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Perform obligation deduplication to avoid buggy ExistentialMismatch #73485

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merged 1 commit into from
Jun 27, 2020
Merged

Perform obligation deduplication to avoid buggy ExistentialMismatch #73485

merged 1 commit into from
Jun 27, 2020

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estebank
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@estebank estebank commented Jun 18, 2020 •
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Address #59326.

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r? @eddyb

(rust_highfive has picked a reviewer for you, use r? to override)

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 18, 2020
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@bors try @rust-timer queue

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Awaiting bors try build completion

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bors commented Jun 18, 2020

⌛ Trying commit b7f2396 with merge c9f613bb7aaebcb256e34b959196f56f62ca74c8...

@estebank estebank mentioned this pull request Jun 18, 2020
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hellow554
hellow554 reviewed Jun 18, 2020
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src/librustc_middle/ty/relate.rs
Comment on lines +627 to +628
a_v.sort_by(|a, b| a.stable_cmp(tcx, b));
a_v.dedup();
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Is it correct, that the first one is a sort_by, but the next one a plain dedup, instead of dedup_by?

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You're right, that is probably a potential bug. On the repro case that I posted it didn't cause problems, but I'll change it after the perf run has completed (don't want to break anything by force-pushing to this branch before then).

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I'm not sure if dedup will cause trouble in practice and don't know whether dedup_by_key might introduce a slight slowdown. Either way, this PR seems to solve bad rejection part of the ticket.

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bors commented Jun 18, 2020

☀️ Try build successful - checks-azure
Build commit: c9f613bb7aaebcb256e34b959196f56f62ca74c8 (c9f613bb7aaebcb256e34b959196f56f62ca74c8)

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Queued c9f613bb7aaebcb256e34b959196f56f62ca74c8 with parent e55d3f9, future comparison URL.

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Finished benchmarking try commit (c9f613bb7aaebcb256e34b959196f56f62ca74c8): comparison url.

@estebank estebank added beta-nominated Nominated for backporting to the compiler in the beta channel. stable-nominated Nominated for backporting to the compiler in the stable channel. labels Jun 19, 2020
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Adding T-compiler so our tools are able to fetch it and include it on the weekly agenda.

@spastorino spastorino added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Jun 24, 2020
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r? @nikomatsakis as per https://rust-lang.zulipchat.com/#narrow/stream/238009-t-compiler.2Fmeetings/topic/.5Bweekly.20meeting.5D.202020-06-25.20.2354818/near/201977869

@rust-highfive rust-highfive assigned nikomatsakis and unassigned eddyb Jun 25, 2020
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@bors r+

As I said on Zulip, this doesn't seem like the "right fix" to me, but it is a fix, and I don't see it causing any fresh problems, and there's an imminent regression, so r+.

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bors commented Jun 26, 2020

📌 Commit b7f2396 has been approved by nikomatsakis

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 26, 2020
nikomatsakis
nikomatsakis reviewed Jun 26, 2020
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src/librustc_middle/ty/relate.rs
if a.len() != b.len() {
let tcx = relation.tcx();

// FIXME: this is wasteful, but want to do a perf run to see how slow it is.
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I wonder if we should open up a FIXME issue for this..? To try and prevent the duplicates in the first place and figure out where they come from?

@Manishearth Manishearth mentioned this pull request Jun 26, 2020
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bors added a commit to rust-lang-ci/rust that referenced this pull request Jun 27, 2020
@bors
Auto merge of rust-lang#73779 - Manishearth:rollup-lwqd9jm, r=Manishe…
394e1b4 
…arth

Rollup of 12 pull requests

Successful merges:

 - rust-lang#72771 (Warn if linking to a private item)
 - rust-lang#72937 (Fortanix SGX target libunwind build process changes)
 - rust-lang#73485 (Perform obligation deduplication to avoid buggy `ExistentialMismatch`)
 - rust-lang#73529 (Add liballoc impl SpecFromElem for i8)
 - rust-lang#73579 (add missing doc links)
 - rust-lang#73627 (Shortcuts for min/max on double-ended BTreeMap/BTreeSet iterators)
 - rust-lang#73691 (Bootstrap: detect Windows based on sys.platform)
 - rust-lang#73694 (Document the Self keyword)
 - rust-lang#73718 (Document the super keyword)
 - rust-lang#73728 (Document some invariants correctly/more)
 - rust-lang#73738 (Remove irrelevant comment)
 - rust-lang#73765 (Remove blank line)

Failed merges:

r? @ghost
@bors bors merged commit f13d09a into rust-lang:master Jun 27, 2020
@lcnr lcnr mentioned this pull request Jun 27, 2020
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pnkfelix commented Jul 2, 2020

discussed in T-compiler meeting. Approved for beta-backport.

@pnkfelix pnkfelix added the beta-accepted Accepted for backporting to the compiler in the beta channel. label Jul 2, 2020
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pnkfelix commented Jul 2, 2020

stable nom was also discussed. Stable backport approved.

@pnkfelix pnkfelix added the stable-accepted Accepted for backporting to the compiler in the stable channel. label Jul 2, 2020
@Elinvynia Elinvynia mentioned this pull request Jul 6, 2020
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@Mark-Simulacrum Mark-Simulacrum removed beta-nominated Nominated for backporting to the compiler in the beta channel. stable-accepted Accepted for backporting to the compiler in the stable channel. stable-nominated Nominated for backporting to the compiler in the stable channel. labels Jul 10, 2020
@Mark-Simulacrum Mark-Simulacrum mentioned this pull request Jul 10, 2020
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bors added a commit to rust-lang-ci/rust that referenced this pull request Jul 13, 2020
@bors
Auto merge of rust-lang#74219 - Mark-Simulacrum:beta-next, r=Mark-Sim…
e99e642 
…ulacrum

[beta] next

Backports of:

* rustdoc: Fix doc aliases with crate filtering rust-lang#73644
* rustdoc: Rename invalid_codeblock_attribute lint to be plural rust-lang#74131
* rustc_lexer: Simplify shebang parsing once more rust-lang#73596
* Perform obligation deduplication to avoid buggy `ExistentialMismatch` rust-lang#73485
* Reorder order in which MinGW libs are linked to fix recent breakage rust-lang#73184
* Change how compiler-builtins gets many CGUs rust-lang#73136
* Fix wasm32 being broken due to a NodeJS version bump rust-lang#73885
@cuviper cuviper added this to the 1.46 milestone May 2, 2024
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