Use proper ToLength() operation in %ArrayConcat()

LOG=N
R=dslomov@chromium.org
BUG=

Review URL: https://codereview.chromium.org/799853003

Cr-Commit-Position: refs/heads/master@{#25828}

src/bootstrapper.cc

@@ -1525,6 +1525,7 @@ void Genesis::InstallNativeFunctions() {
   INSTALL_NATIVE(JSFunction, "ToInteger", to_integer_fun);
   INSTALL_NATIVE(JSFunction, "ToUint32", to_uint32_fun);
   INSTALL_NATIVE(JSFunction, "ToInt32", to_int32_fun);
+  INSTALL_NATIVE(JSFunction, "ToLength", to_length_fun);
 
   INSTALL_NATIVE(JSFunction, "GlobalEval", global_eval_fun);
   INSTALL_NATIVE(JSFunction, "Instantiate", instantiate_fun);

src/contexts.h

@@ -98,6 +98,7 @@ enum BindingFlags {
   V(TO_INTEGER_FUN_INDEX, JSFunction, to_integer_fun)                          \
   V(TO_UINT32_FUN_INDEX, JSFunction, to_uint32_fun)                            \
   V(TO_INT32_FUN_INDEX, JSFunction, to_int32_fun)                              \
+  V(TO_LENGTH_FUN_INDEX, JSFunction, to_length_fun)                            \
   V(GLOBAL_EVAL_FUN_INDEX, JSFunction, global_eval_fun)                        \
   V(INSTANTIATE_FUN_INDEX, JSFunction, instantiate_fun)                        \
   V(CONFIGURE_INSTANCE_FUN_INDEX, JSFunction, configure_instance_fun)          \
@@ -416,6 +417,7 @@ class Context: public FixedArray {
     ARRAY_VALUES_ITERATOR_INDEX,
     SCRIPT_CONTEXT_TABLE_INDEX,
     MAP_CACHE_INDEX,
+    TO_LENGTH_FUN_INDEX,
 
     // Properties from here are treated as weak references by the full GC.
     // Scavenge treats them as strong references.

src/execution.cc

@@ -545,6 +545,12 @@ MaybeHandle<Object> Execution::ToInt32(
 }
 
 
+MaybeHandle<Object> Execution::ToLength(
+    Isolate* isolate, Handle<Object> obj) {
+  RETURN_NATIVE_CALL(to_length, { obj });
+}
+
+
 MaybeHandle<Object> Execution::NewDate(Isolate* isolate, double time) {
   Handle<Object> time_obj = isolate->factory()->NewNumber(time);
   RETURN_NATIVE_CALL(create_date, { time_obj });

src/execution.h

@@ -69,6 +69,11 @@ class Execution FINAL : public AllStatic {
   MUST_USE_RESULT static MaybeHandle<Object> ToUint32(
       Isolate* isolate, Handle<Object> obj);
 
+
+  // ES6, draft 10-14-14, section 7.1.15
+  MUST_USE_RESULT static MaybeHandle<Object> ToLength(
+      Isolate* isolate, Handle<Object> obj);
+
   // ECMA-262 9.8
   MUST_USE_RESULT static MaybeHandle<Object> ToString(
       Isolate* isolate, Handle<Object> obj);

src/runtime/runtime-array.cc

@@ -461,8 +461,12 @@ static bool IterateElements(Isolate* isolate, Handle<JSObject> receiver,
     Handle<Object> key(isolate->heap()->length_string(), isolate);
     ASSIGN_RETURN_ON_EXCEPTION_VALUE(isolate, val,
         Runtime::GetObjectProperty(isolate, receiver, key), false);
-    // TODO(caitp): implement ToLength() abstract operation for C++
-    val->ToUint32(&length);
+    // TODO(caitp): Support larger element indexes (up to 2^53-1).
+    if (!val->ToUint32(&length)) {
+      ASSIGN_RETURN_ON_EXCEPTION_VALUE(isolate, val,
+          Execution::ToLength(isolate, val), false);
+      val->ToUint32(&length);
+    }
   }
 
   switch (receiver->GetElementsKind()) {

test/mjsunit/harmony/array-concat.js

@@ -40,6 +40,110 @@
 })();
 
 
+(function testConcatArrayLikeStringLength() {
+  "use strict";
+  var obj = {
+    "length": "6",
+    "1": "A",
+    "3": "B",
+    "5": "C"
+  };
+  obj[Symbol.isConcatSpreadable] = true;
+  var obj2 = { length: 3, "0": "0", "1": "1", "2": "2" };
+  var arr = ["X", "Y", "Z"];
+  assertEquals([void 0, "A", void 0, "B", void 0, "C",
+               { "length": 3, "0": "0", "1": "1", "2": "2" },
+               "X", "Y", "Z"], Array.prototype.concat.call(obj, obj2, arr));
+})();
+
+
+(function testConcatArrayLikeNegativeLength() {
+  "use strict";
+  var obj = {
+    "length": -6,
+    "1": "A",
+    "3": "B",
+    "5": "C"
+  };
+  obj[Symbol.isConcatSpreadable] = true;
+  assertEquals([], [].concat(obj));
+  obj.length = -6.7;
+  assertEquals([], [].concat(obj));
+  obj.length = "-6";
+  assertEquals([], [].concat(obj));
+})();
+
+
+(function testConcatArrayLikeToLengthThrows() {
+  "use strict";
+  var obj = {
+    "length": {valueOf: null, toString: null},
+    "1": "A",
+    "3": "B",
+    "5": "C"
+  };
+  obj[Symbol.isConcatSpreadable] = true;
+  var obj2 = { length: 3, "0": "0", "1": "1", "2": "2" };
+  var arr = ["X", "Y", "Z"];
+  assertThrows(function() {
+    Array.prototype.concat.call(obj, obj2, arr);
+  }, TypeError);
+})();
+
+
+(function testConcatArrayLikePrimitiveNonNumberLength() {
+  "use strict";
+  var obj = {
+    "1": "A",
+    "3": "B",
+    "5": "C"
+  };
+  obj[Symbol.isConcatSpreadable] = true;
+  obj.length = {toString: function() { return "SIX"; }, valueOf: null };
+  assertEquals([], [].concat(obj));
+  obj.length = {toString: null, valueOf: function() { return "SIX"; } };
+  assertEquals([], [].concat(obj));
+})();
+
+
+(function testConcatArrayLikeLengthToStringThrows() {
+  "use strict";
+  function MyError() {}
+  var obj = {
+    "length": { toString: function() {
+        throw new MyError();
+      }, valueOf: null
+    },
+    "1": "A",
+    "3": "B",
+    "5": "C"
+  };
+  obj[Symbol.isConcatSpreadable] = true;
+  assertThrows(function() {
+    [].concat(obj);
+  }, MyError);
+})();
+
+
+(function testConcatArrayLikeLengthValueOfThrows() {
+  "use strict";
+  function MyError() {}
+  var obj = {
+    "length": { valueOf: function() {
+      throw new MyError();
+    }, toString: null
+  },
+  "1": "A",
+  "3": "B",
+  "5": "C"
+};
+obj[Symbol.isConcatSpreadable] = true;
+assertThrows(function() {
+  [].concat(obj);
+}, MyError);
+})();
+
+
 (function testConcatHoleyArray() {
   "use strict";
   var arr = [];