Fix error message while array destructuring undefined

Previously,
  ➜  v8 (master) ✔ ./out.gn/x64.optdebug/d8
  V8 version 6.1.0 (candidate)
  d8> var x = undefined
  undefined
  d8> var [a] = x
  (d8):1: TypeError: Cannot read property 'Symbol(Symbol.iterator)' of undefined
  var [a] = x
            ^
  TypeError: Cannot read property 'Symbol(Symbol.iterator)' of undefined
      at (d8):1:11

Now,
  ➜  v8 (fix-iterator) ✔ ./out.gn/x64.optdebug/d8
  V8 version 6.1.0 (candidate)
  d8> var x = undefined
  undefined
  d8> var [a] = x
  (d8):1: TypeError: x is not iterable
  var [a] = x
            ^
  TypeError: x is not iterable
      at (d8):1:11


Bug: v8:6599, v8:6513
Change-Id: I71287a19166af0289e8f7708b8f41ad003ae87ae
Reviewed-on: https://chromium-review.googlesource.com/571175
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46723}

src/ic/ic.cc

@@ -551,6 +551,10 @@ MaybeHandle<Object> LoadIC::Load(Handle<Object> object, Handle<Name> name) {
       PatchCache(name, slow_stub());
       TRACE_IC("LoadIC", name);
     }
+
+    if (*name == isolate()->heap()->iterator_symbol()) {
+      return Runtime::ThrowIteratorError(isolate(), object);
+    }
     return TypeError(MessageTemplate::kNonObjectPropertyLoad, object, name);
   }
 

src/runtime/runtime-internal.cc

@@ -393,19 +393,14 @@ bool ComputeLocation(Isolate* isolate, MessageLocation* target) {
 }
 
 Handle<String> RenderCallSite(Isolate* isolate, Handle<Object> object,
-                              MessageTemplate::Template* id) {
+                              CallPrinter::IteratorHint* hint) {
   MessageLocation location;
   if (ComputeLocation(isolate, &location)) {
     ParseInfo info(location.shared());
     if (parsing::ParseAny(&info, isolate)) {
       CallPrinter printer(isolate, location.shared()->IsUserJavaScript());
       Handle<String> str = printer.Print(info.literal(), location.start_pos());
-      CallPrinter::IteratorHint type = printer.GetIteratorHint();
-      if (type == CallPrinter::IteratorHint::kNormal) {
-        *id = MessageTemplate::kNotIterable;
-      } else if (type == CallPrinter::IteratorHint::kAsync) {
-        *id = MessageTemplate::kNotAsyncIterable;
-      }
+      *hint = printer.GetIteratorHint();
       if (str->length() > 0) return str;
     } else {
       isolate->clear_pending_exception();
@@ -414,14 +409,43 @@ Handle<String> RenderCallSite(Isolate* isolate, Handle<Object> object,
   return Object::TypeOf(isolate, object);
 }
 
+void UpdateIteratorTemplate(CallPrinter::IteratorHint hint,
+                            MessageTemplate::Template* id) {
+  if (hint == CallPrinter::IteratorHint::kNormal) {
+    *id = MessageTemplate::kNotIterable;
+  }
+
+  if (hint == CallPrinter::IteratorHint::kAsync) {
+    *id = MessageTemplate::kNotAsyncIterable;
+  }
+}
+
 }  // namespace
 
+MaybeHandle<Object> Runtime::ThrowIteratorError(Isolate* isolate,
+                                                Handle<Object> object) {
+  CallPrinter::IteratorHint hint;
+  Handle<String> callsite = RenderCallSite(isolate, object, &hint);
+  MessageTemplate::Template id = MessageTemplate::kNonObjectPropertyLoad;
+
+  if (hint == CallPrinter::kNone) {
+    Handle<Symbol> iterator_symbol = isolate->factory()->iterator_symbol();
+    THROW_NEW_ERROR(isolate, NewTypeError(id, iterator_symbol, callsite),
+                    Object);
+  }
+
+  UpdateIteratorTemplate(hint, &id);
+  THROW_NEW_ERROR(isolate, NewTypeError(id, callsite), Object);
+}
+
 RUNTIME_FUNCTION(Runtime_ThrowCalledNonCallable) {
   HandleScope scope(isolate);
   DCHECK_EQ(1, args.length());
   CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
+  CallPrinter::IteratorHint hint;
+  Handle<String> callsite = RenderCallSite(isolate, object, &hint);
   MessageTemplate::Template id = MessageTemplate::kCalledNonCallable;
-  Handle<String> callsite = RenderCallSite(isolate, object, &id);
+  UpdateIteratorTemplate(hint, &id);
   THROW_NEW_ERROR_RETURN_FAILURE(isolate, NewTypeError(id, callsite));
 }
 
@@ -437,8 +461,9 @@ RUNTIME_FUNCTION(Runtime_ThrowConstructedNonConstructable) {
   HandleScope scope(isolate);
   DCHECK_EQ(1, args.length());
   CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
+  CallPrinter::IteratorHint hint;
+  Handle<String> callsite = RenderCallSite(isolate, object, &hint);
   MessageTemplate::Template id = MessageTemplate::kNotConstructor;
-  Handle<String> callsite = RenderCallSite(isolate, object, &id);
   THROW_NEW_ERROR_RETURN_FAILURE(isolate, NewTypeError(id, callsite));
 }
 

src/runtime/runtime.h

@@ -781,6 +781,9 @@ class Runtime : public AllStatic {
 
   MUST_USE_RESULT static MaybeHandle<JSArray> GetInternalProperties(
       Isolate* isolate, Handle<Object>);
+
+  MUST_USE_RESULT static MaybeHandle<Object> ThrowIteratorError(
+      Isolate* isolate, Handle<Object> object);
 };
 
 

test/message/destructuring-array-non-iterable-undefined.js

+// Copyright 2017 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.
+
+var x = undefined;
+var [y] = x;

test/message/destructuring-array-non-iterable-undefined.out

+*%(basename)s:6: TypeError: x is not iterable
+var [y] = x;
+          ^
+TypeError: x is not iterable
+    at *%(basename)s:6:11