[es6] Self-assignment in a default parameter initializer should throw

src/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_PREPARSER_H
 #define V8_PREPARSER_H
 
 #include "src/bailout-reason.h"
 #include "src/expression-classifier.h"
 #include "src/func-name-inferrer.h"
@@ skipping 1690 matching lines @@
     return EmptyExpression();
   }
   inline void MaterializeTemplateCallsiteLiterals();
   PreParserExpression NoTemplateTag() {
     return PreParserExpression::NoTemplateTag();
   }
   static bool IsTaggedTemplate(const PreParserExpression tag) {
     return !tag.IsNoTemplateTag();
   }
 
-  void AddFormalParameter(
-      PreParserFormalParameters* parameters, PreParserExpression pattern,
-      PreParserExpression initializer, bool is_rest) {
+  void AddFormalParameter(PreParserFormalParameters* parameters,
+                          PreParserExpression pattern,
+                          PreParserExpression initializer,
+                          int initializer_end_position, bool is_rest) {
     ++parameters->arity;
   }
   void DeclareFormalParameter(Scope* scope, PreParserIdentifier parameter,
                               ExpressionClassifier* classifier) {
     if (!classifier->is_simple_parameter_list()) {
       scope->SetHasNonSimpleParameters();
     }
   }
 
   void CheckConflictingVarDeclarations(Scope* scope, bool* ok) {}
@@ skipping 2106 matching lines @@
     ExpressionClassifier init_classifier;
     initializer = ParseAssignmentExpression(true, &init_classifier, ok);
     if (!*ok) return;
     ValidateExpression(&init_classifier, ok);
     ValidateFormalParameterInitializer(&init_classifier, ok);
     if (!*ok) return;
     parameters->is_simple = false;
     classifier->RecordNonSimpleParameter();
   }
 
-  Traits::AddFormalParameter(parameters, pattern, initializer, is_rest);
+  Traits::AddFormalParameter(parameters, pattern, initializer,
+                             scanner()->location().end_pos, is_rest);
 }
 
 
 template <class Traits>
 void ParserBase<Traits>::ParseFormalParameterList(
     FormalParametersT* parameters, ExpressionClassifier* classifier, bool* ok) {
   // FormalParameters[Yield,GeneratorParameter] :
   //   [empty]
   //   FormalParameterList[?Yield, ?GeneratorParameter]
   //
@@ skipping 399 matching lines @@
       return;
     }
     has_seen_constructor_ = true;
     return;
   }
 }
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PREPARSER_H