Remove move_semantics4, add rest of move_semantics solutions

exercises/06_move_semantics/move_semantics4.rs

@@ -1,31 +1,18 @@
-// Refactor this code so that instead of passing `vec0` into the `fill_vec`
-// function, the Vector gets created in the function itself and passed back to
-// the test function.
-
-// `fill_vec()` no longer takes `vec: Vec<i32>` as argument - don't change this!
-fn fill_vec() -> Vec<i32> {
-    // Instead, let's create and fill the Vec in here - how do you do that?
-    let mut vec = vec;
-
-    vec.push(88);
-
-    vec
-}
-
 fn main() {
     // You can optionally experiment here.
 }
 
 #[cfg(test)]
 mod tests {
-    use super::*;
-
+    // TODO: Fix the compiler errors only by reordering the lines in the test.
+    // Don't add, change or remove any line.
     #[test]
-    fn move_semantics4() {
-        let vec0 = vec![22, 44, 66];
-
-        let vec1 = fill_vec(vec0);
-
-        assert_eq!(vec1, vec![22, 44, 66, 88]);
+    fn move_semantics5() {
+        let mut x = 100;
+        let y = &mut x;
+        let z = &mut x;
+        *y += 100;
+        *z += 1000;
+        assert_eq!(x, 1200);
     }
 }