Version 3.5.6.

src/messages.js

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 229 matching lines @@
       strict_lhs_prefix:            ["Prefix increment/decrement may not have eval or arguments operand in strict mode"],
       strict_reserved_word:         ["Use of future reserved word in strict mode"],
       strict_delete:                ["Delete of an unqualified identifier in strict mode."],
       strict_delete_property:       ["Cannot delete property '", "%0", "' of ", "%1"],
       strict_const:                 ["Use of const in strict mode."],
       strict_function:              ["In strict mode code, functions can only be declared at top level or immediately within another function." ],
       strict_read_only_property:    ["Cannot assign to read only property '", "%0", "' of ", "%1"],
       strict_cannot_assign:         ["Cannot assign to read only '", "%0", "' in strict mode"],
       strict_poison_pill:           ["'caller', 'callee', and 'arguments' properties may not be accessed on strict mode functions or the arguments objects for calls to them"],
       strict_caller:                ["Illegal access to a strict mode caller function."],
+      unprotected_let:              ["Illegal let declaration in unprotected statement context."],
     };
   }
   var message_type = %MessageGetType(message);
   var format = kMessages[message_type];
   if (!format) return "<unknown message " + message_type + ">";
   return FormatString(format, message);
 }
 
 
 function GetLineNumber(message) {
@@ skipping 860 matching lines @@
     else throw e;
   }
 }
 
 
 InstallFunctions($Error.prototype, DONT_ENUM, ['toString', errorToString]);
 
 // Boilerplate for exceptions for stack overflows. Used from
 // Isolate::StackOverflow().
 const kStackOverflowBoilerplate = MakeRangeError('stack_overflow', []);