 2020 at 18:02, on Zulip):

Dropped variables still included in generator type #57478

Giles Cope (Jan 21 2020 at 18:03, on Zulip):

looks legit

tmandry (Jan 21 2020 at 18:04, on Zulip):

this is something I'd categorize as an "enhancement"

tmandry (Jan 21 2020 at 18:05, on Zulip):

well, it's sort of a bug, but one that's fairly easy to work around

tmandry (Jan 21 2020 at 18:05, on Zulip):

I guess without good diagnostics it can be a pain though

tmandry (Jan 21 2020 at 18:06, on Zulip):

and confusing

tmandry (Jan 21 2020 at 18:06, on Zulip):

I'll tag it OnDeck

Giles Cope (Jan 21 2020 at 18:07, on Zulip):

Does this feed into trying to keep the futures having minimum space in memory?

tmandry (Jan 21 2020 at 18:07, on Zulip):

yes, but the main concern of mine for now is confusing compiler errors

Florian Gilcher (Jan 21 2020 at 18:08, on Zulip):

I think that's a reasonable stance to take, I think it's currently the biggest QOL issue

Giles Cope (Jan 21 2020 at 18:09, on Zulip):

ok - so next thing on that issue would be an example of what we'd like the error to say?

tmandry (Jan 21 2020 at 18:09, on Zulip):

either that, or we just don't emit an error in those cases

tmandry (Jan 21 2020 at 18:10, on Zulip):

the bug is about cases where we've already moved a type out of the generator prior to the yield

tmandry (Jan 21 2020 at 18:10, on Zulip):

we can detect that, and not include it in the GeneratorWitness (iirc)

Giles Cope (Jan 21 2020 at 18:10, on Zulip):

I'm all for that - that would mean smaller futures.

tmandry (Jan 21 2020 at 18:10, on Zulip):

I'll leave a comment about it

tmandry (Jan 21 2020 at 18:10, on Zulip):

okay, moving on

tmandry (Jan 21 2020 at 18:11, on Zulip):

Focus issues

tmandry (Jan 21 2020 at 18:11, on Zulip):

we closed some of these in the last week

tmandry (Jan 21 2020 at 18:12, on Zulip):

some are still ongoing

tmandry (Jan 21 2020 at 18:12, on Zulip):

Unhelpful error messages from borrow checker with async/await #67765

tmandry (Jan 21 2020 at 18:12, on Zulip):

@Aaron Hill have you been able to make progress here?

tmandry (Jan 21 2020 at 18:13, on Zulip):

looks like there are more recent comments on the PR

tmandry (Jan 21 2020 at 18:13, on Zulip):

(back in cache.. this was something we couldn't agree on how to fix, so that's what the work is blocked on)

tmandry (Jan 21 2020 at 18:14, on Zulip):

but it doesn't look like we've come to any consensus on

tmandry (Jan 21 2020 at 18:14, on Zulip):

maybe @Aaron Hill and @nikomatsakis should schedule some time to chat

tmandry (Jan 21 2020 at 18:14, on Zulip):

Confusing/incorrect error message with incoherent implementations and async blocks #67651

tmandry (Jan 21 2020 at 18:16, on Zulip):

okay, this seems to need a refactor of the type checking code for generators

tmandry (Jan 21 2020 at 18:16, on Zulip):

(well, not a pure refactor per se, we'd change the behavior)

tmandry (Jan 21 2020 at 18:17, on Zulip):

and it seems like there's a "direction of exploration" that niko makes clear.. but it's still a bit open ended

tmandry (Jan 21 2020 at 18:18, on Zulip):

I guess I'm wondering if @nikomatsakis should stay assigned, or if they've already done all the investigation here

tmandry (Jan 21 2020 at 18:19, on Zulip):

I'll leave a comment, I guess

tmandry (Jan 21 2020 at 18:19, on Zulip):

not Send due to await retainment #67611

nikomatsakis (Jan 21 2020 at 18:20, on Zulip):

:wave: -- sorry, I was actually at a dr app't until recently, back now

nikomatsakis (Jan 21 2020 at 18:21, on Zulip):

(took longer than anticipated, not sure how much I'll be able to be online today)

tmandry (Jan 21 2020 at 18:21, on Zulip):

:wave:

nikomatsakis (Jan 21 2020 at 18:21, on Zulip):

anyway re: #67651 I hope to do a bit more investigation there

tmandry (Jan 21 2020 at 18:22, on Zulip):

okay, good to know

tmandry (Jan 21 2020 at 18:23, on Zulip):

for #67611, I left some ideas but the conversation doesn't seem to be gaining any traction :)

nikomatsakis (Jan 21 2020 at 18:24, on Zulip):

yeah that's a tricky one

nikomatsakis (Jan 21 2020 at 18:24, on Zulip):

I read @Matthew Jasper's comment -- I guess I'm not 100% sure what I think yet, I have to re-read the MIR changes

tmandry (Jan 21 2020 at 18:25, on Zulip):

okay, well I guess we'll discuss it more outside the meeting

tmandry (Jan 21 2020 at 18:26, on Zulip):

async fn presence affects an unrelated error message #66312

nikomatsakis (Jan 21 2020 at 18:26, on Zulip):

I think this is probably a dup of #67651

tmandry (Jan 21 2020 at 18:26, on Zulip):

yeah

tmandry (Jan 21 2020 at 18:27, on Zulip):

should we close or leave open?

tmandry (Jan 21 2020 at 18:27, on Zulip):

if you're investigating more, I guess we can leave it open until we're sure

tmandry (Jan 21 2020 at 18:27, on Zulip):

async/await: awaiting inside a match block captures borrow too eagerly #57017

nikomatsakis (Jan 21 2020 at 18:27, on Zulip):

leave open I think

nikomatsakis (Jan 21 2020 at 18:28, on Zulip):

I think this is fairly blocked :/

nikomatsakis (Jan 21 2020 at 18:29, on Zulip):

I wonder if it might be someting to consider for deeper discussion at Rust All Hands... it's certianly on a list of like "technically complex issues to resolve"

nikomatsakis (Jan 21 2020 at 18:29, on Zulip):

not sure tbqh if Ruts All Hands is a good time to dive into such issues :)

nikomatsakis (Jan 21 2020 at 18:29, on Zulip):

"sometimes"

tmandry (Jan 21 2020 at 18:29, on Zulip):

yeah

tmandry (Jan 21 2020 at 18:30, on Zulip):

if not then, then this is more support for having a regular "design" meeting :)

tmandry (Jan 21 2020 at 18:31, on Zulip):

it seems like there are a number of things blocked on design aspects

nikomatsakis (Jan 21 2020 at 18:31, on Zulip):

Hmm, I'm not so sure

nikomatsakis (Jan 21 2020 at 18:31, on Zulip):

What are you thinking of?

nikomatsakis (Jan 21 2020 at 18:31, on Zulip):

I guess it depends on how far out you zoom

nikomatsakis (Jan 21 2020 at 18:31, on Zulip):

and what kind of design you're talking about :)

Florian Gilcher (Jan 21 2020 at 18:32, on Zulip):

All-hands is definitely a good place to kick complex issues off

tmandry (Jan 21 2020 at 18:32, on Zulip):

I mean, all the open Focus issues :)

tmandry (Jan 21 2020 at 18:32, on Zulip):

#67765, #67651, #67611

tmandry (Jan 21 2020 at 18:33, on Zulip):

(maybe my definition of design is different)

nikomatsakis (Jan 21 2020 at 18:33, on Zulip):

I see, I guess it depends on how blocked

nikomatsakis (Jan 21 2020 at 18:34, on Zulip):

I guess I just mean that #57017 just seems "a step up" in complexity

nikomatsakis (Jan 21 2020 at 18:34, on Zulip):

compared to the others

tmandry (Jan 21 2020 at 18:34, on Zulip):

yeah, fair enough

nikomatsakis (Jan 21 2020 at 18:34, on Zulip):

but I do have to spend some time on #67765

tmandry (Jan 21 2020 at 18:35, on Zulip):

I guess I'm saying that we should have time to dig into some of the context around the rest of the issues

tmandry (Jan 21 2020 at 18:35, on Zulip):

and spread that context around a bit

tmandry (Jan 21 2020 at 18:35, on Zulip):

anyways, we haven't gotten to the OnDeck issues yet

tmandry (Jan 21 2020 at 18:36, on Zulip):

OnDeck issues

tmandry (Jan 21 2020 at 18:36, on Zulip):

is anyone looking for things to do?

tmandry (Jan 21 2020 at 18:37, on Zulip):

seems like not everyone is around today, so I guess we'll call it

nikomatsakis (Jan 21 2020 at 18:38, on Zulip):

seems good

tmandry (Jan 21 2020 at 18:38, on Zulip):

as always, if anyone wants to pick up something asynchronously, the OnDeck list is a good place to start :)

tmandry (Jan 21 2020 at 18:39, on Zulip):

thanks for coming, y'all

Last update: Feb 25 2020 at 04:15UTC