Avoid temporary Vectors for arrow function parameter lists

src/parser.cc

Index: src/parser.cc
diff --git a/src/parser.cc b/src/parser.cc
index 37e265aa4a059e7530186a301ec9a48ad7b49b1e..cf0ffdea6bb7306bb2de214e165e12d703e3ebe4 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -3272,9 +3272,9 @@ Handle<FixedArray> CompileTimeValue::GetElements(Handle<FixedArray> value) {
 }
 
 
-bool CheckAndCollectArrowParameter(ParserTraits* traits,
-                                   Collector<VariableProxy*>* collector,
-                                   Expression* expression) {
+bool CheckAndDeclareArrowParameter(ParserTraits* traits, Expression* expression,
+                                   Scope* scope, unsigned* num_params,
+                                   Scanner::Location* dupe_loc) {
   // Case for empty parameter lists:
   //   () => ...
   if (expression == NULL) return true;
@@ -3294,7 +3294,14 @@ bool CheckAndCollectArrowParameter(ParserTraits* traits,
         traits->IsFutureStrictReserved(raw_name))
       return false;
 
-    collector->Add(expression->AsVariableProxy());
+    if (scope->IsDeclared(raw_name)) {
+      *dupe_loc = Scanner::Location(
+          expression->position(), expression->position() + raw_name->length());
+      return false;
+    }
+
+    scope->DeclareParameter(raw_name, VAR);
+    ++(*num_params);
     return true;
   }
 
@@ -3306,8 +3313,10 @@ bool CheckAndCollectArrowParameter(ParserTraits* traits,
         binop->right()->is_parenthesized())
       return false;
 
-    return CheckAndCollectArrowParameter(traits, collector, binop->left()) &&
-           CheckAndCollectArrowParameter(traits, collector, binop->right());
+    return CheckAndDeclareArrowParameter(traits, binop->left(), scope,
+                                         num_params, dupe_loc) &&
+           CheckAndDeclareArrowParameter(traits, binop->right(), scope,
+                                         num_params, dupe_loc);
   }
 
   // Any other kind of expression is not a valid parameter list.
@@ -3315,11 +3324,13 @@ bool CheckAndCollectArrowParameter(ParserTraits* traits,
 }
 
 
-Vector<VariableProxy*> ParserTraits::ParameterListFromExpression(
-    Expression* expression, bool* ok) {
-  Collector<VariableProxy*> collector;
-  *ok = CheckAndCollectArrowParameter(this, &collector, expression);
-  return collector.ToVector();
+unsigned ParserTraits::DeclareArrowParametersFromExpression(
+    Expression* expression, Scope* scope, Scanner::Location* dupe_loc,
+    bool* ok) {
+  unsigned num_params = 0;
+  *ok = CheckAndDeclareArrowParameter(this, expression, scope, &num_params,
+                                      dupe_loc);
+  return num_params;
 }