Sure it does, here's one:
http://www.hpl.hp.com/personal/Hans_Boehm/gc/
Rust has a GC in the same sense that C++ has one, which is to say that its GC can be provided by libraries rather than being baked-in to the language.
http://www.hpl.hp.com/personal/Hans_Boehm/gc/
Rust has a GC in the same sense that C++ has one, which is to say that its GC can be provided by libraries rather than being baked-in to the language.
So there's no longer even special syntax for a theoretical GC. Instead the plan is to greatly expand our support for custom pointer types in general, which will make all user-provided pointer types (implemented in whatever libraries our users come up with) first-class citizens. Our own stdlib will include several pointer types of this nature, including: `Rc` (reference counting), `Arc` (atomic (thread-safe) reference counting), `RWArc` (memory-safe Arc for mutable objects), and, yes, a `Gc` type.
And while it's true that we may provide hooks into the runtime to allow the `Gc` type to be implemented more efficiently, any user library will be able to use these hooks to implement its own GC. There won't be any implementation in the language itself.