Generics

Rust supports generics and even allows us to enforce the implementation of certain traits. These constraints can either come as a where clause attached to the function definition or with a colon in the generic type declaration:

fn my_generic_func<T: MyTrait>(t: T) {
    // code 
}

// ... is the same as 

fn my_generic_func <T>(t: T) where T: MyTrait {
    // code
}

// but better use in 2018 and beyond

fn my_generic_func(t: impl MyTrait) {
    // code
}

Additionally, the 2018 impl Trait syntax simplifies single-trait requirements (to do static instead of dynamic dispatch) for input and return parameters, thereby eliminating the need for a Box or lengthy type constraints (such as MyTrait in the preceding snippet). Unless multiple trait implementations are required (for example, fn f(x: T) where T: Clone + Debug + MyTrait {}), the impl Trait syntax allows us to put them where they matter, which is into the parameter list:

fn my_generic_func<T>(t: T) {
    // code 
}

// ... is...