Integer base annotations are dropped in certain contexts

[jon-flatley]

With the following set of structs, the goal is to get the u64 in E::Value to serialize in hex format. The only place where the #[annotate(format = hex)] attribute seems to accomplish this is when it's attached to myB in C.

#[derive(Annotate, Serialize)]
#[serde(untagged)]
pub enum E {
    // We want this u64 to serialize in hex format.
    Value(u64),
}

#[derive(Annotate, Serialize)]
pub struct A {
    myEnum: E,
}

#[derive(Annotate, Serialize)]
pub struct B {
    myA: Option<Vec<A>>,
}

#[derive(Annotate, Serialize)]
pub struct C {
    #[annotate(format = hex)]
    myB: Vec<B>,
}