Interface Dictionary

Source Code/19-30.rs:4–9

0, 1; None, Some(“Jane”)*/
fn main() {
    trait Dictionary { //1
        type Key; //2
        type Count; //3
        fn get(&self, key: Self::Key) -> Option<String>; //4
        fn count(&self, key: Self::Key) -> Self::Count; //5
    }
    struct Record {
        id: u32,
        name: String,