[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..cf88c5ed47e627fdd5587703ea9be81a09d9f3bc 100644
--- a/src/variables.h
+++ b/src/variables.h
@@ -11,6 +11,42 @@
 namespace v8 {
 namespace internal {
 
+class ParameterKind {

[arv (Not doing code reviews), 2015/04/10 15:08:48]

Not sure we need a class for this. Why isn't an enum enough?

[caitp (gmail), 2015/04/10 15:28:00]

I find it more readable, and it should end up being essentially an enum when
compiled anyways. Either way, it's better than having a bunch of separate
boolean flags, imo.

[caitp (gmail), 2015/04/10 15:56:49]

Actually, clang-format isn't keen on this, and it looks too painful to use when
explicit constructors are required :( enum it is then

+ public:
+  enum Kind {
+    NonParameter = -1,
+    Normal,
+    Rest,
+    Optional
+  };
+
+  ParameterKind() : kind_(Normal) {}
+  ParameterKind(Kind k) : kind_(k) {}
+  ParameterKind(const ParameterKind& other) : kind_(other.kind_) {}
+
+  bool operator==(const ParameterKind& other) const {
+    return other.kind_ == kind_;
+  }
+  bool operator==(Kind k) const { return k == kind_; }
+
+  ParameterKind& operator=(const ParameterKind& other) {
+    kind_ = other.kind_;
+    return *this;
+  }
+  ParameterKind& operator=(Kind k) {
+    kind_ = k;
+    return *this;
+  }
+
+  bool isParameter() const { return kind_ != NonParameter; }
+  bool isNormalParameter() const { return kind_ == Normal; }
+  bool isRestParameter() const { return kind_ == Rest; }
+  bool isOptionalParameter() const { return kind_ == Optional; }
+
+ private:
+  Kind kind_;
+};
+
 // 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 +183,24 @@ 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.isParameter() && !parameter_kind_.isParameter());
+    parameter_kind_ = kind;
+  }
+
+  inline const ParameterKind& parameter_kind() const {
+    // Only access for function parameters
+    DCHECK(parameter_kind_.isParameter());
+    return parameter_kind_;
+  }
+
+  bool isParameter() const { return parameter_kind_.isParameter(); }
+  bool isRestParameter() const { return parameter_kind_.isRestParameter(); }
+  bool isOptionalParameter() const {
+    return parameter_kind_.isOptionalParameter();
+  }
+
  private:
   Scope* scope_;
   const AstRawString* name_;
@@ -172,6 +226,7 @@ class Variable: public ZoneObject {
   bool is_used_;
   InitializationFlag initialization_flag_;
   MaybeAssignedFlag maybe_assigned_;
+  ParameterKind parameter_kind_;
 };