Critical-review §2 B6 finding: extractAssignedVariable handled
`const X = ...` and `X = ...` but missed every modern JS/TS
destructuring pattern. Sinks downstream of destructured/spread vars
produced false negatives at the propagation step.
Patterns now recognized:
- `const { x } = source` object destructuring
- `const { x, y } = source` multi-key
- `const { secret: alias } = source` renamed (key NOT bound)
- `const { x, ...spread } = source` object rest
- `const { a, b: { c } } = source` nested object (key NOT bound)
- `const [a, b] = source` array destructuring
- `const [first, ...rest] = source` array rest
- `const [a, [b, c]] = source` nested array
- `const { user: { id }, ...rest }` mixed nested
Implementation: regex-based two-pass walker. Pass 1 detects whether
the LHS is a destructuring pattern (`{...}` or `[...]`). If yes, the
new `extractDestructuredNames` helper walks the pattern body via a
balanced-bracket depth counter, recurses into nested patterns, and
distinguishes keys (`key:`) from bindings. If no, the plain-decl
branch matches `\b(?:const|let|var)\s+(\w+)`.
Plain-assignment branch (`X = ...` without keyword) and Python-style
patterns are unchanged.
The function is now exported for direct unit testing — same pattern
as `_resetCacheForTest` in policy-loader. The internal walker
(`extractDestructuredNames`) remains module-private.
Tests: +19 cases in tests/scanners/taint-destructuring.test.mjs:
- 5 pre-B6 patterns (regression guard: plain decl, plain assign,
no-match on equality)
- 12 destructuring patterns covering object/array/rest/nested
- 2 non-destructuring regressions (return literal, arrow param)
Existing taint-tracer.test.mjs and taint.test.mjs unchanged — both
green (14 → 14, fixture-based integration tests not affected).
Suite: 1551 → 1570 (+19). All green.
68b9ea2692