SI-8553 WrappedArray throws exception on lastIndexWhere when index out of range

Adds a check in `IndexedSeqOptimized#lastIndexWhere(A => Boolean, Int)`
to begin searching in the end of the collection if `end` is greater than
the collection's length.

Discussed in
https://groups.google.com/d/topic/scala-internals/-MacXivbY0Q/discussion.

2 files changed, 17 insertions, 1 deletions

diff --git a/src/library/scala/collection/IndexedSeqOptimized.scala b/src/library/scala/collection/IndexedSeqOptimized.scala
index ade04e4de8..42cb37aa24 100755
--- a/src/library/scala/collection/IndexedSeqOptimized.scala
+++ b/src/library/scala/collection/IndexedSeqOptimized.scala
@@ -206,7 +206,7 @@ trait IndexedSeqOptimized[+A, +Repr] extends Any with IndexedSeqLike[A, Repr] {
 
   override /*SeqLike*/
   def lastIndexWhere(p: A => Boolean, end: Int): Int = {
-    var i = end
+    var i = math.min(end, length - 1)
     while (i >= 0 && !p(this(i))) i -= 1
     i
   }
diff --git a/test/junit/scala/collection/IndexedSeqOptimizedTest.scala b/test/junit/scala/collection/IndexedSeqOptimizedTest.scala
new file mode 100644
index 0000000000..e5382907af
--- /dev/null
+++ b/test/junit/scala/collection/IndexedSeqOptimizedTest.scala
@@ -0,0 +1,16 @@
+package scala.collection
+
+import org.junit.runner.RunWith
+import org.junit.runners.JUnit4
+import org.junit.Assert._
+import org.junit.Test
+
+@RunWith(classOf[JUnit4])
+class IndexedSeqOptimizedTest {
+
+  @Test
+  def notThrowsAnExceptionInLastIndexOf() {
+    assertEquals(0, (Array(2): collection.mutable.WrappedArray[Int]).lastIndexWhere(_ => true, 1))
+    assertEquals(2, "abc123".lastIndexWhere(_.isLetter, 6))
+  }
+}