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

src/variables.h

Index: src/variables.h
diff --git a/src/variables.h b/src/variables.h
index 545c3bd1f5bfae92e9adbe9c013e4dd65f2331fa..8ff38b0fadd655135c0c8ec92a8f36067cf5c576 100644
--- a/src/variables.h
+++ b/src/variables.h
@@ -11,6 +11,13 @@
 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
@@ -147,6 +154,24 @@ class Variable: public ZoneObject {
     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_;
@@ -172,6 +197,7 @@ class Variable: public ZoneObject {
   bool is_used_;
   InitializationFlag initialization_flag_;
   MaybeAssignedFlag maybe_assigned_;
+  ParameterKind parameter_kind_;
 };