perf(linter): use Cell instead of RefCell

[overlookmotel]

Follow-on after #12724. Small perf optimization.

Cell is cheaper than RefCell, because it doesn't do runtime aliasing checks. It's preferable when the contained type is small and Copy, as is the case here (usize).

[overlookmotel]

• perf(linter): use Cell instead of RefCell #13330 👈 (View in Graphite)
• main

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[Copilot]

Pull Request Overview

This PR optimizes the linter's ContextHost struct by replacing RefCell<usize> with Cell<usize> for the current_sub_host_index field. This is a performance optimization that leverages Cell's lower overhead compared to RefCell when dealing with small Copy types.

• Replace RefCell<usize> with Cell<usize> for current_sub_host_index
• Update all usage patterns to use Cell's get() and set() methods instead of borrow() and borrow_mut()
• Refactor the next_sub_host method to use bounds checking instead of relying on Option::is_some()

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[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #13330 will not alter performance

_{Comparing 08-27-perf_linter_use_cell_instead_of_refcell_ (827fe1c) with main (9c9f80d)¹}

Summary

✅ 34 untouched benchmarks

Footnotes

1. No successful run was found on main (827fe1c) during the generation of this report, so 9c9f80d was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[overlookmotel]

Merge activity

• Aug 27, 3:22 PM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Aug 27, 3:22 PM UTC: overlookmotel added this pull request to the Graphite merge queue.
• Aug 27, 3:27 PM UTC: Merged by the Graphite merge queue.