rustc_parse: Stop returning `Option` from statement parsing by petrochenkov · Pull Request #159849 · rust-lang/rust

petrochenkov · 2026-07-24T15:57:40Z

parse_stmt_without_recovery had one corner case in which it returned Ok(None) - when parsing immediately encountered a closing brace }, possibly after parsing outer attributes.

It is simpler to never call parse_stmt_without_recovery in such contexts than deal with a possibility of no statement being returned without an error.
So this PR changes the function's return type from PResult<'a, Option<Stmt>> to PResult<'a, Stmt> and adjusts one call site to check for a closing brace.

rustbot · 2026-07-24T15:57:51Z

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

cc @fmease

Some changes occurred in compiler/rustc_attr_parsing

cc @jdonszelmann, @JonathanBrouwer

rustbot · 2026-07-24T15:57:56Z

r? @hanna-kruppe

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petrochenkov · 2026-07-24T16:01:03Z

        } else if self.eat(exp!(Semi)) {
            // Do not attempt to parse an expression if we're done here.
-            self.error_outer_attrs(attrs);
+            self.error_outer_attrs(attrs)?;


Note: what we did here previously was recovery, which is a bit sus in a function ending with _without_recovery and without checking for may_recover. So we no longer recover now.

View changes since the review

petrochenkov · 2026-07-24T16:02:45Z

-        } else if self.token != token::CloseBrace {
+        } else if self.token == token::CloseBrace {
+            self.error_outer_attrs(attrs)?;
+            self.dcx().span_bug(self.token.span, "don't parse a statement if you see `}`");


Technically this branch is unnecessary, we can just fall through into the last else clause, we'll just get worse error messages like "expected an expression, found }".

View changes since the review

JonathanBrouwer

@bors r+ rollup
This is quite a lot nicer, thanks!

View changes since this review

rust-bors · 2026-07-25T18:42:48Z

📌 Commit 75529d4 has been approved by JonathanBrouwer

It is now in the queue for this repository.

rustc_parse: Stop returning `Option` from statement parsing `parse_stmt_without_recovery` had one corner case in which it returned `Ok(None)` - when parsing immediately encountered a closing brace `}`, possibly after parsing outer attributes. It is simpler to never call `parse_stmt_without_recovery` in such contexts than deal with a possibility of no statement being returned without an error. So this PR changes the function's return type from `PResult<'a, Option<Stmt>>` to `PResult<'a, Stmt>` and adjusts one call site to check for a closing brace.

…uwer Rollup of 24 pull requests Successful merges: - #159638 (bootstrap: Split the `Step` trait into multiple traits) - #159774 (rustc_trait_selection: fix trait solver hang caused by degenerate obligations) - #159837 (line-tables-only test: check that the line number matches the function name) - #159946 (Update Enzyme submodule to imporve llvm-cov) - #159617 (Fix up `#[linkage]` target checking) - #159733 (std: Switch implementations of `thread_local!` for WASI) - #159783 (Check unsafe impls on safe EIIs) - #159810 (Add tuple never coercion collection regression test) - #159821 (Update expect message using the recommended style in binary_heap module) - #159826 (Remove redundant `#[rustc_paren_sugar]` feature gate) - #159846 (Implement `str::copy_from_str`) - #159849 (rustc_parse: Stop returning `Option` from statement parsing) - #159853 (Updated expect messages for `CString` struct and method documentation) - #159875 (More cleanup in `rustc_attr_parsing`) - #159882 (Update expect messages in library/alloc/boxed.rs and library/alloc/string.rs to follow the style guide) - #159891 (Split multiline derives into std/rustc macros) - #159893 (Fix `find_attr` hygiene and `rustc_hir` cleanups) - #159895 (rustc-dev-guide subtree update) - #159902 (Clarify that the expected runtime symbols signature is for the current target only) - #159914 (Fix error in diagnostic on_unmatched_args) - #159917 (spare capacity mut constification) - #159918 (rename abort_unwind → abort_on_unwind) - #159936 (Minor `rustc_ast::ast` doc cleanups) - #159945 (Update expect messages in library/core/src/ptr/non_null.rs)

…uwer Rollup of 28 pull requests Successful merges: - #159638 (bootstrap: Split the `Step` trait into multiple traits) - #159774 (rustc_trait_selection: fix trait solver hang caused by degenerate obligations) - #159837 (line-tables-only test: check that the line number matches the function name) - #159946 (Update Enzyme submodule to imporve llvm-cov) - #159962 (miri subtree update) - #156570 (tests: extend remap-path-prefix-std to all stdlib rlibs) - #159617 (Fix up `#[linkage]` target checking) - #159633 (Improve workings of attribute suggestions) - #159733 (std: Switch implementations of `thread_local!` for WASI) - #159783 (Check unsafe impls on safe EIIs) - #159810 (Add tuple never coercion collection regression test) - #159826 (Remove redundant `#[rustc_paren_sugar]` feature gate) - #159846 (Implement `str::copy_from_str`) - #159849 (rustc_parse: Stop returning `Option` from statement parsing) - #159853 (Updated expect messages for `CString` struct and method documentation) - #159875 (More cleanup in `rustc_attr_parsing`) - #159882 (Update expect messages in library/alloc/boxed.rs and library/alloc/string.rs to follow the style guide) - #159891 (Split multiline derives into std/rustc macros) - #159893 (Fix `find_attr` hygiene and `rustc_hir` cleanups) - #159895 (rustc-dev-guide subtree update) - #159902 (Clarify that the expected runtime symbols signature is for the current target only) - #159914 (Fix error in diagnostic on_unmatched_args) - #159917 (spare capacity mut constification) - #159918 (rename abort_unwind → abort_on_unwind) - #159927 (Remove sve2 from the ImpliedFeatures of AArch64 v9a.) - #159936 (Minor `rustc_ast::ast` doc cleanups) - #159945 (Update expect messages in library/core/src/ptr/non_null.rs) - #159950 (Add CFI tests for return types and never type)

Rollup merge of #159849 - petrochenkov:estmt, r=JonathanBrouwer rustc_parse: Stop returning `Option` from statement parsing `parse_stmt_without_recovery` had one corner case in which it returned `Ok(None)` - when parsing immediately encountered a closing brace `}`, possibly after parsing outer attributes. It is simpler to never call `parse_stmt_without_recovery` in such contexts than deal with a possibility of no statement being returned without an error. So this PR changes the function's return type from `PResult<'a, Option<Stmt>>` to `PResult<'a, Stmt>` and adjusts one call site to check for a closing brace.

…uwer Rollup of 28 pull requests Successful merges: - rust-lang/rust#159638 (bootstrap: Split the `Step` trait into multiple traits) - rust-lang/rust#159774 (rustc_trait_selection: fix trait solver hang caused by degenerate obligations) - rust-lang/rust#159837 (line-tables-only test: check that the line number matches the function name) - rust-lang/rust#159946 (Update Enzyme submodule to imporve llvm-cov) - rust-lang/rust#159962 (miri subtree update) - rust-lang/rust#156570 (tests: extend remap-path-prefix-std to all stdlib rlibs) - rust-lang/rust#159617 (Fix up `#[linkage]` target checking) - rust-lang/rust#159633 (Improve workings of attribute suggestions) - rust-lang/rust#159733 (std: Switch implementations of `thread_local!` for WASI) - rust-lang/rust#159783 (Check unsafe impls on safe EIIs) - rust-lang/rust#159810 (Add tuple never coercion collection regression test) - rust-lang/rust#159826 (Remove redundant `#[rustc_paren_sugar]` feature gate) - rust-lang/rust#159846 (Implement `str::copy_from_str`) - rust-lang/rust#159849 (rustc_parse: Stop returning `Option` from statement parsing) - rust-lang/rust#159853 (Updated expect messages for `CString` struct and method documentation) - rust-lang/rust#159875 (More cleanup in `rustc_attr_parsing`) - rust-lang/rust#159882 (Update expect messages in library/alloc/boxed.rs and library/alloc/string.rs to follow the style guide) - rust-lang/rust#159891 (Split multiline derives into std/rustc macros) - rust-lang/rust#159893 (Fix `find_attr` hygiene and `rustc_hir` cleanups) - rust-lang/rust#159895 (rustc-dev-guide subtree update) - rust-lang/rust#159902 (Clarify that the expected runtime symbols signature is for the current target only) - rust-lang/rust#159914 (Fix error in diagnostic on_unmatched_args) - rust-lang/rust#159917 (spare capacity mut constification) - rust-lang/rust#159918 (rename abort_unwind → abort_on_unwind) - rust-lang/rust#159927 (Remove sve2 from the ImpliedFeatures of AArch64 v9a.) - rust-lang/rust#159936 (Minor `rustc_ast::ast` doc cleanups) - rust-lang/rust#159945 (Update expect messages in library/core/src/ptr/non_null.rs) - rust-lang/rust#159950 (Add CFI tests for return types and never type)

Mark-Simulacrum · 2026-07-27T22:32:27Z

@rust-timer build d1c9ad6

cc upstream perf #159966 (comment)

rust-timer · 2026-07-27T23:50:04Z

Finished benchmarking commit (d1c9ad6): comparison URL.

Overall result: ❌ regressions - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never rustc-perf
@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)	0.2%	[0.2%, 0.3%]	6
Regressions ❌ (secondary)	0.4%	[0.3%, 0.6%]	8
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.2%	[0.2%, 0.3%]	6

Max RSS (memory usage)

Results (primary 2.4%, secondary 3.0%)

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

	mean	range	count
Regressions ❌ (primary)	2.4%	[2.4%, 2.4%]	1
Regressions ❌ (secondary)	3.0%	[3.0%, 3.0%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.4%	[2.4%, 2.4%]	1

Cycles

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

Binary size

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

Bootstrap: 489.277s -> 492.066s (0.57%)
Artifact size: 387.73 MiB -> 387.74 MiB (0.00%)

rustc_parse: Stop returning Option from statement parsing

75529d4

rustbot added A-attributes Area: Attributes (`#[…]`, `#![…]`) 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 Jul 24, 2026

rustbot assigned hanna-kruppe Jul 24, 2026

petrochenkov commented Jul 24, 2026

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JonathanBrouwer assigned JonathanBrouwer and unassigned hanna-kruppe Jul 24, 2026

rustbot assigned nnethercote and unassigned JonathanBrouwer Jul 25, 2026

hanna-kruppe assigned JonathanBrouwer and unassigned nnethercote Jul 25, 2026

JonathanBrouwer approved these changes Jul 25, 2026

View reviewed changes

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 Jul 25, 2026

JonathanBrouwer mentioned this pull request Jul 25, 2026

Rollup of 15 pull requests #159925

Closed

JonathanBrouwer mentioned this pull request Jul 25, 2026

Rollup of 14 pull requests #159931

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JonathanBrouwer mentioned this pull request Jul 26, 2026

Rollup of 25 pull requests #159952

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JonathanBrouwer mentioned this pull request Jul 26, 2026

Rollup of 24 pull requests #159957

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JonathanBrouwer mentioned this pull request Jul 26, 2026

Rollup of 28 pull requests #159966

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rust-bors Bot merged commit d01433c into rust-lang:main Jul 27, 2026
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rustbot added this to the 1.99.0 milestone Jul 27, 2026

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rustc_parse: Stop returning `Option` from statement parsing - #159849

rustc_parse: Stop returning `Option` from statement parsing#159849
rust-bors[bot] merged 1 commit into
rust-lang:mainfrom
petrochenkov:estmt

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Overall result: ❌ regressions - please read:

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