test-type-dependency-inversion.rs

trait X {
    type X;
    fn f() -> Self::X;
}
trait Y {
    type Y;
    fn f(y: Self::Y);
}
trait XY {
    type X: X;
    type Y: Y<Y=<Self::X as X>::X>;
}
fn a<XYType:XY>() {
    XYType::Y::f(XYType::X::f());
}
#[derive(Debug)]
struct TheType(usize);
impl X for TheType {
    type X = Self;
    fn f() -> Self::X {
        TheType(42)
    }
}
impl Y for TheType {
    type Y = Self;
    fn f(y: Self::Y) {
        println!("{:?}", y);
    }
}
impl XY for TheType {
    type X = Self;
    type Y = Self;
}
fn main() {
    a::<TheType>();
}