A Bad Stack

src/first.rs

@@ -40,18 +40,31 @@ impl Default for List {
         Self { head: Link::Empty }
     }
 }
+impl Drop for List {
+    fn drop(&mut self) {
+        let mut cur_link = mem::replace(&mut self.head, Link::Empty);
+        
+        // `while let` == "do this thing until this pattern doesn't match"
+        while let Link::More(mut boxed_node) = cur_link {
+            cur_link = mem::replace(&mut boxed_node.next, Link::Empty);
+            // boxed_node goes out of scope and gets dropped here;
+            // but its Node's `next` field has been set to Link::Empty
+            // so no unbounded recursion occurs.
+        }
+    }
+}
 
+#[cfg(test)]
 mod test {
-    use crate::first;
+    use super::List;
 
     #[test]
     fn basics() {
-        let mut list = first::List::new();
+        let mut list = List::new();
 
         // Check empty list behaves right
         assert_eq!(list.pop(), None);
 
-
         // Populate list
         list.push(1);
         list.push(2);
@@ -60,6 +73,17 @@ mod test {
         // Check normal removal
         assert_eq!(list.pop(), Some(3));
         assert_eq!(list.pop(), Some(2));
-        
+
+        // Push some more just to make sure nothing's corrupted
+        list.push(4);
+        list.push(5);
+
+        // Check normal removal
+        assert_eq!(list.pop(), Some(5));
+        assert_eq!(list.pop(), Some(4));
+
+        // Check exhaustion
+        assert_eq!(list.pop(), Some(1));
+        assert_eq!(list.pop(), None);
     }
 }