| COBOL to Java is a completely different thing and pretty much unrelated. Rust can easily call C libraries and vice versa and so can Zig. A more appropriate and designed rewrite would identify the core pieces of the Zig code that were the primary sources of all the big issues. Then, you rewrite that component in Rust and verify that you get the expected improvements. That keeps the codebase stable, it keeps you honest on actually reducing bugs and issues, and other benefits. Then you either just keep it that way or slowly rinse and repeat. Without doing the analysis of what the core issues were in the first place, the author of Bun can make no claims towards the rewrite. He claims to have fixed flaky tests and improved memory safety. Where is the analysis that shows this? Where is the proof and data? Does he even know where the issues in the Zig codebase were at? I saw a commit where a test had a one second sleep put in place. Compare this to say the Racket rewrite where a significant portion of the C core was replaced by Chez Scheme and Racket itself. There were several blog posts doing both pre- and post-analysis, and Racket has far less users than Bun. This rewrite is totally unprofessional and has been poorly and even antagonistically communicated. The author was on this site just days ago telling everyone to relax and that he'd probably throw out this code, and that was even after it had been brought up that this wasn't pre-communicated to users. If I was a dependent in Bun, I would migrate off immediately. So I push back in the idea that this is the way to do a rewrite like this. |
That was until he empirically checked that, contrary to his hypothesis, Claude is _really_ good at mechanical rewrites that preserve functionality and add a type system that prevents the general class of errors that are inherent in Zig's language features, which he has mentioned previously.
I push back against the idea that you need extremely thorough analysis for certain things that end up becoming obvious after working a long time with a codebase. It's clear that Zig doesn't cover certain guarantees that make code robust but Rust does, and this has been documented over and over again because we have examples (with better and worse execution) of the classes of bugs Rust helps and uncover and how a port can go better or worse.
A language with a thorough test suite written in another language with complete coverage is about as good a use case as you can get to support a language rewrite. Ultimately this is about the developer's preference of one language over the other and avoiding simple bugs. What more do you need?