Repository: rust
Issue: Tracking Issue for NonZeroXxx::from_mut/from_mut_unchecked (nonzero_from_mut)
Labels: T-libs-api,C-tracking-issue

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Feature gate: `#![feature(nonzero_from_mut)]`

This is a tracking issue for the associated functions `NonZeroXxx::from_mut` and `NonZeroXxx::from_mut_unchecked`.

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These associated functions allow converting a mutable reference to a primitive integer (`&mut xxx`) into the equivalent `&mut NonZeroXxx`, with or without validation. The safety is guaranteed by the mutable reference, but currently there is no way to perform this conversion without relying on an unsafe transparent cast.

### Public API

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```rust
// core::num

// $NonZeroInt is one of all signed and unsigned non-zero integer types in core::num,
// and $int is the corresponding primitive type.
impl $NonZeroInt {
    pub fn from_mut(n: &mut $int) -> Option<&mut $NonZeroInt>;
    pub unsafe fn from_mut_unchecked(n: &mut int) -> &mut $NonZeroInt;
}
```

### Steps / History

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- [x] ACP: rust-lang/libs-team#129
- [x] Implementation: #103730
- [ ] Final comment period (FCP)[^1]
- [ ] Stabilization PR

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### Unresolved Questions

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- None yet.

[^1]: https://std-dev-guide.rust-lang.org/feature-lifecycle/stabilization.html