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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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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New rules:
attributes.diagnostics.must_use.syntaxattributes.diagnostics.must_use.duplicates