Revert "Factor formal argument parsing into ParserBase"

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"
 #include "src/func-name-inferrer.h"
 #include "src/hashmap.h"
 #include "src/scanner.h"
 #include "src/scopes.h"
 #include "src/token.h"
 
 namespace v8 {
 namespace internal {
 
-
-// When parsing the formal parameters of a function, we usually don't yet know
-// if the function will be strict, so we cannot yet produce errors for
-// parameter names or duplicates.  Instead, we remember the locations of these
-// errors if they occur and produce the errors later.
-class FormalParameterErrorLocations BASE_EMBEDDED {
- public:
-  FormalParameterErrorLocations()
-      : eval_or_arguments(Scanner::Location::invalid()),
-        undefined(Scanner::Location::invalid()),
-        duplicate(Scanner::Location::invalid()),
-        reserved(Scanner::Location::invalid()) {}
-
-  Scanner::Location eval_or_arguments;
-  Scanner::Location undefined;
-  Scanner::Location duplicate;
-  Scanner::Location reserved;
-};
-
-
 // Common base class shared between parser and pre-parser. Traits encapsulate
 // the differences between Parser and PreParser:
 
 // - Return types: For example, Parser functions return Expression* and
 // PreParser functions return PreParserExpression.
 
 // - Creating parse tree nodes: Parser generates an AST during the recursive
 // descent. PreParser doesn't create a tree. Instead, it passes around minimal
 // data objects (PreParserExpression, PreParserIdentifier etc.) which contain
 // just enough data for the upper layer functions. PreParserFactory is
@@ skipping 14 matching lines @@
 //     typedef GeneratorVariable;
 //     // Return types for traversing functions.
 //     typedef Identifier;
 //     typedef Expression;
 //     typedef FunctionLiteral;
 //     typedef ClassLiteral;
 //     typedef ObjectLiteralProperty;
 //     typedef Literal;
 //     typedef ExpressionList;
 //     typedef PropertyList;
-//     typedef FormalParameter;
-//     typedef FormalParameterList;
 //     // For constructing objects returned by the traversing functions.
 //     typedef Factory;
 //   };
 //   // ...
 // };
 
 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::FormalParameterList FormalParameterListT;
   typedef typename Traits::Type::FunctionLiteral FunctionLiteralT;
   typedef typename Traits::Type::Literal LiteralT;
   typedef typename Traits::Type::ObjectLiteralProperty ObjectLiteralPropertyT;
 
   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),
@@ skipping 412 matching lines @@
       Traits::ReportMessageAt(function_name_loc, "strong_undefined");
       *ok = false;
       return;
     }
   }
 
   // Checking the parameter names of a function literal. This has to be done
   // after parsing the function, since the function can declare itself strict.
   void CheckFunctionParameterNames(LanguageMode language_mode,
                                    bool strict_params,
-                                   const FormalParameterErrorLocations& locs,
+                                   const Scanner::Location& eval_args_loc,
+                                   const Scanner::Location& undefined_loc,
+                                   const Scanner::Location& dupe_loc,
+                                   const Scanner::Location& reserved_loc,
                                    bool* ok) {
     if (is_sloppy(language_mode) && !strict_params) return;
-    if (is_strict(language_mode) && locs.eval_or_arguments.IsValid()) {
-      Traits::ReportMessageAt(locs.eval_or_arguments, "strict_eval_arguments");
+    if (is_strict(language_mode) && eval_args_loc.IsValid()) {
+      Traits::ReportMessageAt(eval_args_loc, "strict_eval_arguments");
       *ok = false;
       return;
     }
-    if (is_strict(language_mode) && locs.reserved.IsValid()) {
-      Traits::ReportMessageAt(locs.reserved, "unexpected_strict_reserved");
-      *ok = false;
-      return;
-    }
-    if (is_strong(language_mode) && locs.undefined.IsValid()) {
-      Traits::ReportMessageAt(locs.undefined, "strong_undefined");
+    if (is_strong(language_mode) && undefined_loc.IsValid()) {
+      Traits::ReportMessageAt(undefined_loc, "strong_undefined");
       *ok = false;
       return;
     }
     // TODO(arv): When we add support for destructuring in setters we also need
     // to check for duplicate names.
-    if (locs.duplicate.IsValid()) {
-      Traits::ReportMessageAt(locs.duplicate, "strict_param_dupe");
+    if (dupe_loc.IsValid()) {
+      Traits::ReportMessageAt(dupe_loc, "strict_param_dupe");
       *ok = false;
       return;
     }
+    if (reserved_loc.IsValid()) {
+      Traits::ReportMessageAt(reserved_loc, "unexpected_strict_reserved");
+      *ok = false;
+      return;
+    }
   }
 
   // Determine precedence of given token.
   static int Precedence(Token::Value token, bool accept_IN) {
     if (token == Token::IN && !accept_IN)
       return 0;  // 0 precedence will terminate binary expression parsing
     return Token::Precedence(token);
   }
 
   typename Traits::Type::Factory* factory() {
@@ skipping 57 matching lines @@
   ExpressionT ParseYieldExpression(bool* ok);
   ExpressionT ParseConditionalExpression(bool accept_IN, bool* ok);
   ExpressionT ParseBinaryExpression(int prec, bool accept_IN, bool* ok);
   ExpressionT ParseUnaryExpression(bool* ok);
   ExpressionT ParsePostfixExpression(bool* ok);
   ExpressionT ParseLeftHandSideExpression(bool* ok);
   ExpressionT ParseMemberWithNewPrefixesExpression(bool* ok);
   ExpressionT ParseMemberExpression(bool* ok);
   ExpressionT ParseMemberExpressionContinuation(ExpressionT expression,
                                                 bool* ok);
-  ExpressionT ParseArrowFunctionLiteral(
-      int start_pos, FormalParameterListT params,
-      const FormalParameterErrorLocations& error_locs, bool has_rest, bool* ok);
+  ExpressionT ParseArrowFunctionLiteral(int start_pos, ExpressionT params_ast,
+                                        bool* ok);
   ExpressionT ParseTemplateLiteral(ExpressionT tag, int start, bool* ok);
   void AddTemplateExpression(ExpressionT);
   ExpressionT ParseSuperExpression(bool is_new, bool* ok);
 
-  FormalParameterT ParseFormalParameter(DuplicateFinder* duplicate_finder,
-                                        FormalParameterErrorLocations* locs,
-                                        bool* ok);
-  FormalParameterListT ParseFormalParameterList(
-      FormalParameterErrorLocations* locs, bool* is_rest, bool* ok);
-  void CheckArityRestrictions(
-      int param_count, FunctionLiteral::ArityRestriction arity_restriction,
-      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, const char* message, bool* ok);
 
   // Used to validate property names in object literals and class literals
   enum PropertyKind {
     kAccessorProperty,
@@ skipping 189 matching lines @@
     ValidArrowParam valid_arrow_param_list =
         (op == Token::COMMA && !left.is_parenthesized() &&
          !right.is_parenthesized()) ?
              std::min(left.ValidateArrowParams(), right.ValidateArrowParams())
              : kInvalidArrowParam;
     return PreParserExpression(
         TypeField::encode(kBinaryOperationExpression) |
         IsValidArrowParamListField::encode(valid_arrow_param_list));
   }
 
+  static PreParserExpression EmptyArrowParamList() {
+    // Any expression for which IsValidArrowParamList() returns true
+    // will work here.
+    return FromIdentifier(PreParserIdentifier::Default());
+  }
+
   static PreParserExpression StringLiteral() {
     return PreParserExpression(TypeField::encode(kStringLiteralExpression));
   }
 
   static PreParserExpression UseStrictStringLiteral() {
     return PreParserExpression(TypeField::encode(kStringLiteralExpression) |
                                IsUseStrictField::encode(true));
   }
 
   static PreParserExpression UseStrongStringLiteral() {
@@ skipping 70 matching lines @@
 
   bool IsCall() const {
     return TypeField::decode(code_) == kExpression &&
            ExpressionTypeField::decode(code_) == kCallExpression;
   }
 
   bool IsValidReferenceExpression() const {
     return IsIdentifier() || IsProperty();
   }
 
-  bool IsValidArrowParamList(FormalParameterErrorLocations* locs,
-                             const Scanner::Location& params_loc) const {
+  bool IsValidArrowParamList(Scanner::Location* undefined_loc) const {
     ValidArrowParam valid = ValidateArrowParams();
     if (ParenthesizationField::decode(code_) == kMultiParenthesizedExpression) {
       return false;
     }
-    switch (valid) {
-      case kInvalidArrowParam:
-        return false;
-      case kInvalidStrongArrowParam:
-        locs->undefined = params_loc;
-        return true;
-      case kInvalidStrictReservedArrowParam:
-        locs->reserved = params_loc;
-        return true;
-      case kInvalidStrictEvalArgumentsArrowParam:
-        locs->eval_or_arguments = params_loc;
-        return true;
-      default:
-        DCHECK_EQ(valid, kValidArrowParam);
-        return true;
+    if (valid == kValidArrowParam) {
+      return true;
+    } else if (valid == kInvalidStrongArrowParam) {
+      // Return true for now regardless of strong mode for compatibility with
+      // parser.
+      *undefined_loc = Scanner::Location();
+      return true;
+    } else {
+      return false;
     }
   }
 
   // At the moment PreParser doesn't track these expression types.
   bool IsFunctionLiteral() const { return false; }
   bool IsCallNew() const { return false; }
 
   bool IsNoTemplateTag() const {
     return TypeField::decode(code_) == kExpression &&
            ExpressionTypeField::decode(code_) == kNoTemplateTagExpression;
@@ skipping 46 matching lines @@
   };
 
   enum ExpressionType {
     kThisExpression,
     kThisPropertyExpression,
     kPropertyExpression,
     kCallExpression,
     kNoTemplateTagExpression
   };
 
-  // These validity constraints are ordered such that a value of N implies lack
-  // of errors M < N.
   enum ValidArrowParam {
     kInvalidArrowParam,
-    kInvalidStrictEvalArgumentsArrowParam,
-    kInvalidStrictReservedArrowParam,
     kInvalidStrongArrowParam,
     kValidArrowParam
   };
 
   explicit PreParserExpression(uint32_t expression_code)
       : code_(expression_code) {}
 
   V8_INLINE ValidArrowParam ValidateArrowParams() const {
     if (IsBinaryOperation()) {
       return IsValidArrowParamListField::decode(code_);
     }
     if (!IsIdentifier()) {
       return kInvalidArrowParam;
     }
     PreParserIdentifier ident = AsIdentifier();
-    // In strict mode, eval and arguments are not valid formal parameter names.
-    if (ident.IsEval() || ident.IsArguments()) {
-      return kInvalidStrictEvalArgumentsArrowParam;
+    // A valid identifier can be an arrow function parameter
+    // except for eval, arguments, yield, and reserved keywords.
+    if (ident.IsEval() || ident.IsArguments() ||
+        ident.IsFutureStrictReserved()) {
+      return kInvalidArrowParam;
     }
-    // In strict mode, future reserved words are not valid either, and as they
-    // produce different errors we allot them their own error code.
-    if (ident.IsFutureStrictReserved()) {
-      return kInvalidStrictReservedArrowParam;
-    }
-    // In strong mode, 'undefined' isn't a valid formal parameter name either.
+    // In strong mode, 'undefined' is similarly restricted.
     if (ident.IsUndefined()) {
       return kInvalidStrongArrowParam;
     }
     return kValidArrowParam;
   }
 
   // The first five bits are for the Type and Parenthesization.
   typedef BitField<Type, 0, 3> TypeField;
   typedef BitField<Parenthesization, TypeField::kNext, 2> ParenthesizationField;
 
   // The rest of the bits are interpreted depending on the value
   // of the Type field, so they can share the storage.
   typedef BitField<ExpressionType, ParenthesizationField::kNext, 3>
       ExpressionTypeField;
   typedef BitField<bool, ParenthesizationField::kNext, 1> IsUseStrictField;
   typedef BitField<bool, IsUseStrictField::kNext, 1> IsUseStrongField;
-  typedef BitField<ValidArrowParam, ParenthesizationField::kNext, 3>
+  typedef BitField<ValidArrowParam, ParenthesizationField::kNext, 2>
       IsValidArrowParamListField;
   typedef BitField<PreParserIdentifier::Type, ParenthesizationField::kNext, 10>
       IdentifierTypeField;
 
   uint32_t code_;
 };
 
 
-// The pre-parser doesn't need to build lists of expressions, identifiers, or
-// the like.
-template <typename T>
-class PreParserList {
+// PreParserExpressionList doesn't actually store the expressions because
+// PreParser doesn't need to.
+class PreParserExpressionList {
  public:
   // These functions make list->Add(some_expression) work (and do nothing).
-  PreParserList() : length_(0) {}
-  PreParserList* operator->() { return this; }
-  void Add(T, void*) { ++length_; }
+  PreParserExpressionList() : length_(0) {}
+  PreParserExpressionList* operator->() { return this; }
+  void Add(PreParserExpression, void*) { ++length_; }
   int length() const { return length_; }
  private:
   int length_;
 };
 
 
-typedef PreParserList<PreParserExpression> PreParserExpressionList;
-typedef PreParserList<PreParserIdentifier> PreParserFormalParameterList;
-
-
 class PreParserStatement {
  public:
   static PreParserStatement Default() {
     return PreParserStatement(kUnknownStatement);
   }
 
   static PreParserStatement Jump() {
     return PreParserStatement(kJumpStatement);
   }
 
@@ skipping 44 matching lines @@
     kUseStrictExpressionStatement,
     kUseStrongExpressionStatement,
     kFunctionDeclaration
   };
 
   explicit PreParserStatement(Type code) : code_(code) {}
   Type code_;
 };
 
 
-typedef PreParserList<PreParserStatement> PreParserStatementList;
+
+// PreParserStatementList doesn't actually store the statements because
+// the PreParser does not need them.
+class PreParserStatementList {
+ public:
+  // These functions make list->Add(some_expression) work as no-ops.
+  PreParserStatementList() {}
+  PreParserStatementList* operator->() { return this; }
+  void Add(PreParserStatement, void*) {}
+};
 
 
 class PreParserFactory {
  public:
   explicit PreParserFactory(void* unused_value_factory) {}
   PreParserExpression NewStringLiteral(PreParserIdentifier identifier,
                                        int pos) {
     return PreParserExpression::Default();
   }
   PreParserExpression NewNumberLiteral(double number,
@@ skipping 144 matching lines @@
     // 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 PreParserFormalParameterList FormalParameterList;
     typedef PreParserStatementList StatementList;
 
     // 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) {
@@ skipping 123 matching lines @@
   // "null" return type creators.
   static PreParserIdentifier EmptyIdentifier() {
     return PreParserIdentifier::Default();
   }
   static PreParserIdentifier EmptyIdentifierString() {
     return PreParserIdentifier::Default();
   }
   static PreParserExpression EmptyExpression() {
     return PreParserExpression::Default();
   }
+  static PreParserExpression EmptyArrowParamList() {
+    return PreParserExpression::EmptyArrowParamList();
+  }
   static PreParserExpression EmptyLiteral() {
     return PreParserExpression::Default();
   }
   static PreParserExpression EmptyObjectLiteralProperty() {
     return PreParserExpression::Default();
   }
   static PreParserExpression EmptyFunctionLiteral() {
     return PreParserExpression::Default();
   }
   static PreParserExpressionList NullExpressionList() {
     return PreParserExpressionList();
   }
-  static PreParserIdentifier EmptyFormalParameter() {
-    return PreParserIdentifier::Default();
-  }
-  static PreParserFormalParameterList NullFormalParameterList() {
-    return PreParserFormalParameterList();
-  }
 
   // Odd-ball literal creators.
   static PreParserExpression GetLiteralTheHole(int position,
                                                PreParserFactory* factory) {
     return PreParserExpression::Default();
   }
 
   // Producing data during the recursive descent.
   PreParserIdentifier GetSymbol(Scanner* scanner);
   PreParserIdentifier GetNumberAsSymbol(Scanner* scanner);
@@ skipping 44 matching lines @@
   }
 
   static PreParserStatementList NewStatementList(int size, Zone* zone) {
     return PreParserStatementList();
   }
 
   static PreParserExpressionList NewPropertyList(int size, Zone* zone) {
     return PreParserExpressionList();
   }
 
-  static PreParserFormalParameterList NewFormalParameterList(int size,
-                                                             Zone* zone) {
-    return PreParserFormalParameterList();
-  }
-
   V8_INLINE void SkipLazyFunctionBody(PreParserIdentifier function_name,
                                       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 PreParserFormalParameterList ParseArrowFunctionFormalParameterList(
-      PreParserExpression expression, const Scanner::Location& params_loc,
-      FormalParameterErrorLocations* error_locs, bool* is_rest, bool* ok);
+  // Utility functions
+  int DeclareArrowParametersFromExpression(PreParserExpression expression,
+                                           Scope* scope,
+                                           Scanner::Location* undefined_loc,
+                                           Scanner::Location* dupe_loc,
+                                           bool* ok) {
+    // TODO(aperez): Detect duplicated identifiers in paramlists.
+    *ok = expression.IsValidArrowParamList(undefined_loc);
+    return 0;
+  }
 
   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();
   }
 
-  int DeclareFormalParameters(PreParserFormalParameterList params, Scope* scope,
-                              bool has_rest) {
-    return params->length();
-  }
-
   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,
       FunctionLiteral::ArityRestriction arity_restriction, bool* ok);
 
@@ skipping 168 matching lines @@
   return pre_parser_->factory()->NewCall(function, args, pos);
 }
 
 PreParserExpression PreParserTraits::SpreadCallNew(PreParserExpression function,
                                                    PreParserExpressionList args,
                                                    int pos) {
   return pre_parser_->factory()->NewCallNew(function, args, pos);
 }
 
 
-PreParserFormalParameterList
-PreParserTraits::ParseArrowFunctionFormalParameterList(
-    PreParserExpression params, const Scanner::Location& params_loc,
-    FormalParameterErrorLocations* error_locs, bool* is_rest, bool* ok) {
-  // TODO(wingo): Detect duplicated identifiers in paramlists.  Detect parameter
-  // lists that are too long.
-  if (!params.IsValidArrowParamList(error_locs, params_loc)) {
-    *ok = false;
-    ReportMessageAt(params_loc, "malformed_arrow_function_parameter_list");
-    return this->NullFormalParameterList();
-  }
-
-  return PreParserFormalParameterList();
-}
-
-
 PreParserStatementList PreParser::ParseEagerFunctionBody(
     PreParserIdentifier function_name, int pos, 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();
@@ skipping 275 matching lines @@
     case Token::LBRACK:
       result = this->ParseArrayLiteral(CHECK_OK);
       break;
 
     case Token::LBRACE:
       result = this->ParseObjectLiteral(CHECK_OK);
       break;
 
     case Token::LPAREN:
       Consume(Token::LPAREN);
-      if (allow_harmony_arrow_functions() && Check(Token::RPAREN)) {
-        // As a primary expression, the only thing that can follow "()" is "=>".
-        FormalParameterListT params = this->NewFormalParameterList(0, zone());
-        FormalParameterErrorLocations error_locs;
-        bool has_rest = false;
-        result = this->ParseArrowFunctionLiteral(beg_pos, params, error_locs,
-                                                 has_rest, CHECK_OK);
+      if (allow_harmony_arrow_functions() && peek() == Token::RPAREN) {
+        // Arrow functions are the only expression type constructions
+        // for which an empty parameter list "()" is valid input.
+        Consume(Token::RPAREN);
+        result = this->ParseArrowFunctionLiteral(
+            beg_pos, this->EmptyArrowParamList(), CHECK_OK);
       } else {
         // Heuristically try to detect immediately called functions before
         // seeing the call parentheses.
         parenthesized_function_ = (peek() == Token::FUNCTION);
         result = this->ParseExpression(true, CHECK_OK);
         result->increase_parenthesization_level();
         Expect(Token::RPAREN, CHECK_OK);
       }
       break;
 
@@ skipping 437 matching lines @@
     return this->ParseYieldExpression(ok);
   }
 
   if (fni_ != NULL) fni_->Enter();
   ParserBase<Traits>::Checkpoint checkpoint(this);
   ExpressionT expression =
       this->ParseConditionalExpression(accept_IN, CHECK_OK);
 
   if (allow_harmony_arrow_functions() && peek() == Token::ARROW) {
     checkpoint.Restore();
-    FormalParameterErrorLocations error_locs;
-    Scanner::Location loc(lhs_location.beg_pos, scanner()->location().end_pos);
-    bool has_rest = false;
-    FormalParameterListT params = this->ParseArrowFunctionFormalParameterList(
-        expression, loc, &error_locs, &has_rest, CHECK_OK);
-    expression = this->ParseArrowFunctionLiteral(
-        lhs_location.beg_pos, params, error_locs, has_rest, CHECK_OK);
+    expression = this->ParseArrowFunctionLiteral(lhs_location.beg_pos,
+                                                 expression, CHECK_OK);
     return expression;
   }
 
   if (!Token::IsAssignmentOp(peek())) {
     if (fni_ != NULL) fni_->Leave();
     // Parsed conditional expression only (no assignment).
     return expression;
   }
 
   expression = this->CheckAndRewriteReferenceExpression(
@@ skipping 513 matching lines @@
       default:
         return expression;
     }
   }
   DCHECK(false);
   return this->EmptyExpression();
 }
 
 
 template <class Traits>
-typename ParserBase<Traits>::FormalParameterT
-ParserBase<Traits>::ParseFormalParameter(DuplicateFinder* duplicate_finder,
-                                         FormalParameterErrorLocations* locs,
-                                         bool* ok) {
-  // FormalParameter[Yield,GeneratorParameter] :
-  //   BindingElement[?Yield, ?GeneratorParameter]
-  bool is_strict_reserved;
-  IdentifierT name =
-      ParseIdentifierOrStrictReservedWord(&is_strict_reserved, ok);
-  if (!*ok) return this->EmptyFormalParameter();
-
-  // Store locations for possible future error reports.
-  if (!locs->eval_or_arguments.IsValid() && this->IsEvalOrArguments(name)) {
-    locs->eval_or_arguments = scanner()->location();
-  }
-  if (!locs->undefined.IsValid() && this->IsUndefined(name)) {
-    locs->undefined = scanner()->location();
-  }
-  if (!locs->reserved.IsValid() && is_strict_reserved) {
-    locs->reserved = scanner()->location();
-  }
-  if (!locs->duplicate.IsValid() && duplicate_finder != nullptr) {
-    int prev_value = scanner()->FindSymbol(duplicate_finder, 1);
-    if (prev_value != 0) locs->duplicate = scanner()->location();
-  }
-
-  return name;
-}
-
-
-template <class Traits>
-typename ParserBase<Traits>::FormalParameterListT
-ParserBase<Traits>::ParseFormalParameterList(
-    FormalParameterErrorLocations* locs, bool* is_rest, 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]
-
-  FormalParameterListT result = this->NewFormalParameterList(4, zone_);
-  DuplicateFinder duplicate_finder(scanner()->unicode_cache());
-
-  if (peek() != Token::RPAREN) {
-    do {
-      *is_rest = allow_harmony_rest_params() && Check(Token::ELLIPSIS);
-      FormalParameterT param =
-          ParseFormalParameter(&duplicate_finder, locs, ok);
-      if (!*ok) return this->NullFormalParameterList();
-      result->Add(param, zone());
-      if (result->length() > Code::kMaxArguments) {
-        ReportMessage("too_many_parameters");
-        *ok = false;
-        return this->NullFormalParameterList();
-      }
-    } while (!*is_rest && Check(Token::COMMA));
-  }
-
-  if (is_rest && peek() == Token::COMMA) {
-    ReportMessageAt(scanner()->peek_location(), "param_after_rest");
-    *ok = false;
-    return this->NullFormalParameterList();
-  }
-
-  return result;
-}
-
-
-template <class Traits>
-void ParserBase<Traits>::CheckArityRestrictions(
-    int param_count, FunctionLiteral::ArityRestriction arity_restriction,
-    int formals_start_pos, int formals_end_pos, bool* ok) {
-  switch (arity_restriction) {
-    case FunctionLiteral::GETTER_ARITY:
-      if (param_count != 0) {
-        ReportMessageAt(Scanner::Location(formals_start_pos, formals_end_pos),
-                        "bad_getter_arity");
-        *ok = false;
-      }
-      break;
-    case FunctionLiteral::SETTER_ARITY:
-      if (param_count != 1) {
-        ReportMessageAt(Scanner::Location(formals_start_pos, formals_end_pos),
-                        "bad_setter_arity");
-        *ok = false;
-      }
-      break;
-    default:
-      break;
-  }
-}
-
-
-template <class Traits>
 typename ParserBase<Traits>::ExpressionT
-ParserBase<Traits>::ParseArrowFunctionLiteral(
-    int start_pos, FormalParameterListT params,
-    const FormalParameterErrorLocations& error_locs, bool has_rest, bool* ok) {
+ParserBase<Traits>::ParseArrowFunctionLiteral(int start_pos,
+                                              ExpressionT params_ast,
+                                              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();
   }
 
   Scope* scope = this->NewScope(scope_, ARROW_SCOPE);
   typename Traits::Type::StatementList body;
   int num_parameters = -1;
   int materialized_literal_count = -1;
   int expected_property_count = -1;
   int handler_count = 0;
   Scanner::Location super_loc;
 
   {
     typename Traits::Type::Factory function_factory(ast_value_factory());
     FunctionState function_state(&function_state_, &scope_, scope,
                                  kArrowFunction, &function_factory);
-    num_parameters = this->DeclareFormalParameters(params, scope_, has_rest);
+    Scanner::Location undefined_loc = Scanner::Location::invalid();
+    Scanner::Location dupe_loc = Scanner::Location::invalid();
+    // TODO(arv): Pass in eval_args_loc and reserved_loc here.
+    num_parameters = Traits::DeclareArrowParametersFromExpression(
+        params_ast, scope_, &undefined_loc, &dupe_loc, ok);
+    if (!*ok) {
+      ReportMessageAt(
+          Scanner::Location(start_pos, scanner()->location().beg_pos),
+          "malformed_arrow_function_parameter_list");
+      return this->EmptyExpression();
+    }
+
+    if (undefined_loc.IsValid()) {
+      // Workaround for preparser not keeping track of positions.
+      undefined_loc = Scanner::Location(start_pos,
+                                        scanner()->location().end_pos);
+    }
+    if (num_parameters > Code::kMaxArguments) {
+      ReportMessageAt(Scanner::Location(params_ast->position(), position()),
+                      "too_many_parameters");
+      *ok = false;
+      return this->EmptyExpression();
+    }
 
     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());
@@ skipping 18 matching lines @@
       body->Add(factory()->NewReturnStatement(expression, pos), zone());
       materialized_literal_count = function_state.materialized_literal_count();
       expected_property_count = function_state.expected_property_count();
       handler_count = function_state.handler_count();
     }
     super_loc = function_state.super_call_location();
 
     scope->set_start_position(start_pos);
     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.
+    // Arrow function *parameter lists* are always checked as in strict mode.
+    // TODO(arv): eval_args_loc and reserved_loc needs to be set by
+    // DeclareArrowParametersFromExpression.
+    Scanner::Location eval_args_loc = Scanner::Location::invalid();
+    Scanner::Location reserved_loc = Scanner::Location::invalid();
     const bool use_strict_params = true;
     this->CheckFunctionParameterNames(language_mode(), use_strict_params,
-                                      error_locs, CHECK_OK);
+                                      eval_args_loc, undefined_loc, dupe_loc,
+                                      reserved_loc, CHECK_OK);
 
     // Validate strict mode.
     if (is_strict(language_mode())) {
       CheckStrictOctalLiteral(start_pos, scanner()->location().end_pos,
                               CHECK_OK);
       this->CheckConflictingVarDeclarations(scope, CHECK_OK);
     }
   }
 
   FunctionLiteralT function_literal = factory()->NewFunctionLiteral(
@@ skipping 192 matching lines @@
       *ok = false;
       return;
     }
     has_seen_constructor_ = true;
     return;
   }
 }
 } }  // v8::internal
 
 #endif  // V8_PREPARSER_H