Implement LWG-3090 What is [time.duration.cons]/4's "no overflow is induced in the conversion" intended to mean? (#6050)

Co-authored-by: Stephan T. Lavavej <stl@microsoft.com>

Author: frederick-vs-ja

stl/inc/__msvc_chrono.hpp

@@ -129,8 +129,10 @@ namespace chrono {
             : _MyRep(static_cast<_Rep>(_Val)) {}
 
         template <class _Rep2, class _Period2,
-            enable_if_t<treat_as_floating_point_v<_Rep>
-                            || (_Ratio_divide_sfinae<_Period2, _Period>::den == 1 && !treat_as_floating_point_v<_Rep2>),
+            enable_if_t<is_convertible_v<const _Rep2&, _Rep>
+                            && (treat_as_floating_point_v<_Rep>
+                                || (_Ratio_divide_sfinae<_Period2, _Period>::den == 1
+                                    && !treat_as_floating_point_v<_Rep2>) ),
                 int> = 0>
         constexpr duration(const duration<_Rep2, _Period2>& _Dur)
             noexcept(is_arithmetic_v<_Rep> && is_arithmetic_v<_Rep2>) // strengthened

tests/std/tests/P0092R1_polishing_chrono/test.cpp

@@ -5,10 +5,12 @@
 // Tests the new functions added as part of P0092R1, "Polishing Chrono"
 //
 
+#include <__msvc_int128.hpp> // an integer-class type should emulate an arithmetic type, see also GH-1909
 #include <cassert>
 #include <chrono>
 #include <cstdint>
 #include <ratio>
+#include <type_traits>
 
 using namespace std;
 using namespace std::chrono;
@@ -188,6 +190,75 @@ STATIC_ASSERT(floor<seconds>(tp1).time_since_epoch().count() == 1);
 STATIC_ASSERT(ceil<seconds>(tp1).time_since_epoch().count() == 2);
 STATIC_ASSERT(round<seconds>(tp1).time_since_epoch().count() == 2);
 
+// Test LWG-3090 "What is [time.duration.cons]/4's "no overflow is induced in the conversion" intended to mean?"
+constexpr bool test_lwg_3090() {
+    STATIC_ASSERT(is_constructible_v<duration<_Signed128>, seconds>);
+    STATIC_ASSERT(is_constructible_v<duration<_Signed128>, const seconds&>);
+    STATIC_ASSERT(is_convertible_v<seconds, duration<_Signed128>>);
+    STATIC_ASSERT(is_convertible_v<const seconds&, duration<_Signed128>>);
+
+    STATIC_ASSERT(!is_constructible_v<seconds, duration<_Signed128>>);
+    STATIC_ASSERT(!is_constructible_v<seconds, const duration<_Signed128>&>);
+    STATIC_ASSERT(!is_convertible_v<duration<_Signed128>, seconds>);
+    STATIC_ASSERT(!is_convertible_v<const duration<_Signed128>&, seconds>);
+
+    STATIC_ASSERT(is_constructible_v<duration<_Signed128>, minutes>);
+    STATIC_ASSERT(is_constructible_v<duration<_Signed128>, const minutes&>);
+    STATIC_ASSERT(is_convertible_v<minutes, duration<_Signed128>>);
+    STATIC_ASSERT(is_convertible_v<const minutes&, duration<_Signed128>>);
+
+    STATIC_ASSERT(!is_constructible_v<minutes, duration<_Signed128>>);
+    STATIC_ASSERT(!is_constructible_v<minutes, const duration<_Signed128>&>);
+    STATIC_ASSERT(!is_convertible_v<duration<_Signed128>, minutes>);
+    STATIC_ASSERT(!is_convertible_v<const duration<_Signed128>&, minutes>);
+
+    STATIC_ASSERT(!is_constructible_v<duration<_Signed128>, milliseconds>);
+    STATIC_ASSERT(!is_constructible_v<duration<_Signed128>, const milliseconds&>);
+    STATIC_ASSERT(!is_convertible_v<milliseconds, duration<_Signed128>>);
+    STATIC_ASSERT(!is_convertible_v<const milliseconds&, duration<_Signed128>>);
+
+    STATIC_ASSERT(!is_constructible_v<milliseconds, duration<_Signed128>>);
+    STATIC_ASSERT(!is_constructible_v<milliseconds, const duration<_Signed128>&>);
+    STATIC_ASSERT(!is_convertible_v<duration<_Signed128>, milliseconds>);
+    STATIC_ASSERT(!is_convertible_v<const duration<_Signed128>&, milliseconds>);
+
+    STATIC_ASSERT(is_constructible_v<duration<_Unsigned128>, seconds>);
+    STATIC_ASSERT(is_constructible_v<duration<_Unsigned128>, const seconds&>);
+    STATIC_ASSERT(is_convertible_v<seconds, duration<_Unsigned128>>);
+    STATIC_ASSERT(is_convertible_v<const seconds&, duration<_Unsigned128>>);
+
+    STATIC_ASSERT(!is_constructible_v<seconds, duration<_Unsigned128>>);
+    STATIC_ASSERT(!is_constructible_v<seconds, const duration<_Unsigned128>&>);
+    STATIC_ASSERT(!is_convertible_v<duration<_Unsigned128>, seconds>);
+    STATIC_ASSERT(!is_convertible_v<const duration<_Unsigned128>&, seconds>);
+
+    STATIC_ASSERT(is_constructible_v<duration<_Unsigned128>, minutes>);
+    STATIC_ASSERT(is_constructible_v<duration<_Unsigned128>, const minutes&>);
+    STATIC_ASSERT(is_convertible_v<minutes, duration<_Unsigned128>>);
+    STATIC_ASSERT(is_convertible_v<const minutes&, duration<_Unsigned128>>);
+
+    STATIC_ASSERT(!is_constructible_v<minutes, duration<_Unsigned128>>);
+    STATIC_ASSERT(!is_constructible_v<minutes, const duration<_Unsigned128>&>);
+    STATIC_ASSERT(!is_convertible_v<duration<_Unsigned128>, minutes>);
+    STATIC_ASSERT(!is_convertible_v<const duration<_Unsigned128>&, minutes>);
+
+    STATIC_ASSERT(!is_constructible_v<duration<_Unsigned128>, milliseconds>);
+    STATIC_ASSERT(!is_constructible_v<duration<_Unsigned128>, const milliseconds&>);
+    STATIC_ASSERT(!is_convertible_v<milliseconds, duration<_Unsigned128>>);
+    STATIC_ASSERT(!is_convertible_v<const milliseconds&, duration<_Unsigned128>>);
+
+    STATIC_ASSERT(!is_constructible_v<milliseconds, duration<_Unsigned128>>);
+    STATIC_ASSERT(!is_constructible_v<milliseconds, const duration<_Unsigned128>&>);
+    STATIC_ASSERT(!is_convertible_v<duration<_Unsigned128>, milliseconds>);
+    STATIC_ASSERT(!is_convertible_v<const duration<_Unsigned128>&, milliseconds>);
+
+    assert(duration<_Signed128>{seconds{1}}.count() == 1);
+    assert(duration<_Signed128>{minutes{12}}.count() == 720);
+    assert(duration<_Unsigned128>{seconds{123}}.count() == 123);
+    assert(duration<_Unsigned128>{minutes{1234}}.count() == 74040);
+
+    return true;
+}
 
 int overloaded(milliseconds) {
     return 11;
@@ -222,4 +293,7 @@ int main() {
     assert(overloaded(40ms) == 11);
     assert(overloaded(50s) == 22);
     assert(overloaded(duration<int, exa>(60)) == 33);
+
+    STATIC_ASSERT(test_lwg_3090());
+    test_lwg_3090();
 }