feat(allocator): add `Vec::into_boxed_slice`

[DonIsaac]

Note that this PR does not implement the inverse operation (Box::to_vec for [T]).

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[DonIsaac]

• #6195 👈
• #6194
• main

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[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #6195 will not alter performance

_{Comparing don/09-30-feat_allocator_add_vec_into_boxed_slice_ (5ee1ef3) with main (7240ee2)}

Summary

✅ 29 untouched benchmarks

[DonIsaac]

@overlookmotel does it make sense to just abandon this PR?

[overlookmotel]

No, I think we can do it. I just think better to use this version:

pub fn into_boxed_slice(self) -> Box<'alloc, [T]> {
    let slice = self.0.leak();
    let ptr = NonNull::from(slice);
    // SAFETY: `ptr` points to a valid slice `[T]`.
    // Lifetime of returned `Box<'alloc, [T]>` is same as lifetime of consumed `Vec<'alloc, T>`,
    // so data in the `Box` will be valid for its lifetime.
    unsafe { Box::from_non_null(ptr) }
}

It's safe, and won't copy memory.

[overlookmotel]

@DonIsaac Hope you don't mind that I've stepped in to finish this off. Just wanted to close a few open PRs which are close to the finish line. Unless you have any objections, I plan to merge this with the additional commits I've added.

[Boshen]

Merge activity

• Oct 12, 12:29 AM EDT: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Oct 12, 12:29 AM EDT: A user added this pull request to the Graphite merge queue.
• Oct 12, 12:35 AM EDT: A user merged this pull request with the Graphite merge queue.