Optimize `nonstandard_macro_braces` by 99.9683% [1.1b -> 351K] by blyxyas · Pull Request #16808 · rust-lang/rust-clippy

blyxyas · 2026-04-04T10:43:03Z

I know that we shouldn't move lints to pre-expansion, but nonstandard_macro_braces was taking up almost a 25% of the Clippy-exclusive runtime in wasmi-0.35.0, and moving it to pre-expansion lets us not bother as much with expansion data.

Previously, we had to get expansion data via outer_expn_data, which does atomic operations, SessionGlobals operations (so, locking threads), and was generally a very bumpy way of doing things. For example in wasmi we were calling scoped_tls::ScopedKey<rustc_span::SessionGlobals>::with<<rustc_span::hygiene::HygieneData>::with<rustc_span::hygiene::ExpnData, <rustc_span::hygiene::SyntaxContext>::outer_expn_data::{closure#0}>::{closure#0}, rustc_span::hygiene::ExpnData> 5,879,804 times. Thus locking the thread 11,759,608 times.

So personally I think that moving this lint to pre-expansion is worth.

changelog:[nonstandard_macro_braces]: Optimize by 99.97%

rustbot · 2026-04-04T10:43:08Z

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github-actions · 2026-04-04T10:52:23Z

Lintcheck changes for 5f34b6d

Lint	Added	Removed	Changed
`clippy::nonstandard_macro_braces`	0	2	1

This comment will be updated if you push new changes

blyxyas · 2026-04-04T10:53:41Z

I didn't notice those lintcheck differences, I'll fix them

xmakro · 2026-06-02T16:53:28Z

Very nice optimization. Is the intention to change this lint from nursery to correctness?

#17125 only recovers the performance if the lint is disabled. But @blyxyas PR also keeps the performance if this lint is turned on by default.

ada4a

Awesome work! Left some comments, mostly stylistic

Let me take over the review if that's okay

r? @ada4a

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rustbot · 2026-06-29T16:10:29Z

This PR was rebased onto a different master 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.

ada4a

some last naming nits..

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ada4a

Looking great now, thank you for your patience with me:) Could you please squash everything down?

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ada4a · 2026-07-10T12:10:18Z

 mod unnecessary_clippy_cfg;
 mod useless_attribute;
 mod utils;
-


this looks spurious.. could you please remove this change?

Done, I've also squashed

blyxyas added the G-performance-project Goal: For issues and PRs related to the Clippy Performance Project label Apr 4, 2026

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blyxyas force-pushed the perf-nonstandard_macro_braces branch from efddb12 to 4a457cc Compare June 3, 2026 08:59

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perf: skip nonstandard_macro_braces work when the lint is disabled #17125

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blyxyas force-pushed the perf-nonstandard_macro_braces branch from 61386b9 to 54496c9 Compare June 14, 2026 17:05

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rust-cloud-vms Bot force-pushed the perf-nonstandard_macro_braces branch from 0fdca09 to c00ffe5 Compare July 9, 2026 23:31

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[Perf] Move nonstandard_macro_braces to pre-expansion

5f34b6d

rust-cloud-vms Bot force-pushed the perf-nonstandard_macro_braces branch from b3b24d4 to 5f34b6d Compare July 10, 2026 13:40

ada4a added this pull request to the merge queue Jul 10, 2026

Merged via the queue into rust-lang:master with commit e5251c9 Jul 10, 2026
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This was referenced Jul 10, 2026

Snippet rework #14724

Open

Require the use of as _ for indirectly used traits in Clippy sources #17369

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