--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/template/dependent-name14.C	Mon May 25 07:50:57 2020 +0900
@@ -0,0 +1,38 @@
+// PR c++/90711
+// { dg-do compile { target c++11 } }
+
+namespace test {
+    void EXISTS(int);
+}
+
+template<typename... ARGS>
+struct stub_void {
+    typedef void type;
+};
+template<typename... ARGS>
+using stub_void_t = typename stub_void<ARGS...>::type;
+
+#if !defined(SUPPRESS)
+template<typename O, typename = void>
+struct has_to_string {
+    static constexpr bool value = false;
+};
+
+template<typename O>
+struct has_to_string<O, stub_void_t<decltype(EXISTS(O{}))>> {
+    static constexpr bool value = true;
+};
+#endif
+
+template<typename O, typename = void>
+struct has_std_to_string {
+    static constexpr bool value = false;
+};
+
+template<typename O>
+struct has_std_to_string<O, stub_void_t<decltype(test::EXISTS(O{}))>> {
+    static constexpr bool value = true;
+};
+
+static_assert (has_std_to_string<int>::value, "");
+