asref-interface.rs

#[derive(Debug)]
struct X(pub i32);

impl AsRef<X> for X {
    fn as_ref(&self) -> &X {
        self
    }
}

fn f<A: AsRef<X> + std::fmt::Debug>(x: A) {
    dbg!("f", x);
}

trait K {
    fn h(&self);
}

impl K for X {
    fn h(&self) {
        // fine.
        f(self)
    }
}

impl X where Self: AsRef<X> {
    fn g(&self)  {
        // not fine.
        f(self);
    }
    
    fn p<A: K + AsRef<X> + std::fmt::Debug>(x: A) {
        f(x);
    }
}

fn main() {
    let v = X(42);
    v.g();
    v.h();
    X::p(v);
    X::g(v);
    f(v);
}