[es6] re-implement rest parameters via desugaring

src/preparser.h

Index: src/preparser.h
diff --git a/src/preparser.h b/src/preparser.h
index 8680f88bf940ff208f9b419ca90d048e98917374..a0ff0ce45f68fcffa92f1712da5b9564abfded6e 100644
--- a/src/preparser.h
+++ b/src/preparser.h
@@ -3511,6 +3511,11 @@ ParserBase<Traits>::ParseSuperExpression(bool is_new,
     scope = scope->DeclarationScope();
   }
 
+  if (scope->is_block_scope() && scope->is_declaration_scope()) {
+    scope = scope->outer_scope();
+    DCHECK(scope->is_function_scope());
+  }
+
   FunctionKind kind = scope->function_kind();
   if (IsConciseMethod(kind) || IsAccessorFunction(kind) ||
       i::IsConstructor(kind)) {
@@ -3554,7 +3559,11 @@ ParserBase<Traits>::ParseNewTargetExpression(bool* ok) {
     DCHECK_NOT_NULL(scope);
     scope = scope->DeclarationScope();
   }
-
+  if (scope->is_block_scope() && scope->is_declaration_scope()) {
+    // Inner function scope
+    scope = scope->outer_scope();
+    DCHECK(scope->is_function_scope());
+  }
   if (!scope->is_function_scope()) {
     ReportMessageAt(scanner()->location(),
                     MessageTemplate::kUnexpectedNewTarget);
@@ -3700,7 +3709,6 @@ int ParserBase<Traits>::ParseFormalParameterList(
       return -1;
     }
   }
-
   return parameter_count;
 }