merged fixes for scala#1691 and scala#1721 to 2.7.x branch

Author: lrytz

src/library/scala/List.scala

@@ -54,6 +54,8 @@ object List {
    *  @return     the sorted list of all integers in range [start;end).
    */
   def range(start: Int, end: Int, step: Int): List[Int] = {
+    if (step == 0)
+      throw new IllegalArgumentException("step is zero")
     val b = new ListBuffer[Int]
     var i = start
     while ((step <= 0 || i < end) && (step >= 0 || i > end)) {
@@ -71,7 +73,9 @@ object List {
    *
    *  @param start the start value of the list
    *  @param end  the end value of the list
-   *  @param step the increment function of the list, must be monotonically increasing or decreasing
+   *  @param step the increment function of the list, which given <code>v<sub>n</sub></code>,
+   *              computes <code>v<sub>n+1</sub></code>. Must be monotonically increasing
+   *              or decreasing.
    *  @return     the sorted list of all integers in range [start;end).
    */
   def range(start: Int, end: Int, step: Int => Int): List[Int] = {
@@ -81,7 +85,10 @@ object List {
     var i = start
     while ((!up || i < end) && (!down || i > end)) {
       b += i
-      i += step(i)
+      val next = step(i)
+      if (i == next)
+        throw new IllegalArgumentException("the step function did not make any progress on "+ i)
+      i = next
     }
     b.toList
   }

src/library/scala/Seq.scala

@@ -470,15 +470,8 @@ trait Seq[+A] extends AnyRef with PartialFunction[Int, A] with Collection[A] {
   /** @return true if this sequence end with that sequence
    *  @see String.endsWith
    */
-  def endsWith[B](that: Seq[B]): Boolean = {
-    val length = this.length
-    val j = that.elements
-    var i = 0
-    var result = true
-    while (result && i < length && j.hasNext)
-      result = apply(length - i - 1) == j.next
-    result && !j.hasNext
-  }
+  def endsWith[B](that: Seq[B]): Boolean =
+    drop(length - that.length).sameElements(that)
 
   /**
    * Searches for the argument sequence in the receiver object, returning

test/files/run/lists.scala

@@ -14,7 +14,9 @@ import testing.SUnit._
 object Test extends TestConsoleMain {
   def suite = new TestSuite(
     Test1, //count, exists, filter, ..
-    Test2  //#468
+    Test2, //#468
+    Test3, //#1691
+    Test4  //#1721
   )
 }
 
@@ -105,3 +107,36 @@ object Test2 extends TestCase("t0468") with Assert {
     assertEquals("check_++", 14, n2 + n3 + n4)
   }
 }
+
+object Test3 extends TestCase("t1691") with Assert {
+  override def enableStackTrace = false
+  override def runTest {
+    try {
+      List.range(1, 10, 0)
+    } catch {
+      case e: IllegalArgumentException => ()
+      case _ => throw new Error("List.range(1, 10, 0)")
+    }
+    try {
+      List.range(1, 10, x => 4)
+    } catch {
+      case e: IllegalArgumentException => ()
+      case _ => throw new Error("List.range(1, 10, x => 4)")
+    }
+    assertEquals(List.range(10, 0, x => x - 2),
+		 List(10, 8, 6, 4, 2))
+  }
+}
+
+object Test4 extends TestCase("t1721") with Assert {
+  override def enableStackTrace = false
+  override def runTest {
+    assertTrue(List(1,2,3).endsWith(List(2,3)))
+    assertFalse(List(1,2,3).endsWith(List(1,3)))
+    assertTrue(List(1,2,3).endsWith(List()))
+    assertFalse(List(1,2,3).endsWith(List(0,1,2,3)))
+    assertTrue(List(1,2,3).endsWith(List(1,2,3)))
+    assertFalse(List().endsWith(List(1,2,3)))
+    assertTrue(List().endsWith(List()))
+  }
+}