Fix Iterator::advance_by contract inconsistency

[rust.git] / library / core / tests / iter / adapters / take.rs

diff --git a/library/core/tests/iter/adapters/take.rs b/library/core/tests/iter/adapters/take.rs
index 89f9cb1e2ed1bd6af4597e3f8e4aa4ace0d6598a..bfb659f0a83780cab58bedecc1bc9c0dd68890ae 100644 (file)
--- a/library/core/tests/iter/adapters/take.rs
+++ b/library/core/tests/iter/adapters/take.rs
@@ -73,6 +73,28 @@ fn test_iterator_take_nth_back() {
     assert_eq!(it.nth_back(1), None);
 }
 
+#[test]
+fn test_take_advance_by() {
+    let mut take = (0..10).take(3);
+    assert_eq!(take.advance_by(2), Ok(()));
+    assert_eq!(take.next(), Some(2));
+    assert_eq!(take.advance_by(1), Err(0));
+
+    assert_eq!((0..0).take(10).advance_by(0), Ok(()));
+    assert_eq!((0..0).take(10).advance_by(1), Err(0));
+    assert_eq!((0..10).take(4).advance_by(5), Err(4));
+
+    let mut take = (0..10).take(3);
+    assert_eq!(take.advance_back_by(2), Ok(()));
+    assert_eq!(take.next(), Some(0));
+    assert_eq!(take.advance_back_by(1), Err(0));
+
+    assert_eq!((0..2).take(1).advance_back_by(10), Err(1));
+    assert_eq!((0..0).take(1).advance_back_by(1), Err(0));
+    assert_eq!((0..0).take(1).advance_back_by(0), Ok(()));
+    assert_eq!((0..usize::MAX).take(100).advance_back_by(usize::MAX), Err(100));
+}
+
 #[test]
 fn test_iterator_take_short() {
     let xs = [0, 1, 2, 3];