Remove AssignmentExpressionFlags enum, handle error checking in callers

src/parsing/preparser.h

 // Copyright 2012 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_PARSING_PREPARSER_H
 #define V8_PARSING_PREPARSER_H
 
 #include "src/ast/scopes.h"
 #include "src/bailout-reason.h"
 #include "src/hashmap.h"
@@ skipping 179 matching lines @@
   PreParserIdentifier AsIdentifier() const {
     DCHECK(IsIdentifier());
     return PreParserIdentifier(IdentifierTypeField::decode(code_));
   }
 
   bool IsAssignment() const {
     return TypeField::decode(code_) == kExpression &&
            ExpressionTypeField::decode(code_) == kAssignment;
   }
 
+  bool IsRewritableAssignmentExpression() const { return IsAssignment(); }
+
   bool IsObjectLiteral() const {
     return TypeField::decode(code_) == kObjectLiteralExpression;
   }
 
   bool IsArrayLiteral() const {
     return TypeField::decode(code_) == kArrayLiteralExpression;
   }
 
   bool IsStringLiteral() const {
     return TypeField::decode(code_) == kStringLiteralExpression;
@@ skipping 951 matching lines @@
     const PreParserFormalParameters& parameters, FunctionKind kind,
     FunctionLiteral::FunctionType function_type, bool* ok) {
   return pre_parser_->ParseEagerFunctionBody(function_name, pos, parameters,
                                              kind, function_type, ok);
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_PREPARSER_H