I haven't been programming Haskell recently.

Is criterion now bundled with GHC?

It seems this library still depends on it (https://github.com/gstew5/snarkl/blob/d6ce72b13e370d2965bb226f28a1135269e7c198/src/testsuite/benchmarks/Main.hs).

The benchmark target (and the test-suite) still have a dependency on criterion, so if you use those you're still restricted to GHC 8.2. But downstream code can depend on the library without that, so this allows people to use snarkl at least up to GHC 9.0 now.

I realized my last comment might not be clear – this doesn’t break anything that has an actual dependency on criterion. The dependency is still in the cabal file for those targets. But the dependency wasn’t used on the snarkl library, so we can remove that dependency to allow snarkl to work with GHC 9 without impacting testing & benchmarking on GHC 8.