[akiselev]

Trait specialization is Rust's answer to several of the abstractions provided in most OOP languages and the initial implementation (with conservative type resolution) has been in nightly for a while. I believe there is still a bit of work to do before stabilization but the feature is under active development. One of the primary challenges is the soundness and predictability of the algorithm that selects the right implementation for each type.

With specialization, instead of inheriting classes, traits can provide blanket and default implementations for types that depend on the traits implemented by that type. So, for example, you can provide several different "impl<T> ExTrait for T" with different trait bounds like "T: Clone", "T: Clone + Send", and "T: Clone + Send + Future<...>". Once the conservative inference algorithm is improved, this will be a much more powerful way to compose functionality than OOP but it will require a different approach to abstraction.

I think the plan is to eventually add trait objects that implement multiple traits which will cover more complex cases of dynamic dispatch like those in virtual inheritance.