Better error reporting for "return();"

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 305 matching lines @@
   T(InvalidLhsInFor, "Invalid left-hand side in for-loop")                     \
   T(InvalidLhsInPostfixOp,                                                     \
     "Invalid left-hand side expression in postfix operation")                  \
   T(InvalidLhsInPrefixOp,                                                      \
     "Invalid left-hand side expression in prefix operation")                   \
   T(InvalidRegExpFlags, "Invalid flags supplied to RegExp constructor '%'")    \
   T(LabelRedeclaration, "Label '%' has already been declared")                 \
   T(MalformedArrowFunParamList, "Malformed arrow function parameter list")     \
   T(MalformedRegExp, "Invalid regular expression: /%/: %")                     \
   T(MalformedRegExpFlags, "Invalid regular expression flags")                  \
+  T(MissingArrow,                                                              \
+    "Expected () to start arrow function, but got '%' instead of '=>'")        \
   T(ModuleExportUndefined, "Export '%' is not defined in module")              \
   T(MultipleDefaultsInSwitch,                                                  \
     "More than one default clause in switch statement")                        \
   T(NewlineAfterThrow, "Illegal newline after throw")                          \
   T(NoCatchOrFinally, "Missing catch or finally after try")                    \
   T(NotIsvar, "builtin %%IS_VAR: not a variable")                              \
   T(ParamAfterRest, "Rest parameter must be last formal parameter")            \
   T(BadSetterRestParameter,                                                    \
     "Setter function argument must not be a rest parameter")                   \
   T(ParenthesisInArgString, "Function arg string contains parenthesis")        \
@@ skipping 116 matching lines @@
 
   static void DefaultMessageReport(Isolate* isolate, const MessageLocation* loc,
                                    Handle<Object> message_obj);
   static Handle<String> GetMessage(Isolate* isolate, Handle<Object> data);
   static SmartArrayPointer<char> GetLocalizedMessage(Isolate* isolate,
                                                      Handle<Object> data);
 };
 } }  // namespace v8::internal
 
 #endif  // V8_MESSAGES_H_