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Diffstat (limited to 'tests/ui/generic-associated-types/collections.rs')
-rw-r--r-- | tests/ui/generic-associated-types/collections.rs | 69 |
1 files changed, 69 insertions, 0 deletions
diff --git a/tests/ui/generic-associated-types/collections.rs b/tests/ui/generic-associated-types/collections.rs new file mode 100644 index 000000000..15f429afb --- /dev/null +++ b/tests/ui/generic-associated-types/collections.rs @@ -0,0 +1,69 @@ +#![feature(associated_type_defaults)] + +// A Collection trait and collection families. Based on +// https://smallcultfollowing.com/babysteps/blog/2016/11/03/ +// associated-type-constructors-part-2-family-traits/ + +// run-pass + +trait Collection<T> { + type Iter<'iter>: Iterator<Item=&'iter T> where T: 'iter, Self: 'iter; + type Family: CollectionFamily; + // Test associated type defaults with parameters + type Sibling<U>: Collection<U> = + <<Self as Collection<T>>::Family as CollectionFamily>::Member<U>; + + fn empty() -> Self; + + fn add(&mut self, value: T); + + fn iterate<'iter>(&'iter self) -> Self::Iter<'iter>; +} + +trait CollectionFamily { + type Member<T>: Collection<T, Family = Self>; +} + +struct VecFamily; + +impl CollectionFamily for VecFamily { + type Member<T> = Vec<T>; +} + +impl<T> Collection<T> for Vec<T> { + type Iter<'iter> = std::slice::Iter<'iter, T> where T: 'iter; + type Family = VecFamily; + + fn empty() -> Self { + Vec::new() + } + + fn add(&mut self, value: T) { + self.push(value) + } + + fn iterate<'iter>(&'iter self) -> Self::Iter<'iter> { + self.iter() + } +} + +fn floatify<C>(ints: &C) -> <<C as Collection<i32>>::Family as CollectionFamily>::Member<f32> +where + C: Collection<i32>, +{ + let mut res = <C::Family as CollectionFamily>::Member::<f32>::empty(); + for &v in ints.iterate() { + res.add(v as f32); + } + res +} + +fn use_floatify() { + let a = vec![1, 2, 3]; + let b = floatify(&a); + assert_eq!(Some(&1.0), b.iterate().next()); +} + +fn main() { + use_floatify(); +} |