Correctly handle nested or-patterns in exhaustiveness #117398

Nadrieril · 2023-10-30T14:32:00Z

I had assumed nested or-patterns were flattened, and they mostly are but not always.

rustbot · 2023-10-30T14:32:08Z

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compiler-errors · 2023-10-30T14:35:28Z

compiler/rustc_mir_build/src/thir/pattern/usefulness.rs

@@ -931,7 +931,7 @@ impl<'p, 'tcx> PatternColumn<'p, 'tcx> {
            let specialized = pat.specialize(pcx, &ctor);
            for (subpat, column) in specialized.iter().zip(&mut specialized_columns) {
                if subpat.is_or_pat() {
-                    column.patterns.extend(subpat.iter_fields())
+                    column.patterns.extend(subpat.flatten_or_pat())


It's kind of a shame that this code has an invariant (right?) that the | patterns must be flattened, but nothing protecting us against that in the first place.

It is a shame indeed. I can see how I could encode it in the type system...

I prefer not to actually. There are a lot of invariants in this file, this one is not one I'd rather spend my complexity budget on

You got me thinking that I should really write down more of these invariants

That would be awesome 😺

compiler-errors

r=me

Nadrieril · 2023-10-30T14:55:33Z

Thanks for the lightspeed reaction time!

@bors r=compiler-errors

bors · 2023-10-30T14:55:37Z

📌 Commit d5e836c has been approved by compiler-errors

It is now in the queue for this repository.

…iaskrgr Rollup of 7 pull requests Successful merges: - rust-lang#116862 (Detect when trait is implemented for type and suggest importing it) - rust-lang#117389 (Some diagnostics improvements of `gen` blocks) - rust-lang#117396 (Don't treat closures/coroutine types as part of the public API) - rust-lang#117398 (Correctly handle nested or-patterns in exhaustiveness) - rust-lang#117403 (Poison check_well_formed if method receivers are invalid to prevent typeck from running on it) - rust-lang#117411 (Improve some diagnostics around `?Trait` bounds) - rust-lang#117414 (Don't normalize to an un-revealed opaque when we hit the recursion limit) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of rust-lang#117398 - Nadrieril:fix-117378, r=compiler-errors Correctly handle nested or-patterns in exhaustiveness I had assumed nested or-patterns were flattened, and they mostly are but not always. Fixes rust-lang#117378

Correctly handle nested or-patterns in column-wise analyses

d5e836c

rustbot assigned TaKO8Ki Oct 30, 2023

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Oct 30, 2023

Nadrieril changed the title ~~Correctly handle nested or-patterns in column-wise analyses~~ Correctly handle nested or-patterns in column-wise pattern analyses Oct 30, 2023

Nadrieril changed the title ~~Correctly handle nested or-patterns in column-wise pattern analyses~~ Correctly handle nested or-patterns in exhaustiveness Oct 30, 2023

compiler-errors reviewed Oct 30, 2023

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compiler-errors approved these changes Oct 30, 2023

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compiler-errors assigned compiler-errors and unassigned TaKO8Ki Oct 30, 2023

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 Oct 30, 2023

matthiaskrgr mentioned this pull request Oct 30, 2023

Rollup of 7 pull requests #117415

Merged

bors merged commit 342483c into rust-lang:master Oct 30, 2023
11 checks passed

rustbot added this to the 1.75.0 milestone Oct 30, 2023

Nadrieril deleted the fix-117378 branch October 30, 2023 23:14

github-actions bot mentioned this pull request Oct 31, 2023

Automated pull from upstream master ferrocene/ferrocene#74

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Nadrieril added the A-exhaustiveness-checking Relating to exhaustiveness / usefulness checking of patterns label Dec 10, 2023

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Correctly handle nested or-patterns in exhaustiveness #117398

Correctly handle nested or-patterns in exhaustiveness #117398

Nadrieril commented Oct 30, 2023 •

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rustbot commented Oct 30, 2023

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Correctly handle nested or-patterns in exhaustiveness #117398

Correctly handle nested or-patterns in exhaustiveness #117398

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