> Managed (GC-ed) pointers are moved to the standard library.

Most uses of the old managed pointer scheme have been excised, but not all just yet (though we have people working on it with great vigor and tireless devotion). They're behind a feature flag though, so it's not possible to use them by accident.

For example, note that the replacement type in question, std::gc::Gc, is still internally backed by the old managed pointers, although this will not be the case once we finally implement a proper garbage collector. And even then if you really need multiple owners of a single value we'd really prefer that you use our reference-counted pointer (std::rc::Rc) instead, along with weak pointers (std::rc::Weak) if your data has cycles. Reference counting in Rust is generally surprisingly cheap, since the refcount only gets bumped if you explicitly clone the pointer; otherwise the pointer simply gets passed around as an owned value.