SI-8932 Fix dropRight/takeRight implementations

I looked up at all the overrides of `IterableLike#takeRight` and
`IterableLike#dropRight` and replaced usages of its argument `n` with
`math.max(n, 0)` every time it was being used in an index subtraction.

Fixes [SI-8932](https://issues.scala-lang.org/browse/SI-8932).

4 files changed, 8 insertions, 8 deletions

diff --git a/src/library/scala/collection/IndexedSeqOptimized.scala b/src/library/scala/collection/IndexedSeqOptimized.scala
index 42cb37aa24..a7e06b4d1a 100755
--- a/src/library/scala/collection/IndexedSeqOptimized.scala
+++ b/src/library/scala/collection/IndexedSeqOptimized.scala
@@ -141,10 +141,10 @@ trait IndexedSeqOptimized[+A, +Repr] extends Any with IndexedSeqLike[A, Repr] {
   def drop(n: Int): Repr = slice(n, length)
 
   override /*IterableLike*/
-  def takeRight(n: Int): Repr = slice(length - n, length)
+  def takeRight(n: Int): Repr = slice(length - math.max(n, 0), length)
 
   override /*IterableLike*/
-  def dropRight(n: Int): Repr = slice(0, length - n)
+  def dropRight(n: Int): Repr = slice(0, length - math.max(n, 0))
 
   override /*TraversableLike*/
   def splitAt(n: Int): (Repr, Repr) = (take(n), drop(n))
diff --git a/src/library/scala/collection/IterableViewLike.scala b/src/library/scala/collection/IterableViewLike.scala
index 668190f700..b84d90c51b 100644
--- a/src/library/scala/collection/IterableViewLike.scala
+++ b/src/library/scala/collection/IterableViewLike.scala
@@ -150,10 +150,10 @@ trait IterableViewLike[+A,
     sliding(size, 1) // we could inherit this, but that implies knowledge of the way the super class is implemented.
 
   override def dropRight(n: Int): This =
-    take(thisSeq.length - n)
+    take(thisSeq.length - math.max(n, 0))
 
   override def takeRight(n: Int): This =
-    drop(thisSeq.length - n)
+    drop(thisSeq.length - math.max(n, 0))
 
   override def stringPrefix = "IterableView"
 }
diff --git a/src/library/scala/collection/immutable/TreeMap.scala b/src/library/scala/collection/immutable/TreeMap.scala
index 8cc99a53e6..662075cd93 100644
--- a/src/library/scala/collection/immutable/TreeMap.scala
+++ b/src/library/scala/collection/immutable/TreeMap.scala
@@ -101,8 +101,8 @@ class TreeMap[A, +B] private (tree: RB.Tree[A, B])(implicit val ordering: Orderi
     else new TreeMap(RB.slice(tree, from, until))
   }
 
-  override def dropRight(n: Int) = take(size - n)
-  override def takeRight(n: Int) = drop(size - n)
+  override def dropRight(n: Int) = take(size - math.max(n, 0))
+  override def takeRight(n: Int) = drop(size - math.max(n, 0))
   override def splitAt(n: Int) = (take(n), drop(n))
 
   private[this] def countWhile(p: ((A, B)) => Boolean): Int = {
diff --git a/src/library/scala/collection/immutable/TreeSet.scala b/src/library/scala/collection/immutable/TreeSet.scala
index 681dbbd1a8..7378211db0 100644
--- a/src/library/scala/collection/immutable/TreeSet.scala
+++ b/src/library/scala/collection/immutable/TreeSet.scala
@@ -87,8 +87,8 @@ class TreeSet[A] private (tree: RB.Tree[A, Unit])(implicit val ordering: Orderin
     else newSet(RB.slice(tree, from, until))
   }
 
-  override def dropRight(n: Int) = take(size - n)
-  override def takeRight(n: Int) = drop(size - n)
+  override def dropRight(n: Int) = take(size - math.max(n, 0))
+  override def takeRight(n: Int) = drop(size - math.max(n, 0))
   override def splitAt(n: Int) = (take(n), drop(n))
 
   private[this] def countWhile(p: A => Boolean): Int = {