--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-alias5.C	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,62 @@
+// PR c++/93377
+// { dg-do compile { target c++2a } }
+
+struct empty
+{};
+
+template <typename c>
+c value;
+
+template <typename c>
+auto func(value<c>);
+
+template <typename, typename...>
+struct alignment_algorithm;
+
+template <typename... args_t>
+struct select
+{
+  template <typename algorithm_t, typename... _args_t>
+  decltype(algorithm_t()(func<_args_t>...)) choose();
+
+  template <typename...>
+  static empty choose();
+
+  using type = decltype(choose<alignment_algorithm<int>, args_t...>());
+};
+
+template <typename, typename... args_t>
+struct select_algorithm : select<args_t...>
+{};
+
+template <typename, typename = void> struct maybe_value { int value; };
+
+template <typename cn>
+struct maybe_value<cn, typename cn::sfinae>;
+
+struct function
+{
+  template <typename algorithm_t,
+            typename = decltype(
+                maybe_value<select_algorithm<algorithm_t, int>>::value)>
+  function(algorithm_t);
+};
+
+template <typename>
+struct alignment_configuration_traits
+{
+  static constexpr bool is_vectorised = 0;
+};
+
+template <typename config_t, typename...>
+struct alignment_algorithm
+{
+  using traits_t = alignment_configuration_traits<config_t>;
+  template <typename indexed_sequence_pairs_t>
+  void operator()(indexed_sequence_pairs_t) requires traits_t::is_vectorised;
+};
+
+int main()
+{
+    function{alignment_algorithm<int>{}};
+}