[klodolph]

You are just using the same storage duration as the containing object instance, and the C++ type system only gives you any guarantees for automatic, static, and thread storage duration. These all correspond directly to lexical scopes. The type system does not have a way to express dynamic storage duration, but Rust does because Rust has move semantics in the type system. C++ has move semantics, but they are runtime semantics built into the implementation of the library and not part of the type system, so you get no compile-time checking that you used move semantics correctly.

Phrased another way, I'm just saying that the C++ type system only expresses two types of storage durations: those tied to lexical scopes and dynamic storage durations, and provides no checks for dynamic storage durations.