这段代码在Playground上运行良好:
struct F<'a> {
x: &'a i32,
}
impl<'a> F<'a> {
fn get<'b>(&'b self) -> &'a i32 {
self.x
}
}
fn main() {
let x = 3;
let y = F { x: &x };
let z = y.get();
}
但是当我将 x
改为可变引用时 (Playground):
struct Foo<'a> {
x: &'a mut i32, // <-- `mut` added
}
impl<'a> Foo<'a> {
fn get(&self) -> &'a i32 {
self.x
}
}
fn main() {
let mut x = 3; // <-- `mut` added
let y = Foo { x: &mut x }; // <-- `mut` added
let z = y.get();
}
我遇到了这个错误:
error[E0312]: lifetime of reference outlives lifetime of borrowed content...
--> src/main.rs:7:9
|
7 | self.x
| ^^^^^^
|
note: ...the reference is valid for the lifetime 'a as defined on the impl at 5:6...
--> src/main.rs:5:6
|
5 | impl<'a> Foo<'a> {
| ^^
note: ...but the borrowed content is only valid for the anonymous lifetime #1 defined on the method body at 6:5
--> src/main.rs:6:5
|
6 | / fn get(&self) -> &'a i32 {
7 | | self.x
8 | | }
| |_____^
为什么会发生这种情况?就我看来,与生命周期有关的因素并没有改变:所有的值/引用仍然像第一个代码片段中一样精确地存在。
f
应该是F
,而且你可以直接调用y.get()
... 我真的很喜欢这个问题! - Matthieu M.