[es6] implement default/optional parameters (WIP / comments)

src/variables.h

 // 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_VARIABLES_H_
 #define V8_VARIABLES_H_
 
 #include "src/ast-value-factory.h"
 #include "src/zone.h"
 
 namespace v8 {
 namespace internal {
 
+enum ParameterKind {
+  NotAParameter = -1,
+  NormalParameter,
+  RestParameter,
+  OptionalParameter
+};
+
 // 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: public ZoneObject {
  public:
   enum Kind { NORMAL, FUNCTION, THIS, NEW_TARGET, ARGUMENTS };
 
   enum Location {
@@ skipping 116 matching lines @@
   }
 
   bool has_strong_mode_reference() const { return has_strong_mode_reference_; }
   int strong_mode_reference_start_position() const {
     return strong_mode_reference_start_position_;
   }
   int strong_mode_reference_end_position() const {
     return strong_mode_reference_end_position_;
   }
 
+  inline void set_parameter_kind(ParameterKind kind) {
+    // Don't specify ParameterKind multiple times
+    DCHECK(kind != NotAParameter && !isParameter());
+    parameter_kind_ = kind;
+  }
+
+  inline const ParameterKind& parameter_kind() const {
+    // Only access for function parameters
+    DCHECK(isParameter());
+    return parameter_kind_;
+  }
+
+  bool isParameter() const { return parameter_kind_ != NotAParameter; }
+  bool isRestParameter() const { return parameter_kind_ == RestParameter; }
+  bool isOptionalParameter() const {
+    return parameter_kind_ == OptionalParameter;
+  }
+
  private:
   Scope* scope_;
   const AstRawString* name_;
   VariableMode mode_;
   Kind kind_;
   Location location_;
   int index_;
   int initializer_position_;
   // Tracks whether the variable is bound to a VariableProxy which is in strong
   // mode, and if yes, the source location of the reference.
   bool has_strong_mode_reference_;
   int strong_mode_reference_start_position_;
   int strong_mode_reference_end_position_;
 
   // 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_;
 
   // Usage info.
   bool force_context_allocation_;  // set by variable resolver
   bool is_used_;
   InitializationFlag initialization_flag_;
   MaybeAssignedFlag maybe_assigned_;
+  ParameterKind parameter_kind_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_VARIABLES_H_