--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts2.C	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,69 @@
+// { dg-do compile { target c++2a } }
+
+template<typename T>
+concept True = true;
+
+template<typename T>
+concept False = false;
+
+template<typename T>
+concept Int = __is_same_as(T, int);
+
+static_assert(True<int>);
+static_assert(!False<int>);
+static_assert(False<int>); // { dg-error "static assertion failed" }
+
+constexpr bool will_be_true() {
+  if (True<int>)
+    return true;
+  return false;
+}
+
+constexpr bool will_be_false() {
+  if (!False<int>)
+    return true;
+  return false;
+}
+
+static_assert(will_be_true());
+static_assert(will_be_false());
+
+template<typename T>
+constexpr bool is_int() {
+  if (Int<T>)
+    return true;
+  return false;
+}
+
+static_assert(is_int<int>());
+static_assert(is_int<void>()); // { dg-error "static assertion failed" }
+
+template<typename T>
+constexpr bool f1() {
+  if (Int<int>) //  Note: always true.
+    return true;
+  return false;
+}
+static_assert(f1<int>());
+static_assert(f1<void>());
+
+
+template<typename T>
+constexpr bool f2() {
+  if constexpr (Int<int>) // Note: always true.
+    return true;
+  return false;
+}
+static_assert(f2<int>());
+static_assert(f2<void>());
+
+template<typename T>
+concept C = true;
+
+int driver() {
+  bool c_int = (C<int>); 
+  if((C<int>))
+    ;
+  return c_int;
+}
+