[Dimank92]

Summary of Changes

Closes #1423.

This PR fixes multiple soundness bypasses where non-lowered O8 map-slot borrow expressions (&m[k]) bypassed HYB-E3104:

1. compiler/crates/hy-check/src/addr_loan.rs:
   • check_stmt_addr_of_loan_projections:
     • Stmt::Local: Only passes allow_slot_loan = true when matches!(l.kind, LocalKind::Define | LocalKind::Let) && l.ty.is_none() && l.names.len() == l.values.len(). LocalKind::Var and type-ascribed declarations cannot lower slot loans and now correctly reject &m[k] with HYB-E3104.
     • Stmt::Assign: Only passes allow_slot_loan = true when *op == AssignOp::Assign && targets.len() == values.len() && targets.iter().all(|t| matches!(&t.kind, PlaceKind::Ident(_))). Index and mixed assignments cannot lower slot loans and now reject &m[k] with HYB-E3104.
   • mark_slot_loans_local & mark_slot_loans_assign:
     • Restricted marking to lowered define/let declarations and all-identifier assignments, aligning the checker state with hy-emit lowering.
   • walk_addr_of_loan_projections (Expr::StructLit):
     • Removed unconditional skip of map_slot_borrow_span on struct literal fields. Fields of type any or generic parameters that were not previously caught by A6 (HYB-E3103) now properly reject unlowered &m[k] with HYB-E3104 (while emit_map_slot_borrow_diag already deduplicates against prior A6 diagnostics).

Maintainer Scorecard & Verification

• Code Quality: Clean alignment with hy-emit O8 slot loan lowering conditions in compiler/crates/hy-emit/src/stmt.rs.
• Tests:
  • compiler/crates/hy-check/tests/slot_loan_callarg_positions.rs: added non_lowered_map_slot_borrow_positions_rejected_issue_1423 verifying all 4 repro cases:
    1. var declaration (var p = &m["a"]) -> rejects with HYB-E3104.
    2. Index assignment target (ptrs[0] = &m["a"]) -> rejects with HYB-E3104.
    3. Mixed-target parallel assignment (q, arr[0] = &m["a"], 1) -> rejects with HYB-E3104.
    4. any-typed struct-literal field (box{p: &m["a"]}) -> rejects with HYB-E3104.
• Pass Rate:
  • cargo test -p hy-check: 100% pass across all tests.

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Payout / Bounty Address (Polygon/Base/Arbitrum/Ethereum USDC):
0xC345C07229307d4f1c7935aD2cAe48e390215808

[limitlessprojects]

Landed on main as a two-parent merge onto the post-#1432 tip (17d2962): your position gates + #1432's loan-preservation semantics, doc-comment conflict resolved in favor of both. Battery on the merged tree: workspace 1775/0, corpus tripwire clear, differential FULL 40+86; over-reach controls (plain-local &n, loan re-loan, non-loan rebind) all stay ACCEPT, and #1424's five non-lowered-position shapes reject E3104.

Clean, well-documented diff — the LocalKind gating and the all-ident-targets condition on mark_slot_loans_assign are exactly the right restriction to what hy-emit lowers. Thanks @Dimank92.