PR c++/68377 - parenthesized expr in fold-expression

	* parser.c (cp_parser_fold_expression): Check TREE_NO_WARNING.

From-SVN: r242561

gcc/cp/ChangeLog

+2016-11-17  Jason Merrill  <jason@redhat.com>
+
+	PR c++/68377
+	* parser.c (cp_parser_fold_expression): Check TREE_NO_WARNING.
+
 2016-11-16  Jason Merrill  <jason@redhat.com>
 
 	PR c++/78373

gcc/cp/parser.c

@@ -4679,7 +4679,9 @@ cp_parser_fold_expression (cp_parser *parser, tree expr1)
   /* The operands of a fold-expression are cast-expressions, so binary or
      conditional expressions are not allowed.  We check this here to avoid
      tentative parsing.  */
-  if (is_binary_op (TREE_CODE (expr1)))
+  if (EXPR_P (expr1) && TREE_NO_WARNING (expr1))
+    /* OK, the expression was parenthesized.  */;
+  else if (is_binary_op (TREE_CODE (expr1)))
     error_at (location_of (expr1),
 	      "binary expression in operand of fold-expression");
   else if (TREE_CODE (expr1) == COND_EXPR)

gcc/testsuite/g++.dg/cpp1z/fold8.C

+// PR c++/68377
+// { dg-options -std=c++1z }
+
+struct Sink { } s;
+template <class T> Sink& operator<<(Sink&, const T&);
+
+template<class... Tx> 
+int f(Tx... xs) {
+  return ((xs+1) + ...);
+}
+
+int main() {
+  s << f(3,4,5) << "\n";
+  return 0;
+}