<分区>
我遇到了一个问题,我将其简化为以下代码:
trait Logger {}
struct DefaultLogger;
impl Logger for DefaultLogger {}
struct A<L> where L: Logger {
logger: Box<L>,
}
impl<L> A<L> where L: Logger {
fn new() -> Self {
let logger = DefaultLogger;
A {
logger: Box::new(logger),
// ^^^^^^ Here is the problem
}
}
}
fn main() {
let a = A::new();
}
产生以下错误:
error[E0308]: mismatched types
--> src/main.rs:16:30
|
16 | logger: Box::new(logger),
| ^^^^^^ expected type parameter, found struct `DefaultLogger`
|
= note: expected type `L`
found type `DefaultLogger`
当我在普通函数(如 main
)中构造特征 A
时,就像我期望的那样。示例:
trait Logger {}
struct DefaultLogger;
impl Logger for DefaultLogger {}
struct A<L> where L: Logger {
logger: Box<L>,
}
fn main() {
let logger = DefaultLogger;
let _a = A {
logger: Box::new(logger),
};
}