如何编写只能与某种类型的迭代器一起使用的迭代器扩展？

如何解决如何编写只能与某种类型的迭代器一起使用的迭代器扩展？

我想分析传入项目的价值并相应地调整/分组传出项目。为此，我需要确保我的扩展只能在迭代器包装特定类型的项目上调用。

我天真的方法是将项目类型固定在我的扩展特征中：

trait Tags: Sized + Iterator<Item = i32> {
    fn tags(self) -> TagsIterator<Self> {
        TagsIterator(self)
    }
}
impl<I: Sized + Iterator<Item = i32>> Tags for I {}

struct TagGroup;

struct TagsIterator<I: Sized + Iterator<Item = i32>>(I);
impl<I: Sized + Iterator<Item = i32>> Iterator for TagsIterator<I> {
    type Item = TagGroup;
    fn next(&mut self) -> Option<Self::Item> {
        unimplemented!()
    }
}

不幸的是它不起作用：

let test = vec![0_i32,1_i32,2_i32];
test.iter().tags();

error[E0599]: the method `tags` exists for struct `std::slice::Iter<'_,i32>`,but its trait bounds were not satisfied
  --> src/main.rs:20:17
   |
20 |       test.iter().tags();
   |                   ^^^^ method cannot be called on `std::slice::Iter<'_,i32>` due to unsatisfied trait bounds
   |
   = note: the following trait bounds were not satisfied:
           `<std::slice::Iter<'_,i32> as Iterator>::Item = i32`
           which is required by `std::slice::Iter<'_,i32>: Tags`
           `<&std::slice::Iter<'_,i32> as Iterator>::Item = i32`
           which is required by `&std::slice::Iter<'_,i32>: Tags`
           `&std::slice::Iter<'_,i32>: Iterator`
           which is required by `&std::slice::Iter<'_,i32>: Tags`
           `<&mut std::slice::Iter<'_,i32> as Iterator>::Item = i32`
           which is required by `&mut std::slice::Iter<'_,i32>: Tags`

我做错了什么？限制扩展特征的传入项目类型的正确方法是什么？