mbe: Implement `unsafe` attribute rules #146535

joshtriplett · 2025-09-14T08:39:32Z

This implements unsafe attr rules for declarative macro_rules! attributes, as specified in RFC 3697.

An invocation of an attribute that uses an unsafe attr rule requires the unsafe(attr(...)) syntax.

An invocation of an attribute that uses an ordinary attr rule must not use the unsafe(attr(...)) syntax.

unsafe is only supported on an attr rule, not any other kind of macro_rules! rule.

Tracking issue for macro_rules! attributes: #143547

rustbot · 2025-09-14T08:39:35Z

Some changes occurred in compiler/rustc_attr_parsing

cc @jdonszelmann

rustbot · 2025-09-14T08:39:37Z

r? @davidtwco

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joshtriplett · 2025-09-14T08:40:22Z

r? @petrochenkov

mu001999

LGTM

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vincenzopalazzo

While I was preparing a talk for the Rust 4linux summit, I did a first pass on this, and it looks good!

Will do a final pass on it next week

Thanks for bringing this forward

View changes since this review

compiler/rustc_expand/src/expand.rs

compiler/rustc_expand/src/mbe/macro_rules.rs

joshtriplett · 2025-09-28T16:54:57Z

@rustbot ready

compiler/rustc_expand/src/expand.rs

petrochenkov · 2025-09-29T16:39:25Z

r=me with the comments updated and review commits squashed.
@rustbot author

This simplifies subsequent initialization of enum variants.

… `LegacyAttr` here `LegacyAttr` is only used for builtin attributes, and builtin attributes have their safety checked by `check_attribute_safety`, so we don't need to check `unsafety` here.

rustbot · 2025-10-01T23:45:55Z

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.

joshtriplett · 2025-10-01T23:46:01Z

@bors r=petrochenkov rollup

bors · 2025-10-01T23:46:04Z

📌 Commit 4fc0a0d has been approved by petrochenkov

It is now in the queue for this repository.

…trochenkov mbe: Implement `unsafe` attribute rules This implements `unsafe attr` rules for declarative `macro_rules!` attributes, as specified in [RFC 3697](rust-lang/rfcs#3697). An invocation of an attribute that uses an `unsafe attr` rule requires the `unsafe(attr(...))` syntax. An invocation of an attribute that uses an ordinary `attr` rule must *not* use the `unsafe(attr(...))` syntax. `unsafe` is only supported on an `attr` rule, not any other kind of `macro_rules!` rule. Tracking issue for `macro_rules!` attributes: rust-lang#143547

Rollup of 10 pull requests Successful merges: - #146281 (Support `#[rustc_align_static]` inside `thread_local!`) - #146535 (mbe: Implement `unsafe` attribute rules) - #146585 (indexing: reword help) - #147004 (Tweak handling of "struct like start" where a struct isn't supported) - #147221 (Forbid `//@ compile-flags: -Cincremental=` in tests) - #147225 (Don't enable shared memory by default with Wasm atomics) - #147227 (implement `Box::take`) - #147231 (Extending `#[rustc_force_inline]` to be applicable to inherent methods) - #147233 (Initialize llvm submodule if not already the case to run citool) - #147236 (Update books) r? `@ghost` `@rustbot` modify labels: rollup

…trochenkov mbe: Implement `unsafe` attribute rules This implements `unsafe attr` rules for declarative `macro_rules!` attributes, as specified in [RFC 3697](rust-lang/rfcs#3697). An invocation of an attribute that uses an `unsafe attr` rule requires the `unsafe(attr(...))` syntax. An invocation of an attribute that uses an ordinary `attr` rule must *not* use the `unsafe(attr(...))` syntax. `unsafe` is only supported on an `attr` rule, not any other kind of `macro_rules!` rule. Tracking issue for `macro_rules!` attributes: rust-lang#143547

Rollup of 9 pull requests Successful merges: - #146281 (Support `#[rustc_align_static]` inside `thread_local!`) - #146535 (mbe: Implement `unsafe` attribute rules) - #146585 (indexing: reword help) - #147004 (Tweak handling of "struct like start" where a struct isn't supported) - #147221 (Forbid `//@ compile-flags: -Cincremental=` in tests) - #147225 (Don't enable shared memory by default with Wasm atomics) - #147227 (implement `Box::take`) - #147233 (Initialize llvm submodule if not already the case to run citool) - #147236 (Update books) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #146535 - joshtriplett:mbe-unsafe-attr, r=petrochenkov mbe: Implement `unsafe` attribute rules This implements `unsafe attr` rules for declarative `macro_rules!` attributes, as specified in [RFC 3697](rust-lang/rfcs#3697). An invocation of an attribute that uses an `unsafe attr` rule requires the `unsafe(attr(...))` syntax. An invocation of an attribute that uses an ordinary `attr` rule must *not* use the `unsafe(attr(...))` syntax. `unsafe` is only supported on an `attr` rule, not any other kind of `macro_rules!` rule. Tracking issue for `macro_rules!` attributes: #143547

Rollup of 9 pull requests Successful merges: - rust-lang/rust#146281 (Support `#[rustc_align_static]` inside `thread_local!`) - rust-lang/rust#146535 (mbe: Implement `unsafe` attribute rules) - rust-lang/rust#146585 (indexing: reword help) - rust-lang/rust#147004 (Tweak handling of "struct like start" where a struct isn't supported) - rust-lang/rust#147221 (Forbid `//@ compile-flags: -Cincremental=` in tests) - rust-lang/rust#147225 (Don't enable shared memory by default with Wasm atomics) - rust-lang/rust#147227 (implement `Box::take`) - rust-lang/rust#147233 (Initialize llvm submodule if not already the case to run citool) - rust-lang/rust#147236 (Update books) r? `@ghost` `@rustbot` modify labels: rollup

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 Sep 14, 2025

rustbot assigned davidtwco Sep 14, 2025

joshtriplett added the A-macros Area: All kinds of macros (custom derive, macro_rules!, proc macros, ..) label Sep 14, 2025

rustbot assigned petrochenkov and unassigned davidtwco Sep 14, 2025

mu001999 approved these changes Sep 15, 2025

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vincenzopalazzo reviewed Sep 16, 2025

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petrochenkov reviewed Sep 25, 2025

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petrochenkov 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 Sep 25, 2025

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Sep 28, 2025

petrochenkov reviewed Sep 29, 2025

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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 Sep 29, 2025

joshtriplett force-pushed the mbe-unsafe-attr branch 2 times, most recently from 8295ecd to 42c3f40 Compare October 1, 2025 23:18

joshtriplett added 5 commits October 1, 2025 16:19

mbe: Rename a local variable to match corresponding field names

30d57ab

This simplifies subsequent initialization of enum variants.

mbe: Support unsafe attribute rules

6bff1ab

mbe: Add parsing tests for unsafe macro rules

05c5b87

mbe: Add tests for unsafe attr invocation

ea0e00c

mbe: expand_invoc: Add comment about not needing to check safety of…

4fc0a0d

… `LegacyAttr` here `LegacyAttr` is only used for builtin attributes, and builtin attributes have their safety checked by `check_attribute_safety`, so we don't need to check `unsafety` here.

joshtriplett force-pushed the mbe-unsafe-attr branch from 42c3f40 to 4fc0a0d Compare October 1, 2025 23:45

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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Oct 1, 2025

Zalathar mentioned this pull request Oct 2, 2025

Rollup of 10 pull requests #147253

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matthiaskrgr mentioned this pull request Oct 2, 2025

Rollup of 9 pull requests #147256

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jhpratt mentioned this pull request Oct 2, 2025

Rollup of 10 pull requests #147260

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matthiaskrgr mentioned this pull request Oct 2, 2025

Rollup of 9 pull requests #147261

Merged

bors merged commit ac7beab into rust-lang:master Oct 2, 2025
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rustbot added this to the 1.92.0 milestone Oct 2, 2025

github-actions bot mentioned this pull request Oct 3, 2025

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