--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-pr67860.C	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,61 @@
+// { dg-do compile { target c++2a } }
+// { dg-additional-options "-fconcepts-ts" }
+
+#include <type_traits>
+
+inline constexpr bool and_impl() { return true; }
+
+template <class OperandFirst, class... OperandsRest>
+constexpr bool and_impl(OperandFirst operand_first,
+                        OperandsRest... operands_rest) {
+  return operand_first && and_impl(operands_rest...);
+}
+
+template <class... Operands> constexpr bool and_(Operands... operands) {
+  return and_impl(operands...);
+}
+
+template <class X> concept bool C() { return true; }
+
+// v1
+template<int, class... Xs>
+  requires and_(C<Xs>()...)
+constexpr int f(const Xs&... xs) {
+  return 0;
+}
+
+// v2
+template<int, class... Xs>
+constexpr int f(const Xs&... xs) {
+  return 1;
+}
+
+int main() {
+  static_assert(f<10>(3.0, 2.0f) == 0);
+  return 0;
+}
+
+// 2nd example
+
+template <typename T, typename... Us>
+concept bool AreType() {
+  return (std::is_same<T,Us>::value && ...);
+  // return true; gives the same overloaded error
+}
+
+// Function with constraint
+template<typename T, AreType<T>... Us>
+constexpr bool isValid(Us... us) {
+  return true;
+}
+
+// Function with no constraint
+template<typename T, typename... U>
+constexpr bool isValid(U... u) {
+  return false;
+}
+
+int main2() {
+  static_assert(isValid<int>(1)); // also isValid<int>(1, 2, 3); etc
+  return 0;
+}