Added 2 tests to list.rs, improve semantic and using Default trait instant of function new

src/kernel/synch.rs

@@ -26,7 +26,7 @@ impl Semaphore {
     /// - *counter* initial value of counter
     /// - *thread_manager* Thread manager which managing threads
     pub fn new(counter: i32) -> Semaphore{
-        Semaphore { counter, waiting_queue: List::new()}
+        Semaphore { counter, waiting_queue: List::default() }
     }
 
     ///     Decrement the value, and wait if it becomes < 0. Checking the
@@ -98,7 +98,7 @@ impl Lock {
     /// ### Parameters
     /// - **thread_manager** Thread manager which managing threads
     pub fn new() -> Lock {
-        Lock { owner: None, waiting_queue: List::new(), free: true }
+        Lock { owner: None, waiting_queue: List::default(), free: true }
     }
 
     ///    Wait until the lock become free.  Checking the
@@ -196,7 +196,7 @@ impl Condition {
     /// ### Parameters
     /// - *thread_manager* Thread manager which managing threads
     pub fn new() -> Condition {
-        Condition{ waiting_queue: List::new()}
+        Condition{ waiting_queue: List::default()}
     }
 
     ///  Block the calling thread (put it in the wait queue).

src/kernel/thread_manager.rs

@@ -28,8 +28,8 @@ impl ThreadManager {
         Self { 
             g_current_thread: Option::None, 
             g_thread_to_be_destroyed: Option::None, 
-            g_alive: List::new(),
-            ready_list: List::new(),
+            g_alive: List::default(),
+            ready_list: List::default(),
         }
     }