Protty

It isn't unexpected that the focus of the Bun Rust rewrite is on the anti-Zig side more than anything, since the internet loves to hate. What is unexpected and unfortunate is that leadership within Bun hasn't tried to steer the conversation away from that at all. There are so many positive and interesting takeaways from this and I'm not really seeing any of them pushed as the primary message. A positive thing that hasn't been talked about at all is how far Bun came thanks to Zig. And even if you dump it now, its meaningful for how good Zig was to even build a product to this point and impact by any metric. I would've loved to see anyone in leadership say this. On the interesting side is how fungible programming languages are nowadays. Programming languages used to be LOCK IN, and they're increasingly not so. You think the Bun rewrite in Rust is good for Rust? Bun has shown they can be in probably any language they want in roughly a week or two. Rust is expendable. Its useful until its not then it can be thrown out. That's interesting! There's been a lot of talk about memory safety and no doubt Rust provides more guarantees than Zig. But I'd love to see a better analysis of why Bun in particular suffered so much rather than take the language-blame path. How could engineering as a practice been more rigorous to prevent this? What were the largest sources of crashes other programs should watch out for? How does Rust prevent them? How could Zig theoretically prevent them? That's interesting. I know the official blog post hasn't come out yet from Bun. But they're smart enough to know that that PR would stir up controversy the moment it opened, or they should've been. And plenty in the company have been tweeting and writing about it. Its somewhat telling to me in various dimensions what they chose to talk about first. I tend to think I'm pretty good at corporate PR/comms (especially when it comes to developer audiences) and I think appealing to the negative is never the right long term strategy; it does work to get short term eyes though.

Unfortunately, I don't use Zig now. Every 1.5-5x human DX productivity boost from Zig features is eclipsed by the 100x boost from coding agents writing Rust: Allocator interface: This is my favorite Zig feature, you feel so galaxy brain using a specialized allocator to optimize a code path (e.g. arena, stack fallback etc). The problem in Rust used to be that there was no Allocator interface equivalent and if you wanted a Vec that used a custom allocator you literally had to copy+paste the std version and modify it to use it (this is what Bumpalo did, look at the source). For a long while now there has been an Allocator trait in nightly, and it seems to be good now. Because it is a trait it is static dispatch, vs Zig's which is based on a vtable. Unlike Zig there isn't a community-wide convention of designing data structures to be parametric based on the allocator, but AI changes the game and makes it trivially to copy paste code and change that. I find it works well enough for my use-case. Arbitrary bit width integers + packed structs: Another beloved Zig feature of mine. It makes it so easy to do DOD-style CPU cache optimizations and stuff like tagged pointers, NaN boxing, etc. and even made bitflags really easy to make. You could always do this in Rust or any systems programming language but it was really ugly/unergonomic. The least worst option was using some crate like bitfield/bitflags which both rely on proc macro magic to work. Now, with coding agents I literally do not care how annoying it is to write the code by hand. Comptime: This is Zig's flashiest feature, no other programming language except maybe for obscure dependent-types langs have compile time evaluation as nice as Zig's. I thought I would miss it a lot, but I actually don't. For me, 95% of comptime usage is to create Zig's version of generic data structures with parametric types. Rust has a better designed type system IMO (see next section). In the remaining 5% of cases, not having comptime sucks. The only reliable way to reach an equivalent is through codegen. I'm making a game right now, and I have hardcoded hitbox geometry data generated from a tool that I want to bake into a data structure. Without comptime, I have to get Claude to write a script that generates the Rust file. However, I don't find myself needing compile time evaluation that much anyway. Rust's type system: I think I'd rather trade having comptime for Rust's better-designed type system, especially for bounded polymorphism (traits/typeclasses). Trying to do the equivalent in Zig is a nightmare. Also, I think that Rust's type system allows you to enforce more variants and prevent coding agents from making common mistakes. In my game I use the euclid crate which essentially allows you to not mix up coordinate spaces (very common problem in graphics programming) by creating specialized types for each coordinate space (e.g. Point or Point) Not having to deal with memory issues: With coding agents allowing 100x more code to be written, this also means you need to scrutinize 100x more Zig code for memory issues. Without formal verification, the surface area of the search space to enumerate to find bugs is just so much larger now. With the magnitude of code being generated now, Rust is even more attractive. Rust's tradeoff was always that it hinders developer productivity especially if you are unfamiliar with borrow checker, but this simply does not matter with coding agents anymore. And if you do use unsafe in Rust there's tools like miri which you can have the coding agent run the code against to make sure it doesn't cause UB or isn't violating Rust's aliasing rules when it comes to unsafe. I still miss writing Zig and find it to be a great language but I like Rust more and coding agents work with better with it.

Competent engineers can write safe C/C++ and Zig but building a team that’s competent as a collective is really hard. Specially if it’s under market pressure to ship quickly. Now that everyone has a very productive intern working with them at all times, this became obvious.