text: // Copyright 2011 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_AST_VARIABLES_H_
  #define V8_AST_VARIABLES_H_
  
  #include "src/ast/ast-value-factory.h"
  #include "src/globals.h"
  #include "src/zone/zone.h"
  
  namespace v8 {
  namespace internal {
  
  // The AST refers to variables via VariableProxies - placeholders for the actual
  // variables. Variables themselves are never directly referred to from the AST,
  // they are maintained by scopes, and referred to from VariableProxies and Slots
  // after binding and variable allocation.
  class Variable final : public ZoneObject {
   public:
    Variable(Scope* scope, const AstRawString* name, VariableMode mode,
             VariableKind kind, InitializationFlag initialization_flag,
             MaybeAssignedFlag maybe_assigned_flag = kNotAssigned);
  
    // The source code for an eval() call may refer to a variable that is
    // in an outer scope about which we don't know anything (it may not
    // be the script scope). scope() is NULL in that case. Currently the
    // scope is only used to follow the context chain length.
    Scope* scope() const { return scope_; }
  
    // This is for adjusting the scope of temporaries used when desugaring
    // parameter initializers.
    void set_scope(Scope* scope) { scope_ = scope; }
  
    Handle<String> name() const { return name_->string(); }
    const AstRawString* raw_name() const { return name_; }
    VariableMode mode() const { return VariableModeField::decode(bit_field_); }
    bool has_forced_context_allocation() const {
      return ForceContextAllocationField::decode(bit_field_);
    }
    void ForceContextAllocation() {
      DCHECK(IsUnallocated() || IsContextSlot() ||
             location() == VariableLocation::MODULE);
      bit_field_ = ForceContextAllocationField::update(bit_field_, true);
    }
    bool is_used() { return IsUsedField::decode(bit_field_); }
    void set_is_used() { bit_field_ = IsUsedField::update(bit_field_, true); }
    MaybeAssignedFlag maybe_assigned() const {
      return MaybeAssignedFlagField::decode(bit_field_);
    }
    void set_maybe_assigned() {
      bit_field_ = MaybeAssignedFlagField::update(bit_field_, kMaybeAssigned);
    }
  
    int initializer_position() { return initializer_position_; }
    void set_initializer_position(int pos) { initializer_position_ = pos; }
  
    bool IsUnallocated() const {
      return location() == VariableLocation::UNALLOCATED;
    }
    bool IsParameter() const { return location() == VariableLocation::PARAMETER; }
    bool IsStackLocal() const { return location() == VariableLocation::LOCAL; }
    bool IsStackAllocated() const { return IsParameter() || IsStackLocal(); }
    bool IsContextSlot() const { return location() == VariableLocation::CONTEXT; }
    bool IsLookupSlot() const { return location() == VariableLocation::LOOKUP; }
    bool IsGlobalObjectProperty() const;
  
    bool is_dynamic() const { return IsDynamicVariableMode(mode()); }
    bool binding_needs_init() const {
      DCHECK(initialization_flag() != kNeedsInitialization ||
             IsLexicalVariableMode(mode()));
      return initialization_flag() == kNeedsInitialization;
    }
    bool throw_on_const_assignment(LanguageMode language_mode) const {
      return kind() != SLOPPY_FUNCTION_NAME_VARIABLE || is_strict(language_mode);
    }
  
    bool is_function() const { return kind() == FUNCTION_VARIABLE; }
    bool is_this() const { return kind() == THIS_VARIABLE; }
    bool is_sloppy_function_name() const {
      return kind() == SLOPPY_FUNCTION_NAME_VARIABLE;
    }
  
    Variable* local_if_not_shadowed() const {
      DCHECK(mode() == DYNAMIC_LOCAL && local_if_not_shadowed_ != NULL);
      return local_if_not_shadowed_;
    }
  
    void set_local_if_not_shadowed(Variable* local) {
      local_if_not_shadowed_ = local;
    }
  
    VariableLocation location() const {
      return LocationField::decode(bit_field_);
    }
    VariableKind kind() const { return VariableKindField::decode(bit_field_); }
    InitializationFlag initialization_flag() const {
      return InitializationFlagField::decode(bit_field_);
    }
  
    int index() const { return index_; }
  
    // Sentinel index values for module exports and imports.
    enum { kModuleExportIndex, kModuleImportIndex };
  
    bool IsExport() const {
      DCHECK(location() == VariableLocation::MODULE);
      return index() == kModuleExportIndex;
    }
  
    void AllocateTo(VariableLocation location, int index) {
      DCHECK(IsUnallocated() ||
             (this->location() == location && this->index() == index));
      DCHECK_IMPLIES(location == VariableLocation::MODULE,
                     index == kModuleExportIndex || index == kModuleImportIndex);
      bit_field_ = LocationField::update(bit_field_, location);
      DCHECK_EQ(location, this->location());
      index_ = index;
    }
  
    static InitializationFlag DefaultInitializationFlag(VariableMode mode) {
      DCHECK(IsDeclaredVariableMode(mode));
      return mode == VAR ? kCreatedInitialized : kNeedsInitialization;
    }
  
   private:
    Scope* scope_;
    const AstRawString* name_;
  
    // If this field is set, this variable references the stored locally bound
    // variable, but it might be shadowed by variable bindings introduced by
    // sloppy 'eval' calls between the reference scope (inclusive) and the
    // binding scope (exclusive).
    Variable* local_if_not_shadowed_;
    int index_;
    int initializer_position_;
    uint16_t bit_field_;
  
    class VariableModeField : public BitField16<VariableMode, 0, 3> {};
    class VariableKindField
        : public BitField16<VariableKind, VariableModeField::kNext, 3> {};
    class LocationField
        : public BitField16<VariableLocation, VariableKindField::kNext, 3> {};
    class ForceContextAllocationField
        : public BitField16<bool, LocationField::kNext, 1> {};
    class IsUsedField
        : public BitField16<bool, ForceContextAllocationField::kNext, 1> {};
    class InitializationFlagField
        : public BitField16<InitializationFlag, IsUsedField::kNext, 2> {};
    class MaybeAssignedFlagField
        : public BitField16<MaybeAssignedFlag, InitializationFlagField::kNext,
                            2> {};
  };
  }  // namespace internal
  }  // namespace v8
  
  #endif  // V8_AST_VARIABLES_H_
  