feat(allocator): implement CloneIn for Box<[T]>

[overlookmotel]

Implement CloneIn for Box<[T]>. Use an efficient implementation which doesn't perform any bounds checks. Hopefully, where T is Copy, compiler will be able to boil this down to a single memcpy call.

(this stack is mostly leftovers from #13450 which turned out not to be required for that PR, but are still useful for other purposes)

[overlookmotel]

• perf(semantic): speed up Scoping::clone_in_with_semantic_ids_with_another_arena #13563
• feat(allocator): implement CloneIn for HashMap #13562
• perf(allocator): remove bounds checks in CloneIn for Vec #13506
• feat(allocator): implement CloneIn for Box<[T]> #13505 👈 (View in Graphite)
• feat(allocator): add Vec::into_boxed_slice method #13503 : 1 other dependent PR (#13504 )
• ci(miri): run Miri on oxc_allocator crate #13528
• main

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[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #13505 will not alter performance

_{Comparing 08-30-feat_allocator_implement_clonein_for_box_t_ (a54a4de) with main (26ab087)¹}

Summary

✅ 37 untouched benchmarks

Footnotes

1. No successful run was found on main (a54a4de) during the generation of this report, so 26ab087 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[Copilot]

Pull Request Overview

This PR implements the CloneIn trait for Box<[T]> to enable efficient arena-allocated cloning of boxed slices. The implementation includes compile-time size and alignment checks to ensure type safety and uses low-level memory operations for optimal performance.

• Adds CloneIn implementation for Box<[T]> with both standard and semantic ID-preserving clone methods
• Includes compile-time assertions to verify size and alignment compatibility between source and target types
• Adds comprehensive test coverage for the new functionality

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[graphite-app]

Merge activity

• Sep 6, 5:24 PM UTC: Boshen added this pull request to the Graphite merge queue.
• Sep 6, 5:30 PM UTC: Merged by the Graphite merge queue.