例如,我希望每个MyTrait
都实现AddAssign<&'a Self>
。这是我在将'a
放在编译器想要的位置后得到的:
trait MyTrait<'a>: 'a + std::ops::AddAssign<&'a Self> {}
fn func<'a, T: MyTrait<'a>>(a: &mut T, b: T) {
*a += &b;
}
此代码失败,并出现以下错误:
error[E0597]: `b` does not live long enough
--> src/main.rs:4:11
|
3 | fn func<'a, T: MyTrait<'a>>(a: &mut T, b: T) {
| -- lifetime `'a` defined here
4 | *a += &b;
| ^^
| |
| borrowed value does not live long enough
| requires that `b` is borrowed for `'a`
5 | }
| - `b` dropped here while still borrowed
For more information about this error, try `rustc --explain E0597`.
如何告诉编译器&b
将只在该和的持续时间内使用?
您可以使用排名更高的特征绑定,使约束在整个生命周期内具有通用性,这样它就不会被限制为使用特征上定义的特征:
pub trait MyTrait: for<'a> std::ops::AddAssign<&'a Self> {}
// ^^^^^^^