1 #![feature(generic_associated_types)]
2 #![feature(associated_type_defaults)]
4 // A Collection trait and collection families. Based on
5 // https://smallcultfollowing.com/babysteps/blog/2016/11/03/
6 // associated-type-constructors-part-2-family-traits/
11 type Iter<'iter>: Iterator<Item=&'iter T> where T: 'iter, Self: 'iter;
12 type Family: CollectionFamily;
13 // Test associated type defaults with parameters
14 type Sibling<U>: Collection<U> =
15 <<Self as Collection<T>>::Family as CollectionFamily>::Member<U>;
19 fn add(&mut self, value: T);
21 fn iterate<'iter>(&'iter self) -> Self::Iter<'iter>;
24 trait CollectionFamily {
25 type Member<T>: Collection<T, Family = Self>;
30 impl CollectionFamily for VecFamily {
31 type Member<T> = Vec<T>;
34 impl<T> Collection<T> for Vec<T> {
35 type Iter<'iter> where T: 'iter = std::slice::Iter<'iter, T>;
36 type Family = VecFamily;
42 fn add(&mut self, value: T) {
46 fn iterate<'iter>(&'iter self) -> Self::Iter<'iter> {
51 fn floatify<C>(ints: &C) -> <<C as Collection<i32>>::Family as CollectionFamily>::Member<f32>
55 let mut res = <C::Family as CollectionFamily>::Member::<f32>::empty();
56 for &v in ints.iterate() {
63 let a = vec![1, 2, 3];
65 assert_eq!(Some(&1.0), b.iterate().next());