Rust 应为关联类型，找到类型参数

我遇到了一个与相关类型有关的问题.我在So上发现了类似的问题，比如下面这些问题:

• Expected type parameter, found opaque type个
• Matching a generic parameter to an associated type in an impl个

但是，虽然与我的案件非常接近，但它们并不相同……

因此，我有一个相关类型的特征:

trait Generator {
    type Item;
    fn next(&mut self) -> Self::Item;
}

泛型方法的另一个特征，它将第一个作为类型参数:

trait Iterator {
    fn iterate<T>(&self, generator: T) -> T::Item
        where T: Generator;
}

到目前为止一切都还好. 现在我想创建一个 struct ，并为它实现Iterator个特征.

struct Baz<R> {      // I want my struct to keep data of the same type as my associated type
    data: Vec<R>,    // So i make my struct generic 
}

impl<R> Iterator for Baz<R>
{
    fn iterate<T>(&self, generator: T) -> T::Item
        where T: Generator<Item = R>     // And specify associated type constraint for generic method
    {
        generator.next()
    }
}

现在我收到了一个错误:

error[E0271]: type mismatch resolving `<T as Generator>::Item == R`
  --> src/main.rs:20:28
   |
17 | impl<R> Iterator for Baz<R>
   |      - this type parameter
...
20 |         where T: Generator<Item = R>
   |                            ^^^^^^^^ expected associated type, found type parameter `R`
   |
   = note: expected associated type `<T as Generator>::Item`
               found type parameter `R`
   = note: you might be missing a type parameter or trait bound
note: the requirement `<T as Generator>::Item == R` appears on the `impl`'s method `iterate` but not on the corresponding trait's method
  --> src/main.rs:9:8
   |
8  | trait Iterator {
   |       -------- in this trait
9  |     fn iterate<T>(&self, generator: T) -> T::Item
   |        ^^^^^^^ this trait's method doesn't have the requirement `<T as Generator>::Item == R`

我想要修复它，我必须使我的Iterator特征成为泛型，并在特征定义中指定约束:

trait Iterator<R> {
    fn iterate<T>(&self, generator: T) -> T::Item
        where T: Generator<Item = R>;
}

还可以更新Iml块:

impl<R> Iterator<R> for Baz<R>
{
    ...
}

但不幸的是，这个特征来自第三方库，所以我不能更新他们的源代码(更确切地说，这是来自serde库的SeqAccess特征)

所以我的问题是:在这种情况下，有没有办法声明关联的类型约束，而不向特征本身添加类型参数？