During my senior year of college (which ended last spring), I worked with two other students on implementing a server-side JavaScript interpreter in Rust. One of us, a grad student (not me!), wrote the garbage collector for it (https://github.com/rustoscript/french-press). We didn't end up finishing the entire language, but we got a sizable chunk of the language features implemented, and more than enough to know that Rust is very well suited to writing programming languages in, including garbage collectors. By far, the most complicated component of getting the garbage collector right was dealing with closures, but that's mostly because JavaScript is a very "unique" language, to put it nicely.
I read that back when you first posted it, which is exactly what came to mind when I was writing my comment. At least to my naive understanding, implementing a garbage collector for Rust is several orders of magnitude more difficult than merely implementing one in Rust.
We've had problems with closures before in Servo, I know that pain :)
> implementing a garbage collector for Rust is several orders of magnitude more difficult than merely implementing one in Rust.
Well, I mean it depends on what you're aiming for. Making a safe optional GC in Rust isn't too hard; rust-gc exists and is not very complicated. Making the compiler support arbitrary pluggable GCs is trickier. GC algorithms themselves can get so complicated that the state of the art research probably eclipses whatever has been done with rust-gc and similar "GCs for rust" so far. If you want a GC for Rust that contains a world-class collection algorithm the complexity is additive but the source of most of the complexity isn't the "for Rust" part, it's the "in Rust" part (A GC for rust will also typically be in Rust).
But also "optional" GCs like those that would be useful in Rust haven't been explored much either, so world class algorithms may not even make sense in this case.
It's ... an interesting set of problems, and very hard to make judgement about what is difficult :)
Thanks for elaborating on that! I'm definitely looking forward to seeing what you all do on the GC front for Rust in the future, even if it's a bit beyond my current comprehensions
I hate to ignore the cool technical knowledge needed to implement a GC for JavaScript, but damn, "french-press" is the best possible name for that project, I love it.
