[9rx]

I would say that RC is GC, yes, as it is most definitely technically true. But it was pjmlp who suggested it originally (Limbo also uses reference counting), so we have clear evidence that others also see reference counting as being GC. We wouldn't have a discussion here otherwise.

[pjmlp]

While RC is a GC algorithm, chapter 5 from GC handbook, it doesn't count when it isn't part of the type system because then it becomes optional and not part of the regular use of the programming language.

Additionally Limbo's GC is a bit more complicaticated than a plain add_ref()/release() pair of library calls.

https://doc.cat-v.org/inferno/concurrent_gc/concurrent_gc.pd...

[9rx]

> because then it becomes optional

Exactly. Optional implies use. So, in case you forgot to read the thread, both Limbo and Rust use GC.