在 Rc 上实现 Trait 不会解析为 Rc<dyn Trait>，以下实现被发现 <Rc<T> as Trait>

问题描述

我试图在 Rc 周围包装一个 DST，目的是克隆它并从代码的各个部分访问它，但在编译时出现以下错误。

这是错误 (playground) 的最小可重现示例：

use std::rc::Rc;

trait Trait<'a> {
    fn return_hello(&self) -> &'a str;
}

impl<'a,F> Trait<'a> for F
where
    F: Fn() -> &'a str
{
    fn return_hello(&self) -> &'a str {
        self()
    }
}

impl<'a,T> Trait<'a> for Rc<T> 
where
    T: Trait<'a>
{
    fn return_hello(&self) -> &'a str {
        (**self).return_hello()
    } 
}

fn caller<'a,T>(t: T) 
where
    T: Trait<'a>
{
    print!("{}\n",t.return_hello());
}

fn main() {
    fn test1<'a>() -> &'a str {
        "Hello from function"
    }
    let test2 = move || "hello from closure";
    
    fn f<'a>() -> &'a str {
        "Hello from Rc"
    }
    let test3: Rc<dyn Trait<'_>> = Rc::new(f);

    caller(test1);
    caller(test2);
    caller(test3);
}

给出：

error[E0277]: the trait bound `Rc<dyn Trait<'_>>: Trait<'_>` is not satisfied
  --> src/main.rs:45:12
   |
25 | fn caller<'a,T>(t: T) 
   |    ------ required by a bound in this
26 | where
27 |     T: Trait<'a>
   |        --------- required by this bound in `caller`
...
45 |     caller(test3);
   |            ^^^^^ the trait `Trait<'_>` is not implemented for `Rc<dyn Trait<'_>>`
   |
   = help: the following implementations were found:
             <Rc<T> as Trait<'a>>

解决方法

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