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Malte Ubl
796fcbb9ce
The optimistic int32-slots fixpoint assumed exactly int32 for parameter, result and captured-box candidates. That is too weak for remainders: with x and n only known to be int32, `(x * 31 + n) % m` may have a negative dividend (and a -0 result), so a kernel called as `v = step(v, n)` could not prove step's result, v stayed a double, and the parameters fell back to doubles too. Unpinned candidates now start one level lower, at non-negative int32. A write that is an int32 but may be negative demotes the slot to int32 and reanalyzes its readers (a parameter that seeds a box demotes the box as well); any other write drops it as before. Slots only ever widen, so the fixpoint still ends with every remaining assumption proven at every write. Int32 contract pins keep their int32 facts. The call-site range retry is unchanged for slots that fail both levels. The direct-call kernel now passes i32 to step.i32 and keeps v an i32 slot (sandbox: 2563 ms -> 964 ms, node 1256 ms). Corpus 5323 pins the non-negative facts and every widening path (negative arguments, results and box writes, -0 remainders, count-down recursion) against Node.