--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-pr68683.C	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,25 @@
+// PR c++/68683
+// { dg-do compile { target c++2a } }
+
+template <typename, typename>
+struct is_same {
+  static constexpr bool value = true;
+};
+
+template <typename T, typename U>
+concept Same = is_same<T, U>::value;
+
+template <typename T>
+concept Integral = requires {
+  { T () } -> Same<typename T::value_type>;
+};
+
+struct A {
+  using value_type = bool;
+};
+
+int main () {
+  Integral<A>;
+  Integral<A>;
+  return 0;
+}