--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/concepts/expression.C	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,20 @@
+// { dg-do run }
+// { dg-options "-std=c++17 -fconcepts" }
+
+#include <cassert>
+#include <iostream>
+
+template<typename T>
+  concept bool C1 = __is_class(T);
+
+template<typename T>
+  concept bool C2() { return __is_class(T); }
+
+template<typename T>
+  concept bool C3() { return requires (T a) { ++a; }; }
+
+int main() {
+  if (C1<int>) assert(false);
+  if (C2<int>()) assert(false);
+  if (!C3<int>()) assert(false);
+}