Leanstral 1.5: Proof abundance for all

>One such bug was in the sign function for zigzag decoding of the datrs/varinteger library. On input Std.U64.MAX, the expression (value + 1) overflowed, causing crashes in debug mode and silent corruption in release mode—an edge case that testing and fuzzing would typically miss.

that library is: https://github.com/datrs/varinteger

it seems probably correct, as there's an identical issue filed on that repo a week before this was published: https://github.com/datrs/varinteger/issues/8 (is this a leanstral employee? they have almost no info and only very sparse activity. or did leanstral perhaps just pick up this issue?)

it's a tiny, surprisingly-poorly tested, long-untouched (8y) library: https://github.com/datrs/varinteger/blob/master/tests/test.r... that has about 1k downloads per day: https://crates.io/crates/varinteger [1] which seems rather low.

I don't think I'd consider that such a smashing success that it's worth bringing up as the sole example tbh. though automated detection is certainly useful. or is this a noteworthy accomplishment for this sub-field? I haven't played with proof-writing LLMs, but given the paucity of training data I wouldn't be surprised if they're a bit rough compared to general coding.

1: https://crates.io/crates/varinteger lists it as https://github.com/mafintosh/varinteger-rs which redirects to https://github.com/datrs/varinteger , so despite looking different at a glance it does appear to be the same library

Halfway thru the article it shows a comparison with several frontier-ish LLMs. But they're all from half a year ago. "Our new model is better than all these Chinese models from 3 generations ago" is pretty funny to me.

particularly "and fuzzing", yea. fuzzing generally does intentionally explore boundary values, from what I've seen. for an encoding library like this, I think it's fair to say that fuzzing is a baseline expectation for any decent code, and it almost certainly would've caught this in seconds.

--- edit

concretely, I made a very simple round-trip test with proptest, and got dozens of failures and this in less than a second:

    thread 'signed_round_trip' (50528) panicked at tests/test.rs:72:1:
    Test failed: attempt to multiply with overflow.
    minimal failing input: value = 4611686018427387904
        successes: 2
        local rejects: 0
        global rejects: 0

Curious that they are pitching Lean 4 for formal verification. I thought that this was more the domain of Isabelle/HOL and TLA+. At least I would have expected a model trained at using all three. Maybe also Isabell/Isar, which seems preferable for forward derivations in linear algebra. Could anyone shed some light on this?

Earnest question: any recommendation to not come off this way in forums?

I created this tool for my own research and have found it really helpful to benchmark different automated theorem provers (my experience so far has been that Claude Code + Codex still out-perform Leanstral). My genuine aim is to share that usefulness with others, not self promote!