feat(minifier): remove unused private class members

[sapphi-red]

Compress

class C {
  #unused = 1;
  #used = 2;
  method() { return this.#used; }
}

to

class C {
  #used = 2;
  method() { return this.#used; }
}

.

The symbol usage is collected in the main traverse. The removal happens in exit_class_body. This way we don't need additional traverse.

[sapphi-red]

• perf(minifier): use oxc_data_structures::stack::Stack for ClassSymbolsStack #14029
• feat(mangler): mangle private class members #14027
• feat(minifier): remove unused private class members #14026 👈 (View in Graphite)
• main

---

How to use the Graphite Merge Queue

Add either label to this PR to merge it via the merge queue:

• 0-merge - adds this PR to the back of the merge queue
• hotfix - for urgent hot fixes, skip the queue and merge this PR next

You must have a Graphite account in order to use the merge queue. Sign up using this link.

An organization admin has enabled the Graphite Merge Queue in this repository.

Please do not merge from GitHub as this will restart CI on PRs being processed by the merge queue.

This stack of pull requests is managed by Graphite. Learn more about stacking.

[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #14026 will not alter performance

_{Comparing 09-22-feat_minifier_remove_unused_private_class_members (aac45ef) with main (a05cb23)¹}

Summary

✅ 37 untouched

Footnotes

1. No successful run was found on main (aac45ef) during the generation of this report, so a05cb23 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 adds optimization to remove unused private class members (fields, methods, and accessors) from JavaScript classes during minification. The implementation tracks private member usage during AST traversal and removes unused members during class body processing.

• Adds tracking mechanism for private member usage across nested class scopes
• Implements removal logic for unused private fields, methods, and accessor properties
• Preserves members with side effects in their initializers

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
crates/oxc_minifier/src/state.rs	Adds ClassSymbolsStack to track private member usage across class scopes
crates/oxc_minifier/src/peephole/remove_unused_private_members.rs	Implements the core logic for removing unused private members with comprehensive tests
crates/oxc_minifier/src/peephole/mod.rs	Integrates the optimization into the traversal pipeline
tasks/track_memory_allocations/allocs_minifier.snap	Updates memory allocation snapshots

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

[graphite-app]

Merge activity

• Sep 24, 3:34 AM UTC: Boshen added this pull request to the Graphite merge queue.
• Sep 24, 3:40 AM UTC: Merged by the Graphite merge queue.