root/src/preparser.cc

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DEFINITIONS

This source file includes following definitions.
  1. PreParseLazyFunction
  2. ReportUnexpectedToken
  3. CheckOctalLiteral
  4. ParseSourceElement
  5. ParseSourceElements
  6. ParseStatement
  7. ParseFunctionDeclaration
  8. ParseBlock
  9. ParseVariableStatement
  10. ParseVariableDeclarations
  11. ParseExpressionOrLabelledStatement
  12. ParseIfStatement
  13. ParseContinueStatement
  14. ParseBreakStatement
  15. ParseReturnStatement
  16. ParseWithStatement
  17. ParseSwitchStatement
  18. ParseDoWhileStatement
  19. ParseWhileStatement
  20. ParseForStatement
  21. ParseThrowStatement
  22. ParseTryStatement
  23. ParseDebuggerStatement
  24. ParseExpression
  25. ParseAssignmentExpression
  26. ParseConditionalExpression
  27. Precedence
  28. ParseBinaryExpression
  29. ParseUnaryExpression
  30. ParsePostfixExpression
  31. ParseLeftHandSideExpression
  32. ParseNewExpression
  33. ParseMemberExpression
  34. ParseMemberWithNewPrefixesExpression
  35. ParsePrimaryExpression
  36. ParseArrayLiteral
  37. CheckDuplicate
  38. ParseObjectLiteral
  39. ParseRegExpLiteral
  40. ParseArguments
  41. ParseFunctionLiteral
  42. ParseLazyFunctionLiteralBody
  43. ParseV8Intrinsic
  44. ExpectSemicolon
  45. LogSymbol
  46. GetStringSymbol
  47. GetIdentifierSymbol
  48. ParseIdentifier
  49. SetStrictModeViolation
  50. CheckDelayedStrictModeViolation
  51. StrictModeIdentifierViolation
  52. ParseIdentifierName
  53. ParseIdentifierNameOrGetOrSet
  54. peek_any_identifier
  55. AddAsciiSymbol
  56. AddUtf16Symbol
  57. AddSymbol
  58. AddNumber
  59. IsNumberCanonical
  60. Hash
  61. Match
  62. BackupKey

// Copyright 2011 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
//       copyright notice, this list of conditions and the following
//       disclaimer in the documentation and/or other materials provided
//       with the distribution.
//     * Neither the name of Google Inc. nor the names of its
//       contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#include <math.h>

#include "../include/v8stdint.h"

#include "allocation.h"
#include "checks.h"
#include "conversions.h"
#include "conversions-inl.h"
#include "globals.h"
#include "hashmap.h"
#include "list.h"
#include "preparse-data-format.h"
#include "preparse-data.h"
#include "preparser.h"
#include "unicode.h"
#include "utils.h"

namespace v8 {

#ifdef _MSC_VER
// Usually defined in math.h, but not in MSVC.
// Abstracted to work
int isfinite(double value);
#endif

namespace preparser {

PreParser::PreParseResult PreParser::PreParseLazyFunction(
    i::LanguageMode mode, i::ParserRecorder* log) {
  log_ = log;
  // Lazy functions always have trivial outer scopes (no with/catch scopes).
  Scope top_scope(&scope_, kTopLevelScope);
  set_language_mode(mode);
  Scope function_scope(&scope_, kFunctionScope);
  ASSERT_EQ(i::Token::LBRACE, scanner_->current_token());
  bool ok = true;
  int start_position = scanner_->peek_location().beg_pos;
  ParseLazyFunctionLiteralBody(&ok);
  if (stack_overflow_) return kPreParseStackOverflow;
  if (!ok) {
    ReportUnexpectedToken(scanner_->current_token());
  } else {
    ASSERT_EQ(i::Token::RBRACE, scanner_->peek());
    if (!is_classic_mode()) {
      int end_pos = scanner_->location().end_pos;
      CheckOctalLiteral(start_position, end_pos, &ok);
      if (ok) {
        CheckDelayedStrictModeViolation(start_position, end_pos, &ok);
      }
    }
  }
  return kPreParseSuccess;
}


// Preparsing checks a JavaScript program and emits preparse-data that helps
// a later parsing to be faster.
// See preparser-data.h for the data.

// The PreParser checks that the syntax follows the grammar for JavaScript,
// and collects some information about the program along the way.
// The grammar check is only performed in order to understand the program
// sufficiently to deduce some information about it, that can be used
// to speed up later parsing. Finding errors is not the goal of pre-parsing,
// rather it is to speed up properly written and correct programs.
// That means that contextual checks (like a label being declared where
// it is used) are generally omitted.

void PreParser::ReportUnexpectedToken(i::Token::Value token) {
  // We don't report stack overflows here, to avoid increasing the
  // stack depth even further.  Instead we report it after parsing is
  // over, in ParseProgram.
  if (token == i::Token::ILLEGAL && stack_overflow_) {
    return;
  }
  i::Scanner::Location source_location = scanner_->location();

  // Four of the tokens are treated specially
  switch (token) {
  case i::Token::EOS:
    return ReportMessageAt(source_location, "unexpected_eos", NULL);
  case i::Token::NUMBER:
    return ReportMessageAt(source_location, "unexpected_token_number", NULL);
  case i::Token::STRING:
    return ReportMessageAt(source_location, "unexpected_token_string", NULL);
  case i::Token::IDENTIFIER:
    return ReportMessageAt(source_location,
                           "unexpected_token_identifier", NULL);
  case i::Token::FUTURE_RESERVED_WORD:
    return ReportMessageAt(source_location, "unexpected_reserved", NULL);
  case i::Token::FUTURE_STRICT_RESERVED_WORD:
    return ReportMessageAt(source_location,
                           "unexpected_strict_reserved", NULL);
  default:
    const char* name = i::Token::String(token);
    ReportMessageAt(source_location, "unexpected_token", name);
  }
}


// Checks whether octal literal last seen is between beg_pos and end_pos.
// If so, reports an error.
void PreParser::CheckOctalLiteral(int beg_pos, int end_pos, bool* ok) {
  i::Scanner::Location octal = scanner_->octal_position();
  if (beg_pos <= octal.beg_pos && octal.end_pos <= end_pos) {
    ReportMessageAt(octal, "strict_octal_literal", NULL);
    scanner_->clear_octal_position();
    *ok = false;
  }
}


#define CHECK_OK  ok);                      \
  if (!*ok) return kUnknownSourceElements;  \
  ((void)0
#define DUMMY )  // to make indentation work
#undef DUMMY


PreParser::Statement PreParser::ParseSourceElement(bool* ok) {
  // (Ecma 262 5th Edition, clause 14):
  // SourceElement:
  //    Statement
  //    FunctionDeclaration
  //
  // In harmony mode we allow additionally the following productions
  // SourceElement:
  //    LetDeclaration
  //    ConstDeclaration

  switch (peek()) {
    case i::Token::FUNCTION:
      return ParseFunctionDeclaration(ok);
    case i::Token::LET:
    case i::Token::CONST:
      return ParseVariableStatement(kSourceElement, ok);
    default:
      return ParseStatement(ok);
  }
}


PreParser::SourceElements PreParser::ParseSourceElements(int end_token,
                                                         bool* ok) {
  // SourceElements ::
  //   (Statement)* <end_token>

  bool allow_directive_prologue = true;
  while (peek() != end_token) {
    Statement statement = ParseSourceElement(CHECK_OK);
    if (allow_directive_prologue) {
      if (statement.IsUseStrictLiteral()) {
        set_language_mode(harmony_scoping_ ?
                          i::EXTENDED_MODE : i::STRICT_MODE);
      } else if (!statement.IsStringLiteral()) {
        allow_directive_prologue = false;
      }
    }
  }
  return kUnknownSourceElements;
}


#undef CHECK_OK
#define CHECK_OK  ok);                   \
  if (!*ok) return Statement::Default();  \
  ((void)0
#define DUMMY )  // to make indentation work
#undef DUMMY


PreParser::Statement PreParser::ParseStatement(bool* ok) {
  // Statement ::
  //   Block
  //   VariableStatement
  //   EmptyStatement
  //   ExpressionStatement
  //   IfStatement
  //   IterationStatement
  //   ContinueStatement
  //   BreakStatement
  //   ReturnStatement
  //   WithStatement
  //   LabelledStatement
  //   SwitchStatement
  //   ThrowStatement
  //   TryStatement
  //   DebuggerStatement

  // Note: Since labels can only be used by 'break' and 'continue'
  // statements, which themselves are only valid within blocks,
  // iterations or 'switch' statements (i.e., BreakableStatements),
  // labels can be simply ignored in all other cases; except for
  // trivial labeled break statements 'label: break label' which is
  // parsed into an empty statement.

  // Keep the source position of the statement
  switch (peek()) {
    case i::Token::LBRACE:
      return ParseBlock(ok);

    case i::Token::CONST:
    case i::Token::LET:
    case i::Token::VAR:
      return ParseVariableStatement(kStatement, ok);

    case i::Token::SEMICOLON:
      Next();
      return Statement::Default();

    case i::Token::IF:
      return ParseIfStatement(ok);

    case i::Token::DO:
      return ParseDoWhileStatement(ok);

    case i::Token::WHILE:
      return ParseWhileStatement(ok);

    case i::Token::FOR:
      return ParseForStatement(ok);

    case i::Token::CONTINUE:
      return ParseContinueStatement(ok);

    case i::Token::BREAK:
      return ParseBreakStatement(ok);

    case i::Token::RETURN:
      return ParseReturnStatement(ok);

    case i::Token::WITH:
      return ParseWithStatement(ok);

    case i::Token::SWITCH:
      return ParseSwitchStatement(ok);

    case i::Token::THROW:
      return ParseThrowStatement(ok);

    case i::Token::TRY:
      return ParseTryStatement(ok);

    case i::Token::FUNCTION: {
      i::Scanner::Location start_location = scanner_->peek_location();
      Statement statement = ParseFunctionDeclaration(CHECK_OK);
      i::Scanner::Location end_location = scanner_->location();
      if (!is_classic_mode()) {
        ReportMessageAt(start_location.beg_pos, end_location.end_pos,
                        "strict_function", NULL);
        *ok = false;
        return Statement::Default();
      } else {
        return statement;
      }
    }

    case i::Token::DEBUGGER:
      return ParseDebuggerStatement(ok);

    default:
      return ParseExpressionOrLabelledStatement(ok);
  }
}


PreParser::Statement PreParser::ParseFunctionDeclaration(bool* ok) {
  // FunctionDeclaration ::
  //   'function' Identifier '(' FormalParameterListopt ')' '{' FunctionBody '}'
  Expect(i::Token::FUNCTION, CHECK_OK);

  Identifier identifier = ParseIdentifier(CHECK_OK);
  i::Scanner::Location location = scanner_->location();

  Expression function_value = ParseFunctionLiteral(CHECK_OK);

  if (function_value.IsStrictFunction() &&
      !identifier.IsValidStrictVariable()) {
    // Strict mode violation, using either reserved word or eval/arguments
    // as name of strict function.
    const char* type = "strict_function_name";
    if (identifier.IsFutureStrictReserved()) {
      type = "strict_reserved_word";
    }
    ReportMessageAt(location, type, NULL);
    *ok = false;
  }
  return Statement::FunctionDeclaration();
}


PreParser::Statement PreParser::ParseBlock(bool* ok) {
  // Block ::
  //   '{' Statement* '}'

  // Note that a Block does not introduce a new execution scope!
  // (ECMA-262, 3rd, 12.2)
  //
  Expect(i::Token::LBRACE, CHECK_OK);
  while (peek() != i::Token::RBRACE) {
    if (is_extended_mode()) {
      ParseSourceElement(CHECK_OK);
    } else {
      ParseStatement(CHECK_OK);
    }
  }
  Expect(i::Token::RBRACE, ok);
  return Statement::Default();
}


PreParser::Statement PreParser::ParseVariableStatement(
    VariableDeclarationContext var_context,
    bool* ok) {
  // VariableStatement ::
  //   VariableDeclarations ';'

  Statement result = ParseVariableDeclarations(var_context,
                                               NULL,
                                               NULL,
                                               CHECK_OK);
  ExpectSemicolon(CHECK_OK);
  return result;
}


// If the variable declaration declares exactly one non-const
// variable, then *var is set to that variable. In all other cases,
// *var is untouched; in particular, it is the caller's responsibility
// to initialize it properly. This mechanism is also used for the parsing
// of 'for-in' loops.
PreParser::Statement PreParser::ParseVariableDeclarations(
    VariableDeclarationContext var_context,
    VariableDeclarationProperties* decl_props,
    int* num_decl,
    bool* ok) {
  // VariableDeclarations ::
  //   ('var' | 'const') (Identifier ('=' AssignmentExpression)?)+[',']
  //
  // The ES6 Draft Rev3 specifies the following grammar for const declarations
  //
  // ConstDeclaration ::
  //   const ConstBinding (',' ConstBinding)* ';'
  // ConstBinding ::
  //   Identifier '=' AssignmentExpression
  //
  // TODO(ES6):
  // ConstBinding ::
  //   BindingPattern '=' AssignmentExpression
  bool require_initializer = false;
  if (peek() == i::Token::VAR) {
    Consume(i::Token::VAR);
  } else if (peek() == i::Token::CONST) {
    // TODO(ES6): The ES6 Draft Rev4 section 12.2.2 reads:
    //
    // ConstDeclaration : const ConstBinding (',' ConstBinding)* ';'
    //
    // * It is a Syntax Error if the code that matches this production is not
    //   contained in extended code.
    //
    // However disallowing const in classic mode will break compatibility with
    // existing pages. Therefore we keep allowing const with the old
    // non-harmony semantics in classic mode.
    Consume(i::Token::CONST);
    switch (language_mode()) {
      case i::CLASSIC_MODE:
        break;
      case i::STRICT_MODE: {
        i::Scanner::Location location = scanner_->peek_location();
        ReportMessageAt(location, "strict_const", NULL);
        *ok = false;
        return Statement::Default();
      }
      case i::EXTENDED_MODE:
        if (var_context != kSourceElement &&
            var_context != kForStatement) {
          i::Scanner::Location location = scanner_->peek_location();
          ReportMessageAt(location.beg_pos, location.end_pos,
                          "unprotected_const", NULL);
          *ok = false;
          return Statement::Default();
        }
        require_initializer = true;
        break;
    }
  } else if (peek() == i::Token::LET) {
    // ES6 Draft Rev4 section 12.2.1:
    //
    // LetDeclaration : let LetBindingList ;
    //
    // * It is a Syntax Error if the code that matches this production is not
    //   contained in extended code.
    if (!is_extended_mode()) {
      i::Scanner::Location location = scanner_->peek_location();
      ReportMessageAt(location.beg_pos, location.end_pos,
                      "illegal_let", NULL);
      *ok = false;
      return Statement::Default();
    }
    Consume(i::Token::LET);
    if (var_context != kSourceElement &&
        var_context != kForStatement) {
      i::Scanner::Location location = scanner_->peek_location();
      ReportMessageAt(location.beg_pos, location.end_pos,
                      "unprotected_let", NULL);
      *ok = false;
      return Statement::Default();
    }
  } else {
    *ok = false;
    return Statement::Default();
  }

  // The scope of a var/const declared variable anywhere inside a function
  // is the entire function (ECMA-262, 3rd, 10.1.3, and 12.2). The scope
  // of a let declared variable is the scope of the immediately enclosing
  // block.
  int nvars = 0;  // the number of variables declared
  do {
    // Parse variable name.
    if (nvars > 0) Consume(i::Token::COMMA);
    Identifier identifier  = ParseIdentifier(CHECK_OK);
    if (!is_classic_mode() && !identifier.IsValidStrictVariable()) {
      StrictModeIdentifierViolation(scanner_->location(),
                                    "strict_var_name",
                                    identifier,
                                    ok);
      return Statement::Default();
    }
    nvars++;
    if (peek() == i::Token::ASSIGN || require_initializer) {
      Expect(i::Token::ASSIGN, CHECK_OK);
      ParseAssignmentExpression(var_context != kForStatement, CHECK_OK);
      if (decl_props != NULL) *decl_props = kHasInitializers;
    }
  } while (peek() == i::Token::COMMA);

  if (num_decl != NULL) *num_decl = nvars;
  return Statement::Default();
}


PreParser::Statement PreParser::ParseExpressionOrLabelledStatement(bool* ok) {
  // ExpressionStatement | LabelledStatement ::
  //   Expression ';'
  //   Identifier ':' Statement

  Expression expr = ParseExpression(true, CHECK_OK);
  if (expr.IsRawIdentifier()) {
    ASSERT(!expr.AsIdentifier().IsFutureReserved());
    ASSERT(is_classic_mode() || !expr.AsIdentifier().IsFutureStrictReserved());
    if (peek() == i::Token::COLON) {
      Consume(i::Token::COLON);
      return ParseStatement(ok);
    }
    // Preparsing is disabled for extensions (because the extension details
    // aren't passed to lazily compiled functions), so we don't
    // accept "native function" in the preparser.
  }
  // Parsed expression statement.
  ExpectSemicolon(CHECK_OK);
  return Statement::ExpressionStatement(expr);
}


PreParser::Statement PreParser::ParseIfStatement(bool* ok) {
  // IfStatement ::
  //   'if' '(' Expression ')' Statement ('else' Statement)?

  Expect(i::Token::IF, CHECK_OK);
  Expect(i::Token::LPAREN, CHECK_OK);
  ParseExpression(true, CHECK_OK);
  Expect(i::Token::RPAREN, CHECK_OK);
  ParseStatement(CHECK_OK);
  if (peek() == i::Token::ELSE) {
    Next();
    ParseStatement(CHECK_OK);
  }
  return Statement::Default();
}


PreParser::Statement PreParser::ParseContinueStatement(bool* ok) {
  // ContinueStatement ::
  //   'continue' [no line terminator] Identifier? ';'

  Expect(i::Token::CONTINUE, CHECK_OK);
  i::Token::Value tok = peek();
  if (!scanner_->HasAnyLineTerminatorBeforeNext() &&
      tok != i::Token::SEMICOLON &&
      tok != i::Token::RBRACE &&
      tok != i::Token::EOS) {
    ParseIdentifier(CHECK_OK);
  }
  ExpectSemicolon(CHECK_OK);
  return Statement::Default();
}


PreParser::Statement PreParser::ParseBreakStatement(bool* ok) {
  // BreakStatement ::
  //   'break' [no line terminator] Identifier? ';'

  Expect(i::Token::BREAK, CHECK_OK);
  i::Token::Value tok = peek();
  if (!scanner_->HasAnyLineTerminatorBeforeNext() &&
      tok != i::Token::SEMICOLON &&
      tok != i::Token::RBRACE &&
      tok != i::Token::EOS) {
    ParseIdentifier(CHECK_OK);
  }
  ExpectSemicolon(CHECK_OK);
  return Statement::Default();
}


PreParser::Statement PreParser::ParseReturnStatement(bool* ok) {
  // ReturnStatement ::
  //   'return' [no line terminator] Expression? ';'

  // Consume the return token. It is necessary to do the before
  // reporting any errors on it, because of the way errors are
  // reported (underlining).
  Expect(i::Token::RETURN, CHECK_OK);

  // An ECMAScript program is considered syntactically incorrect if it
  // contains a return statement that is not within the body of a
  // function. See ECMA-262, section 12.9, page 67.
  // This is not handled during preparsing.

  i::Token::Value tok = peek();
  if (!scanner_->HasAnyLineTerminatorBeforeNext() &&
      tok != i::Token::SEMICOLON &&
      tok != i::Token::RBRACE &&
      tok != i::Token::EOS) {
    ParseExpression(true, CHECK_OK);
  }
  ExpectSemicolon(CHECK_OK);
  return Statement::Default();
}


PreParser::Statement PreParser::ParseWithStatement(bool* ok) {
  // WithStatement ::
  //   'with' '(' Expression ')' Statement
  Expect(i::Token::WITH, CHECK_OK);
  if (!is_classic_mode()) {
    i::Scanner::Location location = scanner_->location();
    ReportMessageAt(location, "strict_mode_with", NULL);
    *ok = false;
    return Statement::Default();
  }
  Expect(i::Token::LPAREN, CHECK_OK);
  ParseExpression(true, CHECK_OK);
  Expect(i::Token::RPAREN, CHECK_OK);

  Scope::InsideWith iw(scope_);
  ParseStatement(CHECK_OK);
  return Statement::Default();
}


PreParser::Statement PreParser::ParseSwitchStatement(bool* ok) {
  // SwitchStatement ::
  //   'switch' '(' Expression ')' '{' CaseClause* '}'

  Expect(i::Token::SWITCH, CHECK_OK);
  Expect(i::Token::LPAREN, CHECK_OK);
  ParseExpression(true, CHECK_OK);
  Expect(i::Token::RPAREN, CHECK_OK);

  Expect(i::Token::LBRACE, CHECK_OK);
  i::Token::Value token = peek();
  while (token != i::Token::RBRACE) {
    if (token == i::Token::CASE) {
      Expect(i::Token::CASE, CHECK_OK);
      ParseExpression(true, CHECK_OK);
    } else {
      Expect(i::Token::DEFAULT, CHECK_OK);
    }
    Expect(i::Token::COLON, CHECK_OK);
    token = peek();
    while (token != i::Token::CASE &&
           token != i::Token::DEFAULT &&
           token != i::Token::RBRACE) {
      ParseStatement(CHECK_OK);
      token = peek();
    }
  }
  Expect(i::Token::RBRACE, ok);
  return Statement::Default();
}


PreParser::Statement PreParser::ParseDoWhileStatement(bool* ok) {
  // DoStatement ::
  //   'do' Statement 'while' '(' Expression ')' ';'

  Expect(i::Token::DO, CHECK_OK);
  ParseStatement(CHECK_OK);
  Expect(i::Token::WHILE, CHECK_OK);
  Expect(i::Token::LPAREN, CHECK_OK);
  ParseExpression(true, CHECK_OK);
  Expect(i::Token::RPAREN, ok);
  if (peek() == i::Token::SEMICOLON) Consume(i::Token::SEMICOLON);
  return Statement::Default();
}


PreParser::Statement PreParser::ParseWhileStatement(bool* ok) {
  // WhileStatement ::
  //   'while' '(' Expression ')' Statement

  Expect(i::Token::WHILE, CHECK_OK);
  Expect(i::Token::LPAREN, CHECK_OK);
  ParseExpression(true, CHECK_OK);
  Expect(i::Token::RPAREN, CHECK_OK);
  ParseStatement(ok);
  return Statement::Default();
}


PreParser::Statement PreParser::ParseForStatement(bool* ok) {
  // ForStatement ::
  //   'for' '(' Expression? ';' Expression? ';' Expression? ')' Statement

  Expect(i::Token::FOR, CHECK_OK);
  Expect(i::Token::LPAREN, CHECK_OK);
  if (peek() != i::Token::SEMICOLON) {
    if (peek() == i::Token::VAR || peek() == i::Token::CONST ||
        peek() == i::Token::LET) {
      bool is_let = peek() == i::Token::LET;
      int decl_count;
      VariableDeclarationProperties decl_props = kHasNoInitializers;
      ParseVariableDeclarations(
          kForStatement, &decl_props, &decl_count, CHECK_OK);
      bool accept_IN = decl_count == 1 &&
          !(is_let && decl_props == kHasInitializers);
      if (peek() == i::Token::IN && accept_IN) {
        Expect(i::Token::IN, CHECK_OK);
        ParseExpression(true, CHECK_OK);
        Expect(i::Token::RPAREN, CHECK_OK);

        ParseStatement(CHECK_OK);
        return Statement::Default();
      }
    } else {
      ParseExpression(false, CHECK_OK);
      if (peek() == i::Token::IN) {
        Expect(i::Token::IN, CHECK_OK);
        ParseExpression(true, CHECK_OK);
        Expect(i::Token::RPAREN, CHECK_OK);

        ParseStatement(CHECK_OK);
        return Statement::Default();
      }
    }
  }

  // Parsed initializer at this point.
  Expect(i::Token::SEMICOLON, CHECK_OK);

  if (peek() != i::Token::SEMICOLON) {
    ParseExpression(true, CHECK_OK);
  }
  Expect(i::Token::SEMICOLON, CHECK_OK);

  if (peek() != i::Token::RPAREN) {
    ParseExpression(true, CHECK_OK);
  }
  Expect(i::Token::RPAREN, CHECK_OK);

  ParseStatement(ok);
  return Statement::Default();
}


PreParser::Statement PreParser::ParseThrowStatement(bool* ok) {
  // ThrowStatement ::
  //   'throw' [no line terminator] Expression ';'

  Expect(i::Token::THROW, CHECK_OK);
  if (scanner_->HasAnyLineTerminatorBeforeNext()) {
    i::Scanner::Location pos = scanner_->location();
    ReportMessageAt(pos, "newline_after_throw", NULL);
    *ok = false;
    return Statement::Default();
  }
  ParseExpression(true, CHECK_OK);
  ExpectSemicolon(ok);
  return Statement::Default();
}


PreParser::Statement PreParser::ParseTryStatement(bool* ok) {
  // TryStatement ::
  //   'try' Block Catch
  //   'try' Block Finally
  //   'try' Block Catch Finally
  //
  // Catch ::
  //   'catch' '(' Identifier ')' Block
  //
  // Finally ::
  //   'finally' Block

  // In preparsing, allow any number of catch/finally blocks, including zero
  // of both.

  Expect(i::Token::TRY, CHECK_OK);

  ParseBlock(CHECK_OK);

  bool catch_or_finally_seen = false;
  if (peek() == i::Token::CATCH) {
    Consume(i::Token::CATCH);
    Expect(i::Token::LPAREN, CHECK_OK);
    Identifier id = ParseIdentifier(CHECK_OK);
    if (!is_classic_mode() && !id.IsValidStrictVariable()) {
      StrictModeIdentifierViolation(scanner_->location(),
                                    "strict_catch_variable",
                                    id,
                                    ok);
      return Statement::Default();
    }
    Expect(i::Token::RPAREN, CHECK_OK);
    { Scope::InsideWith iw(scope_);
      ParseBlock(CHECK_OK);
    }
    catch_or_finally_seen = true;
  }
  if (peek() == i::Token::FINALLY) {
    Consume(i::Token::FINALLY);
    ParseBlock(CHECK_OK);
    catch_or_finally_seen = true;
  }
  if (!catch_or_finally_seen) {
    *ok = false;
  }
  return Statement::Default();
}


PreParser::Statement PreParser::ParseDebuggerStatement(bool* ok) {
  // In ECMA-262 'debugger' is defined as a reserved keyword. In some browser
  // contexts this is used as a statement which invokes the debugger as if a
  // break point is present.
  // DebuggerStatement ::
  //   'debugger' ';'

  Expect(i::Token::DEBUGGER, CHECK_OK);
  ExpectSemicolon(ok);
  return Statement::Default();
}


#undef CHECK_OK
#define CHECK_OK  ok);                     \
  if (!*ok) return Expression::Default();  \
  ((void)0
#define DUMMY )  // to make indentation work
#undef DUMMY


// Precedence = 1
PreParser::Expression PreParser::ParseExpression(bool accept_IN, bool* ok) {
  // Expression ::
  //   AssignmentExpression
  //   Expression ',' AssignmentExpression

  Expression result = ParseAssignmentExpression(accept_IN, CHECK_OK);
  while (peek() == i::Token::COMMA) {
    Expect(i::Token::COMMA, CHECK_OK);
    ParseAssignmentExpression(accept_IN, CHECK_OK);
    result = Expression::Default();
  }
  return result;
}


// Precedence = 2
PreParser::Expression PreParser::ParseAssignmentExpression(bool accept_IN,
                                                           bool* ok) {
  // AssignmentExpression ::
  //   ConditionalExpression
  //   LeftHandSideExpression AssignmentOperator AssignmentExpression

  i::Scanner::Location before = scanner_->peek_location();
  Expression expression = ParseConditionalExpression(accept_IN, CHECK_OK);

  if (!i::Token::IsAssignmentOp(peek())) {
    // Parsed conditional expression only (no assignment).
    return expression;
  }

  if (!is_classic_mode() &&
      expression.IsIdentifier() &&
      expression.AsIdentifier().IsEvalOrArguments()) {
    i::Scanner::Location after = scanner_->location();
    ReportMessageAt(before.beg_pos, after.end_pos,
                    "strict_lhs_assignment", NULL);
    *ok = false;
    return Expression::Default();
  }

  i::Token::Value op = Next();  // Get assignment operator.
  ParseAssignmentExpression(accept_IN, CHECK_OK);

  if ((op == i::Token::ASSIGN) && expression.IsThisProperty()) {
    scope_->AddProperty();
  }

  return Expression::Default();
}


// Precedence = 3
PreParser::Expression PreParser::ParseConditionalExpression(bool accept_IN,
                                                            bool* ok) {
  // ConditionalExpression ::
  //   LogicalOrExpression
  //   LogicalOrExpression '?' AssignmentExpression ':' AssignmentExpression

  // We start using the binary expression parser for prec >= 4 only!
  Expression expression = ParseBinaryExpression(4, accept_IN, CHECK_OK);
  if (peek() != i::Token::CONDITIONAL) return expression;
  Consume(i::Token::CONDITIONAL);
  // In parsing the first assignment expression in conditional
  // expressions we always accept the 'in' keyword; see ECMA-262,
  // section 11.12, page 58.
  ParseAssignmentExpression(true, CHECK_OK);
  Expect(i::Token::COLON, CHECK_OK);
  ParseAssignmentExpression(accept_IN, CHECK_OK);
  return Expression::Default();
}


int PreParser::Precedence(i::Token::Value tok, bool accept_IN) {
  if (tok == i::Token::IN && !accept_IN)
    return 0;  // 0 precedence will terminate binary expression parsing

  return i::Token::Precedence(tok);
}


// Precedence >= 4
PreParser::Expression PreParser::ParseBinaryExpression(int prec,
                                                       bool accept_IN,
                                                       bool* ok) {
  Expression result = ParseUnaryExpression(CHECK_OK);
  for (int prec1 = Precedence(peek(), accept_IN); prec1 >= prec; prec1--) {
    // prec1 >= 4
    while (Precedence(peek(), accept_IN) == prec1) {
      Next();
      ParseBinaryExpression(prec1 + 1, accept_IN, CHECK_OK);
      result = Expression::Default();
    }
  }
  return result;
}


PreParser::Expression PreParser::ParseUnaryExpression(bool* ok) {
  // UnaryExpression ::
  //   PostfixExpression
  //   'delete' UnaryExpression
  //   'void' UnaryExpression
  //   'typeof' UnaryExpression
  //   '++' UnaryExpression
  //   '--' UnaryExpression
  //   '+' UnaryExpression
  //   '-' UnaryExpression
  //   '~' UnaryExpression
  //   '!' UnaryExpression

  i::Token::Value op = peek();
  if (i::Token::IsUnaryOp(op)) {
    op = Next();
    ParseUnaryExpression(ok);
    return Expression::Default();
  } else if (i::Token::IsCountOp(op)) {
    op = Next();
    i::Scanner::Location before = scanner_->peek_location();
    Expression expression = ParseUnaryExpression(CHECK_OK);
    if (!is_classic_mode() &&
        expression.IsIdentifier() &&
        expression.AsIdentifier().IsEvalOrArguments()) {
      i::Scanner::Location after = scanner_->location();
      ReportMessageAt(before.beg_pos, after.end_pos,
                      "strict_lhs_prefix", NULL);
      *ok = false;
    }
    return Expression::Default();
  } else {
    return ParsePostfixExpression(ok);
  }
}


PreParser::Expression PreParser::ParsePostfixExpression(bool* ok) {
  // PostfixExpression ::
  //   LeftHandSideExpression ('++' | '--')?

  i::Scanner::Location before = scanner_->peek_location();
  Expression expression = ParseLeftHandSideExpression(CHECK_OK);
  if (!scanner_->HasAnyLineTerminatorBeforeNext() &&
      i::Token::IsCountOp(peek())) {
    if (!is_classic_mode() &&
        expression.IsIdentifier() &&
        expression.AsIdentifier().IsEvalOrArguments()) {
      i::Scanner::Location after = scanner_->location();
      ReportMessageAt(before.beg_pos, after.end_pos,
                      "strict_lhs_postfix", NULL);
      *ok = false;
      return Expression::Default();
    }
    Next();
    return Expression::Default();
  }
  return expression;
}


PreParser::Expression PreParser::ParseLeftHandSideExpression(bool* ok) {
  // LeftHandSideExpression ::
  //   (NewExpression | MemberExpression) ...

  Expression result = Expression::Default();
  if (peek() == i::Token::NEW) {
    result = ParseNewExpression(CHECK_OK);
  } else {
    result = ParseMemberExpression(CHECK_OK);
  }

  while (true) {
    switch (peek()) {
      case i::Token::LBRACK: {
        Consume(i::Token::LBRACK);
        ParseExpression(true, CHECK_OK);
        Expect(i::Token::RBRACK, CHECK_OK);
        if (result.IsThis()) {
          result = Expression::ThisProperty();
        } else {
          result = Expression::Default();
        }
        break;
      }

      case i::Token::LPAREN: {
        ParseArguments(CHECK_OK);
        result = Expression::Default();
        break;
      }

      case i::Token::PERIOD: {
        Consume(i::Token::PERIOD);
        ParseIdentifierName(CHECK_OK);
        if (result.IsThis()) {
          result = Expression::ThisProperty();
        } else {
          result = Expression::Default();
        }
        break;
      }

      default:
        return result;
    }
  }
}


PreParser::Expression PreParser::ParseNewExpression(bool* ok) {
  // NewExpression ::
  //   ('new')+ MemberExpression

  // The grammar for new expressions is pretty warped. The keyword
  // 'new' can either be a part of the new expression (where it isn't
  // followed by an argument list) or a part of the member expression,
  // where it must be followed by an argument list. To accommodate
  // this, we parse the 'new' keywords greedily and keep track of how
  // many we have parsed. This information is then passed on to the
  // member expression parser, which is only allowed to match argument
  // lists as long as it has 'new' prefixes left
  unsigned new_count = 0;
  do {
    Consume(i::Token::NEW);
    new_count++;
  } while (peek() == i::Token::NEW);

  return ParseMemberWithNewPrefixesExpression(new_count, ok);
}


PreParser::Expression PreParser::ParseMemberExpression(bool* ok) {
  return ParseMemberWithNewPrefixesExpression(0, ok);
}


PreParser::Expression PreParser::ParseMemberWithNewPrefixesExpression(
    unsigned new_count, bool* ok) {
  // MemberExpression ::
  //   (PrimaryExpression | FunctionLiteral)
  //     ('[' Expression ']' | '.' Identifier | Arguments)*

  // Parse the initial primary or function expression.
  Expression result = Expression::Default();
  if (peek() == i::Token::FUNCTION) {
    Consume(i::Token::FUNCTION);
    Identifier identifier = Identifier::Default();
    if (peek_any_identifier()) {
      identifier = ParseIdentifier(CHECK_OK);
    }
    result = ParseFunctionLiteral(CHECK_OK);
    if (result.IsStrictFunction() && !identifier.IsValidStrictVariable()) {
      StrictModeIdentifierViolation(scanner_->location(),
                                    "strict_function_name",
                                    identifier,
                                    ok);
      return Expression::Default();
    }
  } else {
    result = ParsePrimaryExpression(CHECK_OK);
  }

  while (true) {
    switch (peek()) {
      case i::Token::LBRACK: {
        Consume(i::Token::LBRACK);
        ParseExpression(true, CHECK_OK);
        Expect(i::Token::RBRACK, CHECK_OK);
        if (result.IsThis()) {
          result = Expression::ThisProperty();
        } else {
          result = Expression::Default();
        }
        break;
      }
      case i::Token::PERIOD: {
        Consume(i::Token::PERIOD);
        ParseIdentifierName(CHECK_OK);
        if (result.IsThis()) {
          result = Expression::ThisProperty();
        } else {
          result = Expression::Default();
        }
        break;
      }
      case i::Token::LPAREN: {
        if (new_count == 0) return result;
        // Consume one of the new prefixes (already parsed).
        ParseArguments(CHECK_OK);
        new_count--;
        result = Expression::Default();
        break;
      }
      default:
        return result;
    }
  }
}


PreParser::Expression PreParser::ParsePrimaryExpression(bool* ok) {
  // PrimaryExpression ::
  //   'this'
  //   'null'
  //   'true'
  //   'false'
  //   Identifier
  //   Number
  //   String
  //   ArrayLiteral
  //   ObjectLiteral
  //   RegExpLiteral
  //   '(' Expression ')'

  Expression result = Expression::Default();
  switch (peek()) {
    case i::Token::THIS: {
      Next();
      result = Expression::This();
      break;
    }

    case i::Token::FUTURE_RESERVED_WORD: {
      Next();
      i::Scanner::Location location = scanner_->location();
      ReportMessageAt(location.beg_pos, location.end_pos,
                      "reserved_word", NULL);
      *ok = false;
      return Expression::Default();
    }

    case i::Token::FUTURE_STRICT_RESERVED_WORD:
      if (!is_classic_mode()) {
        Next();
        i::Scanner::Location location = scanner_->location();
        ReportMessageAt(location, "strict_reserved_word", NULL);
        *ok = false;
        return Expression::Default();
      }
      // FALLTHROUGH
    case i::Token::IDENTIFIER: {
      Identifier id = ParseIdentifier(CHECK_OK);
      result = Expression::FromIdentifier(id);
      break;
    }

    case i::Token::NULL_LITERAL:
    case i::Token::TRUE_LITERAL:
    case i::Token::FALSE_LITERAL:
    case i::Token::NUMBER: {
      Next();
      break;
    }
    case i::Token::STRING: {
      Next();
      result = GetStringSymbol();
      break;
    }

    case i::Token::ASSIGN_DIV:
      result = ParseRegExpLiteral(true, CHECK_OK);
      break;

    case i::Token::DIV:
      result = ParseRegExpLiteral(false, CHECK_OK);
      break;

    case i::Token::LBRACK:
      result = ParseArrayLiteral(CHECK_OK);
      break;

    case i::Token::LBRACE:
      result = ParseObjectLiteral(CHECK_OK);
      break;

    case i::Token::LPAREN:
      Consume(i::Token::LPAREN);
      parenthesized_function_ = (peek() == i::Token::FUNCTION);
      result = ParseExpression(true, CHECK_OK);
      Expect(i::Token::RPAREN, CHECK_OK);
      result = result.Parenthesize();
      break;

    case i::Token::MOD:
      result = ParseV8Intrinsic(CHECK_OK);
      break;

    default: {
      Next();
      *ok = false;
      return Expression::Default();
    }
  }

  return result;
}


PreParser::Expression PreParser::ParseArrayLiteral(bool* ok) {
  // ArrayLiteral ::
  //   '[' Expression? (',' Expression?)* ']'
  Expect(i::Token::LBRACK, CHECK_OK);
  while (peek() != i::Token::RBRACK) {
    if (peek() != i::Token::COMMA) {
      ParseAssignmentExpression(true, CHECK_OK);
    }
    if (peek() != i::Token::RBRACK) {
      Expect(i::Token::COMMA, CHECK_OK);
    }
  }
  Expect(i::Token::RBRACK, CHECK_OK);

  scope_->NextMaterializedLiteralIndex();
  return Expression::Default();
}

void PreParser::CheckDuplicate(DuplicateFinder* finder,
                               i::Token::Value property,
                               int type,
                               bool* ok) {
  int old_type;
  if (property == i::Token::NUMBER) {
    old_type = finder->AddNumber(scanner_->literal_ascii_string(), type);
  } else if (scanner_->is_literal_ascii()) {
    old_type = finder->AddAsciiSymbol(scanner_->literal_ascii_string(),
                                      type);
  } else {
    old_type = finder->AddUtf16Symbol(scanner_->literal_utf16_string(), type);
  }
  if (HasConflict(old_type, type)) {
    if (IsDataDataConflict(old_type, type)) {
      // Both are data properties.
      if (is_classic_mode()) return;
      ReportMessageAt(scanner_->location(),
                      "strict_duplicate_property", NULL);
    } else if (IsDataAccessorConflict(old_type, type)) {
      // Both a data and an accessor property with the same name.
      ReportMessageAt(scanner_->location(),
                      "accessor_data_property", NULL);
    } else {
      ASSERT(IsAccessorAccessorConflict(old_type, type));
      // Both accessors of the same type.
      ReportMessageAt(scanner_->location(),
                      "accessor_get_set", NULL);
    }
    *ok = false;
  }
}


PreParser::Expression PreParser::ParseObjectLiteral(bool* ok) {
  // ObjectLiteral ::
  //   '{' (
  //       ((IdentifierName | String | Number) ':' AssignmentExpression)
  //     | (('get' | 'set') (IdentifierName | String | Number) FunctionLiteral)
  //    )*[','] '}'

  Expect(i::Token::LBRACE, CHECK_OK);
  DuplicateFinder duplicate_finder(scanner_->unicode_cache());
  while (peek() != i::Token::RBRACE) {
    i::Token::Value next = peek();
    switch (next) {
      case i::Token::IDENTIFIER:
      case i::Token::FUTURE_RESERVED_WORD:
      case i::Token::FUTURE_STRICT_RESERVED_WORD: {
        bool is_getter = false;
        bool is_setter = false;
        ParseIdentifierNameOrGetOrSet(&is_getter, &is_setter, CHECK_OK);
        if ((is_getter || is_setter) && peek() != i::Token::COLON) {
            i::Token::Value name = Next();
            bool is_keyword = i::Token::IsKeyword(name);
            if (name != i::Token::IDENTIFIER &&
                name != i::Token::FUTURE_RESERVED_WORD &&
                name != i::Token::FUTURE_STRICT_RESERVED_WORD &&
                name != i::Token::NUMBER &&
                name != i::Token::STRING &&
                !is_keyword) {
              *ok = false;
              return Expression::Default();
            }
            if (!is_keyword) {
              LogSymbol();
            }
            PropertyType type = is_getter ? kGetterProperty : kSetterProperty;
            CheckDuplicate(&duplicate_finder, name, type, CHECK_OK);
            ParseFunctionLiteral(CHECK_OK);
            if (peek() != i::Token::RBRACE) {
              Expect(i::Token::COMMA, CHECK_OK);
            }
            continue;  // restart the while
        }
        CheckDuplicate(&duplicate_finder, next, kValueProperty, CHECK_OK);
        break;
      }
      case i::Token::STRING:
        Consume(next);
        CheckDuplicate(&duplicate_finder, next, kValueProperty, CHECK_OK);
        GetStringSymbol();
        break;
      case i::Token::NUMBER:
        Consume(next);
        CheckDuplicate(&duplicate_finder, next, kValueProperty, CHECK_OK);
        break;
      default:
        if (i::Token::IsKeyword(next)) {
          Consume(next);
          CheckDuplicate(&duplicate_finder, next, kValueProperty, CHECK_OK);
        } else {
          // Unexpected token.
          *ok = false;
          return Expression::Default();
        }
    }

    Expect(i::Token::COLON, CHECK_OK);
    ParseAssignmentExpression(true, CHECK_OK);

    // TODO(1240767): Consider allowing trailing comma.
    if (peek() != i::Token::RBRACE) Expect(i::Token::COMMA, CHECK_OK);
  }
  Expect(i::Token::RBRACE, CHECK_OK);

  scope_->NextMaterializedLiteralIndex();
  return Expression::Default();
}


PreParser::Expression PreParser::ParseRegExpLiteral(bool seen_equal,
                                                    bool* ok) {
  if (!scanner_->ScanRegExpPattern(seen_equal)) {
    Next();
    ReportMessageAt(scanner_->location(), "unterminated_regexp", NULL);
    *ok = false;
    return Expression::Default();
  }

  scope_->NextMaterializedLiteralIndex();

  if (!scanner_->ScanRegExpFlags()) {
    Next();
    ReportMessageAt(scanner_->location(), "invalid_regexp_flags", NULL);
    *ok = false;
    return Expression::Default();
  }
  Next();
  return Expression::Default();
}


PreParser::Arguments PreParser::ParseArguments(bool* ok) {
  // Arguments ::
  //   '(' (AssignmentExpression)*[','] ')'

  Expect(i::Token::LPAREN, ok);
  if (!*ok) return -1;
  bool done = (peek() == i::Token::RPAREN);
  int argc = 0;
  while (!done) {
    ParseAssignmentExpression(true, ok);
    if (!*ok) return -1;
    argc++;
    done = (peek() == i::Token::RPAREN);
    if (!done) {
      Expect(i::Token::COMMA, ok);
      if (!*ok) return -1;
    }
  }
  Expect(i::Token::RPAREN, ok);
  return argc;
}


PreParser::Expression PreParser::ParseFunctionLiteral(bool* ok) {
  // Function ::
  //   '(' FormalParameterList? ')' '{' FunctionBody '}'

  // Parse function body.
  ScopeType outer_scope_type = scope_->type();
  bool inside_with = scope_->IsInsideWith();
  Scope function_scope(&scope_, kFunctionScope);
  //  FormalParameterList ::
  //    '(' (Identifier)*[','] ')'
  Expect(i::Token::LPAREN, CHECK_OK);
  int start_position = scanner_->location().beg_pos;
  bool done = (peek() == i::Token::RPAREN);
  DuplicateFinder duplicate_finder(scanner_->unicode_cache());
  while (!done) {
    Identifier id = ParseIdentifier(CHECK_OK);
    if (!id.IsValidStrictVariable()) {
      StrictModeIdentifierViolation(scanner_->location(),
                                    "strict_param_name",
                                    id,
                                    CHECK_OK);
    }
    int prev_value;
    if (scanner_->is_literal_ascii()) {
      prev_value =
          duplicate_finder.AddAsciiSymbol(scanner_->literal_ascii_string(), 1);
    } else {
      prev_value =
          duplicate_finder.AddUtf16Symbol(scanner_->literal_utf16_string(), 1);
    }

    if (prev_value != 0) {
      SetStrictModeViolation(scanner_->location(),
                             "strict_param_dupe",
                             CHECK_OK);
    }
    done = (peek() == i::Token::RPAREN);
    if (!done) {
      Expect(i::Token::COMMA, CHECK_OK);
    }
  }
  Expect(i::Token::RPAREN, CHECK_OK);

  // Determine if the function will be lazily compiled.
  // Currently only happens to top-level functions.
  // Optimistically assume that all top-level functions are lazily compiled.
  bool is_lazily_compiled = (outer_scope_type == kTopLevelScope &&
                             !inside_with && allow_lazy_ &&
                             !parenthesized_function_);
  parenthesized_function_ = false;

  Expect(i::Token::LBRACE, CHECK_OK);
  if (is_lazily_compiled) {
    ParseLazyFunctionLiteralBody(CHECK_OK);
  } else {
    ParseSourceElements(i::Token::RBRACE, ok);
  }
  Expect(i::Token::RBRACE, CHECK_OK);

  if (!is_classic_mode()) {
    int end_position = scanner_->location().end_pos;
    CheckOctalLiteral(start_position, end_position, CHECK_OK);
    CheckDelayedStrictModeViolation(start_position, end_position, CHECK_OK);
    return Expression::StrictFunction();
  }

  return Expression::Default();
}


void PreParser::ParseLazyFunctionLiteralBody(bool* ok) {
  int body_start = scanner_->location().beg_pos;
  log_->PauseRecording();
  ParseSourceElements(i::Token::RBRACE, ok);
  log_->ResumeRecording();
  if (!*ok) return;

  // Position right after terminal '}'.
  ASSERT_EQ(i::Token::RBRACE, scanner_->peek());
  int body_end = scanner_->peek_location().end_pos;
  log_->LogFunction(body_start, body_end,
                    scope_->materialized_literal_count(),
                    scope_->expected_properties(),
                    language_mode());
}


PreParser::Expression PreParser::ParseV8Intrinsic(bool* ok) {
  // CallRuntime ::
  //   '%' Identifier Arguments
  Expect(i::Token::MOD, CHECK_OK);
  if (!allow_natives_syntax_) {
    *ok = false;
    return Expression::Default();
  }
  ParseIdentifier(CHECK_OK);
  ParseArguments(ok);

  return Expression::Default();
}

#undef CHECK_OK


void PreParser::ExpectSemicolon(bool* ok) {
  // Check for automatic semicolon insertion according to
  // the rules given in ECMA-262, section 7.9, page 21.
  i::Token::Value tok = peek();
  if (tok == i::Token::SEMICOLON) {
    Next();
    return;
  }
  if (scanner_->HasAnyLineTerminatorBeforeNext() ||
      tok == i::Token::RBRACE ||
      tok == i::Token::EOS) {
    return;
  }
  Expect(i::Token::SEMICOLON, ok);
}


void PreParser::LogSymbol() {
  int identifier_pos = scanner_->location().beg_pos;
  if (scanner_->is_literal_ascii()) {
    log_->LogAsciiSymbol(identifier_pos, scanner_->literal_ascii_string());
  } else {
    log_->LogUtf16Symbol(identifier_pos, scanner_->literal_utf16_string());
  }
}


PreParser::Expression PreParser::GetStringSymbol() {
  const int kUseStrictLength = 10;
  const char* kUseStrictChars = "use strict";
  LogSymbol();
  if (scanner_->is_literal_ascii() &&
      scanner_->literal_length() == kUseStrictLength &&
      !scanner_->literal_contains_escapes() &&
      !strncmp(scanner_->literal_ascii_string().start(), kUseStrictChars,
               kUseStrictLength)) {
    return Expression::UseStrictStringLiteral();
  }
  return Expression::StringLiteral();
}


PreParser::Identifier PreParser::GetIdentifierSymbol() {
  LogSymbol();
  if (scanner_->current_token() == i::Token::FUTURE_RESERVED_WORD) {
    return Identifier::FutureReserved();
  } else if (scanner_->current_token() ==
             i::Token::FUTURE_STRICT_RESERVED_WORD) {
    return Identifier::FutureStrictReserved();
  }
  if (scanner_->is_literal_ascii()) {
    // Detect strict-mode poison words.
    if (scanner_->literal_length() == 4 &&
        !strncmp(scanner_->literal_ascii_string().start(), "eval", 4)) {
      return Identifier::Eval();
    }
    if (scanner_->literal_length() == 9 &&
        !strncmp(scanner_->literal_ascii_string().start(), "arguments", 9)) {
      return Identifier::Arguments();
    }
  }
  return Identifier::Default();
}


PreParser::Identifier PreParser::ParseIdentifier(bool* ok) {
  i::Token::Value next = Next();
  switch (next) {
    case i::Token::FUTURE_RESERVED_WORD: {
      i::Scanner::Location location = scanner_->location();
      ReportMessageAt(location.beg_pos, location.end_pos,
                      "reserved_word", NULL);
      *ok = false;
      return GetIdentifierSymbol();
    }
    case i::Token::FUTURE_STRICT_RESERVED_WORD:
      if (!is_classic_mode()) {
        i::Scanner::Location location = scanner_->location();
        ReportMessageAt(location.beg_pos, location.end_pos,
                        "strict_reserved_word", NULL);
        *ok = false;
      }
      // FALLTHROUGH
    case i::Token::IDENTIFIER:
      return GetIdentifierSymbol();
    default:
      *ok = false;
      return Identifier::Default();
  }
}


void PreParser::SetStrictModeViolation(i::Scanner::Location location,
                                       const char* type,
                                       bool* ok) {
  if (!is_classic_mode()) {
    ReportMessageAt(location, type, NULL);
    *ok = false;
    return;
  }
  // Delay report in case this later turns out to be strict code
  // (i.e., for function names and parameters prior to a "use strict"
  // directive).
  // It's safe to overwrite an existing violation.
  // It's either from a function that turned out to be non-strict,
  // or it's in the current function (and we just need to report
  // one error), or it's in a unclosed nesting function that wasn't
  // strict (otherwise we would already be in strict mode).
  strict_mode_violation_location_ = location;
  strict_mode_violation_type_ = type;
}


void PreParser::CheckDelayedStrictModeViolation(int beg_pos,
                                                int end_pos,
                                                bool* ok) {
  i::Scanner::Location location = strict_mode_violation_location_;
  if (location.IsValid() &&
      location.beg_pos > beg_pos && location.end_pos < end_pos) {
    ReportMessageAt(location, strict_mode_violation_type_, NULL);
    *ok = false;
  }
}


void PreParser::StrictModeIdentifierViolation(i::Scanner::Location location,
                                              const char* eval_args_type,
                                              Identifier identifier,
                                              bool* ok) {
  const char* type = eval_args_type;
  if (identifier.IsFutureReserved()) {
    type = "reserved_word";
  } else if (identifier.IsFutureStrictReserved()) {
    type = "strict_reserved_word";
  }
  if (!is_classic_mode()) {
    ReportMessageAt(location, type, NULL);
    *ok = false;
    return;
  }
  strict_mode_violation_location_ = location;
  strict_mode_violation_type_ = type;
}


PreParser::Identifier PreParser::ParseIdentifierName(bool* ok) {
  i::Token::Value next = Next();
  if (i::Token::IsKeyword(next)) {
    int pos = scanner_->location().beg_pos;
    const char* keyword = i::Token::String(next);
    log_->LogAsciiSymbol(pos, i::Vector<const char>(keyword,
                                                    i::StrLength(keyword)));
    return Identifier::Default();
  }
  if (next == i::Token::IDENTIFIER ||
      next == i::Token::FUTURE_RESERVED_WORD ||
      next == i::Token::FUTURE_STRICT_RESERVED_WORD) {
    return GetIdentifierSymbol();
  }
  *ok = false;
  return Identifier::Default();
}

#undef CHECK_OK


// This function reads an identifier and determines whether or not it
// is 'get' or 'set'.
PreParser::Identifier PreParser::ParseIdentifierNameOrGetOrSet(bool* is_get,
                                                               bool* is_set,
                                                               bool* ok) {
  Identifier result = ParseIdentifierName(ok);
  if (!*ok) return Identifier::Default();
  if (scanner_->is_literal_ascii() &&
      scanner_->literal_length() == 3) {
    const char* token = scanner_->literal_ascii_string().start();
    *is_get = strncmp(token, "get", 3) == 0;
    *is_set = !*is_get && strncmp(token, "set", 3) == 0;
  }
  return result;
}

bool PreParser::peek_any_identifier() {
  i::Token::Value next = peek();
  return next == i::Token::IDENTIFIER ||
         next == i::Token::FUTURE_RESERVED_WORD ||
         next == i::Token::FUTURE_STRICT_RESERVED_WORD;
}


int DuplicateFinder::AddAsciiSymbol(i::Vector<const char> key, int value) {
  return AddSymbol(i::Vector<const byte>::cast(key), true, value);
}

int DuplicateFinder::AddUtf16Symbol(i::Vector<const uint16_t> key, int value) {
  return AddSymbol(i::Vector<const byte>::cast(key), false, value);
}

int DuplicateFinder::AddSymbol(i::Vector<const byte> key,
                               bool is_ascii,
                               int value) {
  uint32_t hash = Hash(key, is_ascii);
  byte* encoding = BackupKey(key, is_ascii);
  i::HashMap::Entry* entry = map_.Lookup(encoding, hash, true);
  int old_value = static_cast<int>(reinterpret_cast<intptr_t>(entry->value));
  entry->value =
    reinterpret_cast<void*>(static_cast<intptr_t>(value | old_value));
  return old_value;
}


int DuplicateFinder::AddNumber(i::Vector<const char> key, int value) {
  ASSERT(key.length() > 0);
  // Quick check for already being in canonical form.
  if (IsNumberCanonical(key)) {
    return AddAsciiSymbol(key, value);
  }

  int flags = i::ALLOW_HEX | i::ALLOW_OCTALS;
  double double_value = StringToDouble(unicode_constants_, key, flags, 0.0);
  int length;
  const char* string;
  if (!isfinite(double_value)) {
    string = "Infinity";
    length = 8;  // strlen("Infinity");
  } else {
    string = DoubleToCString(double_value,
                             i::Vector<char>(number_buffer_, kBufferSize));
    length = i::StrLength(string);
  }
  return AddSymbol(i::Vector<const byte>(reinterpret_cast<const byte*>(string),
                                         length), true, value);
}


bool DuplicateFinder::IsNumberCanonical(i::Vector<const char> number) {
  // Test for a safe approximation of number literals that are already
  // in canonical form: max 15 digits, no leading zeroes, except an
  // integer part that is a single zero, and no trailing zeros below
  // the decimal point.
  int pos = 0;
  int length = number.length();
  if (number.length() > 15) return false;
  if (number[pos] == '0') {
    pos++;
  } else {
    while (pos < length &&
           static_cast<unsigned>(number[pos] - '0') <= ('9' - '0')) pos++;
  }
  if (length == pos) return true;
  if (number[pos] != '.') return false;
  pos++;
  bool invalid_last_digit = true;
  while (pos < length) {
    byte digit = number[pos] - '0';
    if (digit > '9' - '0') return false;
    invalid_last_digit = (digit == 0);
    pos++;
  }
  return !invalid_last_digit;
}


uint32_t DuplicateFinder::Hash(i::Vector<const byte> key, bool is_ascii) {
  // Primitive hash function, almost identical to the one used
  // for strings (except that it's seeded by the length and ASCII-ness).
  int length = key.length();
  uint32_t hash = (length << 1) | (is_ascii ? 1 : 0) ;
  for (int i = 0; i < length; i++) {
    uint32_t c = key[i];
    hash = (hash + c) * 1025;
    hash ^= (hash >> 6);
  }
  return hash;
}


bool DuplicateFinder::Match(void* first, void* second) {
  // Decode lengths.
  // Length + ASCII-bit is encoded as base 128, most significant heptet first,
  // with a 8th bit being non-zero while there are more heptets.
  // The value encodes the number of bytes following, and whether the original
  // was ASCII.
  byte* s1 = reinterpret_cast<byte*>(first);
  byte* s2 = reinterpret_cast<byte*>(second);
  uint32_t length_ascii_field = 0;
  byte c1;
  do {
    c1 = *s1;
    if (c1 != *s2) return false;
    length_ascii_field = (length_ascii_field << 7) | (c1 & 0x7f);
    s1++;
    s2++;
  } while ((c1 & 0x80) != 0);
  int length = static_cast<int>(length_ascii_field >> 1);
  return memcmp(s1, s2, length) == 0;
}


byte* DuplicateFinder::BackupKey(i::Vector<const byte> bytes,
                                 bool is_ascii) {
  uint32_t ascii_length = (bytes.length() << 1) | (is_ascii ? 1 : 0);
  backing_store_.StartSequence();
  // Emit ascii_length as base-128 encoded number, with the 7th bit set
  // on the byte of every heptet except the last, least significant, one.
  if (ascii_length >= (1 << 7)) {
    if (ascii_length >= (1 << 14)) {
      if (ascii_length >= (1 << 21)) {
        if (ascii_length >= (1 << 28)) {
          backing_store_.Add(static_cast<byte>((ascii_length >> 28) | 0x80));
        }
        backing_store_.Add(static_cast<byte>((ascii_length >> 21) | 0x80u));
      }
      backing_store_.Add(static_cast<byte>((ascii_length >> 14) | 0x80u));
    }
    backing_store_.Add(static_cast<byte>((ascii_length >> 7) | 0x80u));
  }
  backing_store_.Add(static_cast<byte>(ascii_length & 0x7f));

  backing_store_.AddBlock(bytes);
  return backing_store_.EndSequence().start();
}
} }  // v8::preparser

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