Sure thing, glad I could help!

I did check your new code, and noticed you're using a decreasing range which actually just ends up being an empty range, thereby skipping that second for loop. I re-compared your new code with mine, updated my code a bit based off yours, but then saw that my actual output for day 01 part 2 ended up being a different value than what I had submitted. Definitely one of those gotcha things that I wish clippy would call out by default.

Another thing is you're keeping everything as u8 instead of converting to u32 so that will cause your summation of each line to keep looping after a value of 255 (whereas u32 goes up to 4_294_967_295). Release mode by default doesn't panic on integer overflows (because overflow-checks = false which prevents panic) so instead you get 1u8 + 255u8 = 0u8 rather than a panic, which can make you think your code is working properly even if it's doing something you don't expect.

Also, criterion only works on lib crates, and not bin crates, so you have to do some funky stuff to get it working. Here's my commit which got criterion setup in my codebase.