Skip linting unused braces for FunctionArg and MethodArg context for 2024 later by chenyukang · Pull Request #154373 · rust-lang/rust

chenyukang · 2026-03-25T15:12:21Z

unused_braces is a AST level lint, but in Rust 2024 braces around function and method arguments can affect temporary drop scope.

I tried to find a more complete fix for it, but seems all too heavy, which involve AST visitor or need hir related stuff.

Instead of teaching this lint to reason about semantics, so it's better to stop linting those argument-position braces in 2024 later edition.

rustbot · 2026-03-25T15:12:27Z

r? @fmease

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fmease

Sorry for the delay!

I feel like some of the rules are too strict and it's also possible that there are still cases that might not be covered. I'm not an expert on temporary scopes, so I'll reassign.

r? dingxiangfei2009 or reassign

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fmease · 2026-04-15T13:08:42Z

        is_kw: bool,
    );

+    fn is_expr_simple_arg(expr: &ast::Expr) -> bool {


This is a very generic name for a very specific use case. "Simple argument" could mean vastly different things in different contexts. I think this should be renamed to something more specific.

fmease · 2026-04-15T13:10:46Z

+            ast::ExprKind::Lit(_) | ast::ExprKind::Path(..) => true,
+            ast::ExprKind::Type(expr, _) => Self::is_expr_simple_arg(expr),


Surely more kinds of expressions qualify? Like possibly as-casting other "simple" exprs, arrays & tuples of other "simple" exprs and so on.

chenyukang · 2026-04-19T08:21:33Z

@rustbot ready

Enselic · 2026-07-09T03:21:49Z

r? compiler

oli-obk · 2026-07-09T06:59:59Z

+            ast::ExprKind::Array(exprs) | ast::ExprKind::Tup(exprs) => {
+                exprs.iter().all(|expr| Self::is_arg_block_without_temp_scope_change(expr))
+            }
+            _ => false,


exhaustively list them all and add almost all others to the "ok" list:

unary,unsafebindercast,includebytes

binary, index, range,

constblock, path,inlineasm, offsetof

if,while,forloop,loop,match,block

gen, closure, tryblock, try

use, await, break, ret, continue, yield, yeet

assign, assignop,

struct, repeat

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chenyukang · 2026-07-24T00:56:27Z

@rustbot ready

oli-obk

@bors r+ rollup

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rust-bors · 2026-07-28T14:00:25Z

📌 Commit 8e30f04 has been approved by oli-obk

It is now in the queue for this repository.

…d-braces-temp-scope-lite, r=oli-obk Skip linting unused braces for FunctionArg and MethodArg context for 2024 later Fixes rust-lang#154247 `unused_braces` is a AST level lint, but in Rust 2024 braces around function and method arguments can affect temporary drop scope. I tried to find a more complete fix for it, but seems all too heavy, which involve AST visitor or need `hir` related stuff. Instead of teaching this lint to reason about semantics, so it's better to stop linting those argument-position braces in 2024 later edition.

JonathanBrouwer · 2026-07-28T14:40:20Z

💔 I suspect this PR failed tests as part of a rollup
@bors r-

After fixing the problem, consider running a try job for the failed job before re-approving.

Link to failure: https://github.com/rust-lang/rust/actions/runs/30368814940/job/90307165557?pr=160081

rust-bors · 2026-07-28T14:40:28Z

This pull request was unapproved.

This PR was contained in a rollup (#160081), which was unapproved.

View changes since this unapproval

…2024 edition

rustbot · 2026-09-11T07:51:47Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

chenyukang · 2026-09-11T07:54:47Z

fixed the conflict.
@bors r=oli-obk

rust-bors · 2026-09-11T07:54:50Z

📌 Commit ad89677 has been approved by oli-obk

It is now in the queue for this repository.

…d-braces-temp-scope-lite, r=oli-obk Skip linting unused braces for FunctionArg and MethodArg context for 2024 later Fixes rust-lang#154247 `unused_braces` is a AST level lint, but in Rust 2024 braces around function and method arguments can affect temporary drop scope. I tried to find a more complete fix for it, but seems all too heavy, which involve AST visitor or need `hir` related stuff. Instead of teaching this lint to reason about semantics, so it's better to stop linting those argument-position braces in 2024 later edition.

…uwer Rollup of 10 pull requests Successful merges: - #162126 (Rename various resolving functions for consistency, and document them) - #162520 (Refactor `HygieneEncodeContext`) - #154373 (Skip linting unused braces for FunctionArg and MethodArg context for 2024 later ) - #160023 (Refactor the way cg_ssa handles indirect returns (returns via `sret`) — Take 2) - #161482 (Use attribute parser for `#[non_exhaustive]` attribute check) - #161867 (deeper `rustc_builtin_macros` cleanups) - #162099 (small refactor of doc attribute arguments warnings) - #162541 (split `macroless_generic_const_args` in two) - #162549 (The fuchsia team maintains `riscv64gc-unknown-fuchsia`) - #162577 (Fix `i686-pc-windows-msvc` platform support docs and target spec metadata)

…d-braces-temp-scope-lite, r=oli-obk Skip linting unused braces for FunctionArg and MethodArg context for 2024 later Fixes rust-lang#154247 `unused_braces` is a AST level lint, but in Rust 2024 braces around function and method arguments can affect temporary drop scope. I tried to find a more complete fix for it, but seems all too heavy, which involve AST visitor or need `hir` related stuff. Instead of teaching this lint to reason about semantics, so it's better to stop linting those argument-position braces in 2024 later edition.

…uwer Rollup of 11 pull requests Successful merges: - #162520 (Refactor `HygieneEncodeContext`) - #154373 (Skip linting unused braces for FunctionArg and MethodArg context for 2024 later ) - #160023 (Refactor the way cg_ssa handles indirect returns (returns via `sret`) — Take 2) - #160860 (Implement arbitrary casts in custom mir) - #161482 (Use attribute parser for `#[non_exhaustive]` attribute check) - #161867 (deeper `rustc_builtin_macros` cleanups) - #162099 (small refactor of doc attribute arguments warnings) - #162541 (split `macroless_generic_const_args` in two) - #162549 (The fuchsia team maintains `riscv64gc-unknown-fuchsia`) - #162577 (Fix `i686-pc-windows-msvc` platform support docs and target spec metadata) - #162624 (regression test for opaque field projection in closure capture)

Rollup merge of #154373 - chenyukang:yukang-fix-154247-unused-braces-temp-scope-lite, r=oli-obk Skip linting unused braces for FunctionArg and MethodArg context for 2024 later Fixes #154247 `unused_braces` is a AST level lint, but in Rust 2024 braces around function and method arguments can affect temporary drop scope. I tried to find a more complete fix for it, but seems all too heavy, which involve AST visitor or need `hir` related stuff. Instead of teaching this lint to reason about semantics, so it's better to stop linting those argument-position braces in 2024 later edition.

rust-timer · 2026-09-11T16:03:29Z

Note

This PR was benchmarked as part of triage of its containing rollup: triage URL.

Finished benchmarking commit (00df995): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

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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)	4.9%	[4.9%, 4.9%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

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Bootstrap: missing data
Artifact size: 407.63 MiB -> 407.68 MiB (0.01%)

rustbot assigned fmease Mar 25, 2026

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 Mar 25, 2026

chenyukang force-pushed the yukang-fix-154247-unused-braces-temp-scope-lite branch from 73c892b to e120f17 Compare March 26, 2026 14:18

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chenyukang force-pushed the yukang-fix-154247-unused-braces-temp-scope-lite branch from e120f17 to 14cc286 Compare April 19, 2026 08:20

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rustbot assigned oli-obk and unassigned dingxiangfei2009 Jul 9, 2026

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rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 9, 2026

chenyukang force-pushed the yukang-fix-154247-unused-braces-temp-scope-lite branch from 14cc286 to 2e43946 Compare July 10, 2026 04:16

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chenyukang force-pushed the yukang-fix-154247-unused-braces-temp-scope-lite branch from 2e43946 to 88aa4a9 Compare July 10, 2026 04:20

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chenyukang force-pushed the yukang-fix-154247-unused-braces-temp-scope-lite branch from 88aa4a9 to 8e30f04 Compare July 10, 2026 04:40

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oli-obk approved these changes Jul 28, 2026

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Rollup of 11 pull requests #160080

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Rollup of 12 pull requests #160081

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Skip linting unused braces for FunctionArg and MethodArg context for …

ad89677

…2024 edition

chenyukang force-pushed the yukang-fix-154247-unused-braces-temp-scope-lite branch from 8e30f04 to ad89677 Compare September 11, 2026 07:51

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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Sep 11, 2026

JonathanBrouwer mentioned this pull request Sep 11, 2026

Rollup of 7 pull requests #162627

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JonathanBrouwer mentioned this pull request Sep 11, 2026

Rollup of 10 pull requests #162629

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JonathanBrouwer mentioned this pull request Sep 11, 2026

Rollup of 11 pull requests #162631

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Zalathar mentioned this pull request Sep 11, 2026

Rollup of 11 pull requests #162632

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rust-bors Bot merged commit 04b9547 into rust-lang:main Sep 11, 2026
13 checks passed

rustbot added this to the 1.100.0 milestone Sep 11, 2026

		ast::ExprKind::Lit(_) \| ast::ExprKind::Path(..) => true,
		ast::ExprKind::Type(expr, _) => Self::is_expr_simple_arg(expr),

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