Declare the arguments object before creating the function var, to make sure it masks it

src/parsing/parser.cc

Index: src/parsing/parser.cc
diff --git a/src/parsing/parser.cc b/src/parsing/parser.cc
index b1f7c667ef9ac4b5c115bdab0cbef30de7ae5e90..f7965096f9e3a85a989fb00901149ec11e2917e4 100644
--- a/src/parsing/parser.cc
+++ b/src/parsing/parser.cc
@@ -2842,10 +2842,6 @@ FunctionLiteral* Parser::ParseFunctionLiteral(
 
     // Parsing the body may change the language mode in our scope.
     language_mode = scope->language_mode();
-    scope->DeclareArguments(ast_value_factory());
-    if (main_scope != scope) {
-      main_scope->DeclareArguments(ast_value_factory());
-    }
 
     // Validate name and parameter names. We can do this only after parsing the
     // function, since the function can declare itself strict.
@@ -3434,6 +3430,10 @@ ZoneList<Statement*>* Parser::ParseEagerFunctionBody(
     }
   }
 
+  if (!IsArrowFunction(kind)) {
+    function_scope->DeclareArguments(ast_value_factory());

[adamk, 2016/09/22 18:16:57]

Please add a comment here about why this must be declared this late.

+  }
+
   if (function_type == FunctionLiteral::kNamedExpression) {
     Statement* statement;
     if (function_scope->LookupLocal(function_name) == nullptr) {