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我有以下简化代码：

use std::collections::BinaryHeap;
use std::rc::Rc;

struct JobId;
struct Coord;
struct TimeStep;

pub trait HasJob {
    fn id(&self) -> JobId;
    fn start(&self) -> Coord;
    fn end(&self) -> Coord;
    fn earliest_start(&self) -> TimeStep;
    fn latest_finish(&self) -> TimeStep;
}

type JobPtr = Rc<HasJob>;

// a concrete class that implements the above trait
// and other basic traits like Eq, Hash, Ord, etc
pub struct Job {}
// another class that implements the HasJob trait
pub struct JobPrime {}

fn main() {
    // this line raises a compiler error
    let heap: BinaryHeap<JobPtr> = BinaryHeap::with_capacity(10);
}

基本思想是使用 (unique) ids 进行排序。

堆初始化导致以下错误：

error[E0277]: the trait bound `HasJob: std::cmp::Ord` is not satisfied
  --> src/main.rs:24:36
   |
24 |     let heap: BinaryHeap<JobPtr> = BinaryHeap::with_capacity(10);
   |                                    ^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::cmp::Ord` is not implemented for `HasJob`
   |
   = note: required because of the requirements on the impl of `std::cmp::Ord` for `std::rc::Rc<HasJob>`
   = note: required by `<std::collections::BinaryHeap<T>>::with_capacity`

我刚刚开始尝试 Rust 并且拥有 OOP/C++/Java 背景。目的是将HasJob特征用作“接口”并使用它来诱导类型擦除/动态调度 wrt 通用集合/容器 - 一种常见的 OOP 模式。

如果我理解正确，泛型参数BinaryHeap具有传递给它的具体类型需要实现Ord特征的约束。试图用所需的特征扩展原始特征，像这样......

pub trait HasJob: Ord + /*others*/

... 违反了 Rust 的对象安全保证并引发此编译器错误：

error[E0038]: the trait `HasJob` cannot be made into an object
  --> src/main.rs:16:22
   |
16 |     type JobPtr = Rc<HasJob>;
   |                      ^^^^^^ the trait `HasJob` cannot be made into an object
   |
   = note: the trait cannot use `Self` as a type parameter in the supertraits or where-clauses

如何解决上述问题？

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