src/v8/src/parsing/parser-base.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_PARSING_PARSER_BASE_H
#define V8_PARSING_PARSER_BASE_H

#include <vector>

#include "src/ast/ast-source-ranges.h"
#include "src/ast/ast.h"
#include "src/ast/scopes.h"
#include "src/bailout-reason.h"
#include "src/base/hashmap.h"
#include "src/counters.h"
#include "src/globals.h"
#include "src/log.h"
#include "src/messages.h"
#include "src/parsing/expression-classifier.h"
#include "src/parsing/func-name-inferrer.h"
#include "src/parsing/scanner.h"
#include "src/parsing/token.h"

namespace v8 {
namespace internal {

enum FunctionNameValidity {
  kFunctionNameIsStrictReserved,
  kSkipFunctionNameCheck,
  kFunctionNameValidityUnknown
};

enum AllowLabelledFunctionStatement {
  kAllowLabelledFunctionStatement,
  kDisallowLabelledFunctionStatement,
};

enum class ParseFunctionFlags {
  kIsNormal = 0,
  kIsGenerator = 1,
  kIsAsync = 2,
  kIsDefault = 4
};

static inline ParseFunctionFlags operator|(ParseFunctionFlags lhs,
                                           ParseFunctionFlags rhs) {
  typedef unsigned char T;
  return static_cast<ParseFunctionFlags>(static_cast<T>(lhs) |
                                         static_cast<T>(rhs));
}

static inline ParseFunctionFlags& operator|=(ParseFunctionFlags& lhs,
                                             const ParseFunctionFlags& rhs) {
  lhs = lhs | rhs;
  return lhs;
}

static inline bool operator&(ParseFunctionFlags bitfield,
                             ParseFunctionFlags mask) {
  typedef unsigned char T;
  return static_cast<T>(bitfield) & static_cast<T>(mask);
}

struct FormalParametersBase {
  explicit FormalParametersBase(DeclarationScope* scope) : scope(scope) {}

  int num_parameters() const {
    // Don't include the rest parameter into the function's formal parameter
    // count (esp. the SharedFunctionInfo::internal_formal_parameter_count,
    // which says whether we need to create an arguments adaptor frame).
    return arity - has_rest;
  }

  void UpdateArityAndFunctionLength(bool is_optional, bool is_rest) {
    if (!is_optional && !is_rest && function_length == arity) {
      ++function_length;
    }
    ++arity;
  }

  DeclarationScope* scope;
  bool has_rest = false;
  bool is_simple = true;
  int function_length = 0;
  int arity = 0;
};

// Stack-allocated scope to collect source ranges from the parser.
class SourceRangeScope final {
 public:
  enum PositionKind {
    POSITION_BEG,
    POSITION_END,
    PEEK_POSITION_BEG,
    PEEK_POSITION_END,
  };

  SourceRangeScope(Scanner* scanner, SourceRange* range,
                   PositionKind pre_kind = PEEK_POSITION_BEG,
                   PositionKind post_kind = POSITION_END)
      : scanner_(scanner), range_(range), post_kind_(post_kind) {
    range_->start = GetPosition(pre_kind);
    DCHECK_NE(range_->start, kNoSourcePosition);
  }

  ~SourceRangeScope() { Finalize(); }

  const SourceRange& Finalize() {
    if (is_finalized_) return *range_;
    is_finalized_ = true;
    range_->end = GetPosition(post_kind_);
    DCHECK_NE(range_->end, kNoSourcePosition);
    return *range_;
  }

 private:
  int32_t GetPosition(PositionKind kind) {
    switch (kind) {
      case POSITION_BEG:
        return scanner_->location().beg_pos;
      case POSITION_END:
        return scanner_->location().end_pos;
      case PEEK_POSITION_BEG:
        return scanner_->peek_location().beg_pos;
      case PEEK_POSITION_END:
        return scanner_->peek_location().end_pos;
      default:
        UNREACHABLE();
    }
  }

  Scanner* scanner_;
  SourceRange* range_;
  PositionKind post_kind_;
  bool is_finalized_ = false;

  DISALLOW_IMPLICIT_CONSTRUCTORS(SourceRangeScope);
};

// ----------------------------------------------------------------------------
// The CHECK_OK macro is a convenient macro to enforce error
// handling for functions that may fail (by returning !*ok).
//
// CAUTION: This macro appends extra statements after a call,
// thus it must never be used where only a single statement
// is correct (e.g. an if statement branch w/o braces)!

#define CHECK_OK_CUSTOM(x, ...) ok);       \
  if (!*ok) return impl()->x(__VA_ARGS__); \
  ((void)0
#define DUMMY )  // to make indentation work
#undef DUMMY

// Used in functions where the return type is ExpressionT.
#define CHECK_OK CHECK_OK_CUSTOM(NullExpression)

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

// Common base class template shared between parser and pre-parser.
// The Impl parameter is the actual class of the parser/pre-parser,
// following the Curiously Recurring Template Pattern (CRTP).
// The structure of the parser objects is roughly the following:
//
//   // A structure template containing type definitions, needed to
//   // avoid a cyclic dependency.
//   template <typename Impl>
//   struct ParserTypes;
//
//   // The parser base object, which should just implement pure
//   // parser behavior.  The Impl parameter is the actual derived
//   // class (according to CRTP), which implements impure parser
//   // behavior.
//   template <typename Impl>
//   class ParserBase { ... };
//
//   // And then, for each parser variant (e.g., parser, preparser, etc):
//   class Parser;
//
//   template <>
//   class ParserTypes<Parser> { ... };
//
//   class Parser : public ParserBase<Parser> { ... };
//
// The parser base object implements pure parsing, according to the
// language grammar.  Different parser implementations may exhibit
// different parser-driven behavior that is not considered as pure
// parsing, e.g., early error detection and reporting, AST generation, etc.

// The ParserTypes structure encapsulates the differences in the
// types used in parsing methods.  E.g., Parser methods use Expression*
// and PreParser methods use PreParserExpression.  For any given parser
// implementation class Impl, it is expected to contain the following typedefs:
//
// template <>
// struct ParserTypes<Impl> {
//   // Synonyms for ParserBase<Impl> and Impl, respectively.
//   typedef Base;
//   typedef Impl;
//   // Return types for traversing functions.
//   typedef Identifier;
//   typedef Expression;
//   typedef FunctionLiteral;
//   typedef ObjectLiteralProperty;
//   typedef ClassLiteralProperty;
//   typedef ExpressionList;
//   typedef ObjectPropertyList;
//   typedef ClassPropertyList;
//   typedef FormalParameters;
//   typedef Statement;
//   typedef StatementList;
//   typedef Block;
//   typedef BreakableStatement;
//   typedef ForStatement;
//   typedef IterationStatement;
//   // For constructing objects returned by the traversing functions.
//   typedef Factory;
//   // For other implementation-specific tasks.
//   typedef Target;
//   typedef TargetScope;
// };

template <typename Impl>
struct ParserTypes;

template <typename Impl>
class ParserBase {
 public:
  // Shorten type names defined by ParserTypes<Impl>.
  typedef ParserTypes<Impl> Types;
  typedef typename Types::Identifier IdentifierT;
  typedef typename Types::Expression ExpressionT;
  typedef typename Types::FunctionLiteral FunctionLiteralT;
  typedef typename Types::ObjectLiteralProperty ObjectLiteralPropertyT;
  typedef typename Types::ClassLiteralProperty ClassLiteralPropertyT;
  typedef typename Types::Suspend SuspendExpressionT;
  typedef typename Types::RewritableExpression RewritableExpressionT;
  typedef typename Types::ExpressionList ExpressionListT;
  typedef typename Types::FormalParameters FormalParametersT;
  typedef typename Types::Statement StatementT;
  typedef typename Types::StatementList StatementListT;
  typedef typename Types::Block BlockT;
  typedef typename Types::ForStatement ForStatementT;
  typedef typename v8::internal::ExpressionClassifier<Types>
      ExpressionClassifier;

  // All implementation-specific methods must be called through this.
  Impl* impl() { return static_cast<Impl*>(this); }
  const Impl* impl() const { return static_cast<const Impl*>(this); }

  ParserBase(Zone* zone, Scanner* scanner, uintptr_t stack_limit,
             v8::Extension* extension, AstValueFactory* ast_value_factory,
             PendingCompilationErrorHandler* pending_error_handler,
             RuntimeCallStats* runtime_call_stats, Logger* logger,
             int script_id, bool parsing_module, bool parsing_on_main_thread)
      : scope_(nullptr),
        original_scope_(nullptr),
        function_state_(nullptr),
        extension_(extension),
        fni_(nullptr),
        ast_value_factory_(ast_value_factory),
        ast_node_factory_(ast_value_factory, zone),
        runtime_call_stats_(runtime_call_stats),
        logger_(logger),
        parsing_on_main_thread_(parsing_on_main_thread),
        parsing_module_(parsing_module),
        stack_limit_(stack_limit),
        pending_error_handler_(pending_error_handler),
        zone_(zone),
        classifier_(nullptr),
        scanner_(scanner),
        default_eager_compile_hint_(FunctionLiteral::kShouldLazyCompile),
        function_literal_id_(0),
        script_id_(script_id),
        allow_natives_(false),
        allow_harmony_do_expressions_(false),
        allow_harmony_function_sent_(false),
        allow_harmony_public_fields_(false),
        allow_harmony_static_fields_(false),
        allow_harmony_dynamic_import_(false),
        allow_harmony_import_meta_(false),
        allow_harmony_optional_catch_binding_(false),
        allow_harmony_private_fields_(false) {}

#define ALLOW_ACCESSORS(name)                           \
  bool allow_##name() const { return allow_##name##_; } \
  void set_allow_##name(bool allow) { allow_##name##_ = allow; }

  ALLOW_ACCESSORS(natives);
  ALLOW_ACCESSORS(harmony_do_expressions);
  ALLOW_ACCESSORS(harmony_function_sent);
  ALLOW_ACCESSORS(harmony_public_fields);
  ALLOW_ACCESSORS(harmony_static_fields);
  ALLOW_ACCESSORS(harmony_dynamic_import);
  ALLOW_ACCESSORS(harmony_import_meta);
  ALLOW_ACCESSORS(harmony_optional_catch_binding);

#undef ALLOW_ACCESSORS

  bool allow_harmony_bigint() const {
    return scanner()->allow_harmony_bigint();
  }
  void set_allow_harmony_bigint(bool allow) {
    scanner()->set_allow_harmony_bigint(allow);
  }

  bool allow_harmony_private_fields() const {
    return scanner()->allow_harmony_private_fields();
  }
  void set_allow_harmony_private_fields(bool allow) {
    scanner()->set_allow_harmony_private_fields(allow);
  }

  uintptr_t stack_limit() const { return stack_limit_; }

  void set_stack_limit(uintptr_t stack_limit) { stack_limit_ = stack_limit; }

  void set_default_eager_compile_hint(
      FunctionLiteral::EagerCompileHint eager_compile_hint) {
    default_eager_compile_hint_ = eager_compile_hint;
  }

  FunctionLiteral::EagerCompileHint default_eager_compile_hint() const {
    return default_eager_compile_hint_;
  }

  int GetNextFunctionLiteralId() { return ++function_literal_id_; }
  int GetLastFunctionLiteralId() const { return function_literal_id_; }

  void SkipFunctionLiterals(int delta) { function_literal_id_ += delta; }

  void ResetFunctionLiteralId() { function_literal_id_ = 0; }

  // The Zone where the parsing outputs are stored.
  Zone* main_zone() const { return ast_value_factory()->zone(); }

  // The current Zone, which might be the main zone or a temporary Zone.
  Zone* zone() const { return zone_; }

 protected:
  friend class v8::internal::ExpressionClassifier<ParserTypes<Impl>>;

  enum AllowRestrictedIdentifiers {
    kAllowRestrictedIdentifiers,
    kDontAllowRestrictedIdentifiers
  };

  enum LazyParsingResult { kLazyParsingComplete, kLazyParsingAborted };

  enum VariableDeclarationContext {
    kStatementListItem,
    kStatement,
    kForStatement
  };

  class ClassLiteralChecker;
  class ObjectLiteralChecker;

  // ---------------------------------------------------------------------------
  // BlockState and FunctionState implement the parser's scope stack.
  // The parser's current scope is in scope_. BlockState and FunctionState
  // constructors push on the scope stack and the destructors pop. They are also
  // used to hold the parser's per-funcion state.
  class BlockState BASE_EMBEDDED {
   public:
    BlockState(Scope** scope_stack, Scope* scope)
        : scope_stack_(scope_stack), outer_scope_(*scope_stack) {
      *scope_stack_ = scope;
    }

    BlockState(Zone* zone, Scope** scope_stack)
        : BlockState(scope_stack,
                     new (zone) Scope(zone, *scope_stack, BLOCK_SCOPE)) {}

    ~BlockState() { *scope_stack_ = outer_scope_; }

   private:
    Scope** const scope_stack_;
    Scope* const outer_scope_;
  };

  class FunctionState final : public BlockState {
   public:
    FunctionState(FunctionState** function_state_stack, Scope** scope_stack,
                  DeclarationScope* scope);
    ~FunctionState();

    DeclarationScope* scope() const { return scope_->AsDeclarationScope(); }

    void AddProperty() { expected_property_count_++; }
    int expected_property_count() { return expected_property_count_; }

    void DisableOptimization(BailoutReason reason) {
      dont_optimize_reason_ = reason;
    }
    BailoutReason dont_optimize_reason() { return dont_optimize_reason_; }

    FunctionKind kind() const { return scope()->function_kind(); }

    void RewindDestructuringAssignments(int pos) {
      destructuring_assignments_to_rewrite_.Rewind(pos);
    }

    void AdoptDestructuringAssignmentsFromParentState(int pos) {
      const auto& outer_assignments =
          outer_function_state_->destructuring_assignments_to_rewrite_;
      DCHECK_GE(outer_assignments.length(), pos);
      for (int i = pos; i < outer_assignments.length(); ++i) {
        auto expr = outer_assignments[i];
        expr->set_scope(scope_);
        destructuring_assignments_to_rewrite_.Add(expr, scope_->zone());
      }
      outer_function_state_->RewindDestructuringAssignments(pos);
    }

    const ZoneList<RewritableExpressionT>&
    destructuring_assignments_to_rewrite() const {
      return destructuring_assignments_to_rewrite_;
    }

    ZoneList<typename ExpressionClassifier::Error>* GetReportedErrorList() {
      return &reported_errors_;
    }

    ZoneList<RewritableExpressionT>* non_patterns_to_rewrite() {
      return &non_patterns_to_rewrite_;
    }

    bool next_function_is_likely_called() const {
      return next_function_is_likely_called_;
    }

    bool previous_function_was_likely_called() const {
      return previous_function_was_likely_called_;
    }

    void set_next_function_is_likely_called() {
      next_function_is_likely_called_ = true;
    }

    void RecordFunctionOrEvalCall() { contains_function_or_eval_ = true; }
    bool contains_function_or_eval() const {
      return contains_function_or_eval_;
    }

    class FunctionOrEvalRecordingScope {
     public:
      explicit FunctionOrEvalRecordingScope(FunctionState* state)
          : state_(state) {
        prev_value_ = state->contains_function_or_eval_;
        state->contains_function_or_eval_ = false;
      }
      ~FunctionOrEvalRecordingScope() {
        bool found = state_->contains_function_or_eval_;
        if (!found) {
          state_->contains_function_or_eval_ = prev_value_;
        }
      }

     private:
      FunctionState* state_;
      bool prev_value_;
    };

   private:
    void AddDestructuringAssignment(RewritableExpressionT expr) {
      destructuring_assignments_to_rewrite_.Add(expr, scope_->zone());
    }

    // Properties count estimation.
    int expected_property_count_;

    FunctionState** function_state_stack_;
    FunctionState* outer_function_state_;
    DeclarationScope* scope_;

    ZoneList<RewritableExpressionT> destructuring_assignments_to_rewrite_;
    ZoneList<RewritableExpressionT> non_patterns_to_rewrite_;

    ZoneList<typename ExpressionClassifier::Error> reported_errors_;

    // A reason, if any, why this function should not be optimized.
    BailoutReason dont_optimize_reason_;

    // Record whether the next (=== immediately following) function literal is
    // preceded by a parenthesis / exclamation mark. Also record the previous
    // state.
    // These are managed by the FunctionState constructor; the caller may only
    // call set_next_function_is_likely_called.
    bool next_function_is_likely_called_;
    bool previous_function_was_likely_called_;

    // Track if a function or eval occurs within this FunctionState
    bool contains_function_or_eval_;

    friend Impl;
  };

  struct DeclarationDescriptor {
    enum Kind { NORMAL, PARAMETER, FOR_EACH };
    Scope* scope;
    VariableMode mode;
    int declaration_pos;
    int initialization_pos;
    Kind declaration_kind;
  };

  struct DeclarationParsingResult {
    struct Declaration {
      Declaration(ExpressionT pattern, int initializer_position,
                  ExpressionT initializer)
          : pattern(pattern),
            initializer_position(initializer_position),
            initializer(initializer) {}

      ExpressionT pattern;
      int initializer_position;
      int value_beg_position = kNoSourcePosition;
      ExpressionT initializer;
    };

    DeclarationParsingResult()
        : first_initializer_loc(Scanner::Location::invalid()),
          bindings_loc(Scanner::Location::invalid()) {}

    DeclarationDescriptor descriptor;
    std::vector<Declaration> declarations;
    Scanner::Location first_initializer_loc;
    Scanner::Location bindings_loc;
  };

  struct CatchInfo {
   public:
    explicit CatchInfo(ParserBase* parser)
        : name(parser->impl()->NullIdentifier()),
          pattern(parser->impl()->NullExpression()),
          scope(nullptr),
          init_block(parser->impl()->NullStatement()),
          inner_block(parser->impl()->NullStatement()),
          bound_names(1, parser->zone()) {}
    IdentifierT name;
    ExpressionT pattern;
    Scope* scope;
    BlockT init_block;
    BlockT inner_block;
    ZoneList<const AstRawString*> bound_names;
  };

  struct ForInfo {
   public:
    explicit ForInfo(ParserBase* parser)
        : bound_names(1, parser->zone()),
          mode(ForEachStatement::ENUMERATE),
          position(kNoSourcePosition),
          parsing_result() {}
    ZoneList<const AstRawString*> bound_names;
    ForEachStatement::VisitMode mode;
    int position;
    DeclarationParsingResult parsing_result;
  };

  struct ClassInfo {
   public:
    explicit ClassInfo(ParserBase* parser)
        : variable(nullptr),
          extends(parser->impl()->NullExpression()),
          properties(parser->impl()->NewClassPropertyList(4)),
          static_fields(parser->impl()->NewClassPropertyList(4)),
          instance_fields(parser->impl()->NewClassPropertyList(4)),
          constructor(parser->impl()->NullExpression()),
          has_seen_constructor(false),
          has_name_static_property(false),
          has_static_computed_names(false),
          has_static_class_fields(false),
          has_instance_class_fields(false),
          is_anonymous(false),
          static_fields_scope(nullptr),
          instance_fields_scope(nullptr),
          computed_field_count(0) {}
    Variable* variable;
    ExpressionT extends;
    typename Types::ClassPropertyList properties;
    typename Types::ClassPropertyList static_fields;
    typename Types::ClassPropertyList instance_fields;
    FunctionLiteralT constructor;

    // TODO(gsathya): Use a bitfield store all the booleans.
    bool has_seen_constructor;
    bool has_name_static_property;
    bool has_static_computed_names;
    bool has_static_class_fields;
    bool has_instance_class_fields;
    bool is_anonymous;
    DeclarationScope* static_fields_scope;
    DeclarationScope* instance_fields_scope;
    int computed_field_count;
  };

  const AstRawString* ClassFieldVariableName(AstValueFactory* ast_value_factory,
                                             int index) {
    std::string name = ".class-field-" + std::to_string(index);
    return ast_value_factory->GetOneByteString(name.c_str());
  }

  DeclarationScope* NewScriptScope() const {
    return new (zone()) DeclarationScope(zone(), ast_value_factory());
  }

  DeclarationScope* NewVarblockScope() const {
    return new (zone()) DeclarationScope(zone(), scope(), BLOCK_SCOPE);
  }

  ModuleScope* NewModuleScope(DeclarationScope* parent) const {
    return new (zone()) ModuleScope(parent, ast_value_factory());
  }

  DeclarationScope* NewEvalScope(Scope* parent) const {
    return new (zone()) DeclarationScope(zone(), parent, EVAL_SCOPE);
  }

  Scope* NewScope(ScopeType scope_type) const {
    return NewScopeWithParent(scope(), scope_type);
  }

  // This constructor should only be used when absolutely necessary. Most scopes
  // should automatically use scope() as parent, and be fine with
  // NewScope(ScopeType) above.
  Scope* NewScopeWithParent(Scope* parent, ScopeType scope_type) const {
    // Must always use the specific constructors for the blacklisted scope
    // types.
    DCHECK_NE(FUNCTION_SCOPE, scope_type);
    DCHECK_NE(SCRIPT_SCOPE, scope_type);
    DCHECK_NE(MODULE_SCOPE, scope_type);
    DCHECK_NOT_NULL(parent);
    return new (zone()) Scope(zone(), parent, scope_type);
  }

  // Creates a function scope that always allocates in zone(). The function
  // scope itself is either allocated in zone() or in target_zone if one is
  // passed in.
  DeclarationScope* NewFunctionScope(FunctionKind kind,
                                     Zone* target_zone = nullptr) const {
    DCHECK(ast_value_factory());
    if (target_zone == nullptr) target_zone = zone();
    DeclarationScope* result = new (target_zone)
        DeclarationScope(zone(), scope(), FUNCTION_SCOPE, kind);

    // Record presence of an inner function scope
    function_state_->RecordFunctionOrEvalCall();

    // TODO(verwaest): Move into the DeclarationScope constructor.
    if (!IsArrowFunction(kind)) {
      result->DeclareDefaultFunctionVariables(ast_value_factory());
    }
    return result;
  }

  V8_INLINE DeclarationScope* GetDeclarationScope() const {
    return scope()->GetDeclarationScope();
  }
  V8_INLINE DeclarationScope* GetClosureScope() const {
    return scope()->GetClosureScope();
  }

  Scanner* scanner() const { return scanner_; }
  AstValueFactory* ast_value_factory() const { return ast_value_factory_; }
  int position() const { return scanner_->location().beg_pos; }
  int peek_position() const { return scanner_->peek_location().beg_pos; }
  bool stack_overflow() const {
    return pending_error_handler()->stack_overflow();
  }
  void set_stack_overflow() { pending_error_handler()->set_stack_overflow(); }
  int script_id() { return script_id_; }
  void set_script_id(int id) { script_id_ = id; }

  INLINE(Token::Value peek()) {
    if (stack_overflow()) return Token::ILLEGAL;
    return scanner()->peek();
  }

  // Returns the position past the following semicolon (if it exists), and the
  // position past the end of the current token otherwise.
  int PositionAfterSemicolon() {
    return (peek() == Token::SEMICOLON) ? scanner_->peek_location().end_pos
                                        : scanner_->location().end_pos;
  }

  INLINE(Token::Value PeekAhead()) {
    if (stack_overflow()) return Token::ILLEGAL;
    return scanner()->PeekAhead();
  }

  INLINE(Token::Value Next()) {
    if (stack_overflow()) return Token::ILLEGAL;
    {
      if (GetCurrentStackPosition() < stack_limit_) {
        // Any further calls to Next or peek will return the illegal token.
        // The current call must return the next token, which might already
        // have been peek'ed.
        set_stack_overflow();
      }
    }
    return scanner()->Next();
  }

  void Consume(Token::Value token) {
    Token::Value next = Next();
    USE(next);
    USE(token);
    DCHECK(next == token);
  }

  bool Check(Token::Value token) {
    Token::Value next = peek();
    if (next == token) {
      Consume(next);
      return true;
    }
    return false;
  }

  void Expect(Token::Value token, bool* ok) {
    Token::Value next = Next();
    if (next != token) {
      ReportUnexpectedToken(next);
      *ok = false;
    }
  }

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

    Token::Value current = scanner()->current_token();
    Scanner::Location current_location = scanner()->location();
    Token::Value next = Next();

    if (next == Token::SEMICOLON) {
      return;
    }

    *ok = false;
    if (current == Token::AWAIT && !is_async_function()) {
      ReportMessageAt(current_location,
                      MessageTemplate::kAwaitNotInAsyncFunction, kSyntaxError);
      return;
    }

    ReportUnexpectedToken(next);
  }

  // Dummy functions, just useful as arguments to CHECK_OK_CUSTOM.
  static void Void() {}
  template <typename T>
  static T Return(T result) {
    return result;
  }

  bool is_any_identifier(Token::Value token) {
    return token == Token::IDENTIFIER || token == Token::ENUM ||
           token == Token::AWAIT || token == Token::ASYNC ||
           token == Token::ESCAPED_STRICT_RESERVED_WORD ||
           token == Token::FUTURE_STRICT_RESERVED_WORD || token == Token::LET ||
           token == Token::STATIC || token == Token::YIELD;
  }
  bool peek_any_identifier() { return is_any_identifier(peek()); }

  bool CheckContextualKeyword(Token::Value token) {
    if (PeekContextualKeyword(token)) {
      Consume(Token::IDENTIFIER);
      return true;
    }
    return false;
  }

  bool PeekContextualKeyword(Token::Value token) {
    DCHECK(Token::IsContextualKeyword(token));
    return peek() == Token::IDENTIFIER &&
           scanner()->next_contextual_token() == token;
  }

  void ExpectMetaProperty(Token::Value property_name, const char* full_name,
                          int pos, bool* ok);

  void ExpectContextualKeyword(Token::Value token, bool* ok) {
    DCHECK(Token::IsContextualKeyword(token));
    Expect(Token::IDENTIFIER, CHECK_OK_CUSTOM(Void));
    if (scanner()->current_contextual_token() != token) {
      ReportUnexpectedToken(scanner()->current_token());
      *ok = false;
    }
  }

  bool CheckInOrOf(ForEachStatement::VisitMode* visit_mode) {
    if (Check(Token::IN)) {
      *visit_mode = ForEachStatement::ENUMERATE;
      return true;
    } else if (CheckContextualKeyword(Token::OF)) {
      *visit_mode = ForEachStatement::ITERATE;
      return true;
    }
    return false;
  }

  bool PeekInOrOf() {
    return peek() == Token::IN || PeekContextualKeyword(Token::OF);
  }

  // Checks whether an octal literal was last seen between beg_pos and end_pos.
  // Only called for strict mode strings.
  void CheckStrictOctalLiteral(int beg_pos, int end_pos, bool* ok) {
    Scanner::Location octal = scanner()->octal_position();
    if (octal.IsValid() && beg_pos <= octal.beg_pos &&
        octal.end_pos <= end_pos) {
      MessageTemplate::Template message = scanner()->octal_message();
      DCHECK_NE(message, MessageTemplate::kNone);
      impl()->ReportMessageAt(octal, message);
      scanner()->clear_octal_position();
      if (message == MessageTemplate::kStrictDecimalWithLeadingZero) {
        impl()->CountUsage(v8::Isolate::kDecimalWithLeadingZeroInStrictMode);
      }
      *ok = false;
    }
  }

  // Checks if an octal literal or an invalid hex or unicode escape sequence
  // appears in the current template literal token. In the presence of such,
  // either returns false or reports an error, depending on should_throw.
  // Otherwise returns true.
  inline bool CheckTemplateEscapes(bool should_throw, bool* ok) {
    DCHECK(scanner()->current_token() == Token::TEMPLATE_SPAN ||
           scanner()->current_token() == Token::TEMPLATE_TAIL);
    if (!scanner()->has_invalid_template_escape()) {
      return true;
    }

    // Handle error case(s)
    if (should_throw) {
      impl()->ReportMessageAt(scanner()->invalid_template_escape_location(),
                              scanner()->invalid_template_escape_message());
      *ok = false;
    }
    return false;
  }

  void CheckDestructuringElement(ExpressionT element, int beg_pos, int end_pos);

  // Checking the name of a function literal. This has to be done after parsing
  // the function, since the function can declare itself strict.
  void CheckFunctionName(LanguageMode language_mode, IdentifierT function_name,
                         FunctionNameValidity function_name_validity,
                         const Scanner::Location& function_name_loc, bool* ok) {
    if (impl()->IsNull(function_name)) return;
    if (function_name_validity == kSkipFunctionNameCheck) return;
    // The function name needs to be checked in strict mode.
    if (is_sloppy(language_mode)) return;

    if (impl()->IsEvalOrArguments(function_name)) {
      impl()->ReportMessageAt(function_name_loc,
                              MessageTemplate::kStrictEvalArguments);
      *ok = false;
      return;
    }
    if (function_name_validity == kFunctionNameIsStrictReserved) {
      impl()->ReportMessageAt(function_name_loc,
                              MessageTemplate::kUnexpectedStrictReserved);
      *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 Types::Factory* factory() { return &ast_node_factory_; }

  DeclarationScope* GetReceiverScope() const {
    return scope()->GetReceiverScope();
  }
  LanguageMode language_mode() { return scope()->language_mode(); }
  void RaiseLanguageMode(LanguageMode mode) {
    LanguageMode old = scope()->language_mode();
    impl()->SetLanguageMode(scope(), old > mode ? old : mode);
  }
  bool is_generator() const {
    return IsGeneratorFunction(function_state_->kind());
  }
  bool is_async_function() const {
    return IsAsyncFunction(function_state_->kind());
  }
  bool is_async_generator() const {
    return IsAsyncGeneratorFunction(function_state_->kind());
  }
  bool is_resumable() const {
    return IsResumableFunction(function_state_->kind());
  }

  const PendingCompilationErrorHandler* pending_error_handler() const {
    return pending_error_handler_;
  }
  PendingCompilationErrorHandler* pending_error_handler() {
    return pending_error_handler_;
  }

  // Report syntax errors.
  void ReportMessage(MessageTemplate::Template message) {
    Scanner::Location source_location = scanner()->location();
    impl()->ReportMessageAt(source_location, message,
                            static_cast<const char*>(nullptr), kSyntaxError);
  }

  template <typename T>
  void ReportMessage(MessageTemplate::Template message, T arg,
                     ParseErrorType error_type = kSyntaxError) {
    Scanner::Location source_location = scanner()->location();
    impl()->ReportMessageAt(source_location, message, arg, error_type);
  }

  void ReportMessageAt(Scanner::Location location,
                       MessageTemplate::Template message,
                       ParseErrorType error_type) {
    impl()->ReportMessageAt(location, message,
                            static_cast<const char*>(nullptr), error_type);
  }

  void GetUnexpectedTokenMessage(
      Token::Value token, MessageTemplate::Template* message,
      Scanner::Location* location, const char** arg,
      MessageTemplate::Template default_ = MessageTemplate::kUnexpectedToken);

  void ReportUnexpectedToken(Token::Value token);
  void ReportUnexpectedTokenAt(
      Scanner::Location location, Token::Value token,
      MessageTemplate::Template message = MessageTemplate::kUnexpectedToken);

  void ReportClassifierError(
      const typename ExpressionClassifier::Error& error) {
    impl()->ReportMessageAt(error.location, error.message, error.arg,
                            error.type);
  }

  void ValidateExpression(bool* ok) {
    if (!classifier()->is_valid_expression()) {
      ReportClassifierError(classifier()->expression_error());
      *ok = false;
    }
  }

  void ValidateFormalParameterInitializer(bool* ok) {
    if (!classifier()->is_valid_formal_parameter_initializer()) {
      ReportClassifierError(classifier()->formal_parameter_initializer_error());
      *ok = false;
    }
  }

  void ValidateBindingPattern(bool* ok) {
    if (!classifier()->is_valid_binding_pattern()) {
      ReportClassifierError(classifier()->binding_pattern_error());
      *ok = false;
    }
  }

  void ValidateAssignmentPattern(bool* ok) {
    if (!classifier()->is_valid_assignment_pattern()) {
      ReportClassifierError(classifier()->assignment_pattern_error());
      *ok = false;
    }
  }

  void ValidateFormalParameters(LanguageMode language_mode,
                                bool allow_duplicates, bool* ok) {
    if (!allow_duplicates &&
        !classifier()->is_valid_formal_parameter_list_without_duplicates()) {
      ReportClassifierError(classifier()->duplicate_formal_parameter_error());
      *ok = false;
    } else if (is_strict(language_mode) &&
               !classifier()->is_valid_strict_mode_formal_parameters()) {
      ReportClassifierError(classifier()->strict_mode_formal_parameter_error());
      *ok = false;
    }
  }

  bool IsValidArrowFormalParametersStart(Token::Value token) {
    return is_any_identifier(token) || token == Token::LPAREN;
  }

  void ValidateArrowFormalParameters(ExpressionT expr,
                                     bool parenthesized_formals, bool is_async,
                                     bool* ok) {
    if (classifier()->is_valid_binding_pattern()) {
      // A simple arrow formal parameter: IDENTIFIER => BODY.
      if (!impl()->IsIdentifier(expr)) {
        impl()->ReportMessageAt(scanner()->location(),
                                MessageTemplate::kUnexpectedToken,
                                Token::String(scanner()->current_token()));
        *ok = false;
      }
    } else if (!classifier()->is_valid_arrow_formal_parameters()) {
      // If after parsing the expr, we see an error but the expression is
      // neither a valid binding pattern nor a valid parenthesized formal
      // parameter list, show the "arrow formal parameters" error if the formals
      // started with a parenthesis, and the binding pattern error otherwise.
      const typename ExpressionClassifier::Error& error =
          parenthesized_formals ? classifier()->arrow_formal_parameters_error()
                                : classifier()->binding_pattern_error();
      ReportClassifierError(error);
      *ok = false;
    }
    if (is_async && !classifier()->is_valid_async_arrow_formal_parameters()) {
      const typename ExpressionClassifier::Error& error =
          classifier()->async_arrow_formal_parameters_error();
      ReportClassifierError(error);
      *ok = false;
    }
  }

  void ValidateLetPattern(bool* ok) {
    if (!classifier()->is_valid_let_pattern()) {
      ReportClassifierError(classifier()->let_pattern_error());
      *ok = false;
    }
  }

  void BindingPatternUnexpectedToken() {
    MessageTemplate::Template message = MessageTemplate::kUnexpectedToken;
    const char* arg;
    Scanner::Location location = scanner()->peek_location();
    GetUnexpectedTokenMessage(peek(), &message, &location, &arg);
    classifier()->RecordBindingPatternError(location, message, arg);
  }

  void ArrowFormalParametersUnexpectedToken() {
    MessageTemplate::Template message = MessageTemplate::kUnexpectedToken;
    const char* arg;
    Scanner::Location location = scanner()->peek_location();
    GetUnexpectedTokenMessage(peek(), &message, &location, &arg);
    classifier()->RecordArrowFormalParametersError(location, message, arg);
  }

  // Recursive descent functions.
  // All ParseXXX functions take as the last argument an *ok parameter
  // which is set to false if parsing failed; it is unchanged otherwise.
  // By making the 'exception handling' explicit, we are forced to check
  // for failure at the call sites. The family of CHECK_OK* macros can
  // be useful for this.

  // Parses an identifier that is valid for the current scope, in particular it
  // fails on strict mode future reserved keywords in a strict scope. If
  // allow_eval_or_arguments is kAllowEvalOrArguments, we allow "eval" or
  // "arguments" as identifier even in strict mode (this is needed in cases like
  // "var foo = eval;").
  IdentifierT ParseIdentifier(AllowRestrictedIdentifiers, bool* ok);
  IdentifierT ParseAndClassifyIdentifier(bool* ok);
  // Parses an identifier or a strict mode future reserved word, and indicate
  // whether it is strict mode future reserved. Allows passing in function_kind
  // for the case of parsing the identifier in a function expression, where the
  // relevant "function_kind" bit is of the function being parsed, not the
  // containing function.
  IdentifierT ParseIdentifierOrStrictReservedWord(FunctionKind function_kind,
                                                  bool* is_strict_reserved,
                                                  bool* is_await, bool* ok);
  IdentifierT ParseIdentifierOrStrictReservedWord(bool* is_strict_reserved,
                                                  bool* is_await, bool* ok) {
    return ParseIdentifierOrStrictReservedWord(
        function_state_->kind(), is_strict_reserved, is_await, ok);
  }

  IdentifierT ParseIdentifierName(bool* ok);

  ExpressionT ParseRegExpLiteral(bool* ok);

  ExpressionT ParsePrimaryExpression(bool* is_async, bool* ok);
  ExpressionT ParsePrimaryExpression(bool* ok) {
    bool is_async;
    return ParsePrimaryExpression(&is_async, ok);
  }

  // Use when parsing an expression that is known to not be a pattern or part
  // of a pattern.
  V8_INLINE ExpressionT ParseExpression(bool accept_IN, bool* ok);

  // This method does not wrap the parsing of the expression inside a
  // new expression classifier; it uses the top-level classifier instead.
  // It should be used whenever we're parsing something with the "cover"
  // grammar that recognizes both patterns and non-patterns (which roughly
  // corresponds to what's inside the parentheses generated by the symbol
  // "CoverParenthesizedExpressionAndArrowParameterList" in the ES 2017
  // specification).
  ExpressionT ParseExpressionCoverGrammar(bool accept_IN, bool* ok);

  ExpressionT ParseArrayLiteral(bool* ok);

  enum class PropertyKind {
    kAccessorProperty,
    kValueProperty,
    kShorthandProperty,
    kMethodProperty,
    kClassField,
    kSpreadProperty,
    kNotSet
  };

  bool SetPropertyKindFromToken(Token::Value token, PropertyKind* kind);
  ExpressionT ParsePropertyName(IdentifierT* name, PropertyKind* kind,
                                bool* is_generator, bool* is_get, bool* is_set,
                                bool* is_async, bool* is_computed_name,
                                bool* ok);
  ExpressionT ParseObjectLiteral(bool* ok);
  ClassLiteralPropertyT ParseClassPropertyDefinition(
      ClassLiteralChecker* checker, ClassInfo* class_info, bool has_extends,
      bool* is_computed_name, bool* has_seen_constructor,
      ClassLiteralProperty::Kind* property_kind, bool* is_static,
      bool* has_name_static_property, bool* ok);
  ExpressionT ParseClassFieldInitializer(ClassInfo* class_info, bool is_static,
                                         bool* ok);
  ObjectLiteralPropertyT ParseObjectPropertyDefinition(
      ObjectLiteralChecker* checker, bool* is_computed_name,
      bool* is_rest_property, bool* ok);
  ExpressionListT ParseArguments(Scanner::Location* first_spread_pos,
                                 bool maybe_arrow,
                                 bool* is_simple_parameter_list, bool* ok);
  ExpressionListT ParseArguments(Scanner::Location* first_spread_pos,
                                 bool* ok) {
    return ParseArguments(first_spread_pos, false, nullptr, ok);
  }

  ExpressionT ParseAssignmentExpression(bool accept_IN, bool* ok);
  ExpressionT ParseYieldExpression(bool accept_IN, 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* is_async, bool* ok);
  ExpressionT ParseMemberExpression(bool* is_async, bool* ok);
  ExpressionT ParseMemberExpressionContinuation(ExpressionT expression,
                                                bool* is_async, bool* ok);

  // `rewritable_length`: length of the destructuring_assignments_to_rewrite()
  // queue in the parent function state, prior to parsing of formal parameters.
  // If the arrow function is lazy, any items added during formal parameter
  // parsing are removed from the queue.
  ExpressionT ParseArrowFunctionLiteral(bool accept_IN,
                                        const FormalParametersT& parameters,
                                        int rewritable_length, bool* ok);
  void ParseSingleExpressionFunctionBody(StatementListT body, bool is_async,
                                         bool accept_IN, bool* ok);
  void ParseAsyncFunctionBody(Scope* scope, StatementListT body, bool* ok);
  ExpressionT ParseAsyncFunctionLiteral(bool* ok);
  ExpressionT ParseClassLiteral(IdentifierT name,
                                Scanner::Location class_name_location,
                                bool name_is_strict_reserved,
                                int class_token_pos, bool* ok);
  ExpressionT ParseTemplateLiteral(ExpressionT tag, int start, bool tagged,
                                   bool* ok);
  ExpressionT ParseSuperExpression(bool is_new, bool* ok);
  ExpressionT ParseImportExpressions(bool* ok);
  ExpressionT ParseNewTargetExpression(bool* ok);

  void ParseFormalParameter(FormalParametersT* parameters, bool* ok);
  void ParseFormalParameterList(FormalParametersT* parameters, bool* ok);
  void CheckArityRestrictions(int param_count, FunctionKind function_type,
                              bool has_rest, int formals_start_pos,
                              int formals_end_pos, bool* ok);

  BlockT ParseVariableDeclarations(VariableDeclarationContext var_context,
                                   DeclarationParsingResult* parsing_result,
                                   ZoneList<const AstRawString*>* names,
                                   bool* ok);
  StatementT ParseAsyncFunctionDeclaration(ZoneList<const AstRawString*>* names,
                                           bool default_export, bool* ok);
  StatementT ParseFunctionDeclaration(bool* ok);
  StatementT ParseHoistableDeclaration(ZoneList<const AstRawString*>* names,
                                       bool default_export, bool* ok);
  StatementT ParseHoistableDeclaration(int pos, ParseFunctionFlags flags,
                                       ZoneList<const AstRawString*>* names,
                                       bool default_export, bool* ok);
  StatementT ParseClassDeclaration(ZoneList<const AstRawString*>* names,
                                   bool default_export, bool* ok);
  StatementT ParseNativeDeclaration(bool* ok);

  // Consumes the ending }.
  void ParseFunctionBody(StatementListT result, IdentifierT function_name,
                         int pos, const FormalParametersT& parameters,
                         FunctionKind kind,
                         FunctionLiteral::FunctionType function_type, bool* ok);

  // Under some circumstances, we allow preparsing to abort if the preparsed
  // function is "long and trivial", and fully parse instead. Our current
  // definition of "long and trivial" is:
  // - over kLazyParseTrialLimit statements
  // - all starting with an identifier (i.e., no if, for, while, etc.)
  static const int kLazyParseTrialLimit = 200;

  // TODO(nikolaos, marja): The first argument should not really be passed
  // by value. The method is expected to add the parsed statements to the
  // list. This works because in the case of the parser, StatementListT is
  // a pointer whereas the preparser does not really modify the body.
  V8_INLINE void ParseStatementList(StatementListT body, Token::Value end_token,
                                    bool* ok) {
    LazyParsingResult result = ParseStatementList(body, end_token, false, ok);
    USE(result);
    DCHECK_EQ(result, kLazyParsingComplete);
  }
  LazyParsingResult ParseStatementList(StatementListT body,
                                       Token::Value end_token, bool may_abort,
                                       bool* ok);
  StatementT ParseStatementListItem(bool* ok);
  StatementT ParseStatement(ZoneList<const AstRawString*>* labels, bool* ok) {
    return ParseStatement(labels, kDisallowLabelledFunctionStatement, ok);
  }
  StatementT ParseStatement(ZoneList<const AstRawString*>* labels,
                            AllowLabelledFunctionStatement allow_function,
                            bool* ok);
  BlockT ParseBlock(ZoneList<const AstRawString*>* labels, bool* ok);

  // Parse a SubStatement in strict mode, or with an extra block scope in
  // sloppy mode to handle
  // ES#sec-functiondeclarations-in-ifstatement-statement-clauses
  StatementT ParseScopedStatement(ZoneList<const AstRawString*>* labels,
                                  bool* ok);

  StatementT ParseVariableStatement(VariableDeclarationContext var_context,
                                    ZoneList<const AstRawString*>* names,
                                    bool* ok);

  // Magical syntax support.
  ExpressionT ParseV8Intrinsic(bool* ok);

  ExpressionT ParseDoExpression(bool* ok);

  StatementT ParseDebuggerStatement(bool* ok);

  StatementT ParseExpressionOrLabelledStatement(
      ZoneList<const AstRawString*>* labels,
      AllowLabelledFunctionStatement allow_function, bool* ok);
  StatementT ParseIfStatement(ZoneList<const AstRawString*>* labels, bool* ok);
  StatementT ParseContinueStatement(bool* ok);
  StatementT ParseBreakStatement(ZoneList<const AstRawString*>* labels,
                                 bool* ok);
  StatementT ParseReturnStatement(bool* ok);
  StatementT ParseWithStatement(ZoneList<const AstRawString*>* labels,
                                bool* ok);
  StatementT ParseDoWhileStatement(ZoneList<const AstRawString*>* labels,
                                   bool* ok);
  StatementT ParseWhileStatement(ZoneList<const AstRawString*>* labels,
                                 bool* ok);
  StatementT ParseThrowStatement(bool* ok);
  StatementT ParseSwitchStatement(ZoneList<const AstRawString*>* labels,
                                  bool* ok);
  StatementT ParseTryStatement(bool* ok);
  StatementT ParseForStatement(ZoneList<const AstRawString*>* labels, bool* ok);
  StatementT ParseForEachStatementWithDeclarations(
      int stmt_pos, ForInfo* for_info, ZoneList<const AstRawString*>* labels,
      Scope* inner_block_scope, bool* ok);
  StatementT ParseForEachStatementWithoutDeclarations(
      int stmt_pos, ExpressionT expression, int lhs_beg_pos, int lhs_end_pos,
      ForInfo* for_info, ZoneList<const AstRawString*>* labels, bool* ok);

  // Parse a C-style for loop: 'for (<init>; <cond>; <next>) { ... }'
  // "for (<init>;" is assumed to have been parser already.
  ForStatementT ParseStandardForLoop(int stmt_pos,
                                     ZoneList<const AstRawString*>* labels,
                                     ExpressionT* cond, StatementT* next,
                                     StatementT* body, bool* ok);
  // Same as the above, but handles those cases where <init> is a
  // lexical variable declaration.
  StatementT ParseStandardForLoopWithLexicalDeclarations(
      int stmt_pos, StatementT init, ForInfo* for_info,
      ZoneList<const AstRawString*>* labels, bool* ok);
  StatementT ParseForAwaitStatement(ZoneList<const AstRawString*>* labels,
                                    bool* ok);

  bool IsNextLetKeyword();
  bool IsTrivialExpression();

  // 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, int beg_pos, int end_pos,
      MessageTemplate::Template message, bool* ok);
  ExpressionT CheckAndRewriteReferenceExpression(
      ExpressionT expression, int beg_pos, int end_pos,
      MessageTemplate::Template message, ParseErrorType type, bool* ok);

  bool IsValidReferenceExpression(ExpressionT expression);

  bool IsAssignableIdentifier(ExpressionT expression) {
    if (!impl()->IsIdentifier(expression)) return false;
    if (is_strict(language_mode()) &&
        impl()->IsEvalOrArguments(impl()->AsIdentifier(expression))) {
      return false;
    }
    return true;
  }

  bool IsValidPattern(ExpressionT expression) {
    return expression->IsObjectLiteral() || expression->IsArrayLiteral();
  }

  // Due to hoisting, the value of a 'var'-declared variable may actually change
  // even if the code contains only the "initial" assignment, namely when that
  // assignment occurs inside a loop.  For example:
  //
  //   let i = 10;
  //   do { var x = i } while (i--):
  //
  // As a simple and very conservative approximation of this, we explicitly mark
  // as maybe-assigned any non-lexical variable whose initializing "declaration"
  // does not syntactically occur in the function scope.  (In the example above,
  // it occurs in a block scope.)
  //
  // Note that non-lexical variables include temporaries, which may also get
  // assigned inside a loop due to the various rewritings that the parser
  // performs.
  //
  // This also handles marking of loop variables in for-in and for-of loops,
  // as determined by declaration_kind.
  //
  static void MarkLoopVariableAsAssigned(
      Scope* scope, Variable* var,
      typename DeclarationDescriptor::Kind declaration_kind);

  FunctionKind FunctionKindForImpl(bool is_method, bool is_generator,
                                   bool is_async) {
    static const FunctionKind kFunctionKinds[][2][2] = {
        {
            // is_method=false
            {// is_generator=false
             FunctionKind::kNormalFunction, FunctionKind::kAsyncFunction},
            {// is_generator=true
             FunctionKind::kGeneratorFunction,
             FunctionKind::kAsyncGeneratorFunction},
        },
        {
            // is_method=true
            {// is_generator=false
             FunctionKind::kConciseMethod, FunctionKind::kAsyncConciseMethod},
            {// is_generator=true
             FunctionKind::kConciseGeneratorMethod,
             FunctionKind::kAsyncConciseGeneratorMethod},
        }};
    return kFunctionKinds[is_method][is_generator][is_async];
  }

  inline FunctionKind FunctionKindFor(bool is_generator, bool is_async) {
    const bool kIsMethod = false;
    return FunctionKindForImpl(kIsMethod, is_generator, is_async);
  }

  inline FunctionKind MethodKindFor(bool is_generator, bool is_async) {
    const bool kIsMethod = true;
    return FunctionKindForImpl(kIsMethod, is_generator, is_async);
  }

  // Keep track of eval() calls since they disable all local variable
  // optimizations. This checks if expression is an eval call, and if yes,
  // forwards the information to scope.
  Call::PossiblyEval CheckPossibleEvalCall(ExpressionT expression,
                                           Scope* scope) {
    if (impl()->IsIdentifier(expression) &&
        impl()->IsEval(impl()->AsIdentifier(expression))) {
      scope->RecordInnerScopeEvalCall();
      function_state_->RecordFunctionOrEvalCall();
      if (is_sloppy(scope->language_mode())) {
        // For sloppy scopes we also have to record the call at function level,
        // in case it includes declarations that will be hoisted.
        scope->GetDeclarationScope()->RecordEvalCall();
      }

      // This call is only necessary to track evals that may be
      // inside arrow function parameter lists. In that case,
      // Scope::Snapshot::Reparent will move this bit down into
      // the arrow function's scope.
      scope->RecordEvalCall();

      return Call::IS_POSSIBLY_EVAL;
    }
    return Call::NOT_EVAL;
  }

  // Convenience method which determines the type of return statement to emit
  // depending on the current function type.
  inline StatementT BuildReturnStatement(ExpressionT expr, int pos,
                                         int end_pos = kNoSourcePosition) {
    if (impl()->IsNull(expr)) {
      expr = factory()->NewUndefinedLiteral(kNoSourcePosition);
    } else if (is_async_generator()) {
      // In async generators, if there is an explicit operand to the return
      // statement, await the operand.
      expr = factory()->NewAwait(expr, kNoSourcePosition);
    }
    if (is_async_function()) {
      return factory()->NewAsyncReturnStatement(expr, pos, end_pos);
    }
    return factory()->NewReturnStatement(expr, pos, end_pos);
  }

  // Validation per ES6 object literals.
  class ObjectLiteralChecker {
   public:
    explicit ObjectLiteralChecker(ParserBase* parser)
        : parser_(parser), has_seen_proto_(false) {}

    void CheckDuplicateProto(Token::Value property);

   private:
    bool IsProto() const {
      return this->scanner()->CurrentMatchesContextualEscaped(
          Token::PROTO_UNDERSCORED);
    }

    ParserBase* parser() const { return parser_; }
    Scanner* scanner() const { return parser_->scanner(); }

    ParserBase* parser_;
    bool has_seen_proto_;
  };

  // Validation per ES6 class literals.
  class ClassLiteralChecker {
   public:
    explicit ClassLiteralChecker(ParserBase* parser)
        : parser_(parser), has_seen_constructor_(false) {}

    void CheckClassMethodName(Token::Value property, PropertyKind type,
                              bool is_generator, bool is_async, bool is_static,
                              bool* ok);
    void CheckClassFieldName(bool is_static, bool* ok);

   private:
    bool IsConstructor() {
      return this->scanner()->CurrentMatchesContextualEscaped(
          Token::CONSTRUCTOR);
    }
    bool IsPrototype() {
      return this->scanner()->CurrentMatchesContextualEscaped(Token::PROTOTYPE);
    }

    ParserBase* parser() const { return parser_; }
    Scanner* scanner() const { return parser_->scanner(); }

    ParserBase* parser_;
    bool has_seen_constructor_;
  };

  ModuleDescriptor* module() const {
    return scope()->AsModuleScope()->module();
  }
  Scope* scope() const { return scope_; }

  // Stack of expression classifiers.
  // The top of the stack is always pointed to by classifier().
  V8_INLINE ExpressionClassifier* classifier() const {
    DCHECK_NOT_NULL(classifier_);
    return classifier_;
  }

  // Accumulates the classifier that is on top of the stack (inner) to
  // the one that is right below (outer) and pops the inner.
  V8_INLINE void Accumulate(unsigned productions) {
    DCHECK_NOT_NULL(classifier_);
    ExpressionClassifier* previous = classifier_->previous();
    DCHECK_NOT_NULL(previous);
    previous->Accumulate(classifier_, productions);
    classifier_ = previous;
  }

  V8_INLINE void AccumulateNonBindingPatternErrors() {
    this->Accumulate(ExpressionClassifier::AllProductions &
                     ~(ExpressionClassifier::BindingPatternProduction |
                       ExpressionClassifier::LetPatternProduction));
  }

  // Pops and discards the classifier that is on top of the stack
  // without accumulating.
  V8_INLINE void DiscardExpressionClassifier() {
    DCHECK_NOT_NULL(classifier_);
    classifier_->Discard();
    classifier_ = classifier_->previous();
  }

  // Accumulate errors that can be arbitrarily deep in an expression.
  // These correspond to the ECMAScript spec's 'Contains' operation
  // on productions. This includes:
  //
  // - YieldExpression is disallowed in arrow parameters in a generator.
  // - AwaitExpression is disallowed in arrow parameters in an async function.
  // - AwaitExpression is disallowed in async arrow parameters.
  //
  V8_INLINE void AccumulateFormalParameterContainmentErrors() {
    Accumulate(ExpressionClassifier::FormalParameterInitializerProduction |
               ExpressionClassifier::AsyncArrowFormalParametersProduction);
  }

  // Parser base's protected field members.

  Scope* scope_;                   // Scope stack.
  Scope* original_scope_;  // The top scope for the current parsing item.
  FunctionState* function_state_;  // Function state stack.
  v8::Extension* extension_;
  FuncNameInferrer* fni_;
  AstValueFactory* ast_value_factory_;  // Not owned.
  typename Types::Factory ast_node_factory_;
  RuntimeCallStats* runtime_call_stats_;
  internal::Logger* logger_;
  bool parsing_on_main_thread_;
  const bool parsing_module_;
  uintptr_t stack_limit_;
  PendingCompilationErrorHandler* pending_error_handler_;

  // Parser base's private field members.

 private:
  Zone* zone_;
  ExpressionClassifier* classifier_;

  Scanner* scanner_;

  FunctionLiteral::EagerCompileHint default_eager_compile_hint_;

  int function_literal_id_;
  int script_id_;

  bool allow_natives_;
  bool allow_harmony_do_expressions_;
  bool allow_harmony_function_sent_;
  bool allow_harmony_public_fields_;
  bool allow_harmony_static_fields_;
  bool allow_harmony_dynamic_import_;
  bool allow_harmony_import_meta_;
  bool allow_harmony_optional_catch_binding_;
  bool allow_harmony_private_fields_;

  friend class DiscardableZoneScope;
};

template <typename Impl>
ParserBase<Impl>::FunctionState::FunctionState(
    FunctionState** function_state_stack, Scope** scope_stack,
    DeclarationScope* scope)
    : BlockState(scope_stack, scope),
      expected_property_count_(0),
      function_state_stack_(function_state_stack),
      outer_function_state_(*function_state_stack),
      scope_(scope),
      destructuring_assignments_to_rewrite_(16, scope->zone()),
      non_patterns_to_rewrite_(0, scope->zone()),
      reported_errors_(16, scope->zone()),
      dont_optimize_reason_(BailoutReason::kNoReason),
      next_function_is_likely_called_(false),
      previous_function_was_likely_called_(false),
      contains_function_or_eval_(false) {
  *function_state_stack = this;
  if (outer_function_state_) {
    outer_function_state_->previous_function_was_likely_called_ =
        outer_function_state_->next_function_is_likely_called_;
    outer_function_state_->next_function_is_likely_called_ = false;
  }
}

template <typename Impl>
ParserBase<Impl>::FunctionState::~FunctionState() {
  *function_state_stack_ = outer_function_state_;
}

template <typename Impl>
void ParserBase<Impl>::GetUnexpectedTokenMessage(
    Token::Value token, MessageTemplate::Template* message,
    Scanner::Location* location, const char** arg,
    MessageTemplate::Template default_) {
  *arg = nullptr;
  switch (token) {
    case Token::EOS:
      *message = MessageTemplate::kUnexpectedEOS;
      break;
    case Token::SMI:
    case Token::NUMBER:
    case Token::BIGINT:
      *message = MessageTemplate::kUnexpectedTokenNumber;
      break;
    case Token::STRING:
      *message = MessageTemplate::kUnexpectedTokenString;
      break;
    case Token::PRIVATE_NAME:
    case Token::IDENTIFIER:
      *message = MessageTemplate::kUnexpectedTokenIdentifier;
      break;
    case Token::AWAIT:
    case Token::ENUM:
      *message = MessageTemplate::kUnexpectedReserved;
      break;
    case Token::LET:
    case Token::STATIC:
    case Token::YIELD:
    case Token::FUTURE_STRICT_RESERVED_WORD:
      *message = is_strict(language_mode())
                     ? MessageTemplate::kUnexpectedStrictReserved
                     : MessageTemplate::kUnexpectedTokenIdentifier;
      break;
    case Token::TEMPLATE_SPAN:
    case Token::TEMPLATE_TAIL:
      *message = MessageTemplate::kUnexpectedTemplateString;
      break;
    case Token::ESCAPED_STRICT_RESERVED_WORD:
    case Token::ESCAPED_KEYWORD:
      *message = MessageTemplate::kInvalidEscapedReservedWord;
      break;
    case Token::ILLEGAL:
      if (scanner()->has_error()) {
        *message = scanner()->error();
        *location = scanner()->error_location();
      } else {
        *message = MessageTemplate::kInvalidOrUnexpectedToken;
      }
      break;
    case Token::REGEXP_LITERAL:
      *message = MessageTemplate::kUnexpectedTokenRegExp;
      break;
    default:
      const char* name = Token::String(token);
      DCHECK_NOT_NULL(name);
      *arg = name;
      break;
  }
}

template <typename Impl>
void ParserBase<Impl>::ReportUnexpectedToken(Token::Value token) {
  return ReportUnexpectedTokenAt(scanner_->location(), token);
}

template <typename Impl>
void ParserBase<Impl>::ReportUnexpectedTokenAt(
    Scanner::Location source_location, Token::Value token,
    MessageTemplate::Template message) {
  const char* arg;
  GetUnexpectedTokenMessage(token, &message, &source_location, &arg);
  impl()->ReportMessageAt(source_location, message, arg);
}

template <typename Impl>
typename ParserBase<Impl>::IdentifierT ParserBase<Impl>::ParseIdentifier(
    AllowRestrictedIdentifiers allow_restricted_identifiers, bool* ok) {
  ExpressionClassifier classifier(this);
  auto result = ParseAndClassifyIdentifier(CHECK_OK_CUSTOM(NullIdentifier));

  if (allow_restricted_identifiers == kDontAllowRestrictedIdentifiers) {
    ValidateAssignmentPattern(CHECK_OK_CUSTOM(NullIdentifier));
    ValidateBindingPattern(CHECK_OK_CUSTOM(NullIdentifier));
  }

  return result;
}

template <typename Impl>
typename ParserBase<Impl>::IdentifierT
ParserBase<Impl>::ParseAndClassifyIdentifier(bool* ok) {
  Token::Value next = Next();
  if (next == Token::IDENTIFIER || next == Token::ASYNC ||
      (next == Token::AWAIT && !parsing_module_ && !is_async_function())) {
    IdentifierT name = impl()->GetSymbol();

    if (impl()->IsArguments(name) && scope()->ShouldBanArguments()) {
      ReportMessage(MessageTemplate::kArgumentsDisallowedInInitializer);
      *ok = false;
      return impl()->NullIdentifier();
    }

    // When this function is used to read a formal parameter, we don't always
    // know whether the function is going to be strict or sloppy.  Indeed for
    // arrow functions we don't always know that the identifier we are reading
    // is actually a formal parameter.  Therefore besides the errors that we
    // must detect because we know we're in strict mode, we also record any
    // error that we might make in the future once we know the language mode.
    if (impl()->IsEvalOrArguments(name)) {
      classifier()->RecordStrictModeFormalParameterError(
          scanner()->location(), MessageTemplate::kStrictEvalArguments);
      if (is_strict(language_mode())) {
        classifier()->RecordBindingPatternError(
            scanner()->location(), MessageTemplate::kStrictEvalArguments);
      }
    } else if (next == Token::AWAIT) {
      classifier()->RecordAsyncArrowFormalParametersError(
          scanner()->location(), MessageTemplate::kAwaitBindingIdentifier);
    }

    if (classifier()->duplicate_finder() != nullptr &&
        scanner()->IsDuplicateSymbol(classifier()->duplicate_finder(),
                                     ast_value_factory())) {
      classifier()->RecordDuplicateFormalParameterError(scanner()->location());
    }
    return name;
  } else if (is_sloppy(language_mode()) &&
             (next == Token::FUTURE_STRICT_RESERVED_WORD ||
              next == Token::ESCAPED_STRICT_RESERVED_WORD ||
              next == Token::LET || next == Token::STATIC ||
              (next == Token::YIELD && !is_generator()))) {
    classifier()->RecordStrictModeFormalParameterError(
        scanner()->location(), MessageTemplate::kUnexpectedStrictReserved);
    if (next == Token::ESCAPED_STRICT_RESERVED_WORD &&
        is_strict(language_mode())) {
      ReportUnexpectedToken(next);
      *ok = false;
      return impl()->NullIdentifier();
    }
    if (scanner()->IsLet()) {
      classifier()->RecordLetPatternError(
          scanner()->location(), MessageTemplate::kLetInLexicalBinding);
    }
    return impl()->GetSymbol();
  } else {
    ReportUnexpectedToken(next);
    *ok = false;
    return impl()->NullIdentifier();
  }
}

template <class Impl>
typename ParserBase<Impl>::IdentifierT
ParserBase<Impl>::ParseIdentifierOrStrictReservedWord(
    FunctionKind function_kind, bool* is_strict_reserved, bool* is_await,
    bool* ok) {
  Token::Value next = Next();
  if (next == Token::IDENTIFIER || (next == Token::AWAIT && !parsing_module_ &&
                                    !IsAsyncFunction(function_kind)) ||
      next == Token::ASYNC) {
    *is_strict_reserved = false;
    *is_await = next == Token::AWAIT;
  } else if (next == Token::ESCAPED_STRICT_RESERVED_WORD ||
             next == Token::FUTURE_STRICT_RESERVED_WORD || next == Token::LET ||
             next == Token::STATIC ||
             (next == Token::YIELD && !IsGeneratorFunction(function_kind))) {
    *is_strict_reserved = true;
  } else {
    ReportUnexpectedToken(next);
    *ok = false;
    return impl()->NullIdentifier();
  }

  return impl()->GetSymbol();
}

template <typename Impl>
typename ParserBase<Impl>::IdentifierT ParserBase<Impl>::ParseIdentifierName(
    bool* ok) {
  Token::Value next = Next();
  if (next != Token::IDENTIFIER && next != Token::ASYNC &&
      next != Token::ENUM && next != Token::AWAIT && next != Token::LET &&
      next != Token::STATIC && next != Token::YIELD &&
      next != Token::FUTURE_STRICT_RESERVED_WORD &&
      next != Token::ESCAPED_KEYWORD &&
      next != Token::ESCAPED_STRICT_RESERVED_WORD && !Token::IsKeyword(next)) {
    ReportUnexpectedToken(next);
    *ok = false;
    return impl()->NullIdentifier();
  }

  return impl()->GetSymbol();
}

template <typename Impl>
typename ParserBase<Impl>::ExpressionT ParserBase<Impl>::ParseRegExpLiteral(
    bool* ok) {
  int pos = peek_position();
  if (!scanner()->ScanRegExpPattern()) {
    Next();
    ReportMessage(MessageTemplate::kUnterminatedRegExp);
    *ok = false;
    return impl()->NullExpression();
  }

  IdentifierT js_pattern = impl()->GetNextSymbol();
  Maybe<RegExp::Flags> flags = scanner()->ScanRegExpFlags();
  if (flags.IsNothing()) {
    Next();
    ReportMessage(MessageTemplate::kMalformedRegExpFlags);
    *ok = false;
    return impl()->NullExpression();
  }
  int js_flags = flags.FromJust();
  Next();
  return factory()->NewRegExpLiteral(js_pattern, js_flags, pos);
}

template <typename Impl>
typename ParserBase<Impl>::ExpressionT ParserBase<Impl>::ParsePrimaryExpression(
    bool* is_async, bool* ok) {
  // PrimaryExpression ::
  //   'this'
  //   'null'
  //   'true'
  //   'false'
  //   Identifier
  //   Number
  //   String
  //   ArrayLiteral
  //   ObjectLiteral
  //   RegExpLiteral
  //   ClassLiteral
  //   '(' Expression ')'
  //   TemplateLiteral
  //   do Block
  //   AsyncFunctionLiteral

  int beg_pos = peek_position();
  switch (peek()) {
    case Token::THIS: {
      BindingPatternUnexpectedToken();
      Consume(Token::THIS);
      return impl()->ThisExpression(beg_pos);
    }

    case Token::NULL_LITERAL:
    case Token::TRUE_LITERAL:
    case Token::FALSE_LITERAL:
    case Token::SMI:
    case Token::NUMBER:
    case Token::BIGINT:
      BindingPatternUnexpectedToken();
      return impl()->ExpressionFromLiteral(Next(), beg_pos);

    case Token::ASYNC:
      if (!scanner()->HasAnyLineTerminatorAfterNext() &&
          PeekAhead() == Token::FUNCTION) {
        BindingPatternUnexpectedToken();
        Consume(Token::ASYNC);
        return ParseAsyncFunctionLiteral(CHECK_OK);
      }
      // CoverCallExpressionAndAsyncArrowHead
      *is_async = true;
    /* falls through */
    case Token::IDENTIFIER:
    case Token::LET:
    case Token::STATIC:
    case Token::YIELD:
    case Token::AWAIT:
    case Token::ESCAPED_STRICT_RESERVED_WORD:
    case Token::FUTURE_STRICT_RESERVED_WORD: {
      // Using eval or arguments in this context is OK even in strict mode.
      IdentifierT name = ParseAndClassifyIdentifier(CHECK_OK);
      return impl()->ExpressionFromIdentifier(name, beg_pos);
    }

    case Token::STRING: {
      BindingPatternUnexpectedToken();
      Consume(Token::STRING);
      return impl()->ExpressionFromString(beg_pos);
    }

    case Token::ASSIGN_DIV:
    case Token::DIV:
      classifier()->RecordBindingPatternError(
          scanner()->peek_location(), MessageTemplate::kUnexpectedTokenRegExp);
      return ParseRegExpLiteral(ok);

    case Token::LBRACK:
      return ParseArrayLiteral(ok);

    case Token::LBRACE:
      return ParseObjectLiteral(ok);

    case Token::LPAREN: {
      // Arrow function formal parameters are either a single identifier or a
      // list of BindingPattern productions enclosed in parentheses.
      // Parentheses are not valid on the LHS of a BindingPattern, so we use the
      // is_valid_binding_pattern() check to detect multiple levels of
      // parenthesization.
      bool pattern_error = !classifier()->is_valid_binding_pattern();
      classifier()->RecordPatternError(scanner()->peek_location(),
                                       MessageTemplate::kUnexpectedToken,
                                       Token::String(Token::LPAREN));
      if (pattern_error) ArrowFormalParametersUnexpectedToken();
      Consume(Token::LPAREN);
      if (Check(Token::RPAREN)) {
        // ()=>x.  The continuation that looks for the => is in
        // ParseAssignmentExpression.
        classifier()->RecordExpressionError(scanner()->location(),
                                            MessageTemplate::kUnexpectedToken,
                                            Token::String(Token::RPAREN));
        return factory()->NewEmptyParentheses(beg_pos);
      }
      // Heuristically try to detect immediately called functions before
      // seeing the call parentheses.
      if (peek() == Token::FUNCTION ||
          (peek() == Token::ASYNC && PeekAhead() == Token::FUNCTION)) {
        function_state_->set_next_function_is_likely_called();
      }
      ExpressionT expr = ParseExpressionCoverGrammar(true, CHECK_OK);
      Expect(Token::RPAREN, CHECK_OK);
      return expr;
    }

    case Token::CLASS: {
      BindingPatternUnexpectedToken();
      Consume(Token::CLASS);
      int class_token_pos = position();
      IdentifierT name = impl()->NullIdentifier();
      bool is_strict_reserved_name = false;
      Scanner::Location class_name_location = Scanner::Location::invalid();
      if (peek_any_identifier()) {
        bool is_await = false;
        name = ParseIdentifierOrStrictReservedWord(&is_strict_reserved_name,
                                                   &is_await, CHECK_OK);
        class_name_location = scanner()->location();
        if (is_await) {
          classifier()->RecordAsyncArrowFormalParametersError(
              scanner()->location(), MessageTemplate::kAwaitBindingIdentifier);
        }
      }
      return ParseClassLiteral(name, class_name_location,
                               is_strict_reserved_name, class_token_pos, ok);
    }

    case Token::TEMPLATE_SPAN:
    case Token::TEMPLATE_TAIL:
      BindingPatternUnexpectedToken();
      return ParseTemplateLiteral(impl()->NullExpression(), beg_pos, false, ok);

    case Token::MOD:
      if (allow_natives() || extension_ != nullptr) {
        BindingPatternUnexpectedToken();
        return ParseV8Intrinsic(ok);
      }
      break;

    case Token::DO:
      if (allow_harmony_do_expressions()) {
        BindingPatternUnexpectedToken();
        return ParseDoExpression(ok);
      }
      break;

    default:
      break;
  }

  ReportUnexpectedToken(Next());
  *ok = false;
  return impl()->NullExpression();
}

template <typename Impl>
typename ParserBase<Impl>::ExpressionT ParserBase<Impl>::ParseExpression(
    bool accept_IN, bool* ok) {
  ExpressionClassifier classifier(this);
  ExpressionT result = ParseExpressionCoverGrammar(accept_IN, CHECK_OK);
  ValidateExpression(CHECK_OK);
  return result;
}

template <typename Impl>
typename ParserBase<Impl>::ExpressionT
ParserBase<Impl>::ParseExpressionCoverGrammar(bool accept_IN, bool* ok) {
  // Expression ::
  //   AssignmentExpression
  //   Expression ',' AssignmentExpression

  ExpressionT result = impl()->NullExpression();
  while (true) {
    int comma_pos = position();
    ExpressionClassifier binding_classifier(this);
    ExpressionT right;
    if (Check(Token::ELLIPSIS)) {
      // 'x, y, ...z' in CoverParenthesizedExpressionAndArrowParameterList only
      // as the formal parameters of'(x, y, ...z) => foo', and is not itself a
      // valid expression.
      classifier()->RecordExpressionError(scanner()->location(),
                                          MessageTemplate::kUnexpectedToken,
                                          Token::String(Token::ELLIPSIS));
      int ellipsis_pos = position();
      int pattern_pos = peek_position();
      ExpressionT pattern = ParsePrimaryExpression(CHECK_OK);
      if (peek() == Token::ASSIGN) {
        ReportMessage(MessageTemplate::kRestDefaultInitializer);
        *ok = false;
        return result;
      }
      ValidateBindingPattern(CHECK_OK);
      right = factory()->NewSpread(pattern, ellipsis_pos, pattern_pos);
    } else {
      right = ParseAssignmentExpression(accept_IN, CHECK_OK);
    }
    // No need to accumulate binding pattern-related errors, since
    // an Expression can't be a binding pattern anyway.
    AccumulateNonBindingPatternErrors();
    if (!impl()->IsIdentifier(right)) classifier()->RecordNonSimpleParameter();
    if (impl()->IsNull(result)) {
      // First time through the loop.
      result = right;
    } else if (impl()->CollapseNaryExpression(&result, right, Token::COMMA,
                                              comma_pos,
                                              SourceRange::Empty())) {
      // Do nothing, "result" is already updated.
    } else {
      result =
          factory()->NewBinaryOperation(Token::COMMA, result, right, comma_pos);
    }

    if (!Check(Token::COMMA)) break;

    if (right->IsSpread()) {
      classifier()->RecordArrowFormalParametersError(
          scanner()->location(), MessageTemplate::kParamAfterRest);
    }

    if (peek() == Token::RPAREN && PeekAhead() == Token::ARROW) {
      // a trailing comma is allowed at the end of an arrow parameter list
      break;
    }

    // Pass on the 'set_next_function_is_likely_called' flag if we have
    // several function literals separated by comma.
    if (peek() == Token::FUNCTION &&
        function_state_->previous_function_was_likely_called()) {
      function_state_->set_next_function_is_likely_called();
    }
  }

  return result;
}

template <typename Impl>
typename ParserBase<Impl>::ExpressionT ParserBase<Impl>::ParseArrayLiteral(
    bool* ok) {
  // ArrayLiteral ::
  //   '[' Expression? (',' Expression?)* ']'

  int pos = peek_position();
  ExpressionListT values = impl()->NewExpressionList(4);
  int first_spread_index = -1;
  Expect(Token::LBRACK, CHECK_OK);
  while (peek() != Token::RBRACK) {
    ExpressionT elem;
    if (peek() == Token::COMMA) {
      elem = factory()->NewTheHoleLiteral();
    } else if (peek() == Token::ELLIPSIS) {
      int start_pos = peek_position();
      Consume(Token::ELLIPSIS);
      int expr_pos = peek_position();
      ExpressionT argument = ParseAssignmentExpression(true, CHECK_OK);
      elem = factory()->NewSpread(argument, start_pos, expr_pos);

      if (first_spread_index < 0) {
        first_spread_index = values->length();
      }

      if (argument->IsAssignment()) {
        classifier()->RecordPatternError(
            Scanner::Location(start_pos, scanner()->location().end_pos),
            MessageTemplate::kInvalidDestructuringTarget);
      } else {
        CheckDestructuringElement(argument, start_pos,
                                  scanner()->location().end_pos);
      }

      if (peek() == Token::COMMA) {
        classifier()->RecordPatternError(
            Scanner::Location(start_pos, scanner()->location().end_pos),
            MessageTemplate::kElementAfterRest);
      }
    } else {
      int beg_pos = peek_position();
      elem = ParseAssignmentExpression(true, CHECK_OK);
      CheckDestructuringElement(elem, beg_pos, scanner()->location().end_pos);
    }
    values->Add(elem, zone_);
    if (peek() != Token::RBRACK) {
      Expect(Token::COMMA, CHECK_OK);
    }
  }
  Expect(Token::RBRACK, CHECK_OK);

  return factory()->NewArrayLiteral(values, first_spread_index, pos);
}

template <class Impl>
bool ParserBase<Impl>::SetPropertyKindFromToken(Token::Value token,
                                                PropertyKind* kind) {
  // This returns true, setting the property kind, iff the given token is one
  // which must occur after a property name, indicating that the previous token
  // was in fact a name and not a modifier (like the "get" in "get x").
  switch (token) {
    case Token::COLON:
      *kind = PropertyKind::kValueProperty;
      return true;
    case Token::COMMA:
    case Token::RBRACE:
    case Token::ASSIGN:
      *kind = PropertyKind::kShorthandProperty;
      return true;
    case Token::LPAREN:
      *kind = PropertyKind::kMethodProperty;
      return true;
    case Token::MUL:
    case Token::SEMICOLON:
      *kind = PropertyKind::kClassField;
      return true;
    case Token::PRIVATE_NAME:
      *kind = PropertyKind::kClassField;
      return true;
    default:
      break;
  }
  return false;
}

template <class Impl>
typename ParserBase<Impl>::ExpressionT ParserBase<Impl>::ParsePropertyName(
    IdentifierT* name, PropertyKind* kind, bool* is_generator, bool* is_get,
    bool* is_set, bool* is_async, bool* is_computed_name, bool* ok) {
  DCHECK_EQ(*kind, PropertyKind::kNotSet);
  DCHECK(!*is_generator);
  DCHECK(!*is_get);
  DCHECK(!*is_set);
  DCHECK(!*is_async);
  DCHECK(!*is_computed_name);

  *is_generator = Check(Token::MUL);
  if (*is_generator) {
    *kind = PropertyKind::kMethodProperty;
  }

  Token::Value token = peek();
  int pos = peek_position();

  if (!*is_generator && token == Token::ASYNC &&
      !scanner()->HasAnyLineTerminatorAfterNext()) {
    Consume(Token::ASYNC);
    token = peek();
    if (token == Token::MUL && !scanner()->HasAnyLineTerminatorBeforeNext()) {
      Consume(Token::MUL);
      token = peek();
      *is_generator = true;
    } else if (SetPropertyKindFromToken(token, kind)) {
      *name = impl()->GetSymbol();  // TODO(bakkot) specialize on 'async'
      impl()->PushLiteralName(*name);
      return factory()->NewStringLiteral(*name, pos);
    }
    *kind = PropertyKind::kMethodProperty;
    *is_async = true;
    pos = peek_position();
  }

  if (token == Token::IDENTIFIER && !*is_generator && !*is_async) {
    // This is checking for 'get' and 'set' in particular.
    Consume(Token::IDENTIFIER);
    token = peek();
    if (SetPropertyKindFromToken(token, kind) ||
        !scanner()->IsGetOrSet(is_get, is_set)) {
      *name = impl()->GetSymbol();
      impl()->PushLiteralName(*name);
      return factory()->NewStringLiteral(*name, pos);
    }
    *kind = PropertyKind::kAccessorProperty;
    pos = peek_position();
  }

  // For non computed property names we normalize the name a bit:
  //
  //   "12" -> 12
  //   12.3 -> "12.3"
  //   12.30 -> "12.3"
  //   identifier -> "identifier"
  //
  // This is important because we use the property name as a key in a hash
  // table when we compute constant properties.
  ExpressionT expression = impl()->NullExpression();
  switch (token) {
    case Token::STRING:
      Consume(Token::STRING);
      *name = impl()->GetSymbol();
      break;

    case Token::SMI:
      Consume(Token::SMI);
      *name = impl()->GetNumberAsSymbol();
      break;

    case Token::NUMBER:
      Consume(Token::NUMBER);
      *name = impl()->GetNumberAsSymbol();
      break;

    case Token::LBRACK: {
      *name = impl()->NullIdentifier();
      *is_computed_name = true;
      Consume(Token::LBRACK);
      ExpressionClassifier computed_name_classifier(this);
      expression = ParseAssignmentExpression(true, CHECK_OK);
      ValidateExpression(CHECK_OK);
      AccumulateFormalParameterContainmentErrors();
      Expect(Token::RBRACK, CHECK_OK);
      break;
    }

    case Token::ELLIPSIS:
      if (!*is_generator && !*is_async && !*is_get && !*is_set) {
        *name = impl()->NullIdentifier();
        Consume(Token::ELLIPSIS);
        expression = ParseAssignmentExpression(true, CHECK_OK);
        *kind = PropertyKind::kSpreadProperty;

        if (!impl()->IsIdentifier(expression)) {
          classifier()->RecordBindingPatternError(
              scanner()->location(),
              MessageTemplate::kInvalidRestBindingPattern);
        }

        if (!expression->IsValidReferenceExpression()) {
          classifier()->RecordAssignmentPatternError(
              scanner()->location(),
              MessageTemplate::kInvalidRestAssignmentPattern);
        }

        if (peek() != Token::RBRACE) {
          classifier()->RecordPatternError(scanner()->location(),
                                           MessageTemplate::kElementAfterRest);
        }
        return expression;
      }
    // Fall-through.

    default:
      *name = ParseIdentifierName(CHECK_OK);
      break;
  }

  if (*kind == PropertyKind::kNotSet) {
    SetPropertyKindFromToken(peek(), kind);
  }

  if (*is_computed_name) {
    return expression;
  }

  impl()->PushLiteralName(*name);

  uint32_t index;
  return impl()->IsArrayIndex(*name, &index)
             ? factory()->NewNumberLiteral(index, pos)
             : factory()->NewStringLiteral(*name, pos);
}

template <typename Impl>
typename ParserBase<Impl>::ClassLiteralPropertyT
ParserBase<Impl>::ParseClassPropertyDefinition(
    ClassLiteralChecker* checker, ClassInfo* class_info, bool has_extends,
    bool* is_computed_name, bool* has_seen_constructor,
    ClassLiteralProperty::Kind* property_kind, bool* is_static,
    bool* has_name_static_property, bool* ok) {
  DCHECK_NOT_NULL(has_seen_constructor);
  DCHECK_NOT_NULL(has_name_static_property);
  bool is_get = false;
  bool is_set = false;
  bool is_generator = false;
  bool is_async = false;
  *is_static = false;
  *property_kind = ClassLiteralProperty::METHOD;
  PropertyKind kind = PropertyKind::kNotSet;

  Token::Value name_token = peek();
  DCHECK_IMPLIES(name_token == Token::PRIVATE_NAME,
                 allow_harmony_private_fields());

  int name_token_position = scanner()->peek_location().beg_pos;
  IdentifierT name = impl()->NullIdentifier();
  ExpressionT name_expression;
  if (name_token == Token::STATIC) {
    Consume(Token::STATIC);
    name_token_position = scanner()->peek_location().beg_pos;
    if (peek() == Token::LPAREN) {
      kind = PropertyKind::kMethodProperty;
      name = impl()->GetSymbol();  // TODO(bakkot) specialize on 'static'
      name_expression = factory()->NewStringLiteral(name, position());
    } else if (peek() == Token::ASSIGN || peek() == Token::SEMICOLON ||
               peek() == Token::RBRACE) {
      name = impl()->GetSymbol();  // TODO(bakkot) specialize on 'static'
      name_expression = factory()->NewStringLiteral(name, position());
    } else if (peek() == Token::PRIVATE_NAME) {
      DCHECK(allow_harmony_private_fields());
      // TODO(gsathya): Make a better error message for this.
      ReportUnexpectedToken(Next());
      *ok = false;
      return impl()->NullLiteralProperty();
    } else {
      *is_static = true;
      name_expression = ParsePropertyName(&name, &kind, &is_generator, &is_get,
                                          &is_set, &is_async, is_computed_name,
                                          CHECK_OK_CUSTOM(NullLiteralProperty));
    }
  } else if (name_token == Token::PRIVATE_NAME) {
    Consume(Token::PRIVATE_NAME);
    name = impl()->GetSymbol();
    name_expression = factory()->NewStringLiteral(name, position());
  } else {
    name_expression = ParsePropertyName(&name, &kind, &is_generator, &is_get,
                                        &is_set, &is_async, is_computed_name,
                                        CHECK_OK_CUSTOM(NullLiteralProperty));
  }

  if (!*has_name_static_property && *is_static && impl()->IsName(name)) {
    *has_name_static_property = true;
  }

  switch (kind) {
    case PropertyKind::kClassField:
    case PropertyKind::kNotSet:  // This case is a name followed by a name or
                                 // other property. Here we have to assume
                                 // that's an uninitialized field followed by a
                                 // linebreak followed by a property, with ASI
                                 // adding the semicolon. If not, there will be
                                 // a syntax error after parsing the first name
                                 // as an uninitialized field.
    case PropertyKind::kShorthandProperty:
    case PropertyKind::kValueProperty:
      if (allow_harmony_public_fields() || allow_harmony_private_fields()) {
        *property_kind = ClassLiteralProperty::FIELD;
        if (*is_static && !allow_harmony_static_fields()) {
          ReportUnexpectedToken(Next());
          *ok = false;
          return impl()->NullLiteralProperty();
        }
        if (!*is_computed_name && name_token != Token::PRIVATE_NAME) {
          checker->CheckClassFieldName(*is_static,
                                       CHECK_OK_CUSTOM(NullLiteralProperty));
        }
        ExpressionT initializer = ParseClassFieldInitializer(
            class_info, *is_static, CHECK_OK_CUSTOM(NullLiteralProperty));
        ExpectSemicolon(CHECK_OK_CUSTOM(NullLiteralProperty));
        ClassLiteralPropertyT result = factory()->NewClassLiteralProperty(
            name_expression, initializer, *property_kind, *is_static,
            *is_computed_name);
        impl()->SetFunctionNameFromPropertyName(result, name);
        return result;

      } else {
        ReportUnexpectedToken(Next());
        *ok = false;
        return impl()->NullLiteralProperty();
      }

    case PropertyKind::kMethodProperty: {
      DCHECK(!is_get && !is_set);

      // MethodDefinition
      //    PropertyName '(' StrictFormalParameters ')' '{' FunctionBody '}'
      //    '*' PropertyName '(' StrictFormalParameters ')' '{' FunctionBody '}'
      //    async PropertyName '(' StrictFormalParameters ')'
      //        '{' FunctionBody '}'
      //    async '*' PropertyName '(' StrictFormalParameters ')'
      //        '{' FunctionBody '}'

      if (!*is_computed_name) {
        checker->CheckClassMethodName(name_token, PropertyKind::kMethodProperty,
                                      is_generator, is_async, *is_static,
                                      CHECK_OK_CUSTOM(NullLiteralProperty));
      }

      FunctionKind kind = MethodKindFor(is_generator, is_async);

      if (!*is_static && impl()->IsConstructor(name)) {
        *has_seen_constructor = true;
        kind = has_extends ? FunctionKind::kDerivedConstructor
                           : FunctionKind::kBaseConstructor;
      }

      ExpressionT value = impl()->ParseFunctionLiteral(
          name, scanner()->location(), kSkipFunctionNameCheck, kind,
          FLAG_harmony_function_tostring ? name_token_position
                                         : kNoSourcePosition,
          FunctionLiteral::kAccessorOrMethod, language_mode(), nullptr,
          CHECK_OK_CUSTOM(NullLiteralProperty));

      *property_kind = ClassLiteralProperty::METHOD;
      ClassLiteralPropertyT result = factory()->NewClassLiteralProperty(
          name_expression, value, *property_kind, *is_static,
          *is_computed_name);
      impl()->SetFunctionNameFromPropertyName(result, name);
      return result;
    }

    case PropertyKind::kAccessorProperty: {
      DCHECK((is_get || is_set) && !is_generator && !is_async);

      if (!*is_computed_name) {
        checker->CheckClassMethodName(
            name_token, PropertyKind::kAccessorProperty, false, false,
            *is_static, CHECK_OK_CUSTOM(NullLiteralProperty));
        // Make sure the name expression is a string since we need a Name for
        // Runtime_DefineAccessorPropertyUnchecked and since we can determine
        // this statically we can skip the extra runtime check.
        name_expression =
            factory()->NewStringLiteral(name, name_expression->position());
      }

      FunctionKind kind = is_get ? FunctionKind::kGetterFunction
                                 : FunctionKind::kSetterFunction;

      FunctionLiteralT value = impl()->ParseFunctionLiteral(
          name, scanner()->location(), kSkipFunctionNameCheck, kind,
          FLAG_harmony_function_tostring ? name_token_position
                                         : kNoSourcePosition,
          FunctionLiteral::kAccessorOrMethod, language_mode(), nullptr,
          CHECK_OK_CUSTOM(NullLiteralProperty));

      *property_kind =
          is_get ? ClassLiteralProperty::GETTER : ClassLiteralProperty::SETTER;
      ClassLiteralPropertyT result = factory()->NewClassLiteralProperty(
          name_expression, value, *property_kind, *is_static,
          *is_computed_name);
      const AstRawString* prefix =
          is_get ? ast_value_factory()->get_space_string()
                 : ast_value_factory()->set_space_string();
      impl()->SetFunctionNameFromPropertyName(result, name, prefix);
      return result;
    }
    case PropertyKind::kSpreadProperty:
      ReportUnexpectedTokenAt(
          Scanner::Location(name_token_position, name_expression->position()),
          name_token);
      *ok = false;
      return impl()->NullLiteralProperty();
  }
  UNREACHABLE();
}

template <typename Impl>
typename ParserBase<Impl>::ExpressionT
ParserBase<Impl>::ParseClassFieldInitializer(ClassInfo* class_info,
                                             bool is_static, bool* ok) {
  DeclarationScope* initializer_scope = is_static
                                            ? class_info->static_fields_scope
                                            : class_info->instance_fields_scope;

  if (initializer_scope == nullptr) {
    initializer_scope =
        NewFunctionScope(FunctionKind::kClassFieldsInitializerFunction);
    // TODO(gsathya): Make scopes be non contiguous.
    initializer_scope->set_start_position(scanner()->location().end_pos);
    initializer_scope->SetLanguageMode(LanguageMode::kStrict);
  }

  ExpressionT initializer;
  if (Check(Token::ASSIGN)) {
    FunctionState initializer_state(&function_state_, &scope_,
                                    initializer_scope);
    ExpressionClassifier expression_classifier(this);

    initializer =
        ParseAssignmentExpression(true, CHECK_OK_CUSTOM(NullExpression));
    ValidateExpression(CHECK_OK_CUSTOM(NullExpression));
  } else {
    initializer = factory()->NewUndefinedLiteral(kNoSourcePosition);
  }

  initializer_scope->set_end_position(scanner()->location().end_pos);
  if (is_static) {
    class_info->static_fields_scope = initializer_scope;
    class_info->has_static_class_fields = true;
  } else {
    class_info->instance_fields_scope = initializer_scope;
    class_info->has_instance_class_fields = true;
  }

  return initializer;
}

template <typename Impl>
typename ParserBase<Impl>::ObjectLiteralPropertyT
ParserBase<Impl>::ParseObjectPropertyDefinition(ObjectLiteralChecker* checker,
                                                bool* is_computed_name,
                                                bool* is_rest_property,
                                                bool* ok) {
  bool is_get = false;
  bool is_set = false;
  bool is_generator = false;
  bool is_async = false;
  PropertyKind kind = PropertyKind::kNotSet;

  IdentifierT name = impl()->NullIdentifier();
  Token::Value name_token = peek();
  int next_beg_pos = scanner()->peek_location().beg_pos;
  int next_end_pos = scanner()->peek_location().end_pos;

  ExpressionT name_expression = ParsePropertyName(
      &name, &kind, &is_generator, &is_get, &is_set, &is_async,
      is_computed_name, CHECK_OK_CUSTOM(NullLiteralProperty));

  switch (kind) {
    case PropertyKind::kSpreadProperty:
      DCHECK(!is_get && !is_set && !is_generator && !is_async &&
             !*is_computed_name);
      DCHECK(name_token == Token::ELLIPSIS);

      *is_computed_name = true;
      *is_rest_property = true;

      return factory()->NewObjectLiteralProperty(
          factory()->NewTheHoleLiteral(), name_expression,
          ObjectLiteralProperty::SPREAD, true);

    case PropertyKind::kValueProperty: {
      DCHECK(!is_get && !is_set && !is_generator && !is_async);

      if (!*is_computed_name) {
        checker->CheckDuplicateProto(name_token);
      }
      Consume(Token::COLON);
      int beg_pos = peek_position();
      ExpressionT value =
          ParseAssignmentExpression(true, CHECK_OK_CUSTOM(NullLiteralProperty));
      CheckDestructuringElement(value, beg_pos, scanner()->location().end_pos);

      ObjectLiteralPropertyT result = factory()->NewObjectLiteralProperty(
          name_expression, value, *is_computed_name);
      impl()->SetFunctionNameFromPropertyName(result, name);
      return result;
    }

    case PropertyKind::kShorthandProperty: {
      // PropertyDefinition
      //    IdentifierReference
      //    CoverInitializedName
      //
      // CoverInitializedName
      //    IdentifierReference Initializer?
      DCHECK(!is_get && !is_set && !is_generator && !is_async);

      if (!Token::IsIdentifier(name_token, language_mode(),
                               this->is_generator(),
                               parsing_module_ || is_async_function())) {
        ReportUnexpectedToken(Next());
        *ok = false;
        return impl()->NullLiteralProperty();
      }

      DCHECK(!*is_computed_name);

      if (classifier()->duplicate_finder() != nullptr &&
          scanner()->IsDuplicateSymbol(classifier()->duplicate_finder(),
                                       ast_value_factory())) {
        classifier()->RecordDuplicateFormalParameterError(
            scanner()->location());
      }

      if (impl()->IsEvalOrArguments(name) && is_strict(language_mode())) {
        classifier()->RecordBindingPatternError(
            scanner()->location(), MessageTemplate::kStrictEvalArguments);
      }

      if (name_token == Token::LET) {
        classifier()->RecordLetPatternError(
            scanner()->location(), MessageTemplate::kLetInLexicalBinding);
      }
      if (name_token == Token::AWAIT) {
        DCHECK(!is_async_function());
        classifier()->RecordAsyncArrowFormalParametersError(
            Scanner::Location(next_beg_pos, next_end_pos),
            MessageTemplate::kAwaitBindingIdentifier);
      }
      ExpressionT lhs = impl()->ExpressionFromIdentifier(name, next_beg_pos);
      CheckDestructuringElement(lhs, next_beg_pos, next_end_pos);

      ExpressionT value;
      if (peek() == Token::ASSIGN) {
        Consume(Token::ASSIGN);
        ExpressionClassifier rhs_classifier(this);
        ExpressionT rhs = ParseAssignmentExpression(
            true, CHECK_OK_CUSTOM(NullLiteralProperty));
        ValidateExpression(CHECK_OK_CUSTOM(NullLiteralProperty));
        AccumulateFormalParameterContainmentErrors();
        value = factory()->NewAssignment(Token::ASSIGN, lhs, rhs,
                                         kNoSourcePosition);
        classifier()->RecordExpressionError(
            Scanner::Location(next_beg_pos, scanner()->location().end_pos),
            MessageTemplate::kInvalidCoverInitializedName);

        impl()->SetFunctionNameFromIdentifierRef(rhs, lhs);
      } else {
        value = lhs;
      }

      ObjectLiteralPropertyT result = factory()->NewObjectLiteralProperty(
          name_expression, value, ObjectLiteralProperty::COMPUTED, false);
      impl()->SetFunctionNameFromPropertyName(result, name);
      return result;
    }

    case PropertyKind::kMethodProperty: {
      DCHECK(!is_get && !is_set);

      // MethodDefinition
      //    PropertyName '(' StrictFormalParameters ')' '{' FunctionBody '}'
      //    '*' PropertyName '(' StrictFormalParameters ')' '{' FunctionBody '}'

      classifier()->RecordPatternError(
          Scanner::Location(next_beg_pos, scanner()->location().end_pos),
          MessageTemplate::kInvalidDestructuringTarget);

      FunctionKind kind = MethodKindFor(is_generator, is_async);

      ExpressionT value = impl()->ParseFunctionLiteral(
          name, scanner()->location(), kSkipFunctionNameCheck, kind,
          FLAG_harmony_function_tostring ? next_beg_pos : kNoSourcePosition,
          FunctionLiteral::kAccessorOrMethod, language_mode(), nullptr,
          CHECK_OK_CUSTOM(NullLiteralProperty));

      ObjectLiteralPropertyT result = factory()->NewObjectLiteralProperty(
          name_expression, value, ObjectLiteralProperty::COMPUTED,
          *is_computed_name);
      impl()->SetFunctionNameFromPropertyName(result, name);
      return result;
    }

    case PropertyKind::kAccessorProperty: {
      DCHECK((is_get || is_set) && !(is_set && is_get) && !is_generator &&
             !is_async);

      classifier()->RecordPatternError(
          Scanner::Location(next_beg_pos, scanner()->location().end_pos),
          MessageTemplate::kInvalidDestructuringTarget);

      if (!*is_computed_name) {
        // Make sure the name expression is a string since we need a Name for
        // Runtime_DefineAccessorPropertyUnchecked and since we can determine
        // this statically we can skip the extra runtime check.
        name_expression =
            factory()->NewStringLiteral(name, name_expression->position());
      }

      FunctionKind kind = is_get ? FunctionKind::kGetterFunction
                                 : FunctionKind::kSetterFunction;

      FunctionLiteralT value = impl()->ParseFunctionLiteral(
          name, scanner()->location(), kSkipFunctionNameCheck, kind,
          FLAG_harmony_function_tostring ? next_beg_pos : kNoSourcePosition,
          FunctionLiteral::kAccessorOrMethod, language_mode(), nullptr,
          CHECK_OK_CUSTOM(NullLiteralProperty));

      ObjectLiteralPropertyT result = factory()->NewObjectLiteralProperty(
          name_expression, value,
          is_get ? ObjectLiteralProperty::GETTER
                 : ObjectLiteralProperty::SETTER,
          *is_computed_name);
      const AstRawString* prefix =
          is_get ? ast_value_factory()->get_space_string()
                 : ast_value_factory()->set_space_string();
      impl()->SetFunctionNameFromPropertyName(result, name, prefix);
      return result;
    }

    case PropertyKind::kClassField:
    case PropertyKind::kNotSet:
      ReportUnexpectedToken(Next());
      *ok = false;
      return impl()->NullLiteralProperty();
  }
  UNREACHABLE();
}

template <typename Impl>
typename ParserBase<Impl>::ExpressionT ParserBase<Impl>::ParseObjectLiteral(
    bool* ok) {
  // ObjectLiteral ::
  // '{' (PropertyDefinition (',' PropertyDefinition)* ','? )? '}'

  int pos = peek_position();
  typename Types::ObjectPropertyList properties =
      impl()->NewObjectPropertyList(4);
  int number_of_boilerplate_properties = 0;

  bool has_computed_names = false;
  bool has_rest_property = false;
  ObjectLiteralChecker checker(this);

  Expect(Token::LBRACE, CHECK_OK);

  while (peek() != Token::RBRACE) {
    FuncNameInferrer::State fni_state(fni_);

    bool is_computed_name = false;
    bool is_rest_property = false;
    ObjectLiteralPropertyT property = ParseObjectPropertyDefinition(
        &checker, &is_computed_name, &is_rest_property, CHECK_OK);

    if (is_computed_name) {
      has_computed_names = true;
    }

    if (is_rest_property) {
      has_rest_property = true;
    }

    if (impl()->IsBoilerplateProperty(property) && !has_computed_names) {
      // Count CONSTANT or COMPUTED properties to maintain the enumeration
      // order.
      number_of_boilerplate_properties++;
    }

    properties->Add(property, zone());

    if (peek() != Token::RBRACE) {
      // Need {} because of the CHECK_OK macro.
      Expect(Token::COMMA, CHECK_OK);
    }

    if (fni_ != nullptr) fni_->Infer();
  }
  Expect(Token::RBRACE, CHECK_OK);

  // In pattern rewriter, we rewrite rest property to call out to a
  // runtime function passing all the other properties as arguments to
  // this runtime function. Here, we make sure that the number of
  // properties is less than number of arguments allowed for a runtime
  // call.
  if (has_rest_property && properties->length() > Code::kMaxArguments) {
    this->classifier()->RecordPatternError(Scanner::Location(pos, position()),
                                           MessageTemplate::kTooManyArguments);
  }

  return impl()->InitializeObjectLiteral(factory()->NewObjectLiteral(
      properties, number_of_boilerplate_properties, pos, has_rest_property));
}

template <typename Impl>
typename ParserBase<Impl>::ExpressionListT ParserBase<Impl>::ParseArguments(
    Scanner::Location* first_spread_arg_loc, bool maybe_arrow,
    bool* is_simple_parameter_list, bool* ok) {
  // Arguments ::
  //   '(' (AssignmentExpression)*[','] ')'

  Scanner::Location spread_arg = Scanner::Location::invalid();
  ExpressionListT result = impl()->NewExpressionList(4);
  Expect(Token::LPAREN, CHECK_OK_CUSTOM(NullExpressionList));
  bool done = (peek() == Token::RPAREN);
  while (!done) {
    int start_pos = peek_position();
    bool is_spread = Check(Token::ELLIPSIS);
    int expr_pos = peek_position();

    ExpressionT argument =
        ParseAssignmentExpression(true, CHECK_OK_CUSTOM(NullExpressionList));
    if (!impl()->IsIdentifier(argument) &&
        is_simple_parameter_list != nullptr) {
      *is_simple_parameter_list = false;
    }
    if (!maybe_arrow) {
      ValidateExpression(CHECK_OK_CUSTOM(NullExpressionList));
    }
    if (is_spread) {
      if (is_simple_parameter_list != nullptr) {
        *is_simple_parameter_list = false;
      }
      if (!spread_arg.IsValid()) {
        spread_arg.beg_pos = start_pos;
        spread_arg.end_pos = peek_position();
      }
      if (argument->IsAssignment()) {
        classifier()->RecordAsyncArrowFormalParametersError(
            scanner()->location(), MessageTemplate::kRestDefaultInitializer);
      }
      argument = factory()->NewSpread(argument, start_pos, expr_pos);
    }
    result->Add(argument, zone_);

    if (result->length() > Code::kMaxArguments) {
      ReportMessage(MessageTemplate::kTooManyArguments);
      *ok = false;
      return impl()->NullExpressionList();
    }
    done = (peek() != Token::COMMA);
    if (!done) {
      Next();
      if (argument->IsSpread()) {
        classifier()->RecordAsyncArrowFormalParametersError(
            scanner()->location(), MessageTemplate::kParamAfterRest);
      }
      if (peek() == Token::RPAREN) {
        // allow trailing comma
        done = true;
      }
    }
  }
  Scanner::Location location = scanner_->location();
  if (Token::RPAREN != Next()) {
    impl()->ReportMessageAt(location, MessageTemplate::kUnterminatedArgList);
    *ok = false;
    return impl()->NullExpressionList();
  }
  *first_spread_arg_loc = spread_arg;

  if (!maybe_arrow || peek() != Token::ARROW) {
    if (maybe_arrow) {
      ValidateExpression(CHECK_OK_CUSTOM(NullExpressionList));
    }
  }

  return result;
}

// Precedence = 2
template <typename Impl>
typename ParserBase<Impl>::ExpressionT
ParserBase<Impl>::ParseAssignmentExpression(bool accept_IN, bool* ok) {
  // AssignmentExpression ::
  //   ConditionalExpression
  //   ArrowFunction
  //   YieldExpression
  //   LeftHandSideExpression AssignmentOperator AssignmentExpression
  int lhs_beg_pos = peek_position();

  if (peek() == Token::YIELD && is_generator()) {
    return ParseYieldExpression(accept_IN, ok);
  }

  FuncNameInferrer::State fni_state(fni_);
  ExpressionClassifier arrow_formals_classifier(
      this, classifier()->duplicate_finder());

  Scope::Snapshot scope_snapshot(scope());
  int rewritable_length =