rust 强制转换

 

 

use std::ops::Deref;
struct MyBox<T>(T);

impl<T> MyBox<T> {
    fn new(x: T) -> MyBox<T> {
        MyBox(x)
    }
}

//impl<T> Deref for MyBox<T> {
//    type Target = T;
//
//    fn deref(&self) -> &T {
//        &self.0
//    }
//}
fn hello(name: &str) {
    println!("Hello, {}!", name);
}

fn main() {
    let m = MyBox::new(String::from("Rust"));
    hello(&m);
}

 

cargo build
   Compiling hello_world v0.1.0 (/data2/rust/coercion2)
warning: unused import: `std::ops::Deref`
 --> src/main.rs:1:5
  |
1 | use std::ops::Deref;
  |     ^^^^^^^^^^^^^^^
  |
  = note: `#[warn(unused_imports)]` on by default

error[E0308]: mismatched types
  --> src/main.rs:23:11
   |
23 |     hello(&m);
   |           ^^ expected `str`, found struct `MyBox`
   |
   = note: expected reference `&str`
              found reference `&MyBox<std::string::String>`

error: aborting due to previous error; 1 warning emitted

For more information about this error, try `rustc --explain E0308`.
error: could not compile `hello_world`.

To learn more, run the command again with --verbose.