test(gc): assert the sparse cache is old-gen before the containment branch (#7546 follow-up)

[proggeramlug]

#7546's external-edge test asserts the lazy array's sparse cache and its header land on different pages, but never that the cache block is old-gen.

slot_is_external_to short-circuits to true on generation before reaching the containment test. So if an allocator change ever moved a 32 KiB sparse cache into the nursery, the containment branch the test exists to cover would quietly stop running — and the test would still pass.

That is CLAUDE.md's "a gate must assert its subject was live" hazard applied to a test written to close a coverage hole of exactly that kind: #7500's test_dirty_lazy_array_external_cache_scan_marks_bitmap_selected_child was green for its entire life because no producer ever wrote a real entry, so it only ever exercised a hand-planted one.

Adds the missing precondition. Raised by CodeRabbit on #7546; applied here because that agent's worktree was removed before it could — my cleanup, not its error.

33 callback-scanner tests green, cargo fmt --check clean.

Summary by CodeRabbit

• Release

  • Updated the application version to 0.5.1310.

• Bug Fixes

  • Improved runtime validation for sparse cache handling and external reference tracking, helping prevent missed edge cases during memory management.

• Tests

  • Strengthened coverage to ensure cache generation state is validated before related behavior is exercised.

• Documentation

  • Added a changelog entry describing the cache liveness test improvement.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 8736d790-38a6-4b92-99b0-752ae492adc6

📥 Commits

Reviewing files that changed from the base of the PR and between b98fcaa and aa60587.

⛔ Files ignored due to path filters (1)

• Cargo.lock is excluded by !**/*.lock

📒 Files selected for processing (4)

• CLAUDE.md
• Cargo.toml
• changelog.d/7549-cache-oldgen-liveness-assertion.md
• crates/perry-runtime/src/gc/tests/runtime_roots/callback_scanners.rs

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📝 Walkthrough

Walkthrough

The sparse-cache external-edge test now verifies old-generation allocation before checking remembered-set behavior. The workspace version, documented version, and changelog update to reflect the change.

Changes

GC test and release update

Layer / File(s)	Summary
Old-generation precondition for sparse-cache test crates/perry-runtime/src/gc/tests/runtime_roots/callback_scanners.rs, changelog.d/7549-cache-oldgen-liveness-assertion.md	The test asserts old-generation allocation before validating sparse-cache page placement and remembered-set tracking. The changelog documents this precondition.
Version metadata update Cargo.toml, CLAUDE.md	The workspace package version and documented current version change from 0.5.1309 to 0.5.1310.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• PerryTS/perry#7546: The test strengthens the sparse-cache lazy_get regression coverage introduced by this PR.

Suggested reviewers: thehypnoo

✨ 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/7549-cache-oldgen-assertion

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