I find Rust more interesting than I did at the start of the project, since I ended up using algebraic data types all over the place, which Rust has. And it doe

I find Rust more interesting than I did at the start of the project, since I ended up using algebraic data types all over the place, which Rust has. And it doesn't have the runtime issues I mentioned with Go. But the compile times are a dealbreaker. As mentioned in the post, if I had a C++ compiler in my edit-run cycle, I would have never have gotten the project done. From what I understand having a Rust compiler in there would be even worse. I can understand why you think Python is not ideal, and I listed many reasons in the post why it's not. But that is why I used a name OPy -- OPy is purposefully diverging Python. See the Tex analogy. I agree it's an experiment. I didn't make any claims in the post; I specifically mentioned that I would like to prove a point. I agree that I will need to change the Python VM. The speedups can be unlimited in that case that I write an entirely new VM (which is easier than rewriting the very flexible and capable Python VM from scratch). Another thing I didn't mention: it is probably possible to make the shell VM and OPy VM converge. So Oil's runtime could be faster than any other shell, because every shell is a tree interpreter and not a bytecode VM. (The parser might still be slower, but I don't expect that to be an issue.) ---- EDIT: On the other hand, I doubt you can write bash in Rust in less than say 50K to 80K lines of code. I think Rust will still be at least 3x more verbose than Python. It inherently expresses more, so this is fundamental. So even if compile times were not an issue, I still probably wouldn't choose Rust. Also, build dependencies matter a lot for a shell, since it's used to bootstrap embedded systems. I conjecture that shells run all sorts of systems that Rust programs have never run on. Rust isn't as portable as C, or C++.