Update main.rs

对注释进行了翻译

listings/ch04-understanding-ownership/listing-04-04/src/main.rs

@@ -1,30 +1,24 @@
 fn main() {
-    let s1 = gives_ownership();        // gives_ownership moves its return
+    let s1 = gives_ownership();        // gives_ownership 将它的返回值传递给s1
-                                       // value into s1
 
-    let s2 = String::from("hello");    // s2 comes into scope
+    let s2 = String::from("hello");    // s2 进入作用域
 
-    let s3 = takes_and_gives_back(s2); // s2 is moved into
+    let s3 = takes_and_gives_back(s2); // s2 被传入takes_and_gives_back, 
-                                       // takes_and_gives_back, which also
+                                       // 它的返回值又传递给 s3
-                                       // moves its return value into s3
+} // 此处，s3 移出作用域并被丢弃。s2 被 move ，所以无事发生
-} // Here, s3 goes out of scope and is dropped. s2 was moved, so nothing
+  // s1 移出作用域并被丢弃
-  // happens. s1 goes out of scope and is dropped.
 
-fn gives_ownership() -> String {       // gives_ownership will move its
+fn gives_ownership() -> String {       // gives_ownership 将会把返回值传入
-                                       // return value into the function
+                                       // 调用它的函数
-                                       // that calls it
 
-    let some_string = String::from("yours"); // some_string comes into scope
+    let some_string = String::from("yours"); // some_string 进入作用域
 
-    some_string                        // some_string is returned and
+    some_string                        // 返回 some_string 并将其移至调用函数
-                                       // moves out to the calling
-                                       // function
 }
 
 // 该函数将传入字符串并返回该值
 fn takes_and_gives_back(a_string: String) -> String {
-    // a_string comes into
+    // a_string 进入作用域
-    // scope
 
     a_string  // 返回 a_string 并移出给调用的函数
 }