In Rust you don't have to define all struct fields explicitly, for example:

struct MyBox<T>(T);

impl<T> MyBox<T> {
    fn new(x: T) -> MyBox<T> {
        MyBox(x)
    }
}

MyBox contains an instance of generic type T, but how can I refer to it? We haven't declared an explicit property for it! The trick is to pay attention to that (T) in the struct definition, which essentially means we're operating with a tuple. This kind of definitions is known in Rust as Tuple Structs.

In such cases, Rust allows 0-based indexing to access fields within a struct, similarly to tuples, therefore the T instance will be available by accessing self.0.

A more traditional way to declare this struct with an explicit name would be:

struct MyBox<T> {
    x: T,
}

impl<T> MyBox<T> {
    fn new(x: T) -> MyBox<T> {
        MyBox{ x }
    }
}