Stream: t-compiler/wg-prioritization/alerts

Topic: I-prioritize #74215 Breaking change/regression in nightly? H

triagebot (Jul 10 2020 at 14:44, on Zulip):

@WG-prioritization/alerts issue #74215 has been requested for prioritization.


o0Ignition0o - Jeremy Lempereur (Jul 10 2020 at 16:07, on Zulip):

It looks like it works as intended Oo

lcnr (Jul 10 2020 at 22:10, on Zulip):

I personally also think this is expected breakage/unspecified behavior

lcnr (Jul 10 2020 at 22:11, on Zulip):

I am biased as I wrote the PR implementing this change though

lcnr (Jul 10 2020 at 22:13, on Zulip):

"but we could probably change the Hash impl to always hash the ~same number of bytes"

This might be a way to fix this, I don't really have an opinion on if this is worth it though

lcnr (Jul 10 2020 at 22:17, on Zulip):

esp considering that there are other harder to fix reasons why the layout of mem::Discriminant may change between architectures,
e.g. conditional compilation + some interesting (i don't think currently used) optimizations.

So I think it is better for this to be "always" broken than for it to work in most cases and suddently blowing up for some edge case.

DPC (Jul 12 2020 at 19:22, on Zulip):

this is more of a "notice of this isn't covered under stability guarantees of rust releases"

lcnr (Jul 12 2020 at 20:00, on Zulip):

Wait, I just spend some more time looking into this... there is something going wrong here, I would expect a call write_isize in both cases

lcnr (Jul 12 2020 at 20:00, on Zulip):

but that's somehow not the case

lcnr (Jul 12 2020 at 20:50, on Zulip):

oh god :face_palm: this change is still in beta, so I obviously won't get the expected behavior on stable...

DPC (Jul 12 2020 at 21:03, on Zulip):


Santiago Pastorino (Jul 15 2020 at 12:29, on Zulip):

@lcnr what should we do with the prioritization request here? it doesn't seem that we can do much for now?

Santiago Pastorino (Jul 15 2020 at 12:29, on Zulip):

one option is just leave things as they are until we make a decision

lcnr (Jul 15 2020 at 12:34, on Zulip):

I think this is a decision for the lang team for now, so I don't think it's that useful to prioritize this beforehand.

Santiago Pastorino (Jul 15 2020 at 12:35, on Zulip):


lcnr (Jul 15 2020 at 12:56, on Zulip):

will remove I-prioritize and ping rust-lang/lang then

triagebot (Jul 15 2020 at 13:11, on Zulip):

Issue #74215's prioritization request has been removed.

Last update: Apr 10 2021 at 23:15UTC