Update must_use to use the attribute template#1892
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traviscross merged 9 commits intorust-lang:masterfrom Mar 18, 2026
Merged
Update must_use to use the attribute template#1892traviscross merged 9 commits intorust-lang:masterfrom
must_use to use the attribute template#1892traviscross merged 9 commits intorust-lang:masterfrom
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More closely align with the template, and some minor word tweaks.
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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. |
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Let's adjust the section on `must_use` to follow the editorial direction we've been taking.
The admonition for `must_use` claimed that wrapping a value in a block
expression, as in `{ f() };`, suppresses the `unused_must_use` lint.
Testing against rustc shows this isn't true -- the lint explicitly
looks through block expressions (including `unsafe` and labeled
blocks) to their trailing expression before checking. Let's fix that.
On lang, we recently decided (in rust-lang/rust#147382) that `Result<(), E>` and `ControlFlow<B, ()>` should not trigger the `unused_must_use` lint when the error or break type is uninhabited. The rationale is that an infallible result carries nothing the caller needs to handle. Let's document this.
Now that we support destructuring assignment, using `_ = f()` to suppress a `must_use` lint is also probably idiomatic. Let's mention it.
We have two note admonitions at the bottom of the `must_use` section that weren't associated with any particular rule but, by falling below the final rule without identifiers of their own, appeared to be associated with it. Let's give each of these a rule identifier to make this more clear.
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This was referenced Mar 18, 2026
JonathanBrouwer
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Update books ## rust-embedded/book 1 commits in e88aa4403b4bf2071c8df9509160477e40179099..2463edeb8003c5743918b3739a9f6870b86396f5 2026-03-11 17:49:58 UTC to 2026-03-11 17:49:58 UTC - Update teaching material duration for bare-metal Rust (rust-embedded/book#409) ## rust-lang/reference 7 commits in c49e89cc8c7c2c43ca625a8d5b7ad9a53a9ce978..7446bf9697c95d155eef33c6a9d91fbd29a5e359 2026-03-18 01:46:01 UTC to 2026-03-10 18:10:22 UTC - Update `must_use` to use the attribute template (rust-lang/reference#1892) - Add a rule that enum discriminants may not use generic parameters (rust-lang/reference#2206) - Actually move out of Box in moving-out-of-Box test (rust-lang/reference#2204) - Add special cases and links relating to dereferencing boxes (rust-lang/reference#2075) - Move shebang into its own subchapter (rust-lang/reference#2199) - Fields of enums and unions should be allowed to overlap (rust-lang/reference#2168) - [type layout] Clarify size and alignment of pointers to unsized types (rust-lang/reference#2201)
jhpratt
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Update books ## rust-embedded/book 1 commits in e88aa4403b4bf2071c8df9509160477e40179099..2463edeb8003c5743918b3739a9f6870b86396f5 2026-03-11 17:49:58 UTC to 2026-03-11 17:49:58 UTC - Update teaching material duration for bare-metal Rust (rust-embedded/book#409) ## rust-lang/reference 7 commits in c49e89cc8c7c2c43ca625a8d5b7ad9a53a9ce978..7446bf9697c95d155eef33c6a9d91fbd29a5e359 2026-03-18 01:46:01 UTC to 2026-03-10 18:10:22 UTC - Update `must_use` to use the attribute template (rust-lang/reference#1892) - Add a rule that enum discriminants may not use generic parameters (rust-lang/reference#2206) - Actually move out of Box in moving-out-of-Box test (rust-lang/reference#2204) - Add special cases and links relating to dereferencing boxes (rust-lang/reference#2075) - Move shebang into its own subchapter (rust-lang/reference#2199) - Fields of enums and unions should be allowed to overlap (rust-lang/reference#2168) - [type layout] Clarify size and alignment of pointers to unsized types (rust-lang/reference#2201)
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New rules:
attributes.diagnostics.must_use.syntaxattributes.diagnostics.must_use.duplicates