[es6] Refactor FormalParameter

src/parser.h

Index: src/parser.h
diff --git a/src/parser.h b/src/parser.h
index 87269ed619581862cb4038173286a1c4b0d42b28..1974f296f0756b0739ff6970453d1cbad7534a9a 100644
--- a/src/parser.h
+++ b/src/parser.h
@@ -541,10 +541,11 @@ class SingletonLogger;
 
 struct ParserFormalParameters : public PreParserFormalParameters {
   struct Parameter {
-    Parameter(Variable* var, Expression* pattern)
-        : var(var), pattern(pattern) {}
-    Variable* var;
+    Parameter(const AstRawString* name, Expression* pattern, bool is_rest)
+        : name(name), pattern(pattern), is_rest(is_rest) {}
+    const AstRawString* name;
     Expression* pattern;
+    bool is_rest;
   };
 
   explicit ParserFormalParameters(Scope* scope)
@@ -552,8 +553,10 @@ struct ParserFormalParameters : public PreParserFormalParameters {
 
   ZoneList<Parameter> params;
 
-  void AddParameter(Variable* var, Expression* pattern) {
-    params.Add(Parameter(var, pattern), scope->zone());
+  void AddParameter(
+      const AstRawString* name, Expression* pattern, bool is_rest) {
+    params.Add(Parameter(name, pattern, is_rest), scope->zone());
+    DCHECK(arity == params.length());

[adamk, 2015/08/03 18:20:23]

DCHECK_EQ.

Also, it will probably be more clear after the followup, but it seems sad that
the only way to check this consistency is a DCHECK. Especially since the
incrementing code is now duplicated between preparser and parser.

[rossberg, 2015/08/04 13:44:22]

Done.
My thinking was that the parser/preparser duplication should go away eventually,
once statement parsing is unified. But the FormalParameter will stay separate.
So you want to move as little of the logic there as possible.

But maybe you are right, I'll reconsider in the follow-up CL.

   }
 };
 
@@ -579,7 +582,7 @@ class ParserTraits {
     typedef ObjectLiteral::Property* ObjectLiteralProperty;
     typedef ZoneList<v8::internal::Expression*>* ExpressionList;
     typedef ZoneList<ObjectLiteral::Property*>* PropertyList;
-    typedef const v8::internal::AstRawString* FormalParameter;
+    typedef ParserFormalParameters::Parameter FormalParameter;
     typedef ParserFormalParameters FormalParameters;
     typedef ZoneList<v8::internal::Statement*>* StatementList;
 
@@ -1320,7 +1323,7 @@ void ParserTraits::DeclareFormalParameter(
                                  : parser_->ast_value_factory()->empty_string();
   Variable* var =
       parameters->scope->DeclareParameter(name, VAR, is_rest, &is_duplicate);
-  parameters->AddParameter(var, is_simple ? nullptr : pattern);
+  parameters->AddParameter(name, is_simple ? nullptr : pattern, is_rest);
   if (is_duplicate) {
     classifier->RecordDuplicateFormalParameterError(
         parser_->scanner()->location());