如何从另一个特征对象创建特征对象?

最新稳定版本的rust(1.27)允许为特征对象实现特征。( dyn Trait )所以我尝试了 following :

trait T1 {
    fn f1(&self);
}
trait T2 {
    fn f2(&self);
}
impl T2 for dyn T1 {
    fn f2(&self) {
        self.f1()
    }
}
struct S();
impl T1 for S {
    fn f1(&self) {}
}

fn main() {
    let t1 = S();
    let t12: &T1 = &t1;
    t12.f2();
    let t2: &T2 = &t12;
    t2.f2();
}

上述代码导致错误:

error[E0277]: the trait bound `&T1: T2` is not satisfied
  --> src/main.rs:21:19
   |
21 |     let t2: &T2 = &t12;
   |                   -^^^
   |                   |
   |                   the trait `T2` is not implemented for `&T1`
   |                   help: consider removing 1 leading `&`-references
   |
   = help: the following implementations were found:
             <T1 + 'static as T2>
   = note: required for the cast to the object type `T2`

这是令人困惑的 &T1 是的一个实例 dyn T1 还有一个 T2 实施。我们甚至可以通过打电话来证明这一点 f2 在 t12 直接删除最后两行 main 使其编译。

是否可以从标记为不同特征的特征对象创建特征对象?