hrtb

gistfile1.txt

trait A {}

struct SasA{}
impl A for SasA {}

trait Db<'d> {
    type Mem: ?Sized + A + 'd;
    fn d(&self) -> &Self::Mem;
}

trait Trait: for<'d> Db<'d> {
}

struct D {
}

impl<'d> Db<'d> for D {
    type Mem = dyn A + 'd;
    fn d(&self) -> &Self::Mem {
        Box::leak(Box::new(SasA{}))
    }

}

fn main() {
    let d = D{};
    <D as Db>::d(&d);

}