Emit better error message about writable properties

src/messages.h

 // Copyright 2006-2008 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.
 
 // The infrastructure used for (localized) message reporting in V8.
 //
 // Note: there's a big unresolved issue about ownership of the data
 // structures used by this framework.
 
 #ifndef V8_MESSAGES_H_
@@ skipping 217 matching lines @@
     "On strong object %, redefining writable, non-configurable property '%' "  \
     "to be non-writable is deprecated")                                        \
   T(StrongSetProto,                                                            \
     "On strong object %, redefining the internal prototype is deprecated")     \
   T(SymbolKeyFor, "% is not a symbol")                                         \
   T(SymbolToNumber, "Cannot convert a Symbol value to a number")               \
   T(SymbolToString, "Cannot convert a Symbol value to a string")               \
   T(SimdToNumber, "Cannot convert a SIMD value to a number")                   \
   T(UndefinedOrNullToObject, "Cannot convert undefined or null to object")     \
   T(ValueAndAccessor,                                                          \
-    "Invalid property.  A property cannot both have accessors and be "         \
-    "writable or have a value, %")                                             \
+    "Invalid property descriptor.  A property descriptor cannot both have "    \
+    "accessors and specify the value or writability of the property, %")       \

[rossberg, 2015/10/12 09:00:14]

The test seems a bit redundant now. Can we simplify this to

"Invalid property descriptor: cannot both specify accessors and a value or
writable attribute, %"

   T(VarRedeclaration, "Identifier '%' has already been declared")              \
   T(WithExpression, "% has no properties")                                     \
   T(WrongArgs, "%: Arguments list has wrong type")                             \
   /* ReferenceError */                                                         \
   T(NonMethod, "'super' is referenced from non-method")                        \
   T(NotDefined, "% is not defined")                                            \
   T(StrongSuperCallMissing,                                                    \
     "In strong mode, invoking the super constructor in a subclass is "         \
     "required")                                                                \
   T(StrongUnboundGlobal,                                                       \
@@ skipping 242 matching lines @@
   static MUST_USE_RESULT MaybeHandle<String> GetStringifiedProperty(
       Isolate* isolate, LookupIterator* property_lookup,
       Handle<String> default_value);
 
   List<Handle<JSObject> > visited_;
 };
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_MESSAGES_H_