​​wg-async-foundations post-stable triage

​​Agenda for this meeting

  • ​​What to prioritize over the next N weeks
  • ​​What about beyond that
  • ​​How to triage and track things now that async-await is stable
​​

​​Niko’s random idea

  • ​​Two questions, really:
  • ​​What new lang/lib features should we be looking at and in what order?
  • ​​Not what I think we should answer in this meeting
  • ​​Probably good to give a bit of time to think this over
  • ​​I would like to maybe do a series of “educate Niko” videos
  • ​​where I (or others…) interview folks who know things, like cramertj, carl, etc about what they think would be good, their voice of async I/O
  • ​​“workarounds you should know and love”
  • ​​Future strangelove: how I learned to stop worrying and love the workaround

​​Deferred issues

  • ​​Sep 26 — beta branches that carries async-await, last chance to affect stable
  • ​​back-compat makes sense
  • ​​diagnostics and shorter term fixes
  • ​​cramertj: “return type”
  • ​​nikomatsakis: overapproximation of what cross an await
  • ​​drop(foo);​ doesn’t matter
  • ​​comes up a lot with std::mutex​ and futures code
  • ​​but this is something of a gotcha, would prefer a futures-aware mutex is you’re going to use them
  • ​​alternative: “surprisingly hard things” chapter?
  • ​​or update the chapter on shared state
  • ​​afterwards 
​​

​​“Known bugs”

​​Short term

  • ​​
  • ​​inline on fn — should just be an error for now
  • ​​Centril: Why that? #[inline]​ is a hint and may not have any effects at all but I’d like to not add more special rules in the static semantics if avoidable.
  • ​​mark async constructors as inline
  • ​​“Late diagnostics” or “error at point of use”
  • ​​When a future is not send but must be, can we point into the source of the future and not just at the site of use?

​​Long term

​​
  • ​​Overcapture
  • ​​Overapproximation: where the “pre-MIR” analysis determines that we will capture, but we do not
  • ​​Overcapture: the MIR actually does capture, but shouldn’t
  • ​​Short-term fixes:
  • ​​Improve diagnostics
  • ​​Improve documentation
  • ​​UCG interactions
  • ​​#63818
  • ​​“lifetime of underlying stack slots”
  • ​​if you make a raw ptr to a local variable, then move from that variable, can the raw ptr still be used?
  • ​​what if the variable is dead but not moved from? (#63768)