move_semantics3 solution

solutions/06_move_semantics/move_semantics3.rs

@@ -1 +1,22 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+fn fill_vec(mut vec: Vec<i32>) -> Vec<i32> {
+    //      ^^^ added
+    vec.push(88);
+
+    vec
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn move_semantics3() {
+        let vec0 = vec![22, 44, 66];
+        let vec1 = fill_vec(vec0);
+        assert_eq!(vec1, [22, 44, 66, 88]);
+    }
+}