[ESnext] Implement Object Rest

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 23bcd150a801325191373928bf7076cce97ec28c..2c0dc6a598b9b21dc7d817405d3115ac86f348fc 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -2002,8 +2002,24 @@ Maybe<bool> JSReceiver::HasInPrototypeChain(Isolate* isolate,
 
 namespace {
 
-MUST_USE_RESULT Maybe<bool> FastAssign(Handle<JSReceiver> target,
-                                       Handle<Object> source, bool use_set) {
+bool HasElementInJSArray(Isolate* isolate, Handle<JSArray> array,
+                         Handle<Object> search_element) {
+  uint32_t len = 0;
+  bool success = array->length()->ToArrayLength(&len);
+  DCHECK(success);
+
+  if (len == 0) return false;
+
+  int32_t start = 0;
+  ElementsAccessor* elements = array->GetElementsAccessor();
+  Maybe<bool> result =
+      elements->IncludesValue(isolate, array, search_element, start, len);
+  return result.FromJust();
+}
+
+MUST_USE_RESULT Maybe<bool> FastAssign(
+    Handle<JSReceiver> target, Handle<Object> source,
+    MaybeHandle<JSArray> maybe_excluded_properties, bool use_set) {
   // Non-empty strings are the only non-JSReceivers that need to be handled
   // explicitly by Object.assign.
   if (!source->IsJSReceiver()) {
@@ -2033,6 +2049,10 @@ MUST_USE_RESULT Maybe<bool> FastAssign(Handle<JSReceiver> target,
   int length = map->NumberOfOwnDescriptors();
 
   bool stable = true;
+  Handle<JSArray> excluded_properties;
+  if (!maybe_excluded_properties.is_null()) {
+    excluded_properties = maybe_excluded_properties.ToHandleChecked();

[adamk, 2017/01/10 23:22:56]

Pattern for this is:

const bool has_excluded_properties =
maybe_excluded_properties.ToHandle(&excluded_properties);

+  }
 
   for (int i = 0; i < length; i++) {
     Handle<Name> next_key(descriptors->GetKey(i), isolate);
@@ -2076,6 +2096,11 @@ MUST_USE_RESULT Maybe<bool> FastAssign(Handle<JSReceiver> target,
       if (result.IsNothing()) return result;
       if (stable && call_to_js) stable = from->map() == *map;
     } else {
+      if (!maybe_excluded_properties.is_null() &&

[adamk, 2017/01/10 23:22:56]

and then this would be

if (has_excluded_properties && ...)

+          HasElementInJSArray(isolate, excluded_properties, next_key)) {
+        continue;
+      }
+
       // 4a ii 2. Perform ? CreateDataProperty(target, nextKey, propValue).
       bool success;
       LookupIterator it = LookupIterator::PropertyOrElement(
@@ -2089,15 +2114,14 @@ MUST_USE_RESULT Maybe<bool> FastAssign(Handle<JSReceiver> target,
 
   return Just(true);
 }
-
 }  // namespace
 
 // static
-Maybe<bool> JSReceiver::SetOrCopyDataProperties(Isolate* isolate,
-                                                Handle<JSReceiver> target,
-                                                Handle<Object> source,
-                                                bool use_set) {
-  Maybe<bool> fast_assign = FastAssign(target, source, use_set);
+Maybe<bool> JSReceiver::SetOrCopyDataProperties(
+    Isolate* isolate, Handle<JSReceiver> target, Handle<Object> source,
+    MaybeHandle<JSArray> maybe_excluded_properties, bool use_set) {
+  Maybe<bool> fast_assign =
+      FastAssign(target, source, maybe_excluded_properties, use_set);
   if (fast_assign.IsNothing()) return Nothing<bool>();
   if (fast_assign.FromJust()) return Just(true);
 
@@ -2110,6 +2134,11 @@ Maybe<bool> JSReceiver::SetOrCopyDataProperties(Isolate* isolate,
                               GetKeysConversion::kKeepNumbers),
       Nothing<bool>());
 
+  Handle<JSArray> excluded_properties;
+  if (!maybe_excluded_properties.is_null()) {
+    excluded_properties = maybe_excluded_properties.ToHandleChecked();

[adamk, 2017/01/10 23:22:56]

Same here as above

+  }
+
   // 4. Repeat for each element nextKey of keys in List order,
   for (int j = 0; j < keys->length(); ++j) {
     Handle<Object> next_key(keys->get(j), isolate);
@@ -2134,6 +2163,11 @@ Maybe<bool> JSReceiver::SetOrCopyDataProperties(Isolate* isolate,
                                  isolate, target, next_key, prop_value, STRICT),
             Nothing<bool>());
       } else {
+        if (!maybe_excluded_properties.is_null() &&

[adamk, 2017/01/10 23:22:55]

And here.

+            HasElementInJSArray(isolate, excluded_properties, next_key)) {
+          continue;
+        }
+
         // 4a ii 2. Perform ! CreateDataProperty(target, nextKey, propValue).
         bool success;
         LookupIterator it = LookupIterator::PropertyOrElement(