Allow eval/arguments in arrow functions

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 509 matching lines @@
   void CheckFunctionParameterNames(LanguageMode language_mode,
                                    bool strict_params,
                                    const FormalParameterErrorLocations& locs,
                                    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");
       *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");
       *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");
       *ok = false;
       return;
     }
-    if (locs.reserved.IsValid()) {
-      Traits::ReportMessageAt(locs.reserved, "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, ExpressionT params_ast,
-                                        bool* ok);
+  ExpressionT ParseArrowFunctionLiteral(
+      Scope* function_scope, const FormalParameterErrorLocations& error_locs,
+      bool has_rest, bool* ok);
   ExpressionT ParseTemplateLiteral(ExpressionT tag, int start, bool* ok);
   void AddTemplateExpression(ExpressionT);
   ExpressionT ParseSuperExpression(bool is_new, bool* ok);
 
   void ParseFormalParameter(FormalParameterScopeT* scope,
                             FormalParameterErrorLocations* locs, bool is_rest,
                             bool* ok);
   int ParseFormalParameterList(FormalParameterScopeT* scope,
                                FormalParameterErrorLocations* locs,
                                bool* has_rest, bool* ok);
@@ skipping 203 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 {
+  bool IsValidArrowParamList(FormalParameterErrorLocations* locs,
+                             const Scanner::Location& params_loc) const {
     ValidArrowParam valid = ValidateArrowParams();
     if (ParenthesizationField::decode(code_) == kMultiParenthesizedExpression) {
       return false;
     }
-    if (valid == kValidArrowParam) {
-      return true;
-    } else if (valid == kInvalidStrongArrowParam) {
-      // Return true for now regardless of strong mode for compatibility with
-      // parser.
-      locs->undefined = Scanner::Location();
-      return true;
-    } else {
-      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;
     }
   }
 
   // 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();
-    // 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, eval and arguments are not valid formal parameter names.
+    if (ident.IsEval() || ident.IsArguments()) {
+      return kInvalidStrictEvalArgumentsArrowParam;
     }
-    // In strong mode, 'undefined' is similarly restricted.
+    // 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.
     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, 2>
+  typedef BitField<ValidArrowParam, ParenthesizationField::kNext, 3>
       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.
@@ skipping 380 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() {
@@ skipping 67 matching lines @@
                                       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);
 
-  // Utility functions
-  V8_INLINE int DeclareArrowParametersFromExpression(
-      PreParserExpression expression, Scope* scope,
-      FormalParameterErrorLocations* locs, bool* ok) {
-    // TODO(wingo): Detect duplicated identifiers in paramlists.  Detect eval or
-    // arguments.  Detect reserved words.
-    *ok = expression.IsValidArrowParamList(locs);
-    return 0;
-  }
+  V8_INLINE void ParseArrowFunctionFormalParameters(
+      Scope* scope, PreParserExpression expression,
+      const Scanner::Location& params_loc,
+      FormalParameterErrorLocations* error_locs, bool* is_rest, bool* ok);
 
   struct TemplateLiteralState {};
 
   TemplateLiteralState OpenTemplateLiteral(int pos) {
     return TemplateLiteralState();
   }
   void AddTemplateSpan(TemplateLiteralState*, bool) {}
   void AddTemplateExpression(TemplateLiteralState*, PreParserExpression) {}
   PreParserExpression CloseTemplateLiteral(TemplateLiteralState*, int,
                                            PreParserExpression tag) {
@@ skipping 204 matching lines @@
 }
 
 
 bool PreParserTraits::DeclareFormalParameter(
     DuplicateFinder* duplicate_finder, PreParserIdentifier current_identifier,
     bool is_rest) {
   return pre_parser_->scanner()->FindSymbol(duplicate_finder, 1) != 0;
 }
 
 
+void PreParserTraits::ParseArrowFunctionFormalParameters(
+    Scope* scope, 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;
+  }
+}
+
+
 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() && 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);
+      if (allow_harmony_arrow_functions() && Check(Token::RPAREN)) {
+        // As a primary expression, the only thing that can follow "()" is "=>".
+        Scope* scope = this->NewScope(scope_, ARROW_SCOPE);
+        scope->set_start_position(beg_pos);
+        FormalParameterErrorLocations error_locs;
+        bool has_rest = false;
+        result = this->ParseArrowFunctionLiteral(scope, error_locs, has_rest,
+                                                 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();
-    expression = this->ParseArrowFunctionLiteral(lhs_location.beg_pos,
-                                                 expression, CHECK_OK);
+    FormalParameterErrorLocations error_locs;
+    Scanner::Location loc(lhs_location.beg_pos, scanner()->location().end_pos);
+    bool has_rest = false;
+    Scope* scope = this->NewScope(scope_, ARROW_SCOPE);
+    scope->set_start_position(lhs_location.beg_pos);
+    this->ParseArrowFunctionFormalParameters(scope, expression, loc,
+                                             &error_locs, &has_rest, CHECK_OK);
+    expression =
+        this->ParseArrowFunctionLiteral(scope, error_locs, has_rest, 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 607 matching lines @@
         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,
-                                              ExpressionT params_ast,
-                                              bool* ok) {
+ParserBase<Traits>::ParseArrowFunctionLiteral(
+    Scope* scope, const FormalParameterErrorLocations& error_locs,
+    bool has_rest, 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 num_parameters = scope->num_parameters();
   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);
-    FormalParameterErrorLocations error_locs;
-    num_parameters = Traits::DeclareArrowParametersFromExpression(
-        params_ast, scope_, &error_locs, ok);
-    if (!*ok) {
-      ReportMessageAt(
-          Scanner::Location(start_pos, scanner()->location().beg_pos),
-          "malformed_arrow_function_parameter_list");
-      return this->EmptyExpression();
-    }
-
-    if (error_locs.undefined.IsValid()) {
-      // Workaround for preparser not keeping track of positions.
-      error_locs.undefined =
-          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 15 matching lines @@
       parenthesized_function_ = false;
       ExpressionT expression = ParseAssignmentExpression(true, CHECK_OK);
       body = this->NewStatementList(1, zone());
       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.
     const bool use_strict_params = true;
     this->CheckFunctionParameterNames(language_mode(), use_strict_params,
                                       error_locs, CHECK_OK);
 
     // Validate strict mode.
     if (is_strict(language_mode())) {
-      CheckStrictOctalLiteral(start_pos, scanner()->location().end_pos,
-                              CHECK_OK);
+      CheckStrictOctalLiteral(scope->start_position(),
+                              scanner()->location().end_pos, CHECK_OK);
       this->CheckConflictingVarDeclarations(scope, CHECK_OK);
     }
   }
 
   FunctionLiteralT function_literal = factory()->NewFunctionLiteral(
       this->EmptyIdentifierString(), ast_value_factory(), scope, body,
       materialized_literal_count, expected_property_count, handler_count,
       num_parameters, FunctionLiteral::kNoDuplicateParameters,
       FunctionLiteral::ANONYMOUS_EXPRESSION, FunctionLiteral::kIsFunction,
       FunctionLiteral::kNotParenthesized, FunctionKind::kArrowFunction,
-      start_pos);
+      scope->start_position());
 
-  function_literal->set_function_token_position(start_pos);
+  function_literal->set_function_token_position(scope->start_position());
   if (super_loc.IsValid()) function_state_->set_super_call_location(super_loc);
 
   if (fni_ != NULL) this->InferFunctionName(fni_, function_literal);
 
   return function_literal;
 }
 
 
 template <typename Traits>
 typename ParserBase<Traits>::ExpressionT
@@ skipping 174 matching lines @@
       *ok = false;
       return;
     }
     has_seen_constructor_ = true;
     return;
   }
 }
 } }  // v8::internal
 
 #endif  // V8_PREPARSER_H