implement Array#[] for endless ranges

Author: Nicolas Laurent

CHANGELOG.md

@@ -103,7 +103,7 @@ Compatibility:
 * Implemented `Random.bytes`.
 * Added the ability to parse endless ranges.
 * Made `Range#to_a` compatible with endless ranges.
-* Made `Array#[]= ` compatible with endless ranges.
+* Made `Array#[]` and `Array#[]= ` compatible with endless ranges.
 
 Performance:
 

src/main/java/org/truffleruby/core/array/ArrayIndexNode.java

@@ -54,32 +54,46 @@ protected DynamicObject slice(DynamicObject array, int start, int length) {
     @Specialization(guards = "isIntRange(range)")
     protected DynamicObject slice(DynamicObject array, DynamicObject range, NotProvided len,
             @Cached("createBinaryProfile()") ConditionProfile negativeBeginProfile,
-            @Cached("createBinaryProfile()") ConditionProfile negativeEndProfile) {
+            @Cached("createBinaryProfile()") ConditionProfile negativeEndProfile,
+            @Cached("create()") ArrayReadSliceNormalizedNode readNormalizedSliceNode) {
         final int size = getSize(array);
-        final int normalizedIndex = ArrayOperations
+        final int normalizedBegin = ArrayOperations
                 .normalizeIndex(size, Layouts.INT_RANGE.getBegin(range), negativeBeginProfile);
 
-        if (normalizedIndex < 0 || normalizedIndex > size) {
+        if (normalizedBegin < 0 || normalizedBegin > size) {
             return nil();
         } else {
             final int end = ArrayOperations
                     .normalizeIndex(size, Layouts.INT_RANGE.getEnd(range), negativeEndProfile);
             final int exclusiveEnd = ArrayOperations
                     .clampExclusiveIndex(size, Layouts.INT_RANGE.getExcludedEnd(range) ? end : end + 1);
 
-            if (exclusiveEnd <= normalizedIndex) {
+            if (exclusiveEnd <= normalizedBegin) {
                 return allocateObjectNode
                         .allocate(Layouts.BASIC_OBJECT.getLogicalClass(array), ArrayStrategy.NULL_ARRAY_STORE, 0);
             }
 
-            final int length = exclusiveEnd - normalizedIndex;
+            return readNormalizedSliceNode.executeReadSlice(array, normalizedBegin, exclusiveEnd - normalizedBegin);
+        }
+    }
+
+    @Specialization(guards = "isIntEndlessRange(getContext(), range)")
+    protected DynamicObject endlessSlice(DynamicObject array, DynamicObject range, NotProvided len,
+            @Cached("createBinaryProfile()") ConditionProfile negativeBeginProfile,
+            @Cached("create()") ArrayReadSliceNormalizedNode readNormalizedSliceNode) {
+        final int size = getSize(array);
+        final int normalizedBegin = ArrayOperations
+                .normalizeIndex(size, (int) Layouts.OBJECT_RANGE.getBegin(range), negativeBeginProfile);
 
-            if (readNormalizedSliceNode == null) {
-                CompilerDirectives.transferToInterpreterAndInvalidate();
-                readNormalizedSliceNode = insert(ArrayReadSliceNormalizedNodeGen.create());
+        if (normalizedBegin < 0 || normalizedBegin > size) {
+            return nil();
+        } else {
+            if (size == normalizedBegin) {
+                return allocateObjectNode
+                        .allocate(Layouts.BASIC_OBJECT.getLogicalClass(array), ArrayStrategy.NULL_ARRAY_STORE, 0);
             }
 
-            return readNormalizedSliceNode.executeReadSlice(array, normalizedIndex, length);
+            return readNormalizedSliceNode.executeReadSlice(array, normalizedBegin, size - normalizedBegin);
         }
     }
 

src/main/java/org/truffleruby/language/RubyGuards.java

@@ -132,6 +132,12 @@ public static boolean isEndlessRange(RubyContext context, DynamicObject object)
         return isNil(context, Layouts.OBJECT_RANGE.getEnd(object));
     }
 
+    public static boolean isIntEndlessRange(RubyContext context, DynamicObject object) {
+        return isObjectRange(object) && isInteger(Layouts.OBJECT_RANGE.getBegin(object)) && isEndlessRange(
+                context,
+                object);
+    }
+
     public static boolean isRubyRange(Object value) {
         return isIntRange(value) || isLongRange(value) || isObjectRange(value);
     }