Add back prependAll to buffer. Uncomment some ArrayDeque tests.

Author: julienrf

collections/src/main/scala/strawman/collection/mutable/ArrayDeque.scala

@@ -86,7 +86,7 @@ class ArrayDeque[A] protected (
     this
   }
 
-  /*override*/ def prependAll(elems: IterableOnce[A]): this.type = {
+  override def prependAll(elems: IterableOnce[A]): this.type = {
     val it = elems.iterator()
     if (it.nonEmpty) {
       val n = length
@@ -133,7 +133,7 @@ class ArrayDeque[A] protected (
     val n = length
     if (idx == 0) {
       prepend(elem)
-    } else if (idx == n - 1) {
+    } else if (idx == n) {
       addOne(elem)
     } else {
       val finalLength = n + 1

collections/src/main/scala/strawman/collection/mutable/Buffer.scala

@@ -27,6 +27,15 @@ trait Buffer[A]
   /** Alias for `prepend` */
   @`inline` final def +=: (elem: A): this.type = prepend(elem)
 
+  def prependAll(elems: IterableOnce[A]): this.type = { insertAll(0, elems); this }
+
+  /** Inserts a new element at a given index into this buffer.
+    *
+    *  @param idx    the index where the new elements is inserted.
+    *  @param elem   the element to insert.
+    *  @throws   IndexOutOfBoundsException if the index `idx` is not in the valid range
+    *            `0 <= idx <= length`.
+    */
   @throws[IndexOutOfBoundsException]
   def insert(idx: Int, elem: A): Unit
 

test/junit/src/test/scala/strawman/collection/mutable/ArrayDequeTest.scala

@@ -23,15 +23,16 @@ class ArrayDequeTest {
     apply(_.prepend(6).prepend(7).prepend(8))
     apply(_.trimStart(2))
     apply(_.trimEnd(3))
+    apply(_.insert(2, -3))
     apply(_.insertAll(0, collection.Seq(9, 10, 11)))
     apply(_.insertAll(1, collection.Seq(12, 13)))
     apply(_.insertAll(0, collection.Seq(23, 24)))
     apply(_ ++= Seq(25, 26))
     apply(_.insertAll(3, collection.IndexedSeq(18, 33)))
     apply(_.remove(2))
-//    apply(_.prependAll(Seq(14, 15, 16, 17)))
+    apply(_.prependAll(collection.Seq(14, 15, 16, 17)))
     apply(_.remove(1, 5))
-//    apply(_.prependAll(Seq.tabulate(100)(identity)))
+    apply(_.prependAll(Seq.tabulate(100)(identity)))
     apply(b => b.insertAll(b.length - 5, collection.Seq.tabulate(10)(identity)))
     buffer.trimToSize()
     apply(_.addAll(collection.Seq.tabulate(100)(identity)))