SI-8554 Two-arg remove throws exception on large count

ListBuffer now throws exceptions like other buffers do when trying to index out of range.

Also harmonized the order of testing (`count < 0` tested before `n` in range).

Test in scala-collection-laws (gated by SI8554 flag).  Also modified test in run/t6634.scala

5 files changed, 35 insertions, 23 deletions

diff --git a/src/library/scala/collection/mutable/ArrayBuffer.scala b/src/library/scala/collection/mutable/ArrayBuffer.scala
index 011fd415ee..167e04ccbd 100644
--- a/src/library/scala/collection/mutable/ArrayBuffer.scala
+++ b/src/library/scala/collection/mutable/ArrayBuffer.scala
@@ -149,13 +149,16 @@ class ArrayBuffer[A](override protected val initialSize: Int)
   /** Removes the element on a given index position. It takes time linear in
    *  the buffer size.
    *
-   *  @param n       the index which refers to the first element to delete.
-   *  @param count   the number of elements to delete
-   *  @throws IndexOutOfBoundsException if `n` is out of bounds.
+   *  @param n       the index which refers to the first element to remove.
+   *  @param count   the number of elements to remove.
+   *  @throws   IndexOutOfBoundsException if the index `n` is not in the valid range
+   *            `0 <= n <= length - count` (with `count > 0`).
+   *  @throws   IllegalArgumentException if `count < 0`.
    */
   override def remove(n: Int, count: Int) {
-    require(count >= 0, "removing negative number of elements")
-    if (n < 0 || n > size0 - count) throw new IndexOutOfBoundsException(n.toString)
+    if (count < 0) throw new IllegalArgumentException("removing negative number of elements: " + count.toString)
+    else if (count == 0) return  // Did nothing
+    if (n < 0 || n > size0 - count) throw new IndexOutOfBoundsException("at " + n.toString + " deleting " + count.toString)
     copy(n + count, n, size0 - (n + count))
     reduceToSize(size0 - count)
   }
diff --git a/src/library/scala/collection/mutable/BufferLike.scala b/src/library/scala/collection/mutable/BufferLike.scala
index 8d24538620..bd9c61ae6a 100644
--- a/src/library/scala/collection/mutable/BufferLike.scala
+++ b/src/library/scala/collection/mutable/BufferLike.scala
@@ -105,15 +105,18 @@ trait BufferLike[A, +This <: BufferLike[A, This] with Buffer[A]]
     */
   def remove(n: Int): A
 
-  /** Removes a number of elements from a given index position.
+  /** Removes a number of elements from a given index position.  Subclasses of `BufferLike`
+   *  will typically override this method to provide better performance than `count`
+   *  successive calls to single-element `remove`.
    *
    *  @param n  the index which refers to the first element to remove.
    *  @param count  the number of elements to remove.
    *  @throws   IndexOutOfBoundsException if the index `n` is not in the valid range
-   *            `0 <= n <= length - count`.
+   *            `0 <= n <= length - count` (with `count > 0`).
    *  @throws   IllegalArgumentException if `count < 0`.
    */
   def remove(n: Int, count: Int) {
+    if (count < 0) throw new IllegalArgumentException("removing negative number of elements: " + count.toString)
     for (i <- 0 until count) remove(n)
   }
 
diff --git a/src/library/scala/collection/mutable/ListBuffer.scala b/src/library/scala/collection/mutable/ListBuffer.scala
index 2bc6738e53..eece557fe8 100644
--- a/src/library/scala/collection/mutable/ListBuffer.scala
+++ b/src/library/scala/collection/mutable/ListBuffer.scala
@@ -262,13 +262,14 @@ final class ListBuffer[A]
    *
    *  @param n         the index which refers to the first element to remove.
    *  @param count     the number of elements to remove.
+   *  @throws   IndexOutOfBoundsException if the index `n` is not in the valid range
+   *            `0 <= n <= length - count` (with `count > 0`).
+   *  @throws   IllegalArgumentException if `count < 0`.
    */
-  @migration("Invalid input values will be rejected in future releases.", "2.11")
   override def remove(n: Int, count: Int) {
-    if (n >= len)
-      return
-    if (count < 0)
-      throw new IllegalArgumentException(s"removing negative number ($count) of elements")
+    if (count < 0) throw new IllegalArgumentException("removing negative number of elements: " + count.toString)
+    else if (count == 0) return  // Nothing to do
+    if (n < 0 || n > len - count) throw new IndexOutOfBoundsException("at " + n.toString + " deleting " + count.toString)
     if (exported) copy()
     val n1 = n max 0
     val count1 = count min (len - n1)
diff --git a/test/files/run/t6634.check b/test/files/run/t6634.check
index f6cbb30c67..b085f397e6 100644
--- a/test/files/run/t6634.check
+++ b/test/files/run/t6634.check
@@ -4,27 +4,31 @@ String OK.
 Length OK.
 
 Trying lb1 ...
+java.lang.IndexOutOfBoundsException: at 6 deleting 6
 Checking ...
 String OK.
 Length OK.
 
 Trying lb2 ...
+java.lang.IndexOutOfBoundsException: at 99 deleting 6
 Checking ...
 String OK.
 Length OK.
 
 Trying lb3 ...
+java.lang.IndexOutOfBoundsException: at 1 deleting 9
 Checking ...
 String OK.
 Length OK.
 
 Trying lb4 ...
+java.lang.IndexOutOfBoundsException: at -1 deleting 1
 Checking ...
 String OK.
 Length OK.
 
 Trying lb5 ...
-java.lang.IllegalArgumentException: removing negative number (-1) of elements
+java.lang.IllegalArgumentException: removing negative number of elements: -1
 Checking ...
 String OK.
 Length OK.
diff --git a/test/files/run/t6634.scala b/test/files/run/t6634.scala
index 759e6d519d..081cca7502 100644
--- a/test/files/run/t6634.scala
+++ b/test/files/run/t6634.scala
@@ -8,7 +8,7 @@ object Test extends App {
   try {
     lb0.remove(5, 0)
   } catch {
-    // Not thrown in 2.10, will be thrown in 2.11
+    // Should not be thrown--nothing is deleted so nothing to do
     case ex: IndexOutOfBoundsException => println(ex)
   }
   checkNotCorrupted(lb0)
@@ -17,8 +17,8 @@ object Test extends App {
   println("Trying lb1 ...")
   try {
     lb1.remove(6, 6)
-  } catch {
-    // Not thrown in 2.10, will be thrown in 2.11
+ } catch {
+    // Not thrown in 2.11, is thrown in 2.12
     case ex: IndexOutOfBoundsException => println(ex)
   }
   checkNotCorrupted(lb1)
@@ -28,7 +28,7 @@ object Test extends App {
   try {
     lb2.remove(99, 6)
   } catch {
-    // Not thrown in 2.10, will be thrown in 2.11
+    // Not thrown in 2.11, is thrown in 2.12
     case ex: IndexOutOfBoundsException => println(ex)
   }
   checkNotCorrupted(lb2)
@@ -38,26 +38,27 @@ object Test extends App {
   try {
     lb3.remove(1, 9)
   } catch {
-    // Not thrown in 2.10, will be thrown in 2.11
-    case ex: IllegalArgumentException => println(ex)
+    // Not thrown in 2.11, is thrown in 2.12
+    case ex: IndexOutOfBoundsException => println(ex)
   }
-  checkNotCorrupted(lb3, "ListBuffer('a)", 1)
+  checkNotCorrupted(lb3)
 
   val lb4 = newLB
   println("Trying lb4 ...")
   try {
     lb4.remove(-1, 1)
   } catch {
-    // Not thrown in 2.10, will be thrown in 2.11
+    // Not thrown in 2.11, is thrown in 2.12
     case ex: IndexOutOfBoundsException => println(ex)
   }
-  checkNotCorrupted(lb4, "ListBuffer('b, 'c, 'd, 'e)", 4)
+  checkNotCorrupted(lb4)
 
   val lb5 = newLB
   println("Trying lb5 ...")
   try {
     lb5.remove(1, -1)
   } catch {
+    // Was thrown prior to 2.12 also
     case ex: IllegalArgumentException => println(ex)
   }
   checkNotCorrupted(lb5)
@@ -77,4 +78,4 @@ object Test extends App {
     else println("!!! length FAILED: " + len)
     println()
   }
-}
\ No newline at end of file
+}