--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/cpp0x/udlit-resolve-char8_t.C	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,38 @@
+// { dg-options "-std=c++17 -fchar8_t" }
+
+#include <cstdint>
+#include <cassert>
+
+int operator"" _foo(const char*)                  { return 0; }
+int operator"" _foo(unsigned long long int)       { return 1; }
+int operator"" _foo(long double)                  { return 2; }
+int operator"" _foo(char)                         { return 3; }
+int operator"" _foo(wchar_t)                      { return 4; }
+int operator"" _foo(char8_t)                      { return 5; }
+int operator"" _foo(char16_t)                     { return 6; }
+int operator"" _foo(char32_t)                     { return 7; }
+int operator"" _foo(const char*, std::size_t)     { return 8; }
+int operator"" _foo(const wchar_t*, std::size_t)  { return 9; }
+int operator"" _foo(const char8_t*, std::size_t)  { return 10; }
+int operator"" _foo(const char16_t*, std::size_t) { return 11; }
+int operator"" _foo(const char32_t*, std::size_t) { return 12; }
+template<char...> int operator"" _foo2()          { return 20; }
+int operator"" _foo2(unsigned long long int)      { return 21; }
+
+int
+main()
+{
+  assert(123_foo == 1);
+  assert(0.123_foo == 2);
+  assert('c'_foo == 3);
+  assert(L'c'_foo == 4);
+  assert(u8'c'_foo == 5);
+  assert(u'c'_foo == 6);
+  assert(U'c'_foo == 7);
+  assert("abc"_foo == 8);
+  assert(L"abc"_foo == 9);
+  assert(u8"abc"_foo == 10);
+  assert(u"abc"_foo == 11);
+  assert(U"abc"_foo == 12);
+  assert(123_foo2 == 21);
+}