Stream: t-compiler

Topic: weekly meeting 2018-08-09


nikomatsakis (Aug 09 2018 at 13:59, on Zulip):

Hello @T-compiler :wave:

oli (Aug 09 2018 at 13:59, on Zulip):

o/

nagisa (Aug 09 2018 at 14:00, on Zulip):

o/

nikomatsakis (Aug 09 2018 at 14:00, on Zulip):

I'm brewing up some coffee, so brb :)

nikomatsakis (Aug 09 2018 at 14:00, on Zulip):

Etherpad: https://public.etherpad-mozilla.org/p/rust-compiler-meeting

nikomatsakis (Aug 09 2018 at 14:06, on Zulip):

ok...

nikomatsakis (Aug 09 2018 at 14:06, on Zulip):

## P-high

nikomatsakis (Aug 09 2018 at 14:07, on Zulip):

#52966 -- New deny(const_err) in unreachable code

nikomatsakis (Aug 09 2018 at 14:07, on Zulip):

Hmm, you're right -- rustc 1.10 through 1.25 do lint this as a warning. 1.26 through 1.28 do not, and now 1.29 lints it again, denied by default.

nikomatsakis (Aug 09 2018 at 14:07, on Zulip):

fun

nikomatsakis (Aug 09 2018 at 14:08, on Zulip):

so I guess the question is .. do we do anything here?

nikomatsakis (Aug 09 2018 at 14:08, on Zulip):

@Oli thoughts?

oli (Aug 09 2018 at 14:08, on Zulip):

This is an expected regression after miri

oli (Aug 09 2018 at 14:08, on Zulip):

I didn't implement the linting for casts, now I did

nikomatsakis (Aug 09 2018 at 14:09, on Zulip):

I think the only real 2 options are

nikomatsakis (Aug 09 2018 at 14:09, on Zulip):

do we leave as is, or do we make const_err warn-by-default again

nikomatsakis (Aug 09 2018 at 14:09, on Zulip):

sounds like "leave as is" is probably fine

nikomatsakis (Aug 09 2018 at 14:10, on Zulip):

(agree? disagree?)

nikomatsakis (Aug 09 2018 at 14:10, on Zulip):

ok

nikomatsakis (Aug 09 2018 at 14:10, on Zulip):

next up: #52849 -- A pretty big performance hit after a recent change

nikomatsakis (Aug 09 2018 at 14:10, on Zulip):

specifically, some kind of CTFE compile-time regression?

oli (Aug 09 2018 at 14:11, on Zulip):

yea, @RalfJ fixed most of it

simulacrum (Aug 09 2018 at 14:11, on Zulip):

perf tests will appear in the next ~5 hours

oli (Aug 09 2018 at 14:11, on Zulip):

still some weird edge cases, but we have benchmark canaries now

nikomatsakis (Aug 09 2018 at 14:12, on Zulip):

ok

nikomatsakis (Aug 09 2018 at 14:12, on Zulip):

:+1:

nikomatsakis (Aug 09 2018 at 14:12, on Zulip):

so we'll leave it as is for now

nikomatsakis (Aug 09 2018 at 14:12, on Zulip):

next: #52390 -- Segfault during tests on rust 1.27.x on macOS

nikomatsakis (Aug 09 2018 at 14:13, on Zulip):

@nagisa is this one of those things you were talking about in the sigsegvs topic?

oli (Aug 09 2018 at 14:14, on Zulip):

feelings in last week's meeting were to close this week XD

nikomatsakis (Aug 09 2018 at 14:14, on Zulip):

oh,I see, this is the TLS thing

nikomatsakis (Aug 09 2018 at 14:14, on Zulip):

ok, let's close

nagisa (Aug 09 2018 at 14:15, on Zulip):

the issues I’ve talked about were about the compiler itself crashing

nikomatsakis (Aug 09 2018 at 14:15, on Zulip):

#52141 -- [Rust 2018] pub use some_crate as some_name breaks glob imports

nikomatsakis (Aug 09 2018 at 14:15, on Zulip):

If someone can investigate this now, please do.
I'll be able to do it in 3-4 weeks.

nikomatsakis (Aug 09 2018 at 14:15, on Zulip):

seems like we might want to find someone to look

nikomatsakis (Aug 09 2018 at 14:16, on Zulip):

cc @eddyb — are you still working on the name resolution code as part of EP2 work?

nikomatsakis (Aug 09 2018 at 14:16, on Zulip):

although there is https://github.com/rust-lang/rust/pull/52923

nikomatsakis (Aug 09 2018 at 14:16, on Zulip):

it looks like @eddyb is working on this, let's assign to them

nikomatsakis (Aug 09 2018 at 14:17, on Zulip):

next is #52140 which looks very similar?

nikomatsakis (Aug 09 2018 at 14:17, on Zulip):

#52140 -- [Rust 2018] pub use can't export crates

nikomatsakis (Aug 09 2018 at 14:18, on Zulip):

I'll assign to @eddyb too :)

nikomatsakis (Aug 09 2018 at 14:18, on Zulip):

since they don't seem to be around to defend themselves :devil:

nikomatsakis (Aug 09 2018 at 14:19, on Zulip):

#52092 -- Recent 12% perf regression in unused-warnings

nikomatsakis (Aug 09 2018 at 14:19, on Zulip):

I have my machine back and can do some profile now

nikomatsakis (Aug 09 2018 at 14:19, on Zulip):

I've done nothing though

nikomatsakis (Aug 09 2018 at 14:19, on Zulip):

I guess I'll give that a go today

nikomatsakis (Aug 09 2018 at 14:19, on Zulip):

#51608 -- Code fails to link on macOS with incremental compilation

nikomatsakis (Aug 09 2018 at 14:20, on Zulip):

@mw thoughts?

mw (Aug 09 2018 at 14:20, on Zulip):

last week we wanted to determine whether this is really p-high

mw (Aug 09 2018 at 14:21, on Zulip):

since none of the stakeholders responded, I guess it's not?

nikomatsakis (Aug 09 2018 at 14:21, on Zulip):

I guess we can downgrade until somebody complains

nikomatsakis (Aug 09 2018 at 14:21, on Zulip):

but -- is this a serious problem that might be affecting others?

nikomatsakis (Aug 09 2018 at 14:22, on Zulip):

or is it something very servo specific?

mw (Aug 09 2018 at 14:22, on Zulip):

it seems to be a very specific case, with explicit linkage for a given global

mw (Aug 09 2018 at 14:23, on Zulip):

since you get a linker error, I think people would have complained more if they ran into it often

nikomatsakis (Aug 09 2018 at 14:23, on Zulip):

ok, downgraded, shall I change you to P-medium?

nikomatsakis (Aug 09 2018 at 14:23, on Zulip):

er, I meant

nikomatsakis (Aug 09 2018 at 14:23, on Zulip):

shall I unassign you?

mw (Aug 09 2018 at 14:23, on Zulip):

yes plz

nikomatsakis (Aug 09 2018 at 14:23, on Zulip):

k

nikomatsakis (Aug 09 2018 at 14:24, on Zulip):

#51212 -- resolve suggestions do not use crate:: when enabled

nikomatsakis (Aug 09 2018 at 14:24, on Zulip):

so, the title is not fully accurate anymore

nikomatsakis (Aug 09 2018 at 14:24, on Zulip):

I believe that there was a quick fix for using crate::

nikomatsakis (Aug 09 2018 at 14:24, on Zulip):

but what won't work is getting suggestions from other crates when extern crate is not present (right @qmx ?)

qmx (Aug 09 2018 at 14:24, on Zulip):

yep

nikomatsakis (Aug 09 2018 at 14:24, on Zulip):

cc @simulacrum I'm not sure if this should be P-high...

qmx (Aug 09 2018 at 14:25, on Zulip):

working on the full solution atm, after your pointers

simulacrum (Aug 09 2018 at 14:25, on Zulip):

P-high because edition critical

simulacrum (Aug 09 2018 at 14:25, on Zulip):

We can downgrade to P-medium, but we want this for the edition for sure

nikomatsakis (Aug 09 2018 at 14:25, on Zulip):

ok, I'll leave as is, @qmx and I have been discussing some and there's been progress

nikomatsakis (Aug 09 2018 at 14:25, on Zulip):

maybe we should make it P-medium but put on a milestone

nikomatsakis (Aug 09 2018 at 14:26, on Zulip):

if it's not already

qmx (Aug 09 2018 at 14:26, on Zulip):

that works for me

nikomatsakis (Aug 09 2018 at 14:26, on Zulip):

oh, it is on one

nikomatsakis (Aug 09 2018 at 14:26, on Zulip):

ok, @qmx, let's sync up later today anyhow

qmx (Aug 09 2018 at 14:26, on Zulip):

there we go

qmx (Aug 09 2018 at 14:26, on Zulip):

:+1:

nikomatsakis (Aug 09 2018 at 14:26, on Zulip):

Compiler crashed with cannot create local mono-item #50865

nikomatsakis (Aug 09 2018 at 14:26, on Zulip):

(man, this far into the meeting before I realized I can copy-and-paste exactly what GH displays...)

nikomatsakis (Aug 09 2018 at 14:27, on Zulip):

lots of backlog here, I remember this now

nikomatsakis (Aug 09 2018 at 14:28, on Zulip):

seems like somebody ought to take charge, but not clear who that person should be

nikomatsakis (Aug 09 2018 at 14:28, on Zulip):

/me contemplates

nikomatsakis (Aug 09 2018 at 14:29, on Zulip):

well, it's RC milestone, let's levae it for now

nikomatsakis (Aug 09 2018 at 14:30, on Zulip):

rust 1.25.0 internal compiler error #49482

nikomatsakis (Aug 09 2018 at 14:30, on Zulip):

cc @mw

nikomatsakis (Aug 09 2018 at 14:31, on Zulip):

I think @mw that we don't necessarily have metadata etc for all things that get a DefId

nikomatsakis (Aug 09 2018 at 14:31, on Zulip):

could that be the problem?

mw (Aug 09 2018 at 14:31, on Zulip):

o yeah, I looked into this a little but it's weird

mw (Aug 09 2018 at 14:31, on Zulip):

they should be in the DefPathTable

nikomatsakis (Aug 09 2018 at 14:32, on Zulip):

yeah, true

mw (Aug 09 2018 at 14:32, on Zulip):

which is all that should be needed here

nikomatsakis (Aug 09 2018 at 14:32, on Zulip):

ok, well, I guess for now I will leave assigned to you?

mw (Aug 09 2018 at 14:32, on Zulip):

I still think it has to do with proc-macro crates being weird about metadata

nikomatsakis (Aug 09 2018 at 14:32, on Zulip):

seems like a likely cause

mw (Aug 09 2018 at 14:33, on Zulip):

yeah, unless you want to see progress :P

nikomatsakis (Aug 09 2018 at 14:33, on Zulip):

:/

nikomatsakis (Aug 09 2018 at 14:34, on Zulip):

is it hard to reproduce?

mw (Aug 09 2018 at 14:34, on Zulip):

no

mw (Aug 09 2018 at 14:34, on Zulip):

there's GH repo that you just need to clone

nikomatsakis (Aug 09 2018 at 14:34, on Zulip):

I guess the question is whether we believe it P-high or not

nikomatsakis (Aug 09 2018 at 14:34, on Zulip):

it is a regression

mw (Aug 09 2018 at 14:34, on Zulip):

I'll try to look into it some more next week

nikomatsakis (Aug 09 2018 at 14:34, on Zulip):

hard to tell how widespread

nikomatsakis (Aug 09 2018 at 14:34, on Zulip):

let's leave as is for now

nikomatsakis (Aug 09 2018 at 14:35, on Zulip):

syntax_pos::symbol::Symbol::gensym() is incompatible with stable hashing. #49300

nikomatsakis (Aug 09 2018 at 14:35, on Zulip):

what should we do about that :point_up: ?

nikomatsakis (Aug 09 2018 at 14:35, on Zulip):

@pnkfelix writes that maybe we should downgrade to P-medium

nikomatsakis (Aug 09 2018 at 14:35, on Zulip):

I believe this was one of those "I don't want to forget about it" sort of things

nikomatsakis (Aug 09 2018 at 14:35, on Zulip):

I'm kind of inclined to agree we should downgrade

mw (Aug 09 2018 at 14:36, on Zulip):

yes, I'm OK with that

mw (Aug 09 2018 at 14:36, on Zulip):

there's an assertion in the code now that should catch this early, I think

nikomatsakis (Aug 09 2018 at 14:36, on Zulip):

ok

nikomatsakis (Aug 09 2018 at 14:37, on Zulip):

Tracking issue for RFC 2093: Infer T: 'x outlives requirements on structs #44493

nikomatsakis (Aug 09 2018 at 14:37, on Zulip):

FCP is complete

nikomatsakis (Aug 09 2018 at 14:37, on Zulip):

I guess we should get someone to stabilize

nikomatsakis (Aug 09 2018 at 14:38, on Zulip):

I bet that @toidiu would be up for that :)

nikomatsakis (Aug 09 2018 at 14:38, on Zulip):

we should port the compiler to use it too .. oh, we have to wait until beta

nikomatsakis (Aug 09 2018 at 14:38, on Zulip):

/me can't wait to stop typing 'cx, 'gcx: 'tcx, 'tcx: 'cx

nikomatsakis (Aug 09 2018 at 14:40, on Zulip):

we should probably split off a separate issue for the new feature gate?

nikomatsakis (Aug 09 2018 at 14:40, on Zulip):

ok, that's all of P-high

nikomatsakis (Aug 09 2018 at 14:40, on Zulip):

40min, sheesh

nikomatsakis (Aug 09 2018 at 14:41, on Zulip):

Stable to beta regressions

nikomatsakis (Aug 09 2018 at 14:41, on Zulip):

Wildcard imports do not seem to propagate as expected for tuple-like struct types having at least one non-pub field #53140

nikomatsakis (Aug 09 2018 at 14:41, on Zulip):

kind of looks like... T-compiler?

nikomatsakis (Aug 09 2018 at 14:41, on Zulip):

bisected to https://github.com/rust-lang/rust/pull/52555

nikomatsakis (Aug 09 2018 at 14:42, on Zulip):

I guess I'll mark as P-high, @Vadim Petrochenkov already assigned themselves...

nikomatsakis (Aug 09 2018 at 14:43, on Zulip):

everything else looks properly categorized

nikomatsakis (Aug 09 2018 at 14:43, on Zulip):

Stable to nightly regressions

nikomatsakis (Aug 09 2018 at 14:43, on Zulip):

Regression importing log’s warn! macro inside of include!()ed file #53205

nikomatsakis (Aug 09 2018 at 14:44, on Zulip):

I'm not really clear on what this is but @Vadim Petrochenkov seems to be on it

nikomatsakis (Aug 09 2018 at 14:44, on Zulip):

P-high I guess, as it's a regression

nikomatsakis (Aug 09 2018 at 14:45, on Zulip):

Stable to stable regressions not previously prioritized

nikomatsakis (Aug 09 2018 at 14:45, on Zulip):

oh dear, many

nikomatsakis (Aug 09 2018 at 14:45, on Zulip):

Internal compiler error: unexpected panic: thread 'main' panicked at 'no entry found for key' #53146

nikomatsakis (Aug 09 2018 at 14:46, on Zulip):

but @Esteban Küber reports "Happens on stable 1.28. Doesn't occur on beta, nightly or 1.27.2."

nikomatsakis (Aug 09 2018 at 14:46, on Zulip):

some kind of impl trait bug I guess

nikomatsakis (Aug 09 2018 at 14:46, on Zulip):

I'm inclined..to close?

nikomatsakis (Aug 09 2018 at 14:46, on Zulip):

/me getting lazy I guess

nikomatsakis (Aug 09 2018 at 14:46, on Zulip):

the question is whether we would do a point release for this

nikomatsakis (Aug 09 2018 at 14:46, on Zulip):

and I think not

nikomatsakis (Aug 09 2018 at 14:47, on Zulip):

(@simulacrum, thoughts?)

simulacrum (Aug 09 2018 at 14:47, on Zulip):

Hm, probably no

simulacrum (Aug 09 2018 at 14:47, on Zulip):

probably good to bisect though

simulacrum (Aug 09 2018 at 14:47, on Zulip):

I'll assign to myself for bisection

nikomatsakis (Aug 09 2018 at 14:48, on Zulip):

ok, I've marked as P-medium in the meantime

nikomatsakis (Aug 09 2018 at 14:48, on Zulip):

rustc doesn't output anything but exits with 101 and doesn't emit any files #52913

nikomatsakis (Aug 09 2018 at 14:48, on Zulip):

regression introduced by @Sunjay Varma in https://github.com/rust-lang/rust/pull/45904, according to @Esteban Küber

nikomatsakis (Aug 09 2018 at 14:49, on Zulip):

or perhaps by me, since I was reviewer :P

nikomatsakis (Aug 09 2018 at 14:49, on Zulip):

oh wait

nikomatsakis (Aug 09 2018 at 14:49, on Zulip):

maybe I misunderstood the comment

nikomatsakis (Aug 09 2018 at 14:50, on Zulip):

I guess queston is how to prioritize this...

nikomatsakis (Aug 09 2018 at 14:50, on Zulip):

P-high I suppose. seems bad. Even though GATs are "not really working", someone could stumble on this by accident.

varkor (Aug 09 2018 at 14:51, on Zulip):

shouldn't any use of a GAT be considered an error until they're actually working?

varkor (Aug 09 2018 at 14:51, on Zulip):

or are there some cases where they work enough that people might be using them?

nikomatsakis (Aug 09 2018 at 14:51, on Zulip):

they don't work

nikomatsakis (Aug 09 2018 at 14:51, on Zulip):

the bug is that rustc emits nothing at all

nikomatsakis (Aug 09 2018 at 14:51, on Zulip):

vs some kind of error

nikomatsakis (Aug 09 2018 at 14:52, on Zulip):

I'm not really clear on why that is :)

nikomatsakis (Aug 09 2018 at 14:52, on Zulip):

rustc fails to raise rlimits for stacksize on mac for doctest runs through make #52801

nikomatsakis (Aug 09 2018 at 14:52, on Zulip):

I have no real idea what to do about this...

nikomatsakis (Aug 09 2018 at 14:52, on Zulip):

is it a regresson really?

nikomatsakis (Aug 09 2018 at 14:53, on Zulip):

I guess it occurs because of the stack guard?

nikomatsakis (Aug 09 2018 at 14:54, on Zulip):

oh, hmm, is the problem that we are trying to "raise" the stack limit but it's already been raised even higher...?

nikomatsakis (Aug 09 2018 at 14:54, on Zulip):

anyway i'm inclined to call this P-medium

nikomatsakis (Aug 09 2018 at 14:56, on Zulip):

ok, that's the list of new regressions

nikomatsakis (Aug 09 2018 at 14:57, on Zulip):

looking at I-nominated issues

nikomatsakis (Aug 09 2018 at 14:57, on Zulip):

one thing is a PSA: we're starting to land PRs that add #![feature(nll)] to all the rust crates

nikomatsakis (Aug 09 2018 at 14:57, on Zulip):

tracking that effort in #53172

nikomatsakis (Aug 09 2018 at 14:58, on Zulip):

Rustdoc ignores traits implemented inside of a function #52545 is nominated

nikomatsakis (Aug 09 2018 at 14:58, on Zulip):

seems like fix is underway

nikomatsakis (Aug 09 2018 at 14:58, on Zulip):

the other nominations all seem stale

oli (Aug 09 2018 at 14:58, on Zulip):

I have a thing nominated by the tools team (I think) for the compiler team. The clippy 1.0 RFC is currently waiting on us to decide on lint uplift of correctness lints: https://github.com/rust-lang/rfcs/blob/b9c8471887f308223c226642cad3a8290731b942/text/0000-clippy-uno.md#correctness-deny

nikomatsakis (Aug 09 2018 at 14:59, on Zulip):

ah, ok

oli (Aug 09 2018 at 14:59, on Zulip):

Should I create an issue with all the lints and put it into FCP?

nikomatsakis (Aug 09 2018 at 14:59, on Zulip):

i.e., to go through that list and decide which lints we will uplift?

oli (Aug 09 2018 at 14:59, on Zulip):

yea basically

nikomatsakis (Aug 09 2018 at 14:59, on Zulip):

that sounds good

nikomatsakis (Aug 09 2018 at 14:59, on Zulip):

perhaps T-compiler + T-lang

oli (Aug 09 2018 at 14:59, on Zulip):

ok, will do

nikomatsakis (Aug 09 2018 at 14:59, on Zulip):

or at least just cc the lang folks

nikomatsakis (Aug 09 2018 at 14:59, on Zulip):

not really clear where that stuff falls to me

nikomatsakis (Aug 09 2018 at 14:59, on Zulip):

doens't matter too much

nikomatsakis (Aug 09 2018 at 15:01, on Zulip):

# beta nominations

toidiu (Aug 09 2018 at 15:01, on Zulip):

yes please :)

nikomatsakis (Aug 09 2018 at 15:02, on Zulip):

Fix NLL migration mode so that reports region errors when necessary. #53045

nikomatsakis (Aug 09 2018 at 15:02, on Zulip):

that one is not approved

nikomatsakis (Aug 09 2018 at 15:02, on Zulip):

but seems like it clearly should be

nikomatsakis (Aug 09 2018 at 15:03, on Zulip):

waiting on our team

nikomatsakis (Aug 09 2018 at 15:03, on Zulip):

(nothing)

nikomatsakis (Aug 09 2018 at 15:04, on Zulip):

ok, we're done!

nikomatsakis (Aug 09 2018 at 15:04, on Zulip):

anybody want to raise anything else?

nikomatsakis (Aug 09 2018 at 15:04, on Zulip):

thanks all <3

Sunjay Varma (Aug 09 2018 at 19:34, on Zulip):

@nikomatsakis The regression you mentioned where no output is produced was already known to us from the very beginning: https://github.com/rust-lang/rust/issues/47206

Sunjay Varma (Aug 09 2018 at 19:34, on Zulip):

We thought it was weird and knew we should look into it but then no one ever did

nikomatsakis (Aug 09 2018 at 20:14, on Zulip):

@Sunjay Varma oh :) forgot about that!

varkor (Aug 09 2018 at 20:21, on Zulip):

although where in assoc ty impls should probably be behind the feature gate too, right?

varkor (Aug 09 2018 at 20:21, on Zulip):

so the example in the new issue shouldn't even get to that stage

nikomatsakis (Aug 09 2018 at 20:23, on Zulip):

might be an oversight, not sure

Last update: Nov 16 2019 at 02:30UTC