Merge pull request #471 from Orefa/patch-3

Update ch10-03-lifetime-syntax.md

src/ch10-03-lifetime-syntax.md

@@ -233,15 +233,14 @@ fn main() {
 
 ```text
 error[E0597]: `string2` does not live long enough
-  --> src/main.rs:15:5
+ --> src/main.rs:6:44
-   |
+  |
-14 |         result = longest(string1.as_str(), string2.as_str());
+6 |         result = longest(string1.as_str(), string2.as_str());
-   |                                            ------- borrow occurs here
+  |                                            ^^^^^^^ borrowed value does not live long enough
-15 |     }
+7 |     }
-   |     ^ `string2` dropped here while still borrowed
+  |     - `string2` dropped here while still borrowed
-16 |     println!("The longest string is {}", result);
+8 |     println!("The longest string is {}", result);
-17 | }
+  |                                          ------ borrow later used here
-   | - borrowed value needs to live until here
 ```
 
 错误表明为了保证 `println!` 中的 `result` 是有效的，`string2` 需要直到外部作用域结束都是有效的。Rust 知道这些是因为（`longest`）函数的参数和返回值都使用了相同的生命周期参数 `'a`。