Fix TwoWaySearcher to work when used with periodic needles.

There is a check in TwoWaySearcher::new to determine whether the needle
is periodic. This is needed because during searching when a match fails,
we cannot advance the position by the entire length of the needle when
it is periodic, but can only advance by the length of the period.

The reason "bananas".contains("nana") (and similar searches) were
returning false was because the periodicity check was wrong.

Closes #16589

1 files changed, 20 insertions, 0 deletions

diff --git a/src/libcoretest/str.rs b/src/libcoretest/str.rs
index bac8d509b13..be2275dcd4a 100644
--- a/src/libcoretest/str.rs
+++ b/src/libcoretest/str.rs
@@ -8,7 +8,27 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+fn check_contains_all_substrings(s: &str) {
+    assert!(s.contains(""));
+    for i in range(0, s.len()) {
+        for j in range(i+1, s.len() + 1) {
+            assert!(s.contains(s.slice(i, j)));
+        }
+    }
+}
+
 #[test]
 fn strslice_issue_16589() {
     assert!("bananas".contains("nana"));
+
+    // prior to the fix for #16589, x.contains("abcdabcd") returned false
+    // test all substrings for good measure
+    check_contains_all_substrings("012345678901234567890123456789bcdabcdabcd");
+}
+
+
+#[test]
+fn test_strslice_contains() {
+    let x = "There are moments, Jeeves, when one asks oneself, 'Do trousers matter?'";
+    check_contains_all_substrings(x);
 }