[Manishearth]

Worth highlighting: library-level GC would not be convenient enough to use pervasively in Rust anyway. library-level GC does not replace Rust's "point".

It's useful to have when you have complex graph structures. Or when implementing language runtimes. I've written a bit about these types of use cases in https://manishearth.github.io/blog/2021/04/05/a-tour-of-safe...

And there's a huge benefit in being able to narrowly use a GC. GCs can be useful in gamedev, but it's a terrible tradeoff to need to use a GC'd language to get them, because then everything is GCd. library-level GC lets you GC the handful of things that need to be GCd, while the bulk of your program uses normal, efficient memory management.

[zorgmonkey]

This is a very important point, careful use of GCs for a special subset of allocations that say have tricky lifetimes for some reason and aren't performance critical could have a much smaller impact on overall application performance than people might otherwise expect.

[Manishearth]

Yeah, and it's even better if you have a GC where you can control when the collection phase happens.

E.g. in a game you can force collection to run between frames, potentially even picking which frames it runs on based on how much time you have. I don't know if that's a good strategy, but it's an example of the type of thing you can do.