Clippy · Correctness

Mutable reference returned from a shared one

clippy::mut_from_ref

Take &mut self or a &mut argument, or return a shared reference: a &mut obtained from a & reference is unsound.

Category: Correctness
Default level: warn
Tier: P1
Producer: Clippy
Diff scope: line

Not a defect when

The function is unsafe and its documented contract makes callers guarantee exclusive access, as in an arena or UnsafeCell-backed pool handing out disjoint slots.

What it reads

Clippy, with the compiler behind it. The only pass that compiles.

Tier

Serious: worth interrupting other work for.

The tier bounds how severe a rule may be; its category bounds the tier.

Diff scope

The changed line itself.

What --scope contextual looks at to decide whether a change caused the finding.

Change it

Turn it off, or make it blocking, without touching the code it flags:

rust-doctor --rule clippy::mut_from_ref=off .
rust-doctor --rule clippy::mut_from_ref=error .

Set it once in rust-doctor.toml

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