Repository: rust
Issue: Tracking Issue for `box_vec_non_null`
Labels: T-libs-api,C-tracking-issue,A-box

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Feature gate: `#![feature(box_vec_non_null)]`

This is a tracking issue for convenience methods for conversion between `NonNull` and `Vec`/`Box`.

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### Public API

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```rust
impl<T: ?Sized> Box<T> {
    pub unsafe fn from_non_null(ptr: NonNull<T>) -> Self { .... }
}
impl<T: ?Sized, A: Allocator> Box<T, A> {
    pub const unsafe fn from_non_null_in(raw: NonNull<T>, alloc: A) -> Self { .... }
    pub fn into_non_null(b: Self) -> NonNull<T> { .... }
    pub fn into_non_null_with_allocator(b: Self) -> (NonNull<T>, A) { .... }
}
impl<T> Vec<T> {
    pub unsafe fn from_parts(ptr: NonNull<T>, length: usize, capacity: usize) -> Self { .... }
}
impl<T, A: Allocator> Vec<T, A> {
    pub unsafe fn from_parts_in(ptr: NonNull<T>, length: usize, capacity: usize, alloc: A) -> Self { .... }
    pub fn into_parts(self) -> (NonNull<T>, usize, usize) { .... }
    pub fn into_parts_with_alloc(self) -> (NonNull<T>, usize, usize, A) { .... }
    pub fn as_non_null(&mut self) -> NonNull<T> { .... }
}
```

### Steps / History

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- [x] Implementation:
  - ACP: https://github.com/rust-lang/libs-team/issues/418
  - Implementation PR: https://github.com/rust-lang/rust/pull/130061
  - ACP 2: https://github.com/rust-lang/libs-team/issues/440
  - Implementation PR 2: https://github.com/rust-lang/rust/pull/130624
- [ ] 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