1 files changed, 80 insertions, 0 deletions
diff --git a/libcxx/test/std/utilities/time/time.hms/time.hms.members/precision.pass.cpp b/libcxx/test/std/utilities/time/time.hms/time.hms.members/precision.pass.cpp
new file mode 100644
index 00000000000..58e0484c908
--- /dev/null
+++ b/libcxx/test/std/utilities/time/time.hms/time.hms.members/precision.pass.cpp
@@ -0,0 +1,80 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+// <chrono>
+
+// template <class Duration>
+// class hh_mm_ss
+// {
+// public:
+//     static unsigned constexpr fractional_width = see below;
+//     using precision                            = see below;
+//
+//   precision is duration<common_type_t<Duration::rep, seconds::rep>, 
+//                                 ratio<1, 10^^fractional_width>>
+   
+#include <chrono>
+#include <cassert>
+
+#include "test_macros.h"
+
+constexpr unsigned long long powers[] = {
+	1ULL,
+	10ULL,
+	100ULL,
+	1000ULL,
+	10000ULL,
+	100000ULL,
+	1000000ULL,
+	10000000ULL,
+	100000000ULL,
+	1000000000ULL,
+	10000000000ULL,
+	100000000000ULL,
+	1000000000000ULL,
+	10000000000000ULL,
+	100000000000000ULL,
+	1000000000000000ULL,
+	10000000000000000ULL,
+	100000000000000000ULL,
+	1000000000000000000ULL,
+	10000000000000000000ULL
+	};
+	
+template <typename Duration, unsigned width>
+constexpr bool check_precision()
+{
+	using HMS = std::chrono::hh_mm_ss<Duration>;
+	using CT  = std::common_type_t<typename Duration::rep, std::chrono::seconds::rep>;
+	using Pre = std::chrono::duration<CT, std::ratio<1, powers[width]>>;
+	return std::is_same_v<typename HMS::precision, Pre>;
+}
+
+int main(int, char**)
+{
+	using microfortnights = std::chrono::duration<int, std::ratio<756, 625>>;
+
+	static_assert( check_precision<std::chrono::hours,                               0>(), "");
+	static_assert( check_precision<std::chrono::minutes,                             0>(), "");
+	static_assert( check_precision<std::chrono::seconds,                             0>(), "");
+	static_assert( check_precision<std::chrono::milliseconds,                        3>(), "");
+	static_assert( check_precision<std::chrono::microseconds,                        6>(), "");
+	static_assert( check_precision<std::chrono::nanoseconds,                         9>(), "");
+	static_assert( check_precision<std::chrono::duration<int, std::ratio<  1,   2>>, 1>(), "");
+	static_assert( check_precision<std::chrono::duration<int, std::ratio<  1,   3>>, 6>(), "");
+	static_assert( check_precision<std::chrono::duration<int, std::ratio<  1,   4>>, 2>(), "");
+	static_assert( check_precision<std::chrono::duration<int, std::ratio<  1,   5>>, 1>(), "");
+	static_assert( check_precision<std::chrono::duration<int, std::ratio<  1,   6>>, 6>(), "");
+	static_assert( check_precision<std::chrono::duration<int, std::ratio<  1,   7>>, 6>(), "");
+	static_assert( check_precision<std::chrono::duration<int, std::ratio<  1,   8>>, 3>(), "");
+	static_assert( check_precision<std::chrono::duration<int, std::ratio<  1,   9>>, 6>(), "");
+	static_assert( check_precision<std::chrono::duration<int, std::ratio<  1,  10>>, 1>(), "");
+	static_assert( check_precision<microfortnights,                                  4>(), "");
+
+	return 0;
+}