[Truffle] No need for a special branch in Array#[].

* ArrayUtils.extractRange can handle start == end == source.length.
* Update wrong documentation (see assertions).

core/src/main/java/org/jruby/truffle/nodes/core/ArrayNodes.java

@@ -642,7 +642,6 @@ public abstract static class IndexNode extends ArrayCoreMethodNode {
         @Child protected AtNode atNode;
 
         private final BranchProfile outOfBounds = BranchProfile.create();
-        private final BranchProfile indexAtEnd = BranchProfile.create();
 
         public IndexNode(RubyContext context, SourceSection sourceSection) {
             super(context, sourceSection);
@@ -666,9 +665,6 @@ public Object sliceIntegerFixnum(RubyArray array, int start, int length) {
             if (normalisedIndex < 0 || normalisedIndex > array.getSize() || length < 0) {
                 outOfBounds.enter();
                 return getContext().getCoreLibrary().getNilObject();
-            } else if (normalisedIndex == array.getSize()) {
-                indexAtEnd.enter();
-                return new RubyArray(getContext().getCoreLibrary().getArrayClass(), null, 0);
             } else {
                 final int end = Math.min(array.getSize(), normalisedIndex + length);
 
@@ -683,9 +679,6 @@ public Object sliceLongFixnum(RubyArray array, int start, int length) {
             if (normalisedIndex < 0 || normalisedIndex > array.getSize() || length < 0) {
                 outOfBounds.enter();
                 return getContext().getCoreLibrary().getNilObject();
-            } else if (normalisedIndex == array.getSize()) {
-                indexAtEnd.enter();
-                return new RubyArray(getContext().getCoreLibrary().getArrayClass(), null, 0);
             } else {
                 final int end = Math.min(array.getSize(), normalisedIndex + length);
 
@@ -700,9 +693,6 @@ public Object sliceFloat(RubyArray array, int start, int length) {
             if (normalisedIndex < 0 || normalisedIndex > array.getSize() || length < 0) {
                 outOfBounds.enter();
                 return getContext().getCoreLibrary().getNilObject();
-            } else if (normalisedIndex == array.getSize()) {
-                indexAtEnd.enter();
-                return new RubyArray(getContext().getCoreLibrary().getArrayClass(), null, 0);
             } else {
                 final int end = Math.min(array.getSize(), normalisedIndex + length);
 
@@ -717,9 +707,6 @@ public Object sliceObject(RubyArray array, int start, int length) {
             if (normalisedIndex < 0 || normalisedIndex > array.getSize() || length < 0) {
                 outOfBounds.enter();
                 return getContext().getCoreLibrary().getNilObject();
-            } else if (normalisedIndex == array.getSize()) {
-                indexAtEnd.enter();
-                return new RubyArray(getContext().getCoreLibrary().getArrayClass(), null, 0);
             } else {
                 final int end = Math.min(array.getSize(), normalisedIndex + length);
 

core/src/main/java/org/jruby/truffle/runtime/util/ArrayUtils.java

@@ -21,7 +21,7 @@ public abstract class ArrayUtils {
     /**
      * Extracts part of an array into a newly allocated Object[] array. Does not perform safety checks on parameters.
      * @param source the source array whose values should be extracted
-     * @param start the start index, must be >= 0 and < source.length
+     * @param start the start index, must be >= 0 and <= source.length
      * @param end the end index (exclusive), must be >= 0 and <= source.length and >= start
      * @return a newly allocated array with the extracted elements and length (end - start)
      */
@@ -45,7 +45,7 @@ private static boolean checkExtractRangeArgs(int[] source, int start, int end) {
     /**
      * Extracts part of an array into a newly allocated Object[] array. Does not perform safety checks on parameters.
      * @param source the source array whose values should be extracted
-     * @param start the start index, must be >= 0 and < source.length
+     * @param start the start index, must be >= 0 and <= source.length
      * @param end the end index (exclusive), must be >= 0 and <= source.length and >= start
      * @return a newly allocated array with the extracted elements and length (end - start)
      */
@@ -69,7 +69,7 @@ private static boolean checkExtractRangeArgs(long[] source, int start, int end)
     /**
      * Extracts part of an array into a newly allocated Object[] array. Does not perform safety checks on parameters.
      * @param source the source array whose values should be extracted
-     * @param start the start index, must be >= 0 and < source.length
+     * @param start the start index, must be >= 0 and <= source.length
      * @param end the end index (exclusive), must be >= 0 and <= source.length and >= start
      * @return a newly allocated array with the extracted elements and length (end - start)
      */
@@ -93,7 +93,7 @@ private static boolean checkExtractRangeArgs(double[] source, int start, int end
     /**
      * Extracts part of an array into a newly allocated Object[] array. Does not perform safety checks on parameters.
      * @param source the source array whose values should be extracted
-     * @param start the start index, must be >= 0 and < source.length
+     * @param start the start index, must be >= 0 and <= source.length
      * @param end the end index (exclusive), must be >= 0 and <= source.length and >= start
      * @return a newly allocated array with the extracted elements and length (end - start)
      */