Update traits3.rs

Author: 13001288072

exercises/traits/traits3.rs

@@ -1,17 +1,8 @@
-// traits3.rs
-//
-// Your task is to implement the Licensed trait for both structures and have
-// them return the same information without writing the same function twice.
-//
-// Consider what you can add to the Licensed trait.
-//
-// Execute `rustlings hint traits3` or use the `hint` watch subcommand for a
-// hint.
-
-// I AM NOT DONE
-
 pub trait Licensed {
-    fn licensing_info(&self) -> String;
+    // 核心修改：为trait方法添加默认实现，实现代码复用
+    fn licensing_info(&self) -> String {
+        String::from("Some information")
+    }
 }
 
 struct SomeSoftware {