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zk-mutant v0.1.1 hotfix

zk-mutant v0.1.1 is a small hotfix release for a breaking discovery bug: comment text was being treated like code, causing a mutant explosion from separator lines and “equations” inside comments.

If you tried zk-mutant on real-world Noir projects and suddenly saw dozens (or hundreds) of irrelevant mutants from // ===== lines or explanatory comments like leaf != 0, this release is for you.

The bug

In v0.1.0, mutation discovery scanned .nr source text for operators like:

  • == ↔ !=
  • < ↔ >=
  • <= ↔ >
  • >= ↔ <

…but it didn’t ignore comment ranges, so any comment containing those characters could become a “mutation candidate”.

Examples that (incorrectly) produced mutants:

// ===========================================================================
// If pubkey IS in tree: leaf != 0, proof generation fails
// If pubkey NOT in tree: leaf == 0, proof succeeds
// Also: a <= b && c >= d || e == f
// ===========================================================================

/*
Block comment too:
leaf != 0
leaf == 0
*/

Impact

  • Noise / false positives in reports
  • Huge mutant counts (wasting execution time and attention)
  • “Breaking” behavior in the sense that the tool becomes much less usable on real codebases with rich comments

The fix in v0.1.1

zk-mutant v0.1.1 now skips mutation candidates inside:

  • line comments (// ...)
  • block comments (/* ... */)

This is implemented via a lightweight comment-range scanner used during discovery, so operator mutation in real code behaves as before, while comment content is ignored.

This fix tracks comment ranges in a simple state machine that also avoids treating // inside strings as a comment opener.

Upgrade

If you installed v0.1.0 via cargo install, upgrade like this:

cargo install zk-mutant --force

Verification / regression coverage

This release includes regression coverage to ensure:

  • comment-only inputs produce 0 mutants
  • operators in actual code are still mutated as before

GitHub tracking:

  • Issue: #1 — “Bug: Mutator generates mutants from comments”
  • Release: v0.1.1 on GitHub

What’s next

main is continuing on the 0.2.0 line (alpha) while release/0.1 exists as a maintenance branch for hotfixes like this.

Next up on the product side: expanding operator sets, improving targeting/filtering, and running zk-mutant against more real Noir projects to learn where the tool is most useful (and where it’s noisy).