Add Splice forget test

src/libcollections/tests/string.rs

@@ -475,6 +475,13 @@ fn test_splice_unbounded() {
     assert_eq!(t, "12345");
 }
 
+#[test]
+fn test_splice_forget() {
+    let mut s = String::from("12345");
+    ::std::mem::forget(s.splice(2..4, "789"));
+    assert_eq!(s, "12345");
+}
+
 #[test]
 fn test_extend_ref() {
     let mut a = "foo".to_string();

src/libcollections/tests/vec.rs

@@ -634,6 +634,14 @@ fn test_splice_unbounded() {
     assert_eq!(t, &[1, 2, 3, 4, 5]);
 }
 
+#[test]
+fn test_splice_forget() {
+    let mut v = vec![1, 2, 3, 4, 5];
+    let a = [10, 11, 12];
+    ::std::mem::forget(v.splice(2..4, a.iter().cloned()));
+    assert_eq!(v, &[1, 2]);
+}
+
 #[test]
 fn test_into_boxed_slice() {
     let xs = vec![1, 2, 3];