trait Base {
    type Item;
    type Item2;
}

trait Service {
    type R;
    type E;
    type C: Base<Item = Self::R, Item2 = Self::E>;
}

struct Inner<T: Service> {
    service: T,
}

struct S1<T: Service> {
    inner: Inner<T>,
}

struct S2 {
    inner: Inner<ServiceImpl>,
}

struct BaseImpl {}
impl Base for BaseImpl {
    type Item = u64;
    type Item2 = String;
}

struct ServiceImpl {}
impl Service for ServiceImpl {
    type R = u64;
    type E = String;
    type C = BaseImpl;
}

fn create() -> ServiceImpl { // хз что тут должно быть
    panic!()
}

fn main() {
    let a = S2 { inner: create() };
}