[parser] Disallow Expression in for..of statements

src/parsing/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 932 matching lines @@
             ReportMessageAt(first_initializer_loc,
                             MessageTemplate::kForOfLoopInitializer);
           } else {
             // TODO(caitp): This should be an error in sloppy mode, too.
             ReportMessageAt(first_initializer_loc,
                             MessageTemplate::kForInLoopInitializer);
           }
           *ok = false;
           return Statement::Default();
         }
-        ParseExpression(true, CHECK_OK);
+
+        if (mode == ForEachStatement::ITERATE) {
+          ExpressionClassifier classifier;
+          ParseAssignmentExpression(true, &classifier, CHECK_OK);
+          ValidateExpression(&classifier, CHECK_OK);
+        } else {
+          ParseExpression(true, CHECK_OK);
+        }
+
         Expect(Token::RPAREN, CHECK_OK);
         ParseSubStatement(CHECK_OK);
         return Statement::Default();
       }
     } else {
       int lhs_beg_pos = peek_position();
       ExpressionClassifier classifier;
       Expression lhs = ParseExpression(false, &classifier, CHECK_OK);
       int lhs_end_pos = scanner()->location().end_pos;
       is_let_identifier_expression =
           lhs.IsIdentifier() && lhs.AsIdentifier().IsLet();
       bool is_for_each = CheckInOrOf(&mode, ok);
       if (!*ok) return Statement::Default();
       bool is_destructuring = is_for_each &&
                               allow_harmony_destructuring_assignment() &&
                               (lhs->IsArrayLiteral() || lhs->IsObjectLiteral());
 
       if (is_destructuring) {
         ValidateAssignmentPattern(&classifier, CHECK_OK);
       } else {
         ValidateExpression(&classifier, CHECK_OK);
       }
 
       if (is_for_each) {
         if (!is_destructuring) {
           lhs = CheckAndRewriteReferenceExpression(
               lhs, lhs_beg_pos, lhs_end_pos, MessageTemplate::kInvalidLhsInFor,
               kSyntaxError, CHECK_OK);
         }
-        ParseExpression(true, CHECK_OK);
+
+        if (mode == ForEachStatement::ITERATE) {
+          ExpressionClassifier classifier;
+          ParseAssignmentExpression(true, &classifier, CHECK_OK);
+          ValidateExpression(&classifier, CHECK_OK);
+        } else {
+          ParseExpression(true, CHECK_OK);
+        }
+
         Expect(Token::RPAREN, CHECK_OK);
         ParseSubStatement(CHECK_OK);
         return Statement::Default();
       }
     }
   }
 
   // Parsed initializer at this point.
   // Detect attempts at 'let' declarations in sloppy mode.
   if (!allow_harmony_sloppy_let() && peek() == Token::IDENTIFIER &&
@@ skipping 289 matching lines @@
     Expect(Token::RBRACE, CHECK_OK);
     return PreParserExpression::Default();
   }
 }
 
 #undef CHECK_OK
 
 
 }  // namespace internal
 }  // namespace v8