Suggest if-let chain continuation on unclosed delimiter - #160592

Diacod-I · 2026-08-05T20:48:14Z

Meant to fix #160550. When an unclosed brace-delimited block begins with && or ||, the "unclosed delimiter" error now points at that line, suggesting the user may have meant to continue an if-let chain.

Records the leading &&/|| span during lexing (in lex_token_tree_open_delim) and surfaces it in report_suspicious_mismatch_block.
Adds a tests/ui/parser regression test.

I did not use an LLM to create a change in this PR.
I used an LLM to create a change in this PR, and I have explained below how it was used.

rustbot · 2026-08-05T20:48:18Z

The parser was modified, potentially altering the grammar of (stable) Rust
which would be a breaking change.

cc @fmease

rustbot · 2026-08-05T20:48:20Z

Thanks for the pull request, and welcome! The Rust Project is excited to review your changes, and you should hear from @JohnTitor (or someone else) some time within the next two weeks.

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estebank · 2026-08-06T06:23:24Z

I seriously thought getting something working was going to be more complex than this ^_^'

We'd want to add some complexity later to better customize the message (there are some cases where this wasn't a let chain), but I'm ok with this for now.

@bors r+

rust-bors · 2026-08-06T06:23:27Z

📌 Commit 39b3ad8 has been approved by estebank

It is now in the queue for this repository.

…im-hint, r=estebank Suggest if-let chain continuation on unclosed delimiter Meant to fix rust-lang#160550. When an unclosed brace-delimited block begins with && or ||, the "unclosed delimiter" error now points at that line, suggesting the user may have meant to continue an if-let chain. - Records the leading `&&`/`||` span during lexing (in lex_token_tree_open_delim) and surfaces it in report_suspicious_mismatch_block. - Adds a `tests/ui/parser` regression test.

Diacod-I · 2026-08-06T08:40:43Z

I seriously thought getting something working was going to be more complex than this ^_^'

We'd want to add some complexity later to better customize the message (there are some cases where this wasn't a let chain), but I'm ok with this for now.

@bors r+

@estebank Hehe, thanks for the approval. This is my first PR. It did take me a while to come up with this, and I realise the messages need more fine-tuning for certain cases, as you mentioned. But I'm glad it's up to satisfaction. Happy to contribute the new customisations as well, just let me know what you'd like.

…im-hint, r=estebank Suggest if-let chain continuation on unclosed delimiter Meant to fix rust-lang#160550. When an unclosed brace-delimited block begins with && or ||, the "unclosed delimiter" error now points at that line, suggesting the user may have meant to continue an if-let chain. - Records the leading `&&`/`||` span during lexing (in lex_token_tree_open_delim) and surfaces it in report_suspicious_mismatch_block. - Adds a `tests/ui/parser` regression test.

…uwer Rollup of 17 pull requests Successful merges: - #159530 (Cap socket send length to c_int::MAX on Apple targets) - #159506 (Allow associated const equality constraints with GCA) - #160006 (Account for desugaring in method call move errors) - #160415 (Split `aarch64-apple{,-macos-26}` => `aarch64-apple{,-macos-26}-{1,2}` jobs) - #160464 (fix: Check the fallback map before queueing child in `visible_parent_map` breadth-first search) - #160555 (Split `apply_primary_terminator_effect`) - #160592 (Suggest if-let chain continuation on unclosed delimiter) - #160600 (Avoid the std DLL copy alongside rustc) - #160156 (check_consts: exhaustively match on CastKind) - #160211 (Rename `#[unroll]` => `#[rustc_unroll]` to mitigate nameres ambiguity) - #160304 (Add tests for fixed new solver issues) - #160398 (rustc_abi: Add `LayoutData::is_variant_uninhabited` method) - #160546 (Update error message in documentation comments) - #160568 (Use `VisitorResult` helper macros) - #160571 (Add regression test for array type recovery in generic arguments) - #160588 (add a test showing polonius alpha is not a subset of datalog polonius) - #160617 (Add a suggestion to MissingUnsafeOnExtern diagnostic)

Rollup merge of #160592 - Diacod-I:if-let-chain-unclosed-delim-hint, r=estebank Suggest if-let chain continuation on unclosed delimiter Meant to fix #160550. When an unclosed brace-delimited block begins with && or ||, the "unclosed delimiter" error now points at that line, suggesting the user may have meant to continue an if-let chain. - Records the leading `&&`/`||` span during lexing (in lex_token_tree_open_delim) and surfaces it in report_suspicious_mismatch_block. - Adds a `tests/ui/parser` regression test.

JonathanBrouwer · 2026-08-06T20:10:49Z

@rust-timer build 406d594

rust-timer · 2026-08-07T17:30:34Z

Finished benchmarking commit (406d594): comparison URL.

Overall result: ✅ improvements - no action needed

Benchmarking means the PR may be perf-sensitive. Consider adding rollup=never if this change is not fit for rolling up.

@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.4%	[-0.5%, -0.2%]	7
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary -2.7%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.7%	[-3.5%, -2.0%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.7%	[-3.5%, -2.0%]	2

Cycles

Results (primary -2.2%, secondary -2.6%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.5%	[2.5%, 2.5%]	1
Improvements ✅ (primary)	-2.2%	[-2.2%, -2.2%]	1
Improvements ✅ (secondary)	-7.7%	[-7.7%, -7.7%]	1
All ❌✅ (primary)	-2.2%	[-2.2%, -2.2%]	1

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 458.35s -> 460.343s (0.43%)
Artifact size: 398.64 MiB -> 398.65 MiB (0.00%)

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 Aug 5, 2026

rustbot assigned JohnTitor Aug 5, 2026

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Diacod-I force-pushed the if-let-chain-unclosed-delim-hint branch from 87cc2ee to 68e51b9 Compare August 5, 2026 20:54

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Suggest if-let chain continuation on unclosed delimiter

39b3ad8

Diacod-I force-pushed the if-let-chain-unclosed-delim-hint branch from 68e51b9 to 39b3ad8 Compare August 6, 2026 01:52

rust-bors Bot 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 Aug 6, 2026

JonathanBrouwer mentioned this pull request Aug 6, 2026

Rollup of 13 pull requests #160609

Closed

JonathanBrouwer mentioned this pull request Aug 6, 2026

Rollup of 13 pull requests #160610

Closed

JonathanBrouwer mentioned this pull request Aug 6, 2026

Rollup of 17 pull requests #160615

Closed

This was referenced Aug 6, 2026

Rollup of 16 pull requests #160623

Closed

Rollup of 17 pull requests #160627

Merged

rust-bors Bot merged commit 8355006 into rust-lang:main Aug 6, 2026
13 checks passed

rustbot added this to the 1.99.0 milestone Aug 6, 2026

Diacod-I deleted the if-let-chain-unclosed-delim-hint branch August 6, 2026 14:54

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Suggest if-let chain continuation on unclosed delimiter - #160592