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Pattern matching regression 1.45.0 -> 1.45.1 (+nightly) #74954
Description
I tried this code:
fn main() {
if let Some([b'@', filename @ ..]) = Some(b"@abc123") {
println!("filename {:?}", filename);
}
}I expected this to compile and print
filename [97, 98, 99, 49, 50, 51]
which it does with 1.45.0
Instead, it failed to compile on both 1.45.1 and nightly:
error[E0425]: cannot find value `filename` in this scope
--> src/main.rs:3:35
|
3 | println!("filename {:?}", filename);
| ^^^^^^^^ not found in this scope
error: aborting due to previous error
Meta
rustc --version --verbose:
rustc 1.45.1 (c367798cf 2020-07-26)
binary: rustc
commit-hash: c367798cfd3817ca6ae908ce675d1d99242af148
commit-date: 2020-07-26
host: x86_64-unknown-linux-gnu
release: 1.45.1
LLVM version: 10.0
Activity
cuviper commentedon Jul 30, 2020
It still works on the playground
1.46.0-beta.2though.There were two compiler backports in 1.45.1 -- the first from #73613 is already on beta too, but the second #74509 is not yet, so maybe that caused the regression?
cuviper commentedon Jul 30, 2020
Actually 174b582 looks more relevant, backported from #74557.
edit: and the followup #74692 was also backported.
Mark-Simulacrum commentedon Jul 30, 2020
cc @petrochenkov @estebank
It sounds like our caution in the stable-backport discussion was merited :/
We'll probably want to back out 174b582, I guess.
nagisa commentedon Jul 30, 2020
I think this is the 2nd instance over the years where we end up with a breaking stable backport. Last time (in 1.27.2) we very quickly prepared another point release. This bug might merit something like that again. I’m going to preliminarily and unilaterally prioritize this as P-critical, but also leave the I-prioritize to ensure the prioritization team looks at this.
Mark-Simulacrum commentedon Jul 30, 2020
I will try and prepare artifacts for a 1.45.2 which reverts the pattern-related commits today, with an aim for a release tomorrow at 1pm eastern (or, if we can't get approval from some compiler team members that quickly, Monday).
Auto merge of rust-lang#74958 - Mark-Simulacrum:stable-next, r=pnkfelix
Auto merge of rust-lang#74963 - JohnTitor:ptn-ice, r=petrochenkov
JohnTitor commentedon Aug 3, 2020
Triage: The nightly failure is fixed by #74963, waiting on 1.45.2 release for stable one.
JohnTitor commentedon Aug 4, 2020
So, the failure has been "fixed" in the both versions, I'm going to close this. If I have missed something, please re-open it :)
rust: Update to version 1.45.2.
rust: Update to version 1.45.2.
rust: Update to version 1.45.2.
rust: Update to version 1.45.2.