[parser] early error when declaration Pattern missing Initializer

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 109 matching lines @@
     "RegExp.prototype.flags getter called on non-object %")                    \
   T(FunctionBind, "Bind must be called on a function")                         \
   T(GeneratorRunning, "Generator is already running")                          \
   T(IllegalInvocation, "Illegal invocation")                                   \
   T(IncompatibleMethodReceiver, "Method % called on incompatible receiver %")  \
   T(InstanceofFunctionExpected,                                                \
     "Expecting a function in instanceof check, but got %")                     \
   T(InstanceofNonobjectProto,                                                  \
     "Function has non-object prototype '%' in instanceof check")               \
   T(InvalidArgument, "invalid_argument")                                       \
+  T(InvalidDestructuringDeclaration,                                           \

[adamk, 2015/11/03 20:13:53]

Looks like we're currently giving bad error messages for this for the const
case, so it seems like this could just be "MissingInitializer" and the message
could be broadened to cover that case too.

+    "Missing initializer in destructuring declaration")                        \
   T(InvalidInOperatorUse, "Cannot use 'in' operator to search for '%' in %")   \
   T(IteratorResultNotAnObject, "Iterator result % is not an object")           \
   T(IteratorValueNotAnObject, "Iterator value % is not an entry object")       \
   T(LanguageID, "Language ID should be string or object.")                     \
   T(MethodCalledOnWrongObject,                                                 \
     "Method % called on a non-object or on a wrong type of object.")           \
   T(MethodInvokedOnNullOrUndefined,                                            \
     "Method invoked on undefined or null value.")                              \
   T(MethodInvokedOnWrongType, "Method invoked on an object that is not %.")    \
   T(NoAccess, "no access")                                                     \
@@ skipping 357 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_