struct Foo(u8);
struct Bar(u8);
struct Baz(u8);

impl From<Baz> for Bar {
    fn from(t: Baz) -> Bar {
        Bar(t.0)
    }
}

impl<T: Into<Bar>> From<T> for Foo {
    fn from(t: T) -> Foo {
        Foo(t.into().0)
    }
}

fn main() {
    let b = Baz(42);
    let f: Foo = b.into();
}