--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libstdc++-v3/testsuite/std/time/clock/file/overview.cc	Mon May 25 07:50:57 2020 +0900
@@ -0,0 +1,43 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <chrono>
+
+using std::chrono::file_clock;
+
+// Cpp17Clock requirements:
+
+// New type so that is_clock<file_clock> specialization isn't used.
+struct C : file_clock { };
+static_assert( std::chrono::is_clock_v<C> );
+
+// Cpp17TrivialClock requirements:
+
+// A trivial clock's rep must be a numeric type, which is true for
+// libstdc++ because we use an integral type.
+static_assert( std::is_integral_v<file_clock::rep> );
+
+// We meet the recursive Cpp17TrivialClock requirement by using the same clock:
+static_assert( std::is_same_v<file_clock::time_point::clock, file_clock> );
+
+// chrono::file_clock requirements:
+
+static_assert( std::is_signed_v<file_clock::rep> );
+static_assert( noexcept(file_clock::now()) );