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Add tests covering the pattern where a function-level `asserts` covers per-iteration abort conditions in an implementation loop. The loop invariant uses `ensures` to carry the partial information needed for both the Check direction (discharge body assertion under asserts) and the Assume direction (force loop to be unable to exit normally when asserts is negated). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Cover variations of the asserts-in-loop pattern: * requires + asserts mix * multiple per-iteration asserts in the body * sequential pair of loops in one function * loop with early break (no asserts needed) * accumulator overflow with closed-form invariant * asserts pinning down a return-value postcondition * mutating state via &mut Plus two failure cases exposing prover limitations: * nested loops with two independent asserts (Assume direction does not propagate inner-loop contradiction outward) * mutating quantified state where the asserts and the natural invariant collapse to the same predicate at iteration zero Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The mutating quantified case is solvable — apply the same `j < i` guard trick used for immutable inputs, but to the cloned `old_v` snapshot. The invariant `forall j < i, safe(old_v[j])` is vacuous at iteration 0, accumulates per-iteration, and at loop exit covers the full range — contradicting the negated asserts. Keep the broken un-guarded version as a fail test showing what does not work and why. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Express the function-level asserts as `forall k, outer_safe(k, n, m)` and accumulate `forall k, k >= i || outer_safe(k, n, m)` in the outer loop invariant — same vacuous-at-zero / collapses-at-exit pattern that works for `positive_check` and `increment_all`. The earlier nested.fail variant used a bounded asserts which doesn't let the prover connect a single conjunctive assertion to the per-iteration abort behaviour spread across two loops. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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