string() coercion on list-type value HARD-ABORTS interpreter (exit 1, uncontainable); blocks --export-root #887

Rationale

string() coercion on a list-type value HARD-ABORTS the interpreter (exit 1), killing the script THROUGH an enclosing try (uncontainable). Enumerating the list is fine; only string() dies. This blocks any generic walker/serializer that coerces values (including the planned --export-root tool). Impact is severe: crash cannot be caught, no fallback available.

Current State

Verified reproduction (2026-08-11, pristine Virgin.root):

string(system.extensions.odbc.data.dll.macCarbon.rFork)
string(system.extensions.odbc.data.dll.macCarbon.rFork) -- regex sibling also crashes

Both are type list with 3 reco children:

• Enumerating the list: works fine
• string() coercion: HARD-ABORT (exit 1, kills script, uncontainable by try/else)

Impact:

• Generic value walker/serializer crashes on list values
• Planned --export-root tool will hit this on Virgin.root paths
• try/else offers NO protection (hard abort)
• No fallback coercion available

Scope:

• At least 2 confirmed list values in Virgin.root
• May be more (census incomplete at time of report)

Desired Outcome

1. Fix string() coercion to handle list type gracefully
2. Return a sensible representation (e.g., string of list length, or JSON array representation)
3. Make the operation catchable by try/else (convert hard-abort to exception)
4. Add regression test: string() on list values must not crash

Recommendation

1. Trace the crash: LLDB backtrace on string(list_value)
2. Identify root cause: Type dispatch in string coercion, missing list handler
3. Implement handler: Return appropriate string representation (length, array notation, etc.)
4. Test: Verify try/else can catch any exceptions (no hard abort)

Exit Criteria

• string(list_value) does not crash
• Returns sensible string representation
• Exceptions are catchable by try/else
• Regression test added: string() on list values
• Planned --export-root tool can handle list values

Related Context

• Found by: ODB census 2026-08-11
• Related issues: system.macintosh iterative walk SEGFAULTS (exit 139); deterministic reproducer for #828/#857 dbgeteof null-deref family #864 (different crash), ROOT_BUILD_FROM_SOURCE_PLAN.md (exporter must special-case list/reco until fixed)
• Code: Coercion verb string(), type dispatch, list handler
• Data: system.extensions.odbc.data.dll.macCarbon.rFork (and sibling), both type list
• Impact: Blocks generic serialization, --export-root tool, census tools

Distinct from Other Issues

• NOT system.macintosh iterative walk SEGFAULTS (exit 139); deterministic reproducer for #828/#857 dbgeteof null-deref family #864 (dbgeteof null-deref) — this is type-dispatch crash, different mechanism
• Data is intact (enumeration works); issue is in coercion logic