--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/concepts/iconv1.C	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,20 @@
+// PR c++/67240
+// { dg-options "-std=c++17 -fconcepts" }
+
+int foo(int x)
+{
+    return x;
+}
+ 
+template <typename T>
+concept bool C1 = requires (T x) {
+    {foo(x)} -> int&;
+};
+
+template <typename T>
+concept bool C2 = requires (T x) {
+    {foo(x)} -> void;
+};
+ 
+static_assert( C1<int> );	// { dg-error "assert" }
+static_assert( C2<int> );	// { dg-error "assert" }