Add meeting notes for 2019/04/30

Author: lqd

working-groups/polonius/minutes/2019.04.30-meeting.md

@@ -0,0 +1,36 @@
+# WG-Polonius meeting minutes: 2019/04/30
+---
+
+Relevant links:
+- The meeting happened in this [Zulip thread](https://rust-lang.zulipchat.com/#narrow/stream/186049-t-compiler.2Fwg-polonius/topic/meeting.202019.2E04.2E30).
+- The [WIP Roadmap](https://paper.dropbox.com/doc/Polonius-Roadmap--AY6C806s~AZK~e7wagmys2_wAg-hk3a9ynduUN2gk1A0NNTF) Paper.
+
+---
+
+In this meeting, we started with a short review of the previous week's work:
+- [Albin] continued work on implementing liveness in [Polonius](https://github.com/rust-lang/polonius/pull/105), and opened the [rustc](https://github.com/rust-lang/rust/pull/60266) part of this work: generating the facts needed by the Polonius computation.
+- [Niko] wrote up some more [notes](https://github.com/rust-lang/polonius/issues/104#issuecomment-488076424) on continuing the liveness work: the next major part being computing the `region_live_at` facts in Polonius analyses instead of rustc.
+- [Rémy] continued the previous week's work of using the results of `LocInsensitive` in `DatafrogOpt` via the `Hybrid` analysis, especially looking for changes in behaviour using polonius and rustc's tests, and ran into the task mentioned the week before: the rustc ui test suite under polonius has more failures than expected.
+- [@lokalmatador] looked into building rustc and the various bits they would need for profiling.
+
+Since the liveness work is a bit complex, has many moving parts, and is generally hard to test, we [talked](https://rust-lang.zulipchat.com/#narrow/stream/186049-t-compiler.2Fwg-polonius/topic/meeting.202019.2E04.2E30/near/164566587) about correctness, testing, rustc's test suite and the need to have a reasonable test suite in general. A first step will be to look into rustc's test suite failures, `ignore`ing irrelevant tests or add `bless`ed output, at the very least to track changes and regressions more easily.
+
+The WIP plan about polonius features and rustc integration/subsumption looks clear:
+- liveness, which we are actively working on now.
+- moves, which should hopefully be smaller, has precedent in the work on Lark, and could be partially/possibly applicable to rustc.
+- regions and region logic, for which we have started working on the easier parts, but also crosses paths with the [traits WG and chalk effort](https://rust-lang.zulipchat.com/#narrow/stream/144729-wg-traits/topic/meeting.202019.2E04.2E29/near/164478317) for the more complex ones.
+
+Useful future tasks we mentioned:
+- after the inaugural talk, it'd be useful to continue the "explaining Polonius" series of videos/talks, focusing on the analysis rules and examples to learn, or remember, why they are the way they are.
+
+----
+For the following week:
+- [Albin] will continue on liveness.
+- [Rémy] will look at the rustc tests in more detail.
+- [Niko] will prepare the next steps in the liveness, to stay ahead of [Albin]'s progress.
+- [@lokalmatador] will familiarize with the steps [Niko] wrote, with available help from the rest of the WG.
+
+[Albin]: https://github.com/albins
+[Niko]: https://github.com/nikomatsakis
+[Rémy]: https://github.com/lqd
+[@lokalmatador]: https://github.com/lokalmatador