[destructuring] Implement parameter pattern matching.

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/v8.h"
 
 #include "src/bailout-reason.h"
@@ skipping 52 matching lines @@
 template <typename Traits>
 class ParserBase : public Traits {
  public:
   // Shorten type names defined by Traits.
   typedef typename Traits::Type::Expression ExpressionT;
   typedef typename Traits::Type::Identifier IdentifierT;
   typedef typename Traits::Type::FormalParameter FormalParameterT;
   typedef typename Traits::Type::FunctionLiteral FunctionLiteralT;
   typedef typename Traits::Type::Literal LiteralT;
   typedef typename Traits::Type::ObjectLiteralProperty ObjectLiteralPropertyT;
+  typedef typename Traits::Type::FormalParameterParsingState
+      FormalParameterParsingStateT;
 
   ParserBase(Zone* zone, Scanner* scanner, uintptr_t stack_limit,
              v8::Extension* extension, AstValueFactory* ast_value_factory,
              ParserRecorder* log, typename Traits::Type::Parser this_object)
       : Traits(this_object),
         parenthesized_function_(false),
         scope_(NULL),
         function_state_(NULL),
         extension_(extension),
         fni_(NULL),
@@ skipping 467 matching lines @@
                !classifier->is_valid_strong_mode_formal_parameters()) {
       ReportClassifierError(classifier->strong_mode_formal_parameter_error());
       *ok = false;
     }
   }
 
   void ValidateArrowFormalParameters(const ExpressionClassifier* classifier,
                                      ExpressionT expr, bool* ok) {
     if (classifier->is_valid_binding_pattern()) {
       // A simple arrow formal parameter: IDENTIFIER => BODY.
-      if (!allow_harmony_destructuring() && !this->IsIdentifier(expr)) {
+      if (!this->IsIdentifier(expr)) {
         Traits::ReportMessageAt(scanner()->location(),
                                 MessageTemplate::kUnexpectedToken,
                                 Token::String(scanner()->current_token()));
         *ok = false;
       }
     } else if (!classifier->is_valid_arrow_formal_parameters()) {
       ReportClassifierError(classifier->arrow_formal_parameters_error());
       *ok = false;
     }
   }
@@ skipping 68 matching lines @@
   ExpressionT ParseUnaryExpression(ExpressionClassifier* classifier, bool* ok);
   ExpressionT ParsePostfixExpression(ExpressionClassifier* classifier,
                                      bool* ok);
   ExpressionT ParseLeftHandSideExpression(ExpressionClassifier* classifier,
                                           bool* ok);
   ExpressionT ParseMemberWithNewPrefixesExpression(
       ExpressionClassifier* classifier, bool* ok);
   ExpressionT ParseMemberExpression(ExpressionClassifier* classifier, bool* ok);
   ExpressionT ParseMemberExpressionContinuation(
       ExpressionT expression, ExpressionClassifier* classifier, bool* ok);
-  ExpressionT ParseArrowFunctionLiteral(Scope* function_scope, bool has_rest,
-                                        const ExpressionClassifier& classifier,
-                                        bool* ok);
+  ExpressionT ParseArrowFunctionLiteral(
+      const FormalParameterParsingStateT& parsing_state,
+      const ExpressionClassifier& classifier, bool* ok);
   ExpressionT ParseTemplateLiteral(ExpressionT tag, int start,
                                    ExpressionClassifier* classifier, bool* ok);
   void AddTemplateExpression(ExpressionT);
   ExpressionT ParseSuperExpression(bool is_new,
                                    ExpressionClassifier* classifier, bool* ok);
   ExpressionT ParseNewTargetExpression(bool* ok);
   ExpressionT ParseStrongInitializationExpression(
       ExpressionClassifier* classifier, bool* ok);
   ExpressionT ParseStrongSuperCallExpression(ExpressionClassifier* classifier,
                                              bool* ok);
 
-  void ParseFormalParameter(Scope* scope, bool is_rest,
+  void ParseFormalParameter(bool is_rest,
+                            FormalParameterParsingStateT* parsing_result,
                             ExpressionClassifier* classifier, bool* ok);
-  int ParseFormalParameterList(Scope* scope, bool* has_rest,
+  int ParseFormalParameterList(FormalParameterParsingStateT* parsing_state,
                                ExpressionClassifier* classifier, bool* ok);
   void CheckArityRestrictions(
       int param_count, FunctionLiteral::ArityRestriction arity_restriction,
       bool has_rest, int formals_start_pos, int formals_end_pos, bool* ok);
 
   // Checks if the expression is a valid reference expression (e.g., on the
   // left-hand side of assignments). Although ruled out by ECMA as early errors,
   // we allow calls for web compatibility and rewrite them to a runtime throw.
   ExpressionT CheckAndRewriteReferenceExpression(
       ExpressionT expression, Scanner::Location location,
@@ skipping 571 matching lines @@
   // Return the object itself as AstVisitor and implement the needed
   // dummy method right in this class.
   PreParserFactory* visitor() { return this; }
   int* ast_properties() {
     static int dummy = 42;
     return &dummy;
   }
 };
 
 
+struct PreParserFormalParameterParsingState {
+  explicit PreParserFormalParameterParsingState(Scope* scope)
+      : scope(scope), has_rest(false), is_simple_parameter_list(true) {}
+  Scope* scope;
+  bool has_rest;
+  bool is_simple_parameter_list;
+};
+
+
 class PreParser;
 
 class PreParserTraits {
  public:
   struct Type {
     // TODO(marja): To be removed. The Traits object should contain all the data
     // it needs.
     typedef PreParser* Parser;
 
     // PreParser doesn't need to store generator variables.
     typedef void GeneratorVariable;
 
     typedef int AstProperties;
 
     // Return types for traversing functions.
     typedef PreParserIdentifier Identifier;
     typedef PreParserExpression Expression;
     typedef PreParserExpression YieldExpression;
     typedef PreParserExpression FunctionLiteral;
     typedef PreParserExpression ClassLiteral;
     typedef PreParserExpression ObjectLiteralProperty;
     typedef PreParserExpression Literal;
     typedef PreParserExpressionList ExpressionList;
     typedef PreParserExpressionList PropertyList;
     typedef PreParserIdentifier FormalParameter;
     typedef PreParserStatementList StatementList;
+    typedef PreParserFormalParameterParsingState FormalParameterParsingState;
 
     // For constructing objects returned by the traversing functions.
     typedef PreParserFactory Factory;
   };
 
   explicit PreParserTraits(PreParser* pre_parser) : pre_parser_(pre_parser) {}
 
   // Helper functions for recursive descent.
   static bool IsEval(PreParserIdentifier identifier) {
     return identifier.IsEval();
@@ skipping 218 matching lines @@
   }
 
   static PreParserStatementList NewStatementList(int size, Zone* zone) {
     return PreParserStatementList();
   }
 
   static PreParserExpressionList NewPropertyList(int size, Zone* zone) {
     return PreParserExpressionList();
   }
 
+  static void AddParameterInitializationBlock(
+      const PreParserFormalParameterParsingState& formal_parameters,
+      PreParserStatementList list, bool* ok) {}
+
   V8_INLINE void SkipLazyFunctionBody(int* materialized_literal_count,
                                       int* expected_property_count, bool* ok) {
     UNREACHABLE();
   }
 
-  V8_INLINE PreParserStatementList
-  ParseEagerFunctionBody(PreParserIdentifier function_name, int pos,
-                         Variable* fvar, Token::Value fvar_init_op,
-                         FunctionKind kind, bool* ok);
+  V8_INLINE PreParserStatementList ParseEagerFunctionBody(
+      PreParserIdentifier function_name, int pos,
+      const PreParserFormalParameterParsingState& formal_parameters,
+      Variable* fvar, Token::Value fvar_init_op, FunctionKind kind, bool* ok);
 
   V8_INLINE void ParseArrowFunctionFormalParameters(
-      Scope* scope, PreParserExpression expression,
-      const Scanner::Location& params_loc, bool* has_rest,
+      PreParserFormalParameterParsingState* parsing_state,
+      PreParserExpression expression, const Scanner::Location& params_loc,
       Scanner::Location* duplicate_loc, bool* ok);
 
   struct TemplateLiteralState {};
 
   TemplateLiteralState OpenTemplateLiteral(int pos) {
     return TemplateLiteralState();
   }
   void AddTemplateSpan(TemplateLiteralState*, bool) {}
   void AddTemplateExpression(TemplateLiteralState*, PreParserExpression) {}
   PreParserExpression CloseTemplateLiteral(TemplateLiteralState*, int,
                                            PreParserExpression tag) {
     if (IsTaggedTemplate(tag)) {
       // Emulate generation of array literals for tag callsite
       // 1st is array of cooked strings, second is array of raw strings
       MaterializeTemplateCallsiteLiterals();
     }
     return EmptyExpression();
   }
   inline void MaterializeTemplateCallsiteLiterals();
   PreParserExpression NoTemplateTag() {
     return PreParserExpression::NoTemplateTag();
   }
   static bool IsTaggedTemplate(const PreParserExpression tag) {
     return !tag.IsNoTemplateTag();
   }
 
-  void DeclareFormalParameter(Scope* scope, PreParserExpression pattern,
+  void DeclareFormalParameter(void* parsing_state, PreParserExpression pattern,
                               ExpressionClassifier* classifier, bool is_rest) {}
 
   void CheckConflictingVarDeclarations(Scope* scope, bool* ok) {}
 
   // Temporary glue; these functions will move to ParserBase.
   PreParserExpression ParseV8Intrinsic(bool* ok);
   PreParserExpression ParseFunctionLiteral(
       PreParserIdentifier name, Scanner::Location function_name_location,
       bool name_is_strict_reserved, FunctionKind kind,
       int function_token_position, FunctionLiteral::FunctionType type,
@@ skipping 130 matching lines @@
   Statement ParseTryStatement(bool* ok);
   Statement ParseDebuggerStatement(bool* ok);
   Expression ParseConditionalExpression(bool accept_IN, bool* ok);
   Expression ParseObjectLiteral(bool* ok);
   Expression ParseV8Intrinsic(bool* ok);
 
   V8_INLINE void SkipLazyFunctionBody(int* materialized_literal_count,
                                       int* expected_property_count, bool* ok);
   V8_INLINE PreParserStatementList
   ParseEagerFunctionBody(PreParserIdentifier function_name, int pos,
+                         const FormalParameterParsingStateT& formal_parameters,
                          Variable* fvar, Token::Value fvar_init_op,
                          FunctionKind kind, bool* ok);
 
   Expression ParseFunctionLiteral(
       Identifier name, Scanner::Location function_name_location,
       bool name_is_strict_reserved, FunctionKind kind, int function_token_pos,
       FunctionLiteral::FunctionType function_type,
       FunctionLiteral::ArityRestriction arity_restriction, bool* ok);
   void ParseLazyFunctionLiteralBody(bool* ok,
                                     Scanner::BookmarkScope* bookmark = nullptr);
@@ skipping 25 matching lines @@
 }
 
 PreParserExpression PreParserTraits::SpreadCallNew(PreParserExpression function,
                                                    PreParserExpressionList args,
                                                    int pos) {
   return pre_parser_->factory()->NewCallNew(function, args, pos);
 }
 
 
 void PreParserTraits::ParseArrowFunctionFormalParameters(
-    Scope* scope, PreParserExpression params,
-    const Scanner::Location& params_loc, bool* has_rest,
+    PreParserFormalParameterParsingState* parsing_state,
+    PreParserExpression params, const Scanner::Location& params_loc,
     Scanner::Location* duplicate_loc, bool* ok) {
   // TODO(wingo): Detect duplicated identifiers in paramlists.  Detect parameter
   // lists that are too long.
 }
 
 
 PreParserStatementList PreParser::ParseEagerFunctionBody(
-    PreParserIdentifier function_name, int pos, Variable* fvar,
-    Token::Value fvar_init_op, FunctionKind kind, bool* ok) {
+    PreParserIdentifier function_name, int pos,
+    const PreParserFormalParameterParsingState& formal_parameters,
+    Variable* fvar, Token::Value fvar_init_op, FunctionKind kind, bool* ok) {
   ParsingModeScope parsing_mode(this, PARSE_EAGERLY);
 
   ParseStatementList(Token::RBRACE, ok);
   if (!*ok) return PreParserStatementList();
 
   Expect(Token::RBRACE, ok);
   return PreParserStatementList();
 }
 
 
 PreParserStatementList PreParserTraits::ParseEagerFunctionBody(
-    PreParserIdentifier function_name, int pos, Variable* fvar,
-    Token::Value fvar_init_op, FunctionKind kind, bool* ok) {
-  return pre_parser_->ParseEagerFunctionBody(function_name, pos, fvar,
-                                             fvar_init_op, kind, ok);
+    PreParserIdentifier function_name, int pos,
+    const PreParserFormalParameterParsingState& formal_parameters,
+    Variable* fvar, Token::Value fvar_init_op, FunctionKind kind, bool* ok) {
+  return pre_parser_->ParseEagerFunctionBody(
+      function_name, pos, formal_parameters, fvar, fvar_init_op, kind, ok);
 }
 
 
 template <class Traits>
 ParserBase<Traits>::FunctionState::FunctionState(
     FunctionState** function_state_stack, Scope** scope_stack, Scope* scope,
     FunctionKind kind, typename Traits::Type::Factory* factory)
     : next_materialized_literal_index_(0),
       expected_property_count_(0),
       this_location_(Scanner::Location::invalid()),
@@ skipping 363 matching lines @@
                                               Token::String(Token::RPAREN));
         // Give a good error to the user who might have typed e.g. "return();".
         if (peek() != Token::ARROW) {
           ReportUnexpectedTokenAt(scanner_->peek_location(), peek(),
                                   MessageTemplate::kMissingArrow);
           *ok = false;
           return this->EmptyExpression();
         }
         Scope* scope =
             this->NewScope(scope_, ARROW_SCOPE, FunctionKind::kArrowFunction);
+        FormalParameterParsingStateT parsing_state(scope);
         scope->set_start_position(beg_pos);
         ExpressionClassifier args_classifier;
-        bool has_rest = false;
-        result = this->ParseArrowFunctionLiteral(scope, has_rest,
-                                                 args_classifier, CHECK_OK);
+        result = this->ParseArrowFunctionLiteral(parsing_state, args_classifier,
+                                                 CHECK_OK);
       } else if (allow_harmony_arrow_functions() &&
                  allow_harmony_rest_params() && Check(Token::ELLIPSIS)) {
         // (...x) => y
         Scope* scope =
             this->NewScope(scope_, ARROW_SCOPE, FunctionKind::kArrowFunction);
+        FormalParameterParsingStateT parsing_state(scope);
         scope->set_start_position(beg_pos);
         ExpressionClassifier args_classifier;
-        const bool has_rest = true;
-        this->ParseFormalParameter(scope, has_rest, &args_classifier, CHECK_OK);
+        const bool is_rest = true;
+        this->ParseFormalParameter(is_rest, &parsing_state, &args_classifier,
+                                   CHECK_OK);
         if (peek() == Token::COMMA) {
           ReportMessageAt(scanner()->peek_location(),
                           MessageTemplate::kParamAfterRest);
           *ok = false;
           return this->EmptyExpression();
         }
         Expect(Token::RPAREN, CHECK_OK);
-        result = this->ParseArrowFunctionLiteral(scope, has_rest,
-                                                 args_classifier, CHECK_OK);
+        result = this->ParseArrowFunctionLiteral(parsing_state, args_classifier,
+                                                 CHECK_OK);
       } else {
         // Heuristically try to detect immediately called functions before
         // seeing the call parentheses.
         parenthesized_function_ = (peek() == Token::FUNCTION);
         result = this->ParseExpression(true, classifier, CHECK_OK);
         Expect(Token::RPAREN, CHECK_OK);
       }
       break;
 
     case Token::CLASS: {
@@ skipping 319 matching lines @@
         name_expression, value,
         is_get ? ObjectLiteralProperty::GETTER : ObjectLiteralProperty::SETTER,
         is_static, *is_computed_name);
 
   } else if (!in_class && allow_harmony_object_literals_ &&
              Token::IsIdentifier(name_token, language_mode(),
                                  this->is_generator())) {
     DCHECK(!*is_computed_name);
     DCHECK(!is_static);
 
+    if (classifier->duplicate_finder() != nullptr &&
+        scanner()->FindSymbol(classifier->duplicate_finder(), 1) != 0) {
+      classifier->RecordDuplicateFormalParameterError(scanner()->location());
+    }
+
     ExpressionT lhs = this->ExpressionFromIdentifier(
         name, next_beg_pos, next_end_pos, scope_, factory());
     if (peek() == Token::ASSIGN) {
       this->ExpressionUnexpectedToken(classifier);
       Consume(Token::ASSIGN);
       ExpressionClassifier rhs_classifier;
       ExpressionT rhs = this->ParseAssignmentExpression(
           true, &rhs_classifier, CHECK_OK_CUSTOM(EmptyObjectLiteralProperty));
       classifier->AccumulateReclassifyingAsPattern(rhs_classifier);
       value = factory()->NewAssignment(Token::ASSIGN, lhs, rhs,
@@ skipping 163 matching lines @@
   //   LeftHandSideExpression AssignmentOperator AssignmentExpression
 
   Scanner::Location lhs_location = scanner()->peek_location();
 
   if (peek() == Token::YIELD && is_generator()) {
     return this->ParseYieldExpression(classifier, ok);
   }
 
   if (fni_ != NULL) fni_->Enter();
   ParserBase<Traits>::Checkpoint checkpoint(this);
-  ExpressionClassifier arrow_formals_classifier;
+  ExpressionClassifier arrow_formals_classifier(classifier->duplicate_finder());
   if (peek() != Token::LPAREN) {
     // The expression we are going to read is not a parenthesized arrow function
     // formal parameter list.
     ArrowFormalParametersUnexpectedToken(&arrow_formals_classifier);
   }
   ExpressionT expression = this->ParseConditionalExpression(
       accept_IN, &arrow_formals_classifier, CHECK_OK);
 
   if (allow_harmony_arrow_functions() && peek() == Token::ARROW) {
     checkpoint.Restore();
     BindingPatternUnexpectedToken(classifier);
     ValidateArrowFormalParameters(&arrow_formals_classifier, expression,
                                   CHECK_OK);
     Scanner::Location loc(lhs_location.beg_pos, scanner()->location().end_pos);
     Scope* scope =
         this->NewScope(scope_, ARROW_SCOPE, FunctionKind::kArrowFunction);
     scope->set_start_position(lhs_location.beg_pos);
     Scanner::Location duplicate_loc = Scanner::Location::invalid();
-    bool has_rest = false;
-    this->ParseArrowFunctionFormalParameters(scope, expression, loc, &has_rest,
+    FormalParameterParsingStateT parsing_state(scope);
+    this->ParseArrowFunctionFormalParameters(&parsing_state, expression, loc,
                                              &duplicate_loc, CHECK_OK);
     if (duplicate_loc.IsValid()) {
       arrow_formals_classifier.RecordDuplicateFormalParameterError(
           duplicate_loc);
     }
     expression = this->ParseArrowFunctionLiteral(
-        scope, has_rest, arrow_formals_classifier, CHECK_OK);
+        parsing_state, arrow_formals_classifier, CHECK_OK);
     return expression;
   }
 
   // "expression" was not itself an arrow function parameter list, but it might
   // form part of one.  Propagate speculative formal parameter error locations.
   classifier->Accumulate(arrow_formals_classifier,
                          ExpressionClassifier::StandardProductions |
                              ExpressionClassifier::FormalParametersProductions);
 
   if (!Token::IsAssignmentOp(peek())) {
@@ skipping 742 matching lines @@
       default:
         return expression;
     }
   }
   DCHECK(false);
   return this->EmptyExpression();
 }
 
 
 template <class Traits>
-void ParserBase<Traits>::ParseFormalParameter(Scope* scope, bool is_rest,
-                                              ExpressionClassifier* classifier,
-                                              bool* ok) {
+void ParserBase<Traits>::ParseFormalParameter(
+    bool is_rest, FormalParameterParsingStateT* parsing_state,
+    ExpressionClassifier* classifier, bool* ok) {
   // FormalParameter[Yield,GeneratorParameter] :
   //   BindingElement[?Yield, ?GeneratorParameter]
 
   Token::Value next = peek();
   ExpressionT pattern = ParsePrimaryExpression(classifier, ok);
   if (!*ok) return;
 
   ValidateBindingPattern(classifier, ok);
   if (!*ok) return;
 
   if (!allow_harmony_destructuring() && !Traits::IsIdentifier(pattern)) {
     ReportUnexpectedToken(next);
     *ok = false;
     return;
   }
 
-  Traits::DeclareFormalParameter(scope, pattern, classifier, is_rest);
+  if (parsing_state->is_simple_parameter_list) {
+    parsing_state->is_simple_parameter_list =
+        !is_rest && Traits::IsIdentifier(pattern);
+  }
+  parsing_state->has_rest = is_rest;
+  if (is_rest && !Traits::IsIdentifier(pattern)) {
+    ReportUnexpectedToken(next);
+    *ok = false;
+    return;
+  }
+  Traits::DeclareFormalParameter(parsing_state, pattern, classifier, is_rest);
 }
 
 
 template <class Traits>
 int ParserBase<Traits>::ParseFormalParameterList(
-    Scope* scope, bool* is_rest, ExpressionClassifier* classifier, bool* ok) {
+    FormalParameterParsingStateT* parsing_state,
+    ExpressionClassifier* classifier, bool* ok) {
   // FormalParameters[Yield,GeneratorParameter] :
   //   [empty]
   //   FormalParameterList[?Yield, ?GeneratorParameter]
   //
   // FormalParameterList[Yield,GeneratorParameter] :
   //   FunctionRestParameter[?Yield]
   //   FormalsList[?Yield, ?GeneratorParameter]
   //   FormalsList[?Yield, ?GeneratorParameter] , FunctionRestParameter[?Yield]
   //
   // FormalsList[Yield,GeneratorParameter] :
   //   FormalParameter[?Yield, ?GeneratorParameter]
   //   FormalsList[?Yield, ?GeneratorParameter] ,
   //     FormalParameter[?Yield,?GeneratorParameter]
 
   int parameter_count = 0;
 
   if (peek() != Token::RPAREN) {
     do {
       if (++parameter_count > Code::kMaxArguments) {
         ReportMessage(MessageTemplate::kTooManyParameters);
         *ok = false;
         return -1;
       }
-      *is_rest = allow_harmony_rest_params() && Check(Token::ELLIPSIS);
-      ParseFormalParameter(scope, *is_rest, classifier, ok);
+      bool is_rest = allow_harmony_rest_params() && Check(Token::ELLIPSIS);
+      ParseFormalParameter(is_rest, parsing_state, classifier, ok);
       if (!*ok) return -1;
-    } while (!*is_rest && Check(Token::COMMA));
+    } while (!parsing_state->has_rest && Check(Token::COMMA));
 
-    if (*is_rest && peek() == Token::COMMA) {
+    if (parsing_state->has_rest && peek() == Token::COMMA) {
       ReportMessageAt(scanner()->peek_location(),
                       MessageTemplate::kParamAfterRest);
       *ok = false;
       return -1;
     }
   }
 
   return parameter_count;
 }
 
@@ skipping 24 matching lines @@
       break;
     default:
       break;
   }
 }
 
 
 template <class Traits>
 typename ParserBase<Traits>::ExpressionT
 ParserBase<Traits>::ParseArrowFunctionLiteral(
-    Scope* scope, bool has_rest, const ExpressionClassifier& formals_classifier,
-    bool* ok) {
+    const FormalParameterParsingStateT& formal_parameters,
+    const ExpressionClassifier& formals_classifier, bool* ok) {
   if (peek() == Token::ARROW && scanner_->HasAnyLineTerminatorBeforeNext()) {
     // ASI inserts `;` after arrow parameters if a line terminator is found.
     // `=> ...` is never a valid expression, so report as syntax error.
     // If next token is not `=>`, it's a syntax error anyways.
     ReportUnexpectedTokenAt(scanner_->peek_location(), Token::ARROW);
     *ok = false;
     return this->EmptyExpression();
   }
 
   typename Traits::Type::StatementList body;
-  int num_parameters = scope->num_parameters();
+  int num_parameters = formal_parameters.scope->num_parameters();
   int materialized_literal_count = -1;
   int expected_property_count = -1;
   Scanner::Location super_loc;
 
   {
     typename Traits::Type::Factory function_factory(ast_value_factory());
-    FunctionState function_state(&function_state_, &scope_, scope,
-                                 kArrowFunction, &function_factory);
+    FunctionState function_state(&function_state_, &scope_,
+                                 formal_parameters.scope, kArrowFunction,
+                                 &function_factory);
 
     Expect(Token::ARROW, CHECK_OK);
 
     if (peek() == Token::LBRACE) {
       // Multiple statement body
       Consume(Token::LBRACE);
       bool is_lazily_parsed =
           (mode() == PARSE_LAZILY && scope_->AllowsLazyCompilation());
       if (is_lazily_parsed) {
         body = this->NewStatementList(0, zone());
         this->SkipLazyFunctionBody(&materialized_literal_count,
                                    &expected_property_count, CHECK_OK);
       } else {
         body = this->ParseEagerFunctionBody(
-            this->EmptyIdentifier(), RelocInfo::kNoPosition, NULL,
-            Token::INIT_VAR, kArrowFunction, CHECK_OK);
+            this->EmptyIdentifier(), RelocInfo::kNoPosition, formal_parameters,
+            NULL, Token::INIT_VAR, kArrowFunction, CHECK_OK);
         materialized_literal_count =
             function_state.materialized_literal_count();
         expected_property_count = function_state.expected_property_count();
       }
     } else {
       // Single-expression body
       int pos = position();
       parenthesized_function_ = false;
       ExpressionClassifier classifier;
       ExpressionT expression =
           ParseAssignmentExpression(true, &classifier, CHECK_OK);
       ValidateExpression(&classifier, CHECK_OK);
       body = this->NewStatementList(1, zone());
+      this->AddParameterInitializationBlock(formal_parameters, body, CHECK_OK);
       body->Add(factory()->NewReturnStatement(expression, pos), zone());
       materialized_literal_count = function_state.materialized_literal_count();
       expected_property_count = function_state.expected_property_count();
     }
     super_loc = function_state.super_location();
 
-    scope->set_end_position(scanner()->location().end_pos);
+    formal_parameters.scope->set_end_position(scanner()->location().end_pos);
 
     // Arrow function formal parameters are parsed as StrictFormalParameterList,
     // which is not the same as "parameters of a strict function"; it only means
     // that duplicates are not allowed.  Of course, the arrow function may
     // itself be strict as well.
     const bool allow_duplicate_parameters = false;
     this->ValidateFormalParameters(&formals_classifier, language_mode(),
                                    allow_duplicate_parameters, CHECK_OK);
 
     // Validate strict mode.
     if (is_strict(language_mode())) {
-      CheckStrictOctalLiteral(scope->start_position(),
+      CheckStrictOctalLiteral(formal_parameters.scope->start_position(),
                               scanner()->location().end_pos, CHECK_OK);
-      this->CheckConflictingVarDeclarations(scope, CHECK_OK);
+      this->CheckConflictingVarDeclarations(formal_parameters.scope, CHECK_OK);
     }
   }
 
   FunctionLiteralT function_literal = factory()->NewFunctionLiteral(
-      this->EmptyIdentifierString(), ast_value_factory(), scope, body,
-      materialized_literal_count, expected_property_count, num_parameters,
+      this->EmptyIdentifierString(), ast_value_factory(),
+      formal_parameters.scope, body, materialized_literal_count,
+      expected_property_count, num_parameters,
       FunctionLiteral::kNoDuplicateParameters,
       FunctionLiteral::ANONYMOUS_EXPRESSION, FunctionLiteral::kIsFunction,
       FunctionLiteral::kShouldLazyCompile, FunctionKind::kArrowFunction,
-      scope->start_position());
+      formal_parameters.scope->start_position());
 
-  function_literal->set_function_token_position(scope->start_position());
+  function_literal->set_function_token_position(
+      formal_parameters.scope->start_position());
   if (super_loc.IsValid()) function_state_->set_super_location(super_loc);
 
   if (fni_ != NULL) this->InferFunctionName(fni_, function_literal);
 
   return function_literal;
 }
 
 
 template <typename Traits>
 typename ParserBase<Traits>::ExpressionT
@@ skipping 180 matching lines @@
       *ok = false;
       return;
     }
     has_seen_constructor_ = true;
     return;
   }
 }
 } }  // v8::internal
 
 #endif  // V8_PREPARSER_H