[es6] implement spread calls

src/harmony-spread.js

+// Copyright 2013 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+'use strict';
+
+// -------------------------------------------------------------------
+
+function SpreadCall(function, thisArg, spread0) {
+  if (!IS_SPEC_FUNCTION(function)) {
+    // TODO(caitp): use name of function rather than value
+    throw MakeTypeError("called_non_callable", [function]);
+  }
+
+  var args = new InternalArray();
+
+  var pos = 3;
+  var count = %_ArgumentsLength();
+
+  for (var index = spread0; index < count; ++index) {
+    var nextSpread = %_Arguments(index);
+
+    while (pos < nextSpread) {
+      args.push(%_Arguments(pos++));
+    }
+
+    var collection = %_Arguments(pos++);
+    var iterable = collection[symbolIterator];
+    var iterator = GetIterator(collection, iterable);
+
+    while (true) {
+      var next = iterator.next();
+
+      if (!IS_OBJECT(next)) {
+        throw MakeTypeError("iterator_result_not_an_object", [next]);
+      }
+
+      if (next.done) {
+        break;
+      }
+
+      args.push(next.value);
+    }
+  }
+
+  while (pos < spread0) {
+    args.push(%_Arguments(pos++));
+  }
+
+  return %Apply(function, thisArg, args, 0, args.length);
+}
+
+
+function SpreadCallNew(function, spread0) {
+  if (!IS_SPEC_FUNCTION(function)) {
+    // TODO(caitp): use name of function rather than value
+    throw MakeTypeError("called_non_callable", [function]);
+  }
+
+  var args = new InternalArray();
+
+  var pos = 2;
+  var count = %_ArgumentsLength();
+
+  for (var index = spread0; index < count; ++index) {
+    var nextSpread = %_Arguments(index);
+
+    while (pos < nextSpread) {
+      args.push(%_Arguments(pos++));
+    }
+
+    var collection = %_Arguments(pos++);
+    var iterable = collection[symbolIterator];
+    var iterator = GetIterator(collection, iterable);
+
+    while (true) {
+      var next = iterator.next();
+
+      if (!IS_OBJECT(next)) {
+        throw MakeTypeError("iterator_result_not_an_object", [next]);
+      }
+
+      if (next.done) {
+        break;
+      }
+
+      args.push(next.value);
+    }
+  }
+
+  while (pos < spread0) {
+    args.push(%_Arguments(pos++));
+  }
+
+  return %ApplyConstruct(function, args, 0, args.length);
+}