Fix let pattern error accumulation

src/expression-classifier.h

 // Copyright 2015 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.
 
 #ifndef V8_EXPRESSION_CLASSIFIER_H
 #define V8_EXPRESSION_CLASSIFIER_H
 
 #include "src/messages.h"
 #include "src/scanner.h"
 #include "src/token.h"
@@ skipping 246 matching lines @@
         assignment_pattern_error_ = inner.assignment_pattern_error_;
       if (errors & DistinctFormalParametersProduction)
         duplicate_formal_parameter_error_ =
             inner.duplicate_formal_parameter_error_;
       if (errors & StrictModeFormalParametersProduction)
         strict_mode_formal_parameter_error_ =
             inner.strict_mode_formal_parameter_error_;
       if (errors & StrongModeFormalParametersProduction)
         strong_mode_formal_parameter_error_ =
             inner.strong_mode_formal_parameter_error_;
+      if (errors & LetPatternProduction)
+        let_pattern_error_ = inner.let_pattern_error_;
     }
 
     // As an exception to the above, the result continues to be a valid arrow
     // formal parameters if the inner expression is a valid binding pattern.
     if (productions & ArrowFormalParametersProduction &&
         is_valid_arrow_formal_parameters()) {
       // Also copy function properties if expecting an arrow function
       // parameter.
       function_properties_ |= inner.function_properties_;
 
@@ skipping 16 matching lines @@
   Error strict_mode_formal_parameter_error_;
   Error strong_mode_formal_parameter_error_;
   Error let_pattern_error_;
   DuplicateFinder* duplicate_finder_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_EXPRESSION_CLASSIFIER_H