fix(runtime): honor RegExp subclass accessors before builtins

[proggeramlug]

Fixes #10700.

Reflect.get now includes accessors declared on a class prototype while walking toward inherited builtins. A RegExp subclass's flags and source getters run with the original instance as this; an own data property still shadows the class getter.

Validation:

• cargo build --profile perry-dev -p perry -p perry-runtime-static -p perry-stdlib-static
• cargo fmt --all -- --check
• scripts/check_file_size.sh
• ./run_parity_tests.sh --filter test_gap_10700_regexp_subclass_getter (1/1 pass with prebuilt compiler/runtime)
• ./run_parity_tests.sh --filter test_gap_regexp_flags_2829_2828 (1/1 pass)
• ./run_parity_tests.sh --filter test_gap_10179_regexp_cache (1/1 pass)

Summary by CodeRabbit

• Bug Fixes
  • Fixed RegExp subclass behavior so class-defined flags and source getters take precedence over inherited built-in accessors.
  • Ensured overridden getters receive the original subclass instance when accessed directly, through reflection, or during string replacement.
  • Preserved expected behavior when properties are shadowed by own data properties, including after those properties are removed.

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

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Plan: Advanced

Run ID: 694534a9-b70d-4674-88a1-6d70f1fb8e5f

📥 Commits

Reviewing files that changed from the base of the PR and between 5b835a7 and c5d32c7.

📒 Files selected for processing (1)

• crates/perry-runtime/src/object/descriptor_state.rs

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📝 Walkthrough

Walkthrough

The runtime now resolves accessors declared on RegExp subclass prototypes before inherited builtin accessors. The change roots the property key, preserves own data-property shadowing, and adds regression coverage for flags, source, reflection, replacement, and deletion behavior.

Changes

RegExp subclass accessor resolution

Layer / File(s)	Summary
Runtime accessor resolution crates/perry-runtime/src/object/descriptor_state.rs	The prototype walk roots the coerced property key and resolves declared-class getters before inherited builtin getters. Own data properties continue to shadow accessors.
Regression validation test-files/test_gap_10700_regexp_subclass_getter.ts, changelog.d/10999-regexp-subclass-getter.md	The test covers overridden flags and source getters, reflection, replacement, prototype data properties, and own-property deletion. The changelog records the fix.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~15 minutes

Change: Bug fix · Severity of issue fixed: Medium

Merge Risk: ⚪ Minimal · up to c5d32

RegExp subclass flags and source reads now honor subclass accessors while preserving own-property shadowing, with regression coverage for the changed behavior. The change is merge-ready.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main runtime change: honoring RegExp subclass accessors before builtin accessors.
Description check	✅ Passed	The description explains the fix, references issue #10700, states the expected behavior, and lists build, formatting, file-size, and parity-test validation. It does not use all template headings or in…
Linked Issues check	✅ Passed	The change in crates/perry-runtime/src/object/descriptor_state.rs resolves declared class-prototype accessors before inherited builtin accessors. The lookup preserves own data-property shadowing. Th…
Out of Scope Changes check	✅ Passed	The changes contain the accessor-resolution fix, its regression test, and a related changelog entry. The tested behavior directly supports [#10700]. No unrelated implementation or test change is shown…
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 2 files.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create a new PR

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[proggeramlug]

Landed on main in merge train 258 (#11078, v0.5.1641), main e27f0a068a.

Carried at head c5d32c76a0. CI on the train head was fully green — 22 jobs, zero failures, the first train since the public-baseline artifact was regenerated, so no known-red line to read past.

This train was bisect-verified: after an earlier 35-PR assembly hit five gap regressions, the lowering-touching PRs were split into probes, and this set (#11070) came back with all six gap shards clean while the other half reproduced all five.

Trains rebase-merge, so commits get new SHAs and GitHub cannot mark this merged. Closed as landed.