6 files changed, 31 insertions, 13 deletions
diff --git a/src/library/scala/collection/Iterator.scala b/src/library/scala/collection/Iterator.scala
index adb97e27e3..4e3abf2286 100644
--- a/src/library/scala/collection/Iterator.scala
+++ b/src/library/scala/collection/Iterator.scala
@@ -1187,9 +1187,8 @@ trait Iterator[+A] extends TraversableOnce[A] {
    *    $willNotTerminateInf
    */
   def copyToArray[B >: A](xs: Array[B], start: Int, len: Int): Unit = {
-    require(start >= 0 && (start < xs.length || xs.length == 0), s"start $start out of range ${xs.length}")
     var i = start
-    val end = start + math.min(len, xs.length - start)
+    val end = start + math.min(len, xs.length - start)   
     while (i < end && hasNext) {
       xs(i) = next()
       i += 1
diff --git a/src/library/scala/collection/mutable/ArrayOps.scala b/src/library/scala/collection/mutable/ArrayOps.scala
index 00491ef20e..2bc41b5802 100644
--- a/src/library/scala/collection/mutable/ArrayOps.scala
+++ b/src/library/scala/collection/mutable/ArrayOps.scala
@@ -40,9 +40,8 @@ trait ArrayOps[T] extends Any with ArrayLike[T, Array[T]] with CustomParalleliza
     arrayElementClass(repr.getClass)
 
   override def copyToArray[U >: T](xs: Array[U], start: Int, len: Int) {
-    var l = math.min(len, repr.length)
-    if (xs.length - start < l) l = xs.length - start max 0
-    Array.copy(repr, 0, xs, start, l)
+    val l = len min repr.length min (xs.length - start)
+    if (l > 0) Array.copy(repr, 0, xs, start, l)
   }
 
   override def toArray[U >: T : ClassTag]: Array[U] = {
diff --git a/src/library/scala/collection/mutable/ArraySeq.scala b/src/library/scala/collection/mutable/ArraySeq.scala
index 577a838315..5a50f4fb27 100644
--- a/src/library/scala/collection/mutable/ArraySeq.scala
+++ b/src/library/scala/collection/mutable/ArraySeq.scala
@@ -87,7 +87,7 @@ extends AbstractSeq[A]
    */
   override def copyToArray[B >: A](xs: Array[B], start: Int, len: Int) {
     val len1 = len min (xs.length - start) min length
-    Array.copy(array, 0, xs, start, len1)
+    if (len1 > 0) Array.copy(array, 0, xs, start, len1)
   }
 
   override def clone(): ArraySeq[A] = {
diff --git a/src/library/scala/collection/mutable/ResizableArray.scala b/src/library/scala/collection/mutable/ResizableArray.scala
index c3047522e2..85a299216e 100644
--- a/src/library/scala/collection/mutable/ResizableArray.scala
+++ b/src/library/scala/collection/mutable/ResizableArray.scala
@@ -74,7 +74,7 @@ trait ResizableArray[A] extends IndexedSeq[A]
    */
    override def copyToArray[B >: A](xs: Array[B], start: Int, len: Int) {
      val len1 = len min (xs.length - start) min length
-     Array.copy(array, 0, xs, start, len1)
+     if (len1 > 0) Array.copy(array, 0, xs, start, len1)
    }
 
   //##########################################################################
diff --git a/test/files/run/t6827.check b/test/files/run/t6827.check
index 3a3a71c67d..4889e05be8 100644
--- a/test/files/run/t6827.check
+++ b/test/files/run/t6827.check
@@ -1,6 +1,6 @@
-start at -5: java.lang.IllegalArgumentException: requirement failed: start -5 out of range 10
-start at -1: java.lang.IllegalArgumentException: requirement failed: start -1 out of range 10
-start at limit: java.lang.IllegalArgumentException: requirement failed: start 10 out of range 10
+start at -5: java.lang.ArrayIndexOutOfBoundsException: -5
+start at -1: java.lang.ArrayIndexOutOfBoundsException: -1
+start at limit: ok
 start at limit-1: ok
 first 10: ok
 read all: ok
@@ -8,8 +8,8 @@ test huge len: ok
 5 from 5: ok
 20 from 5: ok
 test len overflow: ok
-start beyond limit: java.lang.IllegalArgumentException: requirement failed: start 30 out of range 10
+start beyond limit: ok
 read 0: ok
 read -1: ok
-invalid read 0: java.lang.IllegalArgumentException: requirement failed: start 30 out of range 10
-invalid read -1: java.lang.IllegalArgumentException: requirement failed: start 30 out of range 10
+invalid read 0: ok
+invalid read -1: ok
diff --git a/test/files/run/t6827.scala b/test/files/run/t6827.scala
index 8e17af09e2..eb020711bb 100644
--- a/test/files/run/t6827.scala
+++ b/test/files/run/t6827.scala
@@ -31,4 +31,24 @@ object Test extends App {
 
   // okay, see SI-7128
   "...".toIterator.copyToArray(new Array[Char](0), 0, 0)
+
+
+  // Bonus test from @som-snytt to check for overflow in
+  // index calculations.
+  def testOverflow(start: Int, len: Int, expected: List[Char]) {
+    def copyFromIterator = {
+      val arr = Array.fill[Char](3)('-')
+      "abc".toIterator.copyToArray(arr, start, len)
+      arr.toList
+    }
+    def copyFromArray = {
+      val arr = Array.fill[Char](3)('-')
+      "abc".toArray.copyToArray(arr, start, len)
+      arr.toList
+    }
+    assert(copyFromIterator == expected)
+    assert(copyFromArray == expected)
+  }
+  testOverflow(1, Int.MaxValue - 1, "-ab".toList)
+  testOverflow(1, Int.MaxValue, "-ab".toList)
 }