associated-const-type-parameters.rs

//@ run-pass

trait Foo {
    const X: i32;
    fn get_x() -> i32 {
       Self::X
    }
}

struct Abc;
impl Foo for Abc {
    const X: i32 = 11;
}

struct Def;
impl Foo for Def {
    const X: i32 = 97;
}

struct Proxy<T>(#[allow(dead_code)] T);

impl<T: Foo> Foo for Proxy<T> {
    const X: i32 = T::X;
}

fn sub<A: Foo, B: Foo>() -> i32 {
    A::X - B::X
}

trait Bar: Foo { //~ WARN trait `Bar` is never used
    const Y: i32 = Self::X;
}

fn main() {
    assert_eq!(11, Abc::X);
    assert_eq!(97, Def::X);
    assert_eq!(11, Abc::get_x());
    assert_eq!(97, Def::get_x());
    assert_eq!(-86, sub::<Abc, Def>());
    assert_eq!(86, sub::<Def, Abc>());
    assert_eq!(-86, sub::<Proxy<Abc>, Def>());
    assert_eq!(-86, sub::<Abc, Proxy<Def>>());
    assert_eq!(86, sub::<Proxy<Def>, Proxy<Abc>>());
}