Phase 11.3.5. The original try/except (OSError, ValueError): mtime = 0.0
in get_cached_tree is now extracted to a Result-returning helper.
The helper returns Result[float]; the caller uses .data (0.0 fallback) and
can inspect .errors. The convention requires Result[T] for try/except sites
that can fail; the helper satisfies this requirement.
Audit post-migration:
- _get_mtime_safe L48 = INTERNAL_COMPLIANT (Heuristic A) ✓
- get_cached_tree L92 = no try/except for mtime (extracted)
Tests: 24/24 pass (test_ast_parser, test_file_cache_no_top_level_tree_sitter).
ed
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