fix(runtime): refresh rooted arrays during iteration

[proggeramlug]

Summary

Fixes the Array.prototype.find and findIndex mutation-during-iteration failures from the #5898 Test262 worklist. Callback-driven array relocation now refreshes the rooted receiver, and reads beyond a callback-shrunk logical length return absent/undefined instead of stale tail storage.

Changes

• Resolve array-growth and moving-GC forwarding stubs before each callback-loop access, then self-heal the runtime root.
• Check the current logical length before reading inline array elements.
• Add a focused runtime regression test covering forwarding followed by splice shrinkage.

Related issue

Refs #5898 — completes the find/findIndex array-altered-during-loop subcluster.

Test plan

• cargo build --release -p perry-runtime-static -p perry-stdlib-static
• cargo test --release -p perry-runtime forwarded_array_observes_shrunk_length_during_callback_iteration -- --test-threads=1
• Test262 built-ins/Array/prototype/find + findIndex: 36 pass, 0 failures (pinned SHA 4249661388e5d3f92a85186213da140a6481490f)
• Full Test262 built-ins/Array slice: 2498 pass, 0 diff, 29 existing runtime failures, 0 compile failures; selected failures absent
• cargo fmt -p perry-runtime -- --check
• python scripts/check_test_registration.py
• Full workspace test suite (not run locally)

Screenshots / output

Before: 34/36 pass in the selected Test262 directories; both array-altered-during-loop cases failed with stale Bike instead of undefined.

After: 36/36 pass.

Checklist

• I have NOT bumped the workspace version or edited CLAUDE.md / CHANGELOG.md (maintainer handles these at merge)
• My commit follows the loose feat/fix/docs/chore prefix convention used in the log
• I've read CONTRIBUTING.md and agree to the Code of Conduct

Summary by CodeRabbit

• Bug Fixes
  • Improved array iteration reliability when arrays move during memory management.
  • Array accesses now respect the current array length, preventing reads beyond shortened arrays.
  • Correctly handles forwarded arrays, missing elements, and out-of-range lookups.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: df7e11dc-0de1-4659-b67d-f71647abe41f

📥 Commits

Reviewing files that changed from the base of the PR and between f4a7559 and 5c7d3f8.

📒 Files selected for processing (1)

• crates/perry-runtime/src/array/iter_methods.rs

Included review availability: Your plan provides up to 8 included reviews per hour; 4 remain after this review.

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📝 Walkthrough

Walkthrough

RootedIterArray now resolves forwarded arrays on each access, refreshes roots, derives storage from the live header, and prevents reads beyond the current length. A regression test covers growth, shrinkage, forwarding, valid elements, holes, and out-of-range access.

Changes

Rooted array access

Layer / File(s)	Summary
Live header resolution and access validation crates/perry-runtime/src/array/iter_methods.rs	RootedIterArray follows forwarding pointers, refreshes its root, uses the current header, and checks the current length before access. The regression test covers array growth, shrinkage, forwarding, holes, and out-of-range reads.

Estimated code review effort: 3 (Moderate) | ~15–30 minutes

Merge Risk: ⚪ Minimal · up to 5c7d3

This localized runtime change refreshes array roots during find/findIndex iteration and prevents stale values after callback-driven shrinkage; no actionable merge-blocking risk remains beyond normal checks and review.

Suggested reviewers: thehypnoo

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes refreshing rooted arrays during runtime iteration, which is the primary change.
Description check	✅ Passed	The description includes the required summary, changes, issue, test plan, output, and checklist, and it records the unrun full workspace suite.
Docstring Coverage	✅ Passed	Docstring check was indeterminate for this PR — some files could not be analyzed in time. Not blocking.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/5898-array-remaining

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[proggeramlug]

Landed on main via #8680 (squash 81ddd46b2), together with the rest of this batch.

Validated on the merged 4-PR result rather than per-branch: 9 ratchet gates + cargo fmt --check pass, perry-codegen --lib 1194/0, perry-runtime --lib 2651/0 at RUST_TEST_THREADS=1. The squashed tree was verified byte-identical to the merged tree before push.

Version bump stripped per maintainer policy (the Cargo.lock diff was version-only); your changelog.d/ fragment carried through unchanged. Thanks!