fix(runtime): finish string coercion operand rooting

[proggeramlug]

Summary

Finish the four primary operand-rooting sites left open by #6949 after #7811 and #7815:

• root the String split receiver and separator across limit/separator coercion, and refresh the source around result allocations
• root the RegExp.prototype.compile receiver and arguments across source/flags coercion and string allocation
• root the rebound RegExp pattern (and pending flags value) across the second constructor coercion
• root the typed-array view and user-patched toLocaleString closure across prototype lookup and every loop allocation/callback

The separate raw-JSValues-in-Rust-containers shape is now tracked by #7949, so it remains visible without keeping this coercion-specific issue open.

No version bump is included.

Validation

• cargo check -p perry-runtime --lib
• cargo test -p perry-runtime --lib string::tests:: (33 passed)
• cargo test -p perry-runtime --lib regex::tests:: (27 passed)
• full cargo test -p perry-runtime --lib: 2,152 passed; the two existing Windows-only failures remained (global_sink_isolation::every_covered_clear_helper_is_still_called_by_the_guards, path::value_args::tests::both_operands_survive_the_materialisation_window)
• scripts/check_file_size.sh
• no added bare get_raw_{mut,const}_ptr reads

Closes #6949

Summary by CodeRabbit

• Bug Fixes

  • Improved reliability of string splitting, regular expression handling, and typed-array toLocaleString() operations during memory cleanup.
  • Prevented potential data corruption or crashes when values are converted or objects are relocated internally.
  • Preserved existing validation, error behavior, and output while improving runtime stability.

• Documentation

  • Added a changelog entry documenting these runtime reliability improvements.

[coderabbitai]

📝 Walkthrough

Walkthrough

The runtime now roots receivers and operands during ToString coercions, allocations, callbacks, and RegExp updates. String splitting, RegExp construction and compilation, and patched typed-array toLocaleString paths refresh pointers after possible garbage collection.

Changes

GC-safe runtime operations

Layer / File(s)	Summary
RegExp rooting and coercion crates/perry-runtime/src/object/class_registry/construct.rs, crates/perry-runtime/src/regex/compile.rs	RegExp construction and compilation root receivers, patterns, and flags across coercion and allocation. RegExp properties and lastIndex updates use refreshed handles.
Typed-array locale conversion crates/perry-runtime/src/object/native_call_method/typed_array.rs	toLocaleString roots the typed-array receiver and patched callback while reading elements, invoking the callback, and coercing results.
String split allocation safety crates/perry-runtime/src/string/split.rs, changelog.d/7950-string-coerce-rooting-tail.md	String splitting roots source, separator, and result arrays across delimiter, limit, regex, substring, and result allocations. The changelog records the rooting audit.

Estimated code review effort: 3 (Moderate) | ~25 minutes

Possibly related PRs

• PerryTS/perry#6695: Previously modified RegExp compilation semantics in the same function.
• PerryTS/perry#6941: Applies similar runtime rooting and relocated-pointer refreshes to other coercion paths.
• PerryTS/perry#7240: Extends related GC-rooting fixes across RegExp, string splitting, and typed-array coercion paths.

Suggested reviewers: thehypnoo

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the primary runtime change: completing string coercion operand rooting.
Description check	✅ Passed	The description covers the rooting changes, linked issue, validation results, known failures, and version policy; it is sufficiently complete.
Linked Issues check	✅ Passed	The changes implement the four stated operand-rooting objectives for split, RegExp compile and construction, and typed-array toLocaleString in [#6949].
Out of Scope Changes check	✅ Passed	The runtime changes and changelog entry directly support the operand-rooting objectives, with no unrelated code changes identified.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

✨ 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/6949-string-coerce-rooting-tail

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[coderabbitai]

🧹 Nitpick comments (1)

crates/perry-runtime/src/string/split.rs (1)

483-496: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Consider invalidating the stale str_data and s bindings after the array allocation.

str_data borrows the source payload from Line 369. Line 493 allocates the result array, which can move the source. After Line 495 both str_data and the raw s parameter name from-space, yet both remain in scope for the rest of the function. The current code is correct because the loop reads only s_now from s_handle and part_ranges holds offsets. The risk is a later edit that reads str_data again inside the loop; that is the #5062 dangling-source class this file has hit before.

Shadowing the stale bindings makes the invalidation explicit at compile time.

♻️ Proposed guard against a future stale read

     let n = part_ranges.len();
 
     let (arr, _) = s_handle.across_const::<StringHeader, _>(|| {
         crate::array::js_array_alloc_pointer_elements(n as u32)
     });
     let arr_handle = scope.root_raw_mut_ptr(arr);
+    // `str_data` and `s` name pre-allocation addresses from here on. Every
+    // later read must come from `s_handle`.
+    #[allow(unused_variables)]
+    let (str_data, s) = ((), ());

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@crates/perry-runtime/src/string/split.rs` around lines 483 - 496, After the
result array allocation in the split implementation, explicitly invalidate or
shadow the stale str_data and raw s bindings before the loop. Preserve the
existing offset-based part_ranges and s_handle/s_now reads, while making any
later use of the pre-allocation source bindings fail at compile time.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@crates/perry-runtime/src/string/split.rs`:
- Around line 483-496: After the result array allocation in the split
implementation, explicitly invalidate or shadow the stale str_data and raw s
bindings before the loop. Preserve the existing offset-based part_ranges and
s_handle/s_now reads, while making any later use of the pre-allocation source
bindings fail at compile time.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 7867d243-be3b-4e50-893a-c31989f76835

📥 Commits

Reviewing files that changed from the base of the PR and between 2dc1874 and fb5f31f.

📒 Files selected for processing (5)

• changelog.d/7950-string-coerce-rooting-tail.md
• crates/perry-runtime/src/object/class_registry/construct.rs
• crates/perry-runtime/src/object/native_call_method/typed_array.rs
• crates/perry-runtime/src/regex/compile.rs
• crates/perry-runtime/src/string/split.rs