--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/ext/char8_t-udl-1.C	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,19 @@
+// Test overloading for UTF-8 user defined literals when -fchar8_t is not in effect.
+// { dg-do compile }
+// { dg-options "-std=c++17 -fno-char8_t" }
+
+template<typename T1, typename T2>
+  struct is_same
+  { static const bool value = false; };
+
+template<typename T>
+  struct is_same<T, T>
+  { static const bool value = true; };
+
+int operator "" _udcl(char);
+static_assert(is_same<decltype('x'_udcl), int>::value, "Error");
+static_assert(is_same<decltype(u8'x'_udcl), int>::value, "Error");
+
+int operator "" _udsl(const char*, __SIZE_TYPE__);
+static_assert(is_same<decltype("x"_udsl), int>::value, "Error");
+static_assert(is_same<decltype(u8"x"_udsl), int>::value, "Error");