trait From<Src> {
    type Output;

    fn from(src: Src) -> <Self as From<Src>>::Output;
}

trait To: Sized {
    fn to<Dst: From<Self>>(self) ->
        <Dst as From<Self>>::Dst
        //~^ ERROR cannot find associated type `Dst` in trait `From`
    {
        From::from(self)
    }
}

fn main() {}