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      1 // Copyright 2011 the V8 project authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef V8_AST_VARIABLES_H_
      6 #define V8_AST_VARIABLES_H_
      7 
      8 #include "src/ast/ast-value-factory.h"
      9 #include "src/zone.h"
     10 
     11 namespace v8 {
     12 namespace internal {
     13 
     14 // The AST refers to variables via VariableProxies - placeholders for the actual
     15 // variables. Variables themselves are never directly referred to from the AST,
     16 // they are maintained by scopes, and referred to from VariableProxies and Slots
     17 // after binding and variable allocation.
     18 
     19 class ClassVariable;
     20 
     21 class Variable: public ZoneObject {
     22  public:
     23   enum Kind { NORMAL, FUNCTION, CLASS, THIS, ARGUMENTS };
     24 
     25   Variable(Scope* scope, const AstRawString* name, VariableMode mode, Kind kind,
     26            InitializationFlag initialization_flag,
     27            MaybeAssignedFlag maybe_assigned_flag = kNotAssigned);
     28 
     29   virtual ~Variable() {}
     30 
     31   // Printing support
     32   static const char* Mode2String(VariableMode mode);
     33 
     34   // The source code for an eval() call may refer to a variable that is
     35   // in an outer scope about which we don't know anything (it may not
     36   // be the script scope). scope() is NULL in that case. Currently the
     37   // scope is only used to follow the context chain length.
     38   Scope* scope() const { return scope_; }
     39 
     40   // This is for adjusting the scope of temporaries used when desugaring
     41   // parameter initializers.
     42   void set_scope(Scope* scope) { scope_ = scope; }
     43 
     44   Handle<String> name() const { return name_->string(); }
     45   const AstRawString* raw_name() const { return name_; }
     46   VariableMode mode() const { return mode_; }
     47   bool has_forced_context_allocation() const {
     48     return force_context_allocation_;
     49   }
     50   void ForceContextAllocation() {
     51     force_context_allocation_ = true;
     52   }
     53   bool is_used() { return is_used_; }
     54   void set_is_used() { is_used_ = true; }
     55   MaybeAssignedFlag maybe_assigned() const { return maybe_assigned_; }
     56   void set_maybe_assigned() { maybe_assigned_ = kMaybeAssigned; }
     57 
     58   int initializer_position() { return initializer_position_; }
     59   void set_initializer_position(int pos) { initializer_position_ = pos; }
     60 
     61   bool IsVariable(Handle<String> n) const {
     62     return !is_this() && name().is_identical_to(n);
     63   }
     64 
     65   bool IsUnallocated() const {
     66     return location_ == VariableLocation::UNALLOCATED;
     67   }
     68   bool IsParameter() const { return location_ == VariableLocation::PARAMETER; }
     69   bool IsStackLocal() const { return location_ == VariableLocation::LOCAL; }
     70   bool IsStackAllocated() const { return IsParameter() || IsStackLocal(); }
     71   bool IsContextSlot() const { return location_ == VariableLocation::CONTEXT; }
     72   bool IsGlobalSlot() const { return location_ == VariableLocation::GLOBAL; }
     73   bool IsUnallocatedOrGlobalSlot() const {
     74     return IsUnallocated() || IsGlobalSlot();
     75   }
     76   bool IsLookupSlot() const { return location_ == VariableLocation::LOOKUP; }
     77   bool IsGlobalObjectProperty() const;
     78   bool IsStaticGlobalObjectProperty() const;
     79 
     80   bool is_dynamic() const { return IsDynamicVariableMode(mode_); }
     81   bool is_const_mode() const { return IsImmutableVariableMode(mode_); }
     82   bool binding_needs_init() const {
     83     return initialization_flag_ == kNeedsInitialization;
     84   }
     85 
     86   bool is_function() const { return kind_ == FUNCTION; }
     87   bool is_class() const { return kind_ == CLASS; }
     88   bool is_this() const { return kind_ == THIS; }
     89   bool is_arguments() const { return kind_ == ARGUMENTS; }
     90 
     91   // For script scopes, the "this" binding is provided by a ScriptContext added
     92   // to the global's ScriptContextTable.  This binding might not statically
     93   // resolve to a Variable::THIS binding, instead being DYNAMIC_LOCAL.  However
     94   // any variable named "this" does indeed refer to a Variable::THIS binding;
     95   // the grammar ensures this to be the case.  So wherever a "this" binding
     96   // might be provided by the global, use HasThisName instead of is_this().
     97   bool HasThisName(Isolate* isolate) const {
     98     return is_this() || *name() == *isolate->factory()->this_string();
     99   }
    100 
    101   ClassVariable* AsClassVariable() {
    102     DCHECK(is_class());
    103     return reinterpret_cast<ClassVariable*>(this);
    104   }
    105 
    106   // True if the variable is named eval and not known to be shadowed.
    107   bool is_possibly_eval(Isolate* isolate) const {
    108     return IsVariable(isolate->factory()->eval_string());
    109   }
    110 
    111   Variable* local_if_not_shadowed() const {
    112     DCHECK(mode_ == DYNAMIC_LOCAL && local_if_not_shadowed_ != NULL);
    113     return local_if_not_shadowed_;
    114   }
    115 
    116   void set_local_if_not_shadowed(Variable* local) {
    117     local_if_not_shadowed_ = local;
    118   }
    119 
    120   VariableLocation location() const { return location_; }
    121   int index() const { return index_; }
    122   InitializationFlag initialization_flag() const {
    123     return initialization_flag_;
    124   }
    125 
    126   void AllocateTo(VariableLocation location, int index) {
    127     location_ = location;
    128     index_ = index;
    129   }
    130 
    131   void SetFromEval() { is_from_eval_ = true; }
    132 
    133   static int CompareIndex(Variable* const* v, Variable* const* w);
    134 
    135   void RecordStrongModeReference(int start_position, int end_position) {
    136     // Record the earliest reference to the variable. Used in error messages for
    137     // strong mode references to undeclared variables.
    138     if (has_strong_mode_reference_ &&
    139         strong_mode_reference_start_position_ < start_position)
    140       return;
    141     has_strong_mode_reference_ = true;
    142     strong_mode_reference_start_position_ = start_position;
    143     strong_mode_reference_end_position_ = end_position;
    144   }
    145 
    146   bool has_strong_mode_reference() const { return has_strong_mode_reference_; }
    147   int strong_mode_reference_start_position() const {
    148     return strong_mode_reference_start_position_;
    149   }
    150   int strong_mode_reference_end_position() const {
    151     return strong_mode_reference_end_position_;
    152   }
    153   PropertyAttributes DeclarationPropertyAttributes() const {
    154     int property_attributes = NONE;
    155     if (IsImmutableVariableMode(mode_)) {
    156       property_attributes |= READ_ONLY;
    157     }
    158     if (is_from_eval_) {
    159       property_attributes |= EVAL_DECLARED;
    160     }
    161     return static_cast<PropertyAttributes>(property_attributes);
    162   }
    163 
    164  private:
    165   Scope* scope_;
    166   const AstRawString* name_;
    167   VariableMode mode_;
    168   Kind kind_;
    169   VariableLocation location_;
    170   int index_;
    171   int initializer_position_;
    172   // Tracks whether the variable is bound to a VariableProxy which is in strong
    173   // mode, and if yes, the source location of the reference.
    174   bool has_strong_mode_reference_;
    175   int strong_mode_reference_start_position_;
    176   int strong_mode_reference_end_position_;
    177 
    178   // If this field is set, this variable references the stored locally bound
    179   // variable, but it might be shadowed by variable bindings introduced by
    180   // sloppy 'eval' calls between the reference scope (inclusive) and the
    181   // binding scope (exclusive).
    182   Variable* local_if_not_shadowed_;
    183 
    184   // True if this variable is introduced by a sloppy eval
    185   bool is_from_eval_;
    186 
    187   // Usage info.
    188   bool force_context_allocation_;  // set by variable resolver
    189   bool is_used_;
    190   InitializationFlag initialization_flag_;
    191   MaybeAssignedFlag maybe_assigned_;
    192 };
    193 
    194 class ClassVariable : public Variable {
    195  public:
    196   ClassVariable(Scope* scope, const AstRawString* name, VariableMode mode,
    197                 InitializationFlag initialization_flag,
    198                 MaybeAssignedFlag maybe_assigned_flag = kNotAssigned,
    199                 int declaration_group_start = -1)
    200       : Variable(scope, name, mode, Variable::CLASS, initialization_flag,
    201                  maybe_assigned_flag),
    202         declaration_group_start_(declaration_group_start) {}
    203 
    204   int declaration_group_start() const { return declaration_group_start_; }
    205   void set_declaration_group_start(int declaration_group_start) {
    206     declaration_group_start_ = declaration_group_start;
    207   }
    208 
    209  private:
    210   // For classes we keep track of consecutive groups of delcarations. They are
    211   // needed for strong mode scoping checks. TODO(marja, rossberg): Implement
    212   // checks for functions too.
    213   int declaration_group_start_;
    214 };
    215 }  // namespace internal
    216 }  // namespace v8
    217 
    218 #endif  // V8_AST_VARIABLES_H_
    219