## Diamond Recursion Scan — CLEAN

**Scan date:** 2026-03-29
**Pattern:** Recursive cycle/dependency check without visited set (CWE-407 diamond recursion, O(2^D))

### Files examined

- `src/cargo/core/resolver/mod.rs` — `check_cycles`, `visit`
- `src/cargo/ops/tree/graph.rs` — `from_reachable`
- `src/cargo/ops/cargo_compile/mod.rs` — `visit` function in dependency compilation

### Findings

**check_cycles / visit:** Uses two `HashSet<PackageId>` accumulators: `visited` (current DFS path, cleared on backtrack) and `checked` (globally confirmed-clean nodes). Properly prevents diamond re-traversal. O(V+E). CLEAN.

**cargo_compile visit:** Uses `visited: &mut HashSet<Unit>` passed to all recursive calls. O(V+E). CLEAN.

Note: `cargo-0001` and `cargo-0002` cover pre-existing CWE-407 defects in print_stack and add_edge operations.

### Verdict: CLEAN — no diamond recursion CWE-407 found
