Prohibit let in lexical bindings

src/preparser.cc

 // Copyright 2011 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.
 
 #include <cmath>
 
 #include "src/allocation.h"
 #include "src/base/logging.h"
 #include "src/conversions-inl.h"
 #include "src/conversions.h"
@@ skipping 516 matching lines @@
   // ConstDeclaration ::
   //   const ConstBinding (',' ConstBinding)* ';'
   // ConstBinding ::
   //   Identifier '=' AssignmentExpression
   //
   // TODO(ES6):
   // ConstBinding ::
   //   BindingPattern '=' AssignmentExpression
   bool require_initializer = false;
   bool is_strict_const = false;
+  bool lexical = false;
   if (peek() == Token::VAR) {
     if (is_strong(language_mode())) {
       Scanner::Location location = scanner()->peek_location();
       ReportMessageAt(location, MessageTemplate::kStrongVar);
       *ok = false;
       return Statement::Default();
     }
     Consume(Token::VAR);
   } else if (peek() == Token::CONST && allow_const()) {
     // TODO(ES6): The ES6 Draft Rev4 section 12.2.2 reads:
     //
     // ConstDeclaration : const ConstBinding (',' ConstBinding)* ';'
     //
     // * It is a Syntax Error if the code that matches this production is not
     //   contained in extended code.
     //
     // However disallowing const in sloppy mode will break compatibility with
     // existing pages. Therefore we keep allowing const with the old
     // non-harmony semantics in sloppy mode.
     Consume(Token::CONST);
     if (is_strict(language_mode()) ||
         (allow_harmony_sloppy() && !allow_legacy_const())) {
       DCHECK(var_context != kStatement);
       is_strict_const = true;
       require_initializer = var_context != kForStatement;
+      lexical = true;
     }
   } else if (peek() == Token::LET && allow_let()) {
     Consume(Token::LET);
     DCHECK(var_context != kStatement);
+    lexical = true;
   } else {
     *ok = false;
     return Statement::Default();
   }
 
   // The scope of a var/const declared variable anywhere inside a function
   // is the entire function (ECMA-262, 3rd, 10.1.3, and 12.2). The scope
   // of a let declared variable is the scope of the immediately enclosing
   // block.
   int nvars = 0;  // the number of variables declared
   int bindings_start = peek_position();
   do {
     // Parse binding pattern.
     if (nvars > 0) Consume(Token::COMMA);
     {
       ExpressionClassifier pattern_classifier;
       Token::Value next = peek();
       PreParserExpression pattern =
           ParsePrimaryExpression(&pattern_classifier, CHECK_OK);
       ValidateBindingPattern(&pattern_classifier, CHECK_OK);
+      if (lexical) {
+        ValidateLetPattern(&pattern_classifier, CHECK_OK);
+      }
 
       if (!allow_harmony_destructuring() && !pattern.IsIdentifier()) {
         ReportUnexpectedToken(next);
         *ok = false;
         return Statement::Default();
       }
     }
 
     Scanner::Location variable_loc = scanner()->location();
     nvars++;
@@ skipping 636 matching lines @@
   DCHECK(!spread_pos.IsValid());
 
   return Expression::Default();
 }
 
 #undef CHECK_OK
 
 
 }  // namespace internal
 }  // namespace v8