trait Trait {
    fn bar(&self);
}

struct A<T: Trait> {
    a: T,
}

struct B<T: Trait> {
    b: Option<A<T>>,
}

struct C;

impl C {
    fn new() -> Self {
        Self {}
    }
}

impl Trait for C {
    fn bar(&self) {

    }
}

impl<T: Trait> A<T> {
    fn new(a: T) -> Self {
        Self {
            a
        }
    }
}

impl<T: Trait> B<T> {
    fn new() -> Self {
        Self {
            b: None,
        }
    }

    fn process(&mut self) {
        self.b = Some(A::new(C::new()));
    }
}

fn main() {
    let b = B::new();
    b.process();

}