Rust by Example

Of course traits can also be generic. Here we define one which reimplements the Drop trait as a generic method to drop itself and an input.

// Non-copyable types.

struct Empty;

struct Null;

// A trait generic over `T`.

trait DoubleDrop {

// Define a method on the caller type which takes an

// additional single parameter `T` and does nothing with it.

fn double_drop(self, _: T);

}

// Implement `DoubleDrop` for any generic parameter `T` and

// caller `U`.

impl DoubleDrop for U {

// This method takes ownership of both passed arguments,

// deallocating both.

fn double_drop(self, _: T) {}

}

fn main() {

let empty = Empty;

let null  = Null;

// Deallocate `empty` and `null`.

empty.double_drop(null);

//empty;

//null;

// ^ TODO: Try uncommenting these lines.

}

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