Prohibit let in lexical bindings

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 249 matching lines @@
   T(InvalidDataViewOffset, "Start offset is outside the bounds of the buffer") \
   T(InvalidHint, "Invalid hint: %")                                            \
   T(InvalidLanguageTag, "Invalid language tag: %")                             \
   T(InvalidWeakMapKey, "Invalid value used as weak map key")                   \
   T(InvalidWeakSetValue, "Invalid value used in weak set")                     \
   T(InvalidStringLength, "Invalid string length")                              \
   T(InvalidTimeValue, "Invalid time value")                                    \
   T(InvalidTypedArrayAlignment, "% of % should be a multiple of %")            \
   T(InvalidTypedArrayLength, "Invalid typed array length")                     \
   T(InvalidTypedArrayOffset, "Start offset is too large:")                     \
+  T(LetInLexicalBinding, "let is disallowed as a lexically bound name")        \
   T(LocaleMatcher, "Illegal value for localeMatcher:%")                        \
   T(NormalizationForm, "The normalization form should be one of %.")           \
   T(NumberFormatRange, "% argument must be between 0 and 20")                  \
   T(PropertyValueOutOfRange, "% value is out of range.")                       \
   T(StackOverflow, "Maximum call stack size exceeded")                         \
   T(ToPrecisionFormatRange, "toPrecision() argument must be between 1 and 21") \
   T(ToRadixFormatRange, "toString() radix argument must be between 2 and 36")  \
   T(TypedArraySetNegativeOffset, "Start offset is negative")                   \
   T(TypedArraySetSourceTooLarge, "Source is too large")                        \
   T(UnsupportedTimeZone, "Unsupported time zone specified %")                  \
@@ skipping 207 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_