Lexical declarations should not be allowed in Statement

src/parser.cc

Index: src/parser.cc
diff --git a/src/parser.cc b/src/parser.cc
index 51e79bb14cf1c6519de925d6bb1434e06ccc225f..29e010b87260deabbcba23f52d828e4108ac7ddf 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -1711,22 +1711,21 @@ Statement* Parser::ParseStatement(ZoneList<const AstRawString*>* labels,
       return ParseFunctionDeclaration(NULL, ok);
     }
 
-    case Token::CLASS:
-      return ParseClassDeclaration(NULL, ok);
-
     case Token::DEBUGGER:
       return ParseDebuggerStatement(ok);
 
     case Token::VAR:
-    case Token::CONST:
       return ParseVariableStatement(kStatement, NULL, 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, NULL, ok);
       }
-      // Fall through.
+
+    // Fall through.
     default:
       return ParseExpressionOrLabelledStatement(labels, ok);
   }
@@ -2438,6 +2437,26 @@ Statement* Parser::ParseExpressionOrLabelledStatement(
   // ExpressionStatement | LabelledStatement ::
   //   Expression ';'
   //   Identifier ':' Statement
+  //
+  // ExpressionStatement[Yield] :
+  //   [lookahead ∉ {{, function, class, let [}] Expression[In, ?Yield] ;
+
+  switch (peek()) {
+    case Token::FUNCTION:
+    case Token::LBRACE:
+      UNREACHABLE();  // Always handled by the callers.
+    case Token::CLASS:
+      ReportUnexpectedToken(Next());
+      *ok = false;
+      return nullptr;

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

Nit: the rest of the code in this file still uses "NULL"

+
+    // TODO(arv): Handle `let [`
+    // https://code.google.com/p/v8/issues/detail?id=3847
+
+    default:
+      break;
+  }
+
   int pos = peek_position();
   bool starts_with_idenfifier = peek_any_identifier();
   Expression* expr = ParseExpression(true, CHECK_OK);