Improve error reporting for duplicate object template properties.

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index 888f665d21c8d8ab126a7d0ff9703d534094d5aa..1d10a8e222aecfa213e9a9ba1122e2a81494110b 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -5339,15 +5339,59 @@ RUNTIME_FUNCTION(Runtime_AddProperty) {
       static_cast<PropertyAttributes>(unchecked_attributes);
 
 #ifdef DEBUG
+  bool duplicate;
   if (key->IsName()) {
     LookupIterator it(object, Handle<Name>::cast(key),
                       LookupIterator::CHECK_OWN_REAL);
     JSReceiver::GetPropertyAttributes(&it);
-    RUNTIME_ASSERT(!it.IsFound());
+    duplicate = it.IsFound();
   } else {
     uint32_t index = 0;
     RUNTIME_ASSERT(key->ToArrayIndex(&index));
-    RUNTIME_ASSERT(!JSReceiver::HasOwnElement(object, index));
+    duplicate = JSReceiver::HasOwnElement(object, index);
+  }
+  RUNTIME_ASSERT(!duplicate);
+#endif
+
+  Handle<Object> result;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+      isolate, result,
+      Runtime::DefineObjectProperty(object, key, value, attributes));
+  return *result;
+}
+
+
+RUNTIME_FUNCTION(Runtime_AddPropertyForTemplate) {
+  HandleScope scope(isolate);
+  RUNTIME_ASSERT(args.length() == 4);
+
+  CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
+  CONVERT_ARG_HANDLE_CHECKED(Object, key, 1);
+  CONVERT_ARG_HANDLE_CHECKED(Object, value, 2);
+  CONVERT_SMI_ARG_CHECKED(unchecked_attributes, 3);
+  RUNTIME_ASSERT(
+      (unchecked_attributes & ~(READ_ONLY | DONT_ENUM | DONT_DELETE)) == 0);
+  // Compute attributes.
+  PropertyAttributes attributes =
+      static_cast<PropertyAttributes>(unchecked_attributes);
+
+#ifdef DEBUG
+  bool duplicate;
+  if (key->IsName()) {
+    LookupIterator it(object, Handle<Name>::cast(key),
+                      LookupIterator::CHECK_OWN_REAL);
+    JSReceiver::GetPropertyAttributes(&it);
+    duplicate = it.IsFound();
+  } else {
+    uint32_t index = 0;
+    RUNTIME_ASSERT(key->ToArrayIndex(&index));
+    duplicate = JSReceiver::HasOwnElement(object, index);
+  }
+  if (duplicate) {
+    Handle<Object> args[1] = { key };
+    Handle<Object> error = isolate->factory()->NewTypeError(
+        "duplicate_template_property", HandleVector(args, 1));
+    return isolate->Throw(*error);
   }
 #endif