playground.rs

trait StreamingIterator<'a> {
    type Item;
    fn next(&'a mut self) -> Option<Self::Item>;
}

struct Buffer<T> {
    data: Vec<T>,
    pos: usize
}

playground.rs

use std::collections::VecDeque;

// The kind * -> *
trait TypeToType<Input> {
    type Output;
}

struct Vec_;
struct VecDeque_;

Gankra

pub trait Collection {
    fn len(self) -> uint;
    fn is_empty(&self) -> bool; //defaulted
}

pub trait Mutable: Collection {
    fn clear(&mut self);
}

pub trait Container<T>: Collection {