// 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.

#include "src/ast/scopes.h"

#include <set>

#include "src/accessors.h"
#include "src/bootstrapper.h"
#include "src/messages.h"
#include "src/parsing/parser.h"  // for ParseInfo

namespace v8 {
namespace internal {

// ----------------------------------------------------------------------------
// Implementation of LocalsMap
//
// Note: We are storing the handle locations as key values in the hash map.
//       When inserting a new variable via Declare(), we rely on the fact that
//       the handle location remains alive for the duration of that variable
//       use. Because a Variable holding a handle with the same location exists
//       this is ensured.

VariableMap::VariableMap(Zone* zone)
    : ZoneHashMap(ZoneHashMap::PointersMatch, 8, ZoneAllocationPolicy(zone)) {}

Variable* VariableMap::Declare(Zone* zone, Scope* scope,
                               const AstRawString* name, VariableMode mode,
                               Variable::Kind kind,
                               InitializationFlag initialization_flag,
                               MaybeAssignedFlag maybe_assigned_flag) {
  // AstRawStrings are unambiguous, i.e., the same string is always represented
  // by the same AstRawString*.
  // FIXME(marja): fix the type of Lookup.
  Entry* p =
      ZoneHashMap::LookupOrInsert(const_cast<AstRawString*>(name), name->hash(),
                                  ZoneAllocationPolicy(zone));
  if (p->value == NULL) {
    // The variable has not been declared yet -> insert it.
    DCHECK(p->key == name);
    p->value = new (zone) Variable(scope, name, mode, kind, initialization_flag,
                                   maybe_assigned_flag);
  }
  return reinterpret_cast<Variable*>(p->value);
}


Variable* VariableMap::Lookup(const AstRawString* name) {
  Entry* p = ZoneHashMap::Lookup(const_cast<AstRawString*>(name), name->hash());
  if (p != NULL) {
    DCHECK(reinterpret_cast<const AstRawString*>(p->key) == name);
    DCHECK(p->value != NULL);
    return reinterpret_cast<Variable*>(p->value);
  }
  return NULL;
}

SloppyBlockFunctionMap::SloppyBlockFunctionMap(Zone* zone)
    : ZoneHashMap(ZoneHashMap::PointersMatch, 8, ZoneAllocationPolicy(zone)) {}

void SloppyBlockFunctionMap::Declare(Zone* zone, const AstRawString* name,
                                     SloppyBlockFunctionStatement* stmt) {
  // AstRawStrings are unambiguous, i.e., the same string is always represented
  // by the same AstRawString*.
  Entry* p =
      ZoneHashMap::LookupOrInsert(const_cast<AstRawString*>(name), name->hash(),
                                  ZoneAllocationPolicy(zone));
  stmt->set_next(static_cast<SloppyBlockFunctionStatement*>(p->value));
  p->value = stmt;
}


// ----------------------------------------------------------------------------
// Implementation of Scope

Scope::Scope(Zone* zone, Scope* outer_scope, ScopeType scope_type)
    : zone_(zone),
      outer_scope_(outer_scope),
      variables_(zone),
      decls_(4, zone),
      scope_type_(scope_type),
      already_resolved_(false) {
  SetDefaults();
  if (outer_scope == nullptr) {
    // If the outer scope is null, this cannot be a with scope. The outermost
    // scope must be a script scope.
    DCHECK_EQ(SCRIPT_SCOPE, scope_type);
  } else {
    asm_function_ = outer_scope_->asm_module_;
    // Inherit the language mode from the parent scope unless we're a module
    // scope.
    if (!is_module_scope()) language_mode_ = outer_scope->language_mode_;
    force_context_allocation_ =
        !is_function_scope() && outer_scope->has_forced_context_allocation();
    outer_scope_->AddInnerScope(this);
    scope_inside_with_ = outer_scope_->scope_inside_with_ || is_with_scope();
  }
}

Scope::Snapshot::Snapshot(Scope* scope)
    : outer_scope_(scope),
      top_inner_scope_(scope->inner_scope_),
      top_unresolved_(scope->unresolved_),
      top_temp_(scope->GetClosureScope()->temps()->length()) {}

DeclarationScope::DeclarationScope(Zone* zone, Scope* outer_scope,
                                   ScopeType scope_type,
                                   FunctionKind function_kind)
    : Scope(zone, outer_scope, scope_type),
      function_kind_(function_kind),
      temps_(4, zone),
      params_(4, zone),
      sloppy_block_function_map_(zone),
      module_descriptor_(scope_type == MODULE_SCOPE ? new (zone)
                                                          ModuleDescriptor(zone)
                                                    : NULL) {
  SetDefaults();
}

Scope::Scope(Zone* zone, Scope* inner_scope, ScopeType scope_type,
             Handle<ScopeInfo> scope_info)
    : zone_(zone),
      outer_scope_(nullptr),
      variables_(zone),
      decls_(0, zone),
      scope_info_(scope_info),
      scope_type_(scope_type),
      already_resolved_(true) {
  SetDefaults();
  if (!scope_info.is_null()) {
    scope_calls_eval_ = scope_info->CallsEval();
    language_mode_ = scope_info->language_mode();
    num_heap_slots_ = scope_info_->ContextLength();
  }
  // Ensure at least MIN_CONTEXT_SLOTS to indicate a materialized context.
  num_heap_slots_ = Max(num_heap_slots_,
                        static_cast<int>(Context::MIN_CONTEXT_SLOTS));
  if (inner_scope != nullptr) AddInnerScope(inner_scope);
}

DeclarationScope::DeclarationScope(Zone* zone, Scope* inner_scope,
                                   ScopeType scope_type,
                                   Handle<ScopeInfo> scope_info)
    : Scope(zone, inner_scope, scope_type, scope_info),
      function_kind_(scope_info.is_null() ? kNormalFunction
                                          : scope_info->function_kind()),
      temps_(0, zone),
      params_(0, zone),
      sloppy_block_function_map_(zone),
      module_descriptor_(nullptr) {
  SetDefaults();
}

Scope::Scope(Zone* zone, Scope* inner_scope,
             const AstRawString* catch_variable_name)
    : zone_(zone),
      outer_scope_(nullptr),
      variables_(zone),
      decls_(0, zone),
      scope_type_(CATCH_SCOPE),
      already_resolved_(true) {
  SetDefaults();
  if (inner_scope != nullptr) AddInnerScope(inner_scope);
  num_heap_slots_ = Context::MIN_CONTEXT_SLOTS;
  Variable* variable =
      variables_.Declare(zone, this, catch_variable_name, VAR, Variable::NORMAL,
                         kCreatedInitialized);
  AllocateHeapSlot(variable);
}

void DeclarationScope::SetDefaults() {
  is_declaration_scope_ = true;
  has_simple_parameters_ = true;
  receiver_ = nullptr;
  new_target_ = nullptr;
  function_ = nullptr;
  arguments_ = nullptr;
  this_function_ = nullptr;
  arity_ = 0;
  rest_parameter_ = NULL;
  rest_index_ = -1;
}

void Scope::SetDefaults() {
#ifdef DEBUG
  scope_name_ = nullptr;
#endif
  inner_scope_ = nullptr;
  sibling_ = nullptr;
  unresolved_ = nullptr;
  dynamics_ = nullptr;

  start_position_ = kNoSourcePosition;
  end_position_ = kNoSourcePosition;

  num_stack_slots_ = 0;
  num_heap_slots_ = 0;
  num_global_slots_ = 0;

  language_mode_ = is_module_scope() ? STRICT : SLOPPY;

  scope_inside_with_ = false;
  scope_calls_eval_ = false;
  scope_uses_super_property_ = false;
  has_arguments_parameter_ = false;
  asm_module_ = false;
  asm_function_ = false;
  scope_nonlinear_ = false;
  is_hidden_ = false;

  outer_scope_calls_sloppy_eval_ = false;
  inner_scope_calls_eval_ = false;
  force_eager_compilation_ = false;
  force_context_allocation_ = false;

  is_declaration_scope_ = false;
}

bool Scope::HasSimpleParameters() {
  DeclarationScope* scope = GetClosureScope();
  return !scope->is_function_scope() || scope->has_simple_parameters();
}

Scope* Scope::DeserializeScopeChain(Isolate* isolate, Zone* zone,
                                    Context* context,
                                    DeclarationScope* script_scope,
                                    AstValueFactory* ast_value_factory,
                                    DeserializationMode deserialization_mode) {
  // Reconstruct the outer scope chain from a closure's context chain.
  Scope* current_scope = nullptr;
  Scope* innermost_scope = nullptr;
  while (!context->IsNativeContext()) {
    if (context->IsWithContext() || context->IsDebugEvaluateContext()) {
      // For scope analysis, debug-evaluate is equivalent to a with scope.
      Scope* with_scope = new (zone)
          Scope(zone, current_scope, WITH_SCOPE, Handle<ScopeInfo>::null());
      current_scope = with_scope;
      // All the inner scopes are inside a with.
      for (Scope* s = innermost_scope; s != nullptr; s = s->outer_scope()) {
        s->scope_inside_with_ = true;
      }
    } else if (context->IsScriptContext()) {
      ScopeInfo* scope_info = context->scope_info();
      current_scope = new (zone) DeclarationScope(
          zone, current_scope, SCRIPT_SCOPE, Handle<ScopeInfo>(scope_info));
    } else if (context->IsFunctionContext()) {
      ScopeInfo* scope_info = context->closure()->shared()->scope_info();
      current_scope = new (zone) DeclarationScope(
          zone, current_scope, FUNCTION_SCOPE, Handle<ScopeInfo>(scope_info));
      if (scope_info->IsAsmFunction()) current_scope->asm_function_ = true;
      if (scope_info->IsAsmModule()) current_scope->asm_module_ = true;
    } else if (context->IsBlockContext()) {
      ScopeInfo* scope_info = context->scope_info();
      if (scope_info->is_declaration_scope()) {
        current_scope = new (zone) DeclarationScope(
            zone, current_scope, BLOCK_SCOPE, Handle<ScopeInfo>(scope_info));
      } else {
        current_scope = new (zone) Scope(zone, current_scope, BLOCK_SCOPE,
                                         Handle<ScopeInfo>(scope_info));
      }
    } else {
      DCHECK(context->IsCatchContext());
      String* name = context->catch_name();
      current_scope =
          new (zone) Scope(zone, current_scope,
                           ast_value_factory->GetString(handle(name, isolate)));
    }
    if (deserialization_mode == DeserializationMode::kDeserializeOffHeap) {
      current_scope->DeserializeScopeInfo(isolate, ast_value_factory);
    }
    if (innermost_scope == nullptr) innermost_scope = current_scope;
    context = context->previous();
  }

  script_scope->AddInnerScope(current_scope);
  script_scope->PropagateScopeInfo(false);
  return (innermost_scope == NULL) ? script_scope : innermost_scope;
}

void Scope::DeserializeScopeInfo(Isolate* isolate,
                                 AstValueFactory* ast_value_factory) {
  if (scope_info_.is_null()) return;

  DCHECK(ThreadId::Current().Equals(isolate->thread_id()));

  std::set<const AstRawString*> names_seen;
  // Internalize context local & globals variables.
  for (int var = 0; var < scope_info_->ContextLocalCount() +
                              scope_info_->ContextGlobalCount();
       ++var) {
    Handle<String> name_handle(scope_info_->ContextLocalName(var), isolate);
    const AstRawString* name = ast_value_factory->GetString(name_handle);
    if (!names_seen.insert(name).second) continue;
    int index = Context::MIN_CONTEXT_SLOTS + var;
    VariableMode mode = scope_info_->ContextLocalMode(var);
    InitializationFlag init_flag = scope_info_->ContextLocalInitFlag(var);
    MaybeAssignedFlag maybe_assigned_flag =
        scope_info_->ContextLocalMaybeAssignedFlag(var);
    VariableLocation location = var < scope_info_->ContextLocalCount()
                                    ? VariableLocation::CONTEXT
                                    : VariableLocation::GLOBAL;
    Variable::Kind kind = Variable::NORMAL;
    if (index == scope_info_->ReceiverContextSlotIndex()) {
      kind = Variable::THIS;
    }

    Variable* result = variables_.Declare(zone(), this, name, mode, kind,
                                          init_flag, maybe_assigned_flag);
    result->AllocateTo(location, index);
  }

  // We must read parameters from the end since for multiply declared
  // parameters the value of the last declaration of that parameter is used
  // inside a function (and thus we need to look at the last index). Was bug#
  // 1110337.
  for (int index = scope_info_->ParameterCount() - 1; index >= 0; --index) {
    Handle<String> name_handle(scope_info_->ParameterName(index), isolate);
    const AstRawString* name = ast_value_factory->GetString(name_handle);
    if (!names_seen.insert(name).second) continue;

    VariableMode mode = DYNAMIC;
    InitializationFlag init_flag = kCreatedInitialized;
    MaybeAssignedFlag maybe_assigned_flag = kMaybeAssigned;
    VariableLocation location = VariableLocation::LOOKUP;
    Variable::Kind kind = Variable::NORMAL;

    Variable* result = variables_.Declare(zone(), this, name, mode, kind,
                                          init_flag, maybe_assigned_flag);
    result->AllocateTo(location, index);
  }

  // Internalize function proxy for this scope.
  if (scope_info_->HasFunctionName()) {
    AstNodeFactory factory(ast_value_factory);
    Handle<String> name_handle(scope_info_->FunctionName(), isolate);
    const AstRawString* name = ast_value_factory->GetString(name_handle);
    VariableMode mode;
    int index = scope_info_->FunctionContextSlotIndex(*name_handle, &mode);
    if (index >= 0) {
      Variable* result = new (zone())
          Variable(this, name, mode, Variable::NORMAL, kCreatedInitialized);
      VariableProxy* proxy = factory.NewVariableProxy(result);
      VariableDeclaration* declaration =
          factory.NewVariableDeclaration(proxy, this, kNoSourcePosition);
      AsDeclarationScope()->DeclareFunctionVar(declaration);
      result->AllocateTo(VariableLocation::CONTEXT, index);
    }
  }

  scope_info_ = Handle<ScopeInfo>::null();
}

DeclarationScope* Scope::AsDeclarationScope() {
  DCHECK(is_declaration_scope());
  return static_cast<DeclarationScope*>(this);
}

const DeclarationScope* Scope::AsDeclarationScope() const {
  DCHECK(is_declaration_scope());
  return static_cast<const DeclarationScope*>(this);
}

int Scope::num_parameters() const {
  return is_declaration_scope() ? AsDeclarationScope()->num_parameters() : 0;
}

void Scope::Analyze(ParseInfo* info) {
  DCHECK(info->literal() != NULL);
  DeclarationScope* scope = info->literal()->scope();

  // We are compiling one of three cases:
  // 1) top-level code,
  // 2) a function/eval/module on the top-level
  // 3) a function/eval in a scope that was already resolved.
  DCHECK(scope->scope_type() == SCRIPT_SCOPE ||
         scope->outer_scope()->scope_type() == SCRIPT_SCOPE ||
         scope->outer_scope()->already_resolved());

  // Allocate the variables.
  {
    AstNodeFactory ast_node_factory(info->ast_value_factory());
    scope->AllocateVariables(info, &ast_node_factory);
  }

#ifdef DEBUG
  if (info->script_is_native() ? FLAG_print_builtin_scopes
                               : FLAG_print_scopes) {
    scope->Print();
  }
  scope->CheckScopePositions();
  scope->CheckZones();
#endif
}

void DeclarationScope::DeclareThis(AstValueFactory* ast_value_factory) {
  DCHECK(!already_resolved());
  DCHECK(is_declaration_scope());
  DCHECK(has_this_declaration());

  bool subclass_constructor = IsSubclassConstructor(function_kind_);
  Variable* var = variables_.Declare(
      zone(), this, ast_value_factory->this_string(),
      subclass_constructor ? CONST : VAR, Variable::THIS,
      subclass_constructor ? kNeedsInitialization : kCreatedInitialized);
  receiver_ = var;
}

void DeclarationScope::DeclareDefaultFunctionVariables(
    AstValueFactory* ast_value_factory) {
  DCHECK(is_function_scope());
  DCHECK(!is_arrow_scope());
  // Declare 'arguments' variable which exists in all non arrow functions.
  // Note that it might never be accessed, in which case it won't be
  // allocated during variable allocation.
  arguments_ =
      variables_.Declare(zone(), this, ast_value_factory->arguments_string(),
                         VAR, Variable::ARGUMENTS, kCreatedInitialized);

  new_target_ =
      variables_.Declare(zone(), this, ast_value_factory->new_target_string(),
                         CONST, Variable::NORMAL, kCreatedInitialized);

  if (IsConciseMethod(function_kind_) || IsClassConstructor(function_kind_) ||
      IsAccessorFunction(function_kind_)) {
    this_function_ = variables_.Declare(
        zone(), this, ast_value_factory->this_function_string(), CONST,
        Variable::NORMAL, kCreatedInitialized);
  }
}


Scope* Scope::FinalizeBlockScope() {
  DCHECK(is_block_scope());

  if (variables_.occupancy() > 0 ||
      (is_declaration_scope() && calls_sloppy_eval())) {
    return this;
  }

  // Remove this scope from outer scope.
  outer_scope()->RemoveInnerScope(this);

  // Reparent inner scopes.
  if (inner_scope_ != nullptr) {
    Scope* scope = inner_scope_;
    scope->outer_scope_ = outer_scope();
    while (scope->sibling_ != nullptr) {
      scope = scope->sibling_;
      scope->outer_scope_ = outer_scope();
    }
    scope->sibling_ = outer_scope()->inner_scope_;
    outer_scope()->inner_scope_ = inner_scope_;
    inner_scope_ = nullptr;
  }

  // Move unresolved variables
  if (unresolved_ != nullptr) {
    if (outer_scope()->unresolved_ != nullptr) {
      VariableProxy* unresolved = unresolved_;
      while (unresolved->next_unresolved() != nullptr) {
        unresolved = unresolved->next_unresolved();
      }
      unresolved->set_next_unresolved(outer_scope()->unresolved_);
    }
    outer_scope()->unresolved_ = unresolved_;
    unresolved_ = nullptr;
  }

  PropagateUsageFlagsToScope(outer_scope_);

  return NULL;
}

void Scope::Snapshot::Reparent(DeclarationScope* new_parent) const {
  DCHECK_EQ(new_parent, outer_scope_->inner_scope_);
  DCHECK_EQ(new_parent->outer_scope_, outer_scope_);
  DCHECK_EQ(new_parent, new_parent->GetClosureScope());
  DCHECK_NULL(new_parent->inner_scope_);
  DCHECK_NULL(new_parent->unresolved_);
  DCHECK_EQ(0, new_parent->temps()->length());
  Scope* inner_scope = new_parent->sibling_;
  if (inner_scope != top_inner_scope_) {
    for (; inner_scope->sibling() != top_inner_scope_;
         inner_scope = inner_scope->sibling()) {
      inner_scope->outer_scope_ = new_parent;
      DCHECK_NE(inner_scope, new_parent);
    }
    inner_scope->outer_scope_ = new_parent;

    new_parent->inner_scope_ = new_parent->sibling_;
    inner_scope->sibling_ = nullptr;
    // Reset the sibling rather than the inner_scope_ since we
    // want to keep new_parent there.
    new_parent->sibling_ = top_inner_scope_;
  }

  if (outer_scope_->unresolved_ != top_unresolved_) {
    VariableProxy* last = outer_scope_->unresolved_;
    while (last->next_unresolved() != top_unresolved_) {
      last = last->next_unresolved();
    }
    last->set_next_unresolved(nullptr);
    new_parent->unresolved_ = outer_scope_->unresolved_;
    outer_scope_->unresolved_ = top_unresolved_;
  }

  if (outer_scope_->GetClosureScope()->temps()->length() != top_temp_) {
    ZoneList<Variable*>* temps = outer_scope_->GetClosureScope()->temps();
    for (int i = top_temp_; i < temps->length(); i++) {
      Variable* temp = temps->at(i);
      DCHECK_EQ(temp->scope(), temp->scope()->GetClosureScope());
      DCHECK_NE(temp->scope(), new_parent);
      temp->set_scope(new_parent);
      new_parent->AddTemporary(temp);
    }
    temps->Rewind(top_temp_);
  }
}

void Scope::ReplaceOuterScope(Scope* outer) {
  DCHECK_NOT_NULL(outer);
  DCHECK_NOT_NULL(outer_scope_);
  DCHECK(!already_resolved());
  DCHECK(!outer->already_resolved());
  DCHECK(!outer_scope_->already_resolved());
  outer_scope_->RemoveInnerScope(this);
  outer->AddInnerScope(this);
  outer_scope_ = outer;
}


void Scope::PropagateUsageFlagsToScope(Scope* other) {
  DCHECK_NOT_NULL(other);
  DCHECK(!already_resolved());
  DCHECK(!other->already_resolved());
  if (uses_super_property()) other->RecordSuperPropertyUsage();
  if (calls_eval()) other->RecordEvalCall();
}


Variable* Scope::LookupLocal(const AstRawString* name) {
  Variable* result = variables_.Lookup(name);
  if (result != NULL || scope_info_.is_null()) {
    return result;
  }
  Handle<String> name_handle = name->string();
  // The Scope is backed up by ScopeInfo. This means it cannot operate in a
  // heap-independent mode, and all strings must be internalized immediately. So
  // it's ok to get the Handle<String> here.
  // If we have a serialized scope info, we might find the variable there.
  // There should be no local slot with the given name.
  DCHECK(scope_info_->StackSlotIndex(*name_handle) < 0 || is_block_scope());

  // Check context slot lookup.
  VariableMode mode;
  VariableLocation location = VariableLocation::CONTEXT;
  InitializationFlag init_flag;
  MaybeAssignedFlag maybe_assigned_flag;
  int index = ScopeInfo::ContextSlotIndex(scope_info_, name_handle, &mode,
                                          &init_flag, &maybe_assigned_flag);
  if (index < 0) {
    location = VariableLocation::GLOBAL;
    index = ScopeInfo::ContextGlobalSlotIndex(scope_info_, name_handle, &mode,
                                              &init_flag, &maybe_assigned_flag);
  }
  if (index < 0) {
    // Check parameters.
    index = scope_info_->ParameterIndex(*name_handle);
    if (index < 0) return NULL;

    mode = DYNAMIC;
    location = VariableLocation::LOOKUP;
    init_flag = kCreatedInitialized;
    // Be conservative and flag parameters as maybe assigned. Better information
    // would require ScopeInfo to serialize the maybe_assigned bit also for
    // parameters.
    maybe_assigned_flag = kMaybeAssigned;
  } else {
    DCHECK(location != VariableLocation::GLOBAL ||
           (is_script_scope() && IsDeclaredVariableMode(mode) &&
            !IsLexicalVariableMode(mode)));
  }

  Variable::Kind kind = Variable::NORMAL;
  if (location == VariableLocation::CONTEXT &&
      index == scope_info_->ReceiverContextSlotIndex()) {
    kind = Variable::THIS;
  }
  // TODO(marja, rossberg): Correctly declare FUNCTION, CLASS, NEW_TARGET, and
  // ARGUMENTS bindings as their corresponding Variable::Kind.

  Variable* var = variables_.Declare(zone(), this, name, mode, kind, init_flag,
                                     maybe_assigned_flag);
  var->AllocateTo(location, index);
  return var;
}

Variable* DeclarationScope::LookupFunctionVar(const AstRawString* name,
                                              AstNodeFactory* factory) {
  if (function_ != NULL && function_->proxy()->raw_name() == name) {
    return function_->proxy()->var();
  } else if (!scope_info_.is_null()) {
    // If we are backed by a scope info, try to lookup the variable there.
    VariableMode mode;
    int index = scope_info_->FunctionContextSlotIndex(*(name->string()), &mode);
    if (index < 0) return NULL;
    Variable* var = new (zone())
        Variable(this, name, mode, Variable::NORMAL, kCreatedInitialized);
    DCHECK_NOT_NULL(factory);
    VariableProxy* proxy = factory->NewVariableProxy(var);
    VariableDeclaration* declaration =
        factory->NewVariableDeclaration(proxy, this, kNoSourcePosition);
    DCHECK_EQ(factory->zone(), zone());
    DeclareFunctionVar(declaration);
    var->AllocateTo(VariableLocation::CONTEXT, index);
    return var;
  } else {
    return NULL;
  }
}


Variable* Scope::Lookup(const AstRawString* name) {
  for (Scope* scope = this;
       scope != NULL;
       scope = scope->outer_scope()) {
    Variable* var = scope->LookupLocal(name);
    if (var != NULL) return var;
  }
  return NULL;
}

Variable* DeclarationScope::DeclareParameter(
    const AstRawString* name, VariableMode mode, bool is_optional, bool is_rest,
    bool* is_duplicate, AstValueFactory* ast_value_factory) {
  DCHECK(!already_resolved());
  DCHECK(is_function_scope());
  DCHECK(!is_optional || !is_rest);
  Variable* var;
  if (mode == TEMPORARY) {
    var = NewTemporary(name);
  } else {
    var = variables_.Declare(zone(), this, name, mode, Variable::NORMAL,
                             kCreatedInitialized);
    // TODO(wingo): Avoid O(n^2) check.
    *is_duplicate = IsDeclaredParameter(name);
  }
  if (!is_optional && !is_rest && arity_ == params_.length()) {
    ++arity_;
  }
  if (is_rest) {
    DCHECK_NULL(rest_parameter_);
    rest_parameter_ = var;
    rest_index_ = num_parameters();
  }
  params_.Add(var, zone());
  if (name == ast_value_factory->arguments_string()) {
    has_arguments_parameter_ = true;
  }
  return var;
}

Variable* Scope::DeclareLocal(const AstRawString* name, VariableMode mode,
                              InitializationFlag init_flag, Variable::Kind kind,
                              MaybeAssignedFlag maybe_assigned_flag) {
  DCHECK(!already_resolved());
  // This function handles VAR, LET, and CONST modes.  DYNAMIC variables are
  // introduced during variable allocation, and TEMPORARY variables are
  // allocated via NewTemporary().
  DCHECK(IsDeclaredVariableMode(mode));
  return variables_.Declare(zone(), this, name, mode, kind, init_flag,
                            maybe_assigned_flag);
}

Variable* DeclarationScope::DeclareDynamicGlobal(const AstRawString* name) {
  DCHECK(is_script_scope());
  return variables_.Declare(zone(), this, name, DYNAMIC_GLOBAL,
                            Variable::NORMAL, kCreatedInitialized);
}


bool Scope::RemoveUnresolved(VariableProxy* var) {
  if (unresolved_ == var) {
    unresolved_ = var->next_unresolved();
    var->set_next_unresolved(nullptr);
    return true;
  }
  VariableProxy* current = unresolved_;
  while (current != nullptr) {
    VariableProxy* next = current->next_unresolved();
    if (var == next) {
      current->set_next_unresolved(next->next_unresolved());
      var->set_next_unresolved(nullptr);
      return true;
    }
    current = next;
  }
  return false;
}


Variable* Scope::NewTemporary(const AstRawString* name) {
  DeclarationScope* scope = GetClosureScope();
  Variable* var = new(zone()) Variable(scope,
                                       name,
                                       TEMPORARY,
                                       Variable::NORMAL,
                                       kCreatedInitialized);
  scope->AddTemporary(var);
  return var;
}

int DeclarationScope::RemoveTemporary(Variable* var) {
  DCHECK(!already_resolved());
  DCHECK_NOT_NULL(var);
  // Temporaries are only placed in ClosureScopes.
  DCHECK_EQ(GetClosureScope(), this);
  DCHECK_EQ(var->scope()->GetClosureScope(), var->scope());
  // If the temporary is not here, return quickly.
  if (var->scope() != this) return -1;
  // Most likely (always?) any temporary variable we want to remove
  // was just added before, so we search backwards.
  for (int i = temps_.length(); i-- > 0;) {
    if (temps_[i] == var) {
      // Don't shrink temps_, as callers of this method expect
      // the returned indices to be unique per-scope.
      temps_[i] = nullptr;
      return i;
    }
  }
  return -1;
}


void Scope::AddDeclaration(Declaration* declaration) {
  DCHECK(!already_resolved());
  decls_.Add(declaration, zone());
}


Declaration* Scope::CheckConflictingVarDeclarations() {
  int length = decls_.length();
  for (int i = 0; i < length; i++) {
    Declaration* decl = decls_[i];
    VariableMode mode = decl->proxy()->var()->mode();
    // We don't create a separate scope to hold the function name of a function
    // expression, so we have to make sure not to consider it when checking for
    // conflicts (since it's conceptually "outside" the declaration scope).
    if (is_function_scope() && decl == AsDeclarationScope()->function())
      continue;
    if (IsLexicalVariableMode(mode) && !is_block_scope()) continue;

    // Iterate through all scopes until and including the declaration scope.
    Scope* previous = NULL;
    Scope* current = decl->scope();
    // Lexical vs lexical conflicts within the same scope have already been
    // captured in Parser::Declare. The only conflicts we still need to check
    // are lexical vs VAR, or any declarations within a declaration block scope
    // vs lexical declarations in its surrounding (function) scope.
    if (IsLexicalVariableMode(mode)) current = current->outer_scope_;
    do {
      // There is a conflict if there exists a non-VAR binding.
      Variable* other_var =
          current->variables_.Lookup(decl->proxy()->raw_name());
      if (other_var != NULL && IsLexicalVariableMode(other_var->mode())) {
        return decl;
      }
      previous = current;
      current = current->outer_scope_;
    } while (!previous->is_declaration_scope());
  }
  return NULL;
}

Declaration* Scope::CheckLexDeclarationsConflictingWith(
    const ZoneList<const AstRawString*>& names) {
  DCHECK(is_block_scope());
  for (int i = 0; i < names.length(); ++i) {
    Variable* var = LookupLocal(names.at(i));
    if (var != nullptr) {
      // Conflict; find and return its declaration.
      DCHECK(IsLexicalVariableMode(var->mode()));
      const AstRawString* name = names.at(i);
      for (int j = 0; j < decls_.length(); ++j) {
        if (decls_[j]->proxy()->raw_name() == name) {
          return decls_[j];
        }
      }
      DCHECK(false);
    }
  }
  return nullptr;
}

class VarAndOrder {
 public:
  VarAndOrder(Variable* var, int order) : var_(var), order_(order) { }
  Variable* var() const { return var_; }
  int order() const { return order_; }
  static int Compare(const VarAndOrder* a, const VarAndOrder* b) {
    return a->order_ - b->order_;
  }

 private:
  Variable* var_;
  int order_;
};

void Scope::CollectStackAndContextLocals(ZoneList<Variable*>* stack_locals,
                                         ZoneList<Variable*>* context_locals,
                                         ZoneList<Variable*>* context_globals) {
  DCHECK(stack_locals != NULL);
  DCHECK(context_locals != NULL);
  DCHECK(context_globals != NULL);

  // Collect temporaries which are always allocated on the stack, unless the
  // context as a whole has forced context allocation.
  if (is_declaration_scope()) {
    ZoneList<Variable*>* temps = AsDeclarationScope()->temps();
    for (int i = 0; i < temps->length(); i++) {
      Variable* var = (*temps)[i];
      if (var == nullptr) continue;
      if (var->is_used()) {
        if (var->IsContextSlot()) {
          DCHECK(has_forced_context_allocation());
          context_locals->Add(var, zone());
        } else if (var->IsStackLocal()) {
          stack_locals->Add(var, zone());
        } else {
          DCHECK(var->IsParameter());
        }
      }
    }
  }

  // Collect declared local variables.
  ZoneList<VarAndOrder> vars(variables_.occupancy(), zone());
  for (VariableMap::Entry* p = variables_.Start();
       p != NULL;
       p = variables_.Next(p)) {
    Variable* var = reinterpret_cast<Variable*>(p->value);
    if (var->is_used()) {
      vars.Add(VarAndOrder(var, p->order), zone());
    }
  }
  vars.Sort(VarAndOrder::Compare);
  int var_count = vars.length();
  for (int i = 0; i < var_count; i++) {
    Variable* var = vars[i].var();
    if (var->IsStackLocal()) {
      stack_locals->Add(var, zone());
    } else if (var->IsContextSlot()) {
      context_locals->Add(var, zone());
    } else if (var->IsGlobalSlot()) {
      context_globals->Add(var, zone());
    }
  }
}

void DeclarationScope::AllocateVariables(ParseInfo* info,
                                         AstNodeFactory* factory) {
  // 1) Propagate scope information.
  bool outer_scope_calls_sloppy_eval = false;
  if (outer_scope_ != NULL) {
    outer_scope_calls_sloppy_eval =
        outer_scope_->outer_scope_calls_sloppy_eval() |
        outer_scope_->calls_sloppy_eval();
  }
  PropagateScopeInfo(outer_scope_calls_sloppy_eval);

  // 2) Resolve variables.
  ResolveVariablesRecursively(info, factory);

  // 3) Allocate variables.
  AllocateVariablesRecursively(info->ast_value_factory());
}


bool Scope::HasTrivialContext() const {
  // A function scope has a trivial context if it always is the global
  // context. We iteratively scan out the context chain to see if
  // there is anything that makes this scope non-trivial; otherwise we
  // return true.
  for (const Scope* scope = this; scope != NULL; scope = scope->outer_scope_) {
    if (scope->is_eval_scope()) return false;
    if (scope->scope_inside_with_) return false;
    if (scope->ContextLocalCount() > 0) return false;
    if (scope->ContextGlobalCount() > 0) return false;
  }
  return true;
}


bool Scope::HasTrivialOuterContext() const {
  Scope* outer = outer_scope_;
  if (outer == NULL) return true;
  // Note that the outer context may be trivial in general, but the current
  // scope may be inside a 'with' statement in which case the outer context
  // for this scope is not trivial.
  return !scope_inside_with_ && outer->HasTrivialContext();
}


bool Scope::AllowsLazyParsing() const {
  // If we are inside a block scope, we must parse eagerly to find out how
  // to allocate variables on the block scope. At this point, declarations may
  // not have yet been parsed.
  for (const Scope* scope = this; scope != NULL; scope = scope->outer_scope_) {
    if (scope->is_block_scope()) return false;
  }
  return AllowsLazyCompilation();
}


bool Scope::AllowsLazyCompilation() const { return !force_eager_compilation_; }


bool Scope::AllowsLazyCompilationWithoutContext() const {
  return !force_eager_compilation_ && HasTrivialOuterContext();
}


int Scope::ContextChainLength(Scope* scope) {
  int n = 0;
  for (Scope* s = this; s != scope; s = s->outer_scope_) {
    DCHECK(s != NULL);  // scope must be in the scope chain
    if (s->NeedsContext()) n++;
  }
  return n;
}


int Scope::MaxNestedContextChainLength() {
  int max_context_chain_length = 0;
  for (Scope* scope = inner_scope_; scope != nullptr; scope = scope->sibling_) {
    max_context_chain_length = std::max(scope->MaxNestedContextChainLength(),
                                        max_context_chain_length);
  }
  if (NeedsContext()) {
    max_context_chain_length += 1;
  }
  return max_context_chain_length;
}

DeclarationScope* Scope::GetDeclarationScope() {
  Scope* scope = this;
  while (!scope->is_declaration_scope()) {
    scope = scope->outer_scope();
  }
  return scope->AsDeclarationScope();
}

DeclarationScope* Scope::GetClosureScope() {
  Scope* scope = this;
  while (!scope->is_declaration_scope() || scope->is_block_scope()) {
    scope = scope->outer_scope();
  }
  return scope->AsDeclarationScope();
}

DeclarationScope* Scope::GetReceiverScope() {
  Scope* scope = this;
  while (!scope->is_script_scope() &&
         (!scope->is_function_scope() ||
          scope->AsDeclarationScope()->is_arrow_scope())) {
    scope = scope->outer_scope();
  }
  return scope->AsDeclarationScope();
}


Handle<ScopeInfo> Scope::GetScopeInfo(Isolate* isolate) {
  if (scope_info_.is_null()) {
    scope_info_ = ScopeInfo::Create(isolate, zone(), this);
  }
  return scope_info_;
}

Handle<StringSet> Scope::CollectNonLocals(Handle<StringSet> non_locals) {
  // Collect non-local variables referenced in the scope.
  // TODO(yangguo): store non-local variables explicitly if we can no longer
  //                rely on unresolved_ to find them.
  for (VariableProxy* proxy = unresolved_; proxy != nullptr;
       proxy = proxy->next_unresolved()) {
    if (proxy->is_resolved() && proxy->var()->IsStackAllocated()) continue;
    Handle<String> name = proxy->name();
    non_locals = StringSet::Add(non_locals, name);
  }
  for (Scope* scope = inner_scope_; scope != nullptr; scope = scope->sibling_) {
    non_locals = scope->CollectNonLocals(non_locals);
  }
  return non_locals;
}

void DeclarationScope::AnalyzePartially(DeclarationScope* migrate_to,
                                        AstNodeFactory* ast_node_factory) {
  // Gather info from inner scopes.
  PropagateScopeInfo(false);

  // Try to resolve unresolved variables for this Scope and migrate those which
  // cannot be resolved inside. It doesn't make sense to try to resolve them in
  // the outer Scopes here, because they are incomplete.
  MigrateUnresolvableLocals(migrate_to, ast_node_factory, this);

  // Push scope data up to migrate_to. Note that migrate_to and this Scope
  // describe the same Scope, just in different Zones.
  PropagateUsageFlagsToScope(migrate_to);
  if (inner_scope_calls_eval_) {
    migrate_to->inner_scope_calls_eval_ = true;
  }
  DCHECK(!force_eager_compilation_);
  migrate_to->set_start_position(start_position_);
  migrate_to->set_end_position(end_position_);
  migrate_to->language_mode_ = language_mode_;
  migrate_to->arity_ = arity_;
  migrate_to->force_context_allocation_ = force_context_allocation_;
  outer_scope_->RemoveInnerScope(this);
  DCHECK_EQ(outer_scope_, migrate_to->outer_scope_);
  DCHECK_EQ(outer_scope_->zone(), migrate_to->zone());
  DCHECK_EQ(NeedsHomeObject(), migrate_to->NeedsHomeObject());
  DCHECK_EQ(asm_function_, migrate_to->asm_function_);
  DCHECK_EQ(arguments() != nullptr, migrate_to->arguments() != nullptr);
}

#ifdef DEBUG
static const char* Header(ScopeType scope_type, FunctionKind function_kind,
                          bool is_declaration_scope) {
  switch (scope_type) {
    case EVAL_SCOPE: return "eval";
    // TODO(adamk): Should we print concise method scopes specially?
    case FUNCTION_SCOPE:
      if (IsGeneratorFunction(function_kind)) return "function*";
      if (IsAsyncFunction(function_kind)) return "async function";
      if (IsArrowFunction(function_kind)) return "arrow";
      return "function";
    case MODULE_SCOPE: return "module";
    case SCRIPT_SCOPE: return "global";
    case CATCH_SCOPE: return "catch";
    case BLOCK_SCOPE: return is_declaration_scope ? "varblock" : "block";
    case WITH_SCOPE: return "with";
  }
  UNREACHABLE();
  return NULL;
}


static void Indent(int n, const char* str) {
  PrintF("%*s%s", n, "", str);
}


static void PrintName(const AstRawString* name) {
  PrintF("%.*s", name->length(), name->raw_data());
}


static void PrintLocation(Variable* var) {
  switch (var->location()) {
    case VariableLocation::UNALLOCATED:
      break;
    case VariableLocation::PARAMETER:
      PrintF("parameter[%d]", var->index());
      break;
    case VariableLocation::LOCAL:
      PrintF("local[%d]", var->index());
      break;
    case VariableLocation::CONTEXT:
      PrintF("context[%d]", var->index());
      break;
    case VariableLocation::GLOBAL:
      PrintF("global[%d]", var->index());
      break;
    case VariableLocation::LOOKUP:
      PrintF("lookup");
      break;
    case VariableLocation::MODULE:
      PrintF("module");
      break;
  }
}


static void PrintVar(int indent, Variable* var) {
  if (var->is_used() || !var->IsUnallocated()) {
    Indent(indent, Variable::Mode2String(var->mode()));
    PrintF(" ");
    if (var->raw_name()->IsEmpty())
      PrintF(".%p", reinterpret_cast<void*>(var));
    else
      PrintName(var->raw_name());
    PrintF(";  // ");
    PrintLocation(var);
    bool comma = !var->IsUnallocated();
    if (var->has_forced_context_allocation()) {
      if (comma) PrintF(", ");
      PrintF("forced context allocation");
      comma = true;
    }
    if (var->maybe_assigned() == kMaybeAssigned) {
      if (comma) PrintF(", ");
      PrintF("maybe assigned");
    }
    PrintF("\n");
  }
}


static void PrintMap(int indent, VariableMap* map) {
  for (VariableMap::Entry* p = map->Start(); p != NULL; p = map->Next(p)) {
    Variable* var = reinterpret_cast<Variable*>(p->value);
    if (var == NULL) {
      Indent(indent, "<?>\n");
    } else {
      PrintVar(indent, var);
    }
  }
}

void DeclarationScope::PrintParameters() {
  PrintF(" (");
  for (int i = 0; i < params_.length(); i++) {
    if (i > 0) PrintF(", ");
    const AstRawString* name = params_[i]->raw_name();
    if (name->IsEmpty())
      PrintF(".%p", reinterpret_cast<void*>(params_[i]));
    else
      PrintName(name);
  }
  PrintF(")");
}

void Scope::Print(int n) {
  int n0 = (n > 0 ? n : 0);
  int n1 = n0 + 2;  // indentation

  // Print header.
  FunctionKind function_kind = is_function_scope()
                                   ? AsDeclarationScope()->function_kind()
                                   : kNormalFunction;
  Indent(n0, Header(scope_type_, function_kind, is_declaration_scope()));
  if (scope_name_ != nullptr && !scope_name_->IsEmpty()) {
    PrintF(" ");
    PrintName(scope_name_);
  }

  // Print parameters, if any.
  VariableDeclaration* function = nullptr;
  if (is_function_scope()) {
    AsDeclarationScope()->PrintParameters();
    function = AsDeclarationScope()->function();
  }

  PrintF(" { // (%d, %d)\n", start_position(), end_position());

  // Function name, if any (named function literals, only).
  if (function != nullptr) {
    Indent(n1, "// (local) function name: ");
    PrintName(function->proxy()->raw_name());
    PrintF("\n");
  }

  // Scope info.
  if (HasTrivialOuterContext()) {
    Indent(n1, "// scope has trivial outer context\n");
  }
  if (is_strict(language_mode())) {
    Indent(n1, "// strict mode scope\n");
  }
  if (asm_module_) Indent(n1, "// scope is an asm module\n");
  if (asm_function_) Indent(n1, "// scope is an asm function\n");
  if (scope_inside_with_) Indent(n1, "// scope inside 'with'\n");
  if (scope_calls_eval_) Indent(n1, "// scope calls 'eval'\n");
  if (scope_uses_super_property_)
    Indent(n1, "// scope uses 'super' property\n");
  if (outer_scope_calls_sloppy_eval_) {
    Indent(n1, "// outer scope calls 'eval' in sloppy context\n");
  }
  if (inner_scope_calls_eval_) Indent(n1, "// inner scope calls 'eval'\n");
  if (num_stack_slots_ > 0) {
    Indent(n1, "// ");
    PrintF("%d stack slots\n", num_stack_slots_);
  }
  if (num_heap_slots_ > 0) {
    Indent(n1, "// ");
    PrintF("%d heap slots (including %d global slots)\n", num_heap_slots_,
           num_global_slots_);
  }

  // Print locals.
  if (function != nullptr) {
    Indent(n1, "// function var:\n");
    PrintVar(n1, function->proxy()->var());
  }

  if (is_declaration_scope()) {
    bool printed_header = false;
    ZoneList<Variable*>* temps = AsDeclarationScope()->temps();
    for (int i = 0; i < temps->length(); i++) {
      if ((*temps)[i] != nullptr) {
        if (!printed_header) {
          printed_header = true;
          Indent(n1, "// temporary vars:\n");
        }
        PrintVar(n1, (*temps)[i]);
      }
    }
  }

  if (variables_.Start() != NULL) {
    Indent(n1, "// local vars:\n");
    PrintMap(n1, &variables_);
  }

  if (dynamics_ != NULL) {
    Indent(n1, "// dynamic vars:\n");
    PrintMap(n1, dynamics_->GetMap(DYNAMIC));
    PrintMap(n1, dynamics_->GetMap(DYNAMIC_LOCAL));
    PrintMap(n1, dynamics_->GetMap(DYNAMIC_GLOBAL));
  }

  // Print inner scopes (disable by providing negative n).
  if (n >= 0) {
    for (Scope* scope = inner_scope_; scope != nullptr;
         scope = scope->sibling_) {
      PrintF("\n");
      scope->Print(n1);
    }
  }

  Indent(n0, "}\n");
}

void Scope::CheckScopePositions() {
  // A scope is allowed to have invalid positions if it is hidden and has no
  // inner scopes
  if (!is_hidden() && inner_scope_ == nullptr) {
    CHECK_NE(kNoSourcePosition, start_position());
    CHECK_NE(kNoSourcePosition, end_position());
  }
  for (Scope* scope = inner_scope_; scope != nullptr; scope = scope->sibling_) {
    scope->CheckScopePositions();
  }
}

void Scope::CheckZones() {
  for (Scope* scope = inner_scope_; scope != nullptr; scope = scope->sibling_) {
    CHECK_EQ(scope->zone(), zone());
  }
}
#endif  // DEBUG


Variable* Scope::NonLocal(const AstRawString* name, VariableMode mode) {
  if (dynamics_ == NULL) dynamics_ = new (zone()) DynamicScopePart(zone());
  VariableMap* map = dynamics_->GetMap(mode);
  Variable* var = map->Lookup(name);
  if (var == NULL) {
    // Declare a new non-local.
    InitializationFlag init_flag = (mode == VAR)
        ? kCreatedInitialized : kNeedsInitialization;
    var = map->Declare(zone(), NULL, name, mode, Variable::NORMAL, init_flag);
    // Allocate it by giving it a dynamic lookup.
    var->AllocateTo(VariableLocation::LOOKUP, -1);
  }
  return var;
}

Variable* Scope::LookupRecursive(VariableProxy* proxy,
                                 BindingKind* binding_kind,
                                 AstNodeFactory* factory,
                                 Scope* max_outer_scope) {
  DCHECK(binding_kind != NULL);
  if (already_resolved() && is_with_scope()) {
    // Short-cut: if the scope is deserialized from a scope info, variable
    // allocation is already fixed.  We can simply return with dynamic lookup.
    *binding_kind = DYNAMIC_LOOKUP;
    return NULL;
  }

  // Try to find the variable in this scope.
  Variable* var = LookupLocal(proxy->raw_name());

  // We found a variable and we are done. (Even if there is an 'eval' in
  // this scope which introduces the same variable again, the resulting
  // variable remains the same.)
  if (var != NULL) {
    *binding_kind = BOUND;
    return var;
  }

  // We did not find a variable locally. Check against the function variable, if
  // any.
  *binding_kind = UNBOUND;
  var =
      is_function_scope()
          ? AsDeclarationScope()->LookupFunctionVar(proxy->raw_name(), factory)
          : nullptr;
  if (var != NULL) {
    *binding_kind = BOUND;
  } else if (outer_scope_ != nullptr && this != max_outer_scope) {
    var = outer_scope_->LookupRecursive(proxy, binding_kind, factory,
                                        max_outer_scope);
    if (*binding_kind == BOUND && is_function_scope()) {
      var->ForceContextAllocation();
    }
  } else {
    DCHECK(is_script_scope() || this == max_outer_scope);
  }

  // "this" can't be shadowed by "eval"-introduced bindings or by "with" scopes.
  // TODO(wingo): There are other variables in this category; add them.
  bool name_can_be_shadowed = var == nullptr || !var->is_this();

  if (is_with_scope() && name_can_be_shadowed) {
    DCHECK(!already_resolved());
    // The current scope is a with scope, so the variable binding can not be
    // statically resolved. However, note that it was necessary to do a lookup
    // in the outer scope anyway, because if a binding exists in an outer scope,
    // the associated variable has to be marked as potentially being accessed
    // from inside of an inner with scope (the property may not be in the 'with'
    // object).
    if (var != NULL) {
      var->set_is_used();
      var->ForceContextAllocation();
      if (proxy->is_assigned()) var->set_maybe_assigned();
    }
    *binding_kind = DYNAMIC_LOOKUP;
    return NULL;
  } else if (calls_sloppy_eval() && is_declaration_scope() &&
             !is_script_scope() && name_can_be_shadowed) {
    // A variable binding may have been found in an outer scope, but the current
    // scope makes a sloppy 'eval' call, so the found variable may not be
    // the correct one (the 'eval' may introduce a binding with the same name).
    // In that case, change the lookup result to reflect this situation.
    // Only scopes that can host var bindings (declaration scopes) need be
    // considered here (this excludes block and catch scopes), and variable
    // lookups at script scope are always dynamic.
    if (*binding_kind == BOUND) {
      *binding_kind = BOUND_EVAL_SHADOWED;
    } else if (*binding_kind == UNBOUND) {
      *binding_kind = UNBOUND_EVAL_SHADOWED;
    }
  }
  return var;
}

void Scope::ResolveVariable(ParseInfo* info, VariableProxy* proxy,
                            AstNodeFactory* factory) {
  DCHECK(info->script_scope()->is_script_scope());

  // If the proxy is already resolved there's nothing to do
  // (functions and consts may be resolved by the parser).
  if (proxy->is_resolved()) return;

  // Otherwise, try to resolve the variable.
  BindingKind binding_kind;
  Variable* var = LookupRecursive(proxy, &binding_kind, factory);

#ifdef DEBUG
  if (info->script_is_native()) {
    // To avoid polluting the global object in native scripts
    //  - Variables must not be allocated to the global scope.
    CHECK_NOT_NULL(outer_scope());
    //  - Variables must be bound locally or unallocated.
    if (BOUND != binding_kind) {
      // The following variable name may be minified. If so, disable
      // minification in js2c.py for better output.
      Handle<String> name = proxy->raw_name()->string();
      V8_Fatal(__FILE__, __LINE__, "Unbound variable: '%s' in native script.",
               name->ToCString().get());
    }
    VariableLocation location = var->location();
    CHECK(location == VariableLocation::LOCAL ||
          location == VariableLocation::CONTEXT ||
          location == VariableLocation::PARAMETER ||
          location == VariableLocation::UNALLOCATED);
  }
#endif

  switch (binding_kind) {
    case BOUND:
      break;

    case BOUND_EVAL_SHADOWED:
      // We either found a variable binding that might be shadowed by eval  or
      // gave up on it (e.g. by encountering a local with the same in the outer
      // scope which was not promoted to a context, this can happen if we use
      // debugger to evaluate arbitrary expressions at a break point).
      if (var->IsGlobalObjectProperty()) {
        var = NonLocal(proxy->raw_name(), DYNAMIC_GLOBAL);
      } else if (var->is_dynamic()) {
        var = NonLocal(proxy->raw_name(), DYNAMIC);
      } else {
        Variable* invalidated = var;
        var = NonLocal(proxy->raw_name(), DYNAMIC_LOCAL);
        var->set_local_if_not_shadowed(invalidated);
      }
      break;

    case UNBOUND:
      // No binding has been found. Declare a variable on the global object.
      var = info->script_scope()->DeclareDynamicGlobal(proxy->raw_name());
      break;

    case UNBOUND_EVAL_SHADOWED:
      // No binding has been found. But some scope makes a sloppy 'eval' call.
      var = NonLocal(proxy->raw_name(), DYNAMIC_GLOBAL);
      break;

    case DYNAMIC_LOOKUP:
      // The variable could not be resolved statically.
      var = NonLocal(proxy->raw_name(), DYNAMIC);
      break;
  }

  DCHECK(var != NULL);
  if (proxy->is_assigned()) var->set_maybe_assigned();

  proxy->BindTo(var);
}

void Scope::ResolveVariablesRecursively(ParseInfo* info,
                                        AstNodeFactory* factory) {
  DCHECK(info->script_scope()->is_script_scope());

  // Resolve unresolved variables for this scope.
  for (VariableProxy* proxy = unresolved_; proxy != nullptr;
       proxy = proxy->next_unresolved()) {
    ResolveVariable(info, proxy, factory);
  }

  // Resolve unresolved variables for inner scopes.
  for (Scope* scope = inner_scope_; scope != nullptr; scope = scope->sibling_) {
    scope->ResolveVariablesRecursively(info, factory);
  }
}

void Scope::MigrateUnresolvableLocals(DeclarationScope* migrate_to,
                                      AstNodeFactory* ast_node_factory,
                                      DeclarationScope* max_outer_scope) {
  BindingKind binding_kind;
  for (VariableProxy *proxy = unresolved_, *next = nullptr; proxy != nullptr;
       proxy = next) {
    next = proxy->next_unresolved();
    // Note that we pass nullptr as AstNodeFactory: this phase should not create
    // any new AstNodes, since none of the Scopes involved are backed up by
    // ScopeInfo.
    if (LookupRecursive(proxy, &binding_kind, nullptr, max_outer_scope) ==
        nullptr) {
      // Re-create the VariableProxies in the right Zone and insert them into
      // migrate_to.
      DCHECK(!proxy->is_resolved());
      VariableProxy* copy = ast_node_factory->CopyVariableProxy(proxy);
      migrate_to->AddUnresolved(copy);
    }
  }

  for (Scope* scope = inner_scope_; scope != nullptr; scope = scope->sibling_) {
    scope->MigrateUnresolvableLocals(migrate_to, ast_node_factory,
                                     max_outer_scope);
  }
}

void Scope::PropagateScopeInfo(bool outer_scope_calls_sloppy_eval) {
  if (outer_scope_calls_sloppy_eval) {
    outer_scope_calls_sloppy_eval_ = true;
  }

  bool calls_sloppy_eval =
      this->calls_sloppy_eval() || outer_scope_calls_sloppy_eval_;
  for (Scope* inner = inner_scope_; inner != nullptr; inner = inner->sibling_) {
    inner->PropagateScopeInfo(calls_sloppy_eval);
    if (inner->scope_calls_eval_ || inner->inner_scope_calls_eval_) {
      inner_scope_calls_eval_ = true;
    }
    if (inner->force_eager_compilation_) {
      force_eager_compilation_ = true;
    }
    if (asm_module_ && inner->scope_type() == FUNCTION_SCOPE) {
      inner->asm_function_ = true;
    }
  }
}


bool Scope::MustAllocate(Variable* var) {
  DCHECK(var->location() != VariableLocation::MODULE);
  // Give var a read/write use if there is a chance it might be accessed
  // via an eval() call.  This is only possible if the variable has a
  // visible name.
  if ((var->is_this() || !var->raw_name()->IsEmpty()) &&
      (scope_calls_eval_ || inner_scope_calls_eval_ || is_catch_scope() ||
       is_script_scope())) {
    var->set_is_used();
    if (scope_calls_eval_ || inner_scope_calls_eval_) var->set_maybe_assigned();
  }
  DCHECK(!var->has_forced_context_allocation() || var->is_used());
  // Global variables do not need to be allocated.
  return !var->IsGlobalObjectProperty() && var->is_used();
}


bool Scope::MustAllocateInContext(Variable* var) {
  // If var is accessed from an inner scope, or if there is a possibility
  // that it might be accessed from the current or an inner scope (through
  // an eval() call or a runtime with lookup), it must be allocated in the
  // context.
  //
  // Exceptions: If the scope as a whole has forced context allocation, all
  // variables will have context allocation, even temporaries.  Otherwise
  // temporary variables are always stack-allocated.  Catch-bound variables are
  // always context-allocated.
  if (has_forced_context_allocation()) return true;
  if (var->mode() == TEMPORARY) return false;
  if (is_catch_scope()) return true;
  if (is_script_scope() && IsLexicalVariableMode(var->mode())) return true;
  return var->has_forced_context_allocation() || scope_calls_eval_ ||
         inner_scope_calls_eval_;
}


void Scope::AllocateStackSlot(Variable* var) {
  if (is_block_scope()) {
    outer_scope()->GetDeclarationScope()->AllocateStackSlot(var);
  } else {
    var->AllocateTo(VariableLocation::LOCAL, num_stack_slots_++);
  }
}


void Scope::AllocateHeapSlot(Variable* var) {
  var->AllocateTo(VariableLocation::CONTEXT, num_heap_slots_++);
}

void DeclarationScope::AllocateParameterLocals() {
  DCHECK(is_function_scope());

  bool uses_sloppy_arguments = false;

  // Functions have 'arguments' declared implicitly in all non arrow functions.
  if (arguments_ != nullptr) {
    // 'arguments' is used. Unless there is also a parameter called
    // 'arguments', we must be conservative and allocate all parameters to
    // the context assuming they will be captured by the arguments object.
    // If we have a parameter named 'arguments', a (new) value is always
    // assigned to it via the function invocation. Then 'arguments' denotes
    // that specific parameter value and cannot be used to access the
    // parameters, which is why we don't need to allocate an arguments
    // object in that case.
    if (MustAllocate(arguments_) && !has_arguments_parameter_) {
      // In strict mode 'arguments' does not alias formal parameters.
      // Therefore in strict mode we allocate parameters as if 'arguments'
      // were not used.
      // If the parameter list is not simple, arguments isn't sloppy either.
      uses_sloppy_arguments =
          is_sloppy(language_mode()) && has_simple_parameters();
    } else {
      // 'arguments' is unused. Tell the code generator that it does not need to
      // allocate the arguments object by nulling out arguments_.
      arguments_ = nullptr;
    }

  } else {
    DCHECK(is_arrow_scope());
  }

  if (rest_parameter_ && !MustAllocate(rest_parameter_)) {
    rest_parameter_ = nullptr;
  }

  // The same parameter may occur multiple times in the parameters_ list.
  // If it does, and if it is not copied into the context object, it must
  // receive the highest parameter index for that parameter; thus iteration
  // order is relevant!
  for (int i = params_.length() - 1; i >= 0; --i) {
    Variable* var = params_[i];
    if (var == rest_parameter_) continue;

    DCHECK(var->scope() == this);
    if (uses_sloppy_arguments) {
      var->ForceContextAllocation();
    }
    AllocateParameter(var, i);
  }
}

void DeclarationScope::AllocateParameter(Variable* var, int index) {
  if (MustAllocate(var)) {
    if (MustAllocateInContext(var)) {
      DCHECK(var->IsUnallocated() || var->IsContextSlot());
      if (var->IsUnallocated()) {
        AllocateHeapSlot(var);
      }
    } else {
      DCHECK(var->IsUnallocated() || var->IsParameter());
      if (var->IsUnallocated()) {
        var->AllocateTo(VariableLocation::PARAMETER, index);
      }
    }
  } else {
    DCHECK(!var->IsGlobalSlot());
  }
}

void DeclarationScope::AllocateReceiver() {
  if (!has_this_declaration()) return;
  DCHECK_NOT_NULL(receiver());
  DCHECK_EQ(receiver()->scope(), this);
  AllocateParameter(receiver(), -1);
}

void Scope::AllocateNonParameterLocal(Variable* var,
                                      AstValueFactory* ast_value_factory) {
  DCHECK(var->scope() == this);
  DCHECK(var->raw_name() != ast_value_factory->dot_result_string() ||
         !var->IsStackLocal());
  if (var->IsUnallocated() && MustAllocate(var)) {
    if (MustAllocateInContext(var)) {
      AllocateHeapSlot(var);
    } else {
      AllocateStackSlot(var);
    }
  }
}

void Scope::AllocateDeclaredGlobal(Variable* var,
                                   AstValueFactory* ast_value_factory) {
  DCHECK(var->scope() == this);
  DCHECK(var->raw_name() != ast_value_factory->dot_result_string() ||
         !var->IsStackLocal());
  if (var->IsUnallocated()) {
    if (var->IsStaticGlobalObjectProperty()) {
      DCHECK_EQ(-1, var->index());
      DCHECK(var->name()->IsString());
      var->AllocateTo(VariableLocation::GLOBAL, num_heap_slots_++);
      num_global_slots_++;
    } else {
      // There must be only DYNAMIC_GLOBAL in the script scope.
      DCHECK(!is_script_scope() || DYNAMIC_GLOBAL == var->mode());
    }
  }
}

void Scope::AllocateNonParameterLocalsAndDeclaredGlobals(
    AstValueFactory* ast_value_factory) {
  // All variables that have no rewrite yet are non-parameter locals.
  if (is_declaration_scope()) {
    ZoneList<Variable*>* temps = AsDeclarationScope()->temps();
    for (int i = 0; i < temps->length(); i++) {
      if ((*temps)[i] == nullptr) continue;
      AllocateNonParameterLocal((*temps)[i], ast_value_factory);
    }
  }

  ZoneList<VarAndOrder> vars(variables_.occupancy(), zone());
  for (VariableMap::Entry* p = variables_.Start();
       p != NULL;
       p = variables_.Next(p)) {
    Variable* var = reinterpret_cast<Variable*>(p->value);
    vars.Add(VarAndOrder(var, p->order), zone());
  }
  vars.Sort(VarAndOrder::Compare);
  int var_count = vars.length();
  for (int i = 0; i < var_count; i++) {
    AllocateNonParameterLocal(vars[i].var(), ast_value_factory);
  }

  if (FLAG_global_var_shortcuts) {
    for (int i = 0; i < var_count; i++) {
      AllocateDeclaredGlobal(vars[i].var(), ast_value_factory);
    }
  }

  if (is_declaration_scope()) {
    AsDeclarationScope()->AllocateLocals(ast_value_factory);
  }
}

void DeclarationScope::AllocateLocals(AstValueFactory* ast_value_factory) {
  // For now, function_ must be allocated at the very end.  If it gets
  // allocated in the context, it must be the last slot in the context,
  // because of the current ScopeInfo implementation (see
  // ScopeInfo::ScopeInfo(FunctionScope* scope) constructor).
  if (function_ != nullptr) {
    AllocateNonParameterLocal(function_->proxy()->var(), ast_value_factory);
  }

  if (rest_parameter_ != nullptr) {
    AllocateNonParameterLocal(rest_parameter_, ast_value_factory);
  }

  if (new_target_ != nullptr && !MustAllocate(new_target_)) {
    new_target_ = nullptr;
  }

  if (this_function_ != nullptr && !MustAllocate(this_function_)) {
    this_function_ = nullptr;
  }
}

void DeclarationScope::AllocateModuleVariables() {
  for (auto it = module()->regular_imports().begin();
       it != module()->regular_imports().end(); ++it) {
    Variable* var = LookupLocal(it->second->local_name);
    // TODO(neis): Use a meaningful index.
    var->AllocateTo(VariableLocation::MODULE, 42);
  }

  for (auto entry : module()->exports()) {
    if (entry->local_name == nullptr) continue;
    Variable* var = LookupLocal(entry->local_name);
    var->AllocateTo(VariableLocation::MODULE, 42);
  }
}

void Scope::AllocateVariablesRecursively(AstValueFactory* ast_value_factory) {
  if (!already_resolved()) {
    num_stack_slots_ = 0;
  }
  // Allocate variables for inner scopes.
  for (Scope* scope = inner_scope_; scope != nullptr; scope = scope->sibling_) {
    scope->AllocateVariablesRecursively(ast_value_factory);
  }

  // If scope is already resolved, we still need to allocate
  // variables in inner scopes which might not have been resolved yet.
  if (already_resolved()) return;
  // The number of slots required for variables.
  num_heap_slots_ = Context::MIN_CONTEXT_SLOTS;

  // Allocate variables for this scope.
  // Parameters must be allocated first, if any.
  if (is_declaration_scope()) {
    if (is_module_scope()) {
      AsDeclarationScope()->AllocateModuleVariables();
    } else if (is_function_scope()) {
      AsDeclarationScope()->AllocateParameterLocals();
    }
    AsDeclarationScope()->AllocateReceiver();
  }
  AllocateNonParameterLocalsAndDeclaredGlobals(ast_value_factory);

  // Force allocation of a context for this scope if necessary. For a 'with'
  // scope and for a function scope that makes an 'eval' call we need a context,
  // even if no local variables were statically allocated in the scope.
  // Likewise for modules.
  bool must_have_context =
      is_with_scope() || is_module_scope() ||
      (is_function_scope() && calls_sloppy_eval()) ||
      (is_block_scope() && is_declaration_scope() && calls_sloppy_eval());

  // If we didn't allocate any locals in the local context, then we only
  // need the minimal number of slots if we must have a context.
  if (num_heap_slots_ == Context::MIN_CONTEXT_SLOTS && !must_have_context) {
    num_heap_slots_ = 0;
  }

  // Allocation done.
  DCHECK(num_heap_slots_ == 0 || num_heap_slots_ >= Context::MIN_CONTEXT_SLOTS);
}


int Scope::StackLocalCount() const {
  VariableDeclaration* function =
      is_function_scope() ? AsDeclarationScope()->function() : nullptr;
  return num_stack_slots() -
         (function != NULL && function->proxy()->var()->IsStackLocal() ? 1 : 0);
}


int Scope::ContextLocalCount() const {
  if (num_heap_slots() == 0) return 0;
  VariableDeclaration* function =
      is_function_scope() ? AsDeclarationScope()->function() : nullptr;
  bool is_function_var_in_context =
      function != NULL && function->proxy()->var()->IsContextSlot();
  return num_heap_slots() - Context::MIN_CONTEXT_SLOTS - num_global_slots() -
         (is_function_var_in_context ? 1 : 0);
}


int Scope::ContextGlobalCount() const { return num_global_slots(); }

}  // namespace internal
}  // namespace v8