Lexical declarations should not be allowed in Statement

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 144 matching lines @@
 
 
 #define CHECK_OK  ok);                      \
   if (!*ok) return kUnknownSourceElements;  \
   ((void)0
 #define DUMMY )  // to make indentation work
 #undef DUMMY
 
 
 PreParser::Statement PreParser::ParseSourceElement(bool* ok) {
-  // (Ecma 262 5th Edition, clause 14):
-  // SourceElement:
-  //    Statement
-  //    FunctionDeclaration
+  // ECMA 262 6th Edition
+  // StatementListItem[Yield, Return] :
+  //   Statement[?Yield, ?Return]
+  //   Declaration[?Yield]
   //
-  // In harmony mode we allow additionally the following productions
-  // SourceElement:
-  //    LetDeclaration
-  //    ConstDeclaration
-  //    GeneratorDeclaration
+  // Declaration[Yield] :
+  //   HoistableDeclaration[?Yield]
+  //   ClassDeclaration[?Yield]
+  //   LexicalDeclaration[In, ?Yield]
+  //
+  // HoistableDeclaration[Yield, Default] :
+  //   FunctionDeclaration[?Yield, ?Default]
+  //   GeneratorDeclaration[?Yield, ?Default]
+  //
+  // LexicalDeclaration[In, Yield] :
+  //   LetOrConst BindingList[?In, ?Yield] ;
 
   switch (peek()) {
     case Token::FUNCTION:
       return ParseFunctionDeclaration(ok);
     case Token::CLASS:
       return ParseClassDeclaration(ok);
     case Token::CONST:
       return ParseVariableStatement(kSourceElement, ok);
     case Token::LET:
       DCHECK(allow_harmony_scoping());
@@ skipping 113 matching lines @@
         PreParserTraits::ReportMessageAt(start_location.beg_pos,
                                          end_location.end_pos,
                                          "strict_function");
         *ok = false;
         return Statement::Default();
       } else {
         return statement;
       }
     }
 
-    case Token::CLASS:
-      return ParseClassDeclaration(CHECK_OK);
-
     case Token::DEBUGGER:
       return ParseDebuggerStatement(ok);
 
     case Token::VAR:
-    case Token::CONST:
       return ParseVariableStatement(kStatement, ok);
 
-    case Token::LET:
-      DCHECK(allow_harmony_scoping());
-      if (strict_mode() == STRICT) {
+    case Token::CONST:
+      // In ES6 CONST is not allowed as a Statement , only as a
+      // LexicalDeclaration, however we continue to allow it in sloppy mode for
+      // backwards compatibility.
+      if (strict_mode() == SLOPPY) {
         return ParseVariableStatement(kStatement, ok);
       }
-      // Fall through.
+
+    // Fall through.
     default:
       return ParseExpressionOrLabelledStatement(ok);
   }
 }
 
 
 PreParser::Statement PreParser::ParseFunctionDeclaration(bool* ok) {
   // FunctionDeclaration ::
   //   'function' Identifier '(' FormalParameterListopt ')' '{' FunctionBody '}'
   // GeneratorDeclaration ::
@@ skipping 101 matching lines @@
     //
     // * 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 (strict_mode() == STRICT) {
       if (allow_harmony_scoping()) {
         if (var_context != kSourceElement && var_context != kForStatement) {

[adamk, 2015/01/23 20:11:39]

Same dead code as in parser...

           ReportMessageAt(scanner()->peek_location(), "unprotected_const");
           *ok = false;
           return Statement::Default();
         }
         is_strict_const = true;
         require_initializer = var_context != kForStatement;
       } else {
         Scanner::Location location = scanner()->peek_location();
         ReportMessageAt(location, "strict_const");
         *ok = false;
         return Statement::Default();
       }
     }
   } else if (peek() == Token::LET && strict_mode() == STRICT) {
     Consume(Token::LET);
     if (var_context != kSourceElement && var_context != kForStatement) {

[adamk, 2015/01/23 20:11:39]

...and here too.

       ReportMessageAt(scanner()->peek_location(), "unprotected_let");
       *ok = false;
       return Statement::Default();
     }
   } else {
     *ok = false;
     return Statement::Default();
   }
 
   // The scope of a var/const declared variable anywhere inside a function
@@ skipping 18 matching lines @@
   if (num_decl != NULL) *num_decl = nvars;
   return Statement::Default();
 }
 
 
 PreParser::Statement PreParser::ParseExpressionOrLabelledStatement(bool* ok) {
   // ExpressionStatement | LabelledStatement ::
   //   Expression ';'
   //   Identifier ':' Statement
 
+  switch (peek()) {
+    case Token::FUNCTION:
+    case Token::LBRACE:
+      UNREACHABLE();  // Always handled by the callers.
+    case Token::CLASS:
+      ReportUnexpectedToken(Next());
+      *ok = false;
+      return Statement::Default();
+
+    // TODO(arv): Handle `let [`
+    // https://code.google.com/p/v8/issues/detail?id=3847
+
+    default:
+      break;
+  }
+
   bool starts_with_identifier = peek_any_identifier();
   Expression expr = ParseExpression(true, CHECK_OK);
   // Even if the expression starts with an identifier, it is not necessarily an
   // identifier. For example, "foo + bar" starts with an identifier but is not
   // an identifier.
   if (starts_with_identifier && expr.IsIdentifier() && peek() == Token::COLON) {
     // Expression is a single identifier, and not, e.g., a parenthesized
     // identifier.
     DCHECK(!expr.AsIdentifier().IsFutureReserved());
     DCHECK(strict_mode() == SLOPPY ||
@@ skipping 504 matching lines @@
   ParseIdentifier(kAllowEvalOrArguments, CHECK_OK);
   ParseArguments(ok);
 
   return Expression::Default();
 }
 
 #undef CHECK_OK
 
 
 } }  // v8::internal