I don't even get what they gain by Rust - Bun imports Webkit, which is a C++ project, relying on it for stuff like JITing Javascript. I would say that's a major concern, and making sure the JIT doesn't emit anything broken or naughty is completely outside the scope of Rust.

I think their original post lays out the benefits pretty well. I think the realization of some of these benefits is debatable (for example, they probably could have made their existing Zig code faster), but others are straightforward (like having fewer crashes because more of your code is provably “safe” in Rust terms).

(I think wrapping a large, complex C/C++ codebase is where Rust often shines, if you build the right joiner abstractions. PyO3 is a really great example of that.)

> making sure the JIT doesn't emit anything broken or naughty is completely outside the scope of Rust.

It's also outside the scope of the project if they're using Webkit's engine for that part. Which means Bun itself isn't a JIT, it's all the stuff built around the Webkit JIT, so whether or not Rust is useful for the JIT is entirely immaterial to the question of if Bun would benefit from Rust.