[Manishearth]

Cycles of reference counted objects.

It is technically possible to guarantee the absence of leaks by introducing a `?Leak` trait to the language. There was a point in time when many wanted Rust to go that way, but it was ultimately decided against (it complicates other things).

[kibwen]

Note that the trait-based scheme referenced here would only prohibit specific kinds of memory leaks. "Leaking", in its broadest usage, isn't a solvable problem in a Turing-complete language since an infinite loop can be considered a leak.