libstdc++: Fix warnings introduced by type-erasing for chrono commits [PR110739]

The r16-1709-g4b3cefed1a08344495fedec4982d85168bd8173f caused `-Woverflow`
in empty_spec.cc file. This warning is not cause by any issue in shipping
code, and results in taking to much shortcut when implementing a test-only
custom representation type Rep, where long was always used to store a value.
In particular common type for Rep and long long int, was de-facto long.
This is addressed by adding Under template parameter, that controls the type
of stored value, and handling it properly in common_type specializations.
No changes to shipping code are necessary.

Secondly, extracting _M_locale_fmt calls in r16-1712-gcaac94, resulted in __ctx
format parameter no longer being used. This patch removes such parameter
entirely, and replace _FormatContext template parameter, with _OutIter parameter
for __out. For consistency type of the __out is decoupled from _FormatContext,
for functions that still need context:
 * to extract locale (_M_A_a, _M_B_b, _M_c, _M_p, _M_r, _M_subsecs)
 * perform formatting for duration/subseconds (_M_Q, _M_T, _M_S, _M_subsecs)

	PR libstdc++/110739

libstdc++-v3/ChangeLog:

	* include/bits/chrono_io.h (__formatter_chrono::_M_format_to):
	Rename _Out to _OutIter for consistency, and update calls
	to specifier functions.
	(__formatter_chrono::_M_wi, __formatter_chrono::_M_C_y_Y)
	(__formatter_chrono::_M_D_x, __formatter_chrono::_M_d_e)
	(__formatter_chrono::_M_F, __formatter_chrono::_M_g_G)
	(__formatter_chrono::_M_H_I, __formatter_chrono::_M_j)
	(__formatter_chrono::_M_m, __formatter_chrono::_M_M)
	(__formatter_chrono::_M_q, __formatter_chrono::_M_R_X)
	(__formatter_chrono::_M_u_w, __formatter_chrono::_M_U_V_W)
	(__formatter_chrono::_M_z, __formatter_chrono::_M_z):
	Remove _FormatContext parameter, and  introduce _OutIter
	for __out type.
	(__formatter_chrono::_M_a_A, __formatter_chrono::_M_B_b)
	(__formatter_chrono::_M_p, __formatter_chrono::_M_Q)
	(__formatter_chrono::_M_r, __formatter_chrono::_M_S)
	(__formatter_chrono::_M_subsecs, __formatter_chrono::_M_T):
	Introduce separate _OutIter template parameter for __out.
	(__formatter_chrono::_M_c, __formatter_chrono::_M_T):
	Likewise, and adjust calls to specifiers functions.
	* testsuite/std/time/format/empty_spec.cc: Make underlying
	type for Rep configurable.

diff --git a/libstdc++-v3/include/bits/chrono_io.h b/libstdc++-v3/include/bits/chrono_io.h
index bcfd51b98665e066d53c13af4d34c97112313560..0ffbf06a7ff4f23e28cbe5f429d1e846f2177aed 100644 (file)
--- a/libstdc++-v3/include/bits/chrono_io.h
+++ b/libstdc++-v3/include/bits/chrono_io.h
@@ -942,9 +942,9 @@ namespace __format
          return __out;
        }
 
-      template<typename _Out, typename _FormatContext>
-       _Out
-       _M_format_to(const _ChronoData<_CharT>& __t, _Out __out,
+      template<typename _OutIter, typename _FormatContext>
+       _OutIter
+       _M_format_to(const _ChronoData<_CharT>& __t, _OutIter __out,
                     _FormatContext& __fc) const
        {
          auto __first = _M_spec._M_chrono_specs.begin();
@@ -1005,7 +1005,7 @@ namespace __format
                {
                // %\0 is extension for handling weekday index
                case '\0':
-                 __out = _M_wi(__t._M_weekday_index, std::move(__out), __fc);
+                 __out = _M_wi(__t._M_weekday_index, std::move(__out));
                  break;
                case 'a':
                case 'A':
@@ -1022,41 +1022,41 @@ namespace __format
                case 'C':
                case 'y':
                case 'Y':
-                 __out = _M_C_y_Y(__t._M_year, std::move(__out), __fc, __c);
+                 __out = _M_C_y_Y(__t._M_year, std::move(__out), __c);
                  break;
                case 'd':
                case 'e':
-                 __out = _M_d_e(__t._M_day, std::move(__out), __fc, __c);
+                 __out = _M_d_e(__t._M_day, std::move(__out), __c);
                  break;
                case 'D':
                case 'x':
-                 __out = _M_D_x(__t, std::move(__out), __fc);
+                 __out = _M_D_x(__t, std::move(__out));
                  break;
                case 'F':
-                 __out = _M_F(__t, std::move(__out), __fc);
+                 __out = _M_F(__t, std::move(__out));
                  break;
                case 'g':
                case 'G':
-                 __out = _M_g_G(__t, std::move(__out), __fc, __c == 'G');
+                 __out = _M_g_G(__t, std::move(__out), __c == 'G');
                  break;
                case 'H':
                case 'I':
-                 __out = _M_H_I(__t._M_hours, __print_sign(), __fc, __c);
+                 __out = _M_H_I(__t._M_hours, __print_sign(), __c);
                  break;
                case 'j':
-                 __out = _M_j(__t, __print_sign(), __fc);
+                 __out = _M_j(__t, __print_sign());
                  break;
                case 'm':
-                 __out = _M_m(__t._M_month, std::move(__out), __fc);
+                 __out = _M_m(__t._M_month, std::move(__out));
                  break;
                case 'M':
-                 __out = _M_M(__t._M_minutes, __print_sign(), __fc);
+                 __out = _M_M(__t._M_minutes, __print_sign());
                  break;
                case 'p':
                  __out = _M_p(__t._M_hours, std::move(__out), __fc);
                  break;
                case 'q':
-                 __out = _M_q(__t._M_unit_suffix, std::move(__out), __fc);
+                 __out = _M_q(__t._M_unit_suffix, std::move(__out));
                  break;
                case 'Q':
                  __out = _M_Q(__t, __print_sign(), __fc);
@@ -1066,7 +1066,7 @@ namespace __format
                  break;
                case 'R':
                case 'X':
-                 __out = _M_R_X(__t, __print_sign(), __fc, __c != 'R');
+                 __out = _M_R_X(__t, __print_sign(), __c != 'R');
                  break;
                case 'T':
                  __out = _M_T(__t, __print_sign(), __fc);
@@ -1076,18 +1076,18 @@ namespace __format
                  break;
                case 'u':
                case 'w':
-                 __out = _M_u_w(__t._M_weekday, std::move(__out), __fc, __c);
+                 __out = _M_u_w(__t._M_weekday, std::move(__out), __c);
                  break;
                case 'U':
                case 'V':
                case 'W':
-                 __out = _M_U_V_W(__t, std::move(__out), __fc, __c);
+                 __out = _M_U_V_W(__t, std::move(__out), __c);
                  break;
                case 'z':
-                 __out = _M_z(__t._M_zone_offset, std::move(__out), __fc, (bool)__mod);
+                 __out = _M_z(__t._M_zone_offset, std::move(__out), (bool)__mod);
                  break;
                case 'Z':
-                 __out = _M_Z(__t._M_zone_abbrev, std::move(__out), __fc);
+                 __out = _M_Z(__t._M_zone_abbrev, std::move(__out));
                  break;
                case 'n':
                  *__out++ = __literals[0];
@@ -1128,10 +1128,9 @@ namespace __format
          return std::move(__out);
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_wi(unsigned __wi, typename _FormatContext::iterator __out,
-             _FormatContext& __ctx) const
+      template<typename _OutIter>
+       _OutIter
+       _M_wi(unsigned __wi, _OutIter __out) const
        {
          // %\0 Extension to format weekday index, used only by empty format spec
          _CharT __buf[3];
@@ -1142,9 +1141,9 @@ namespace __format
          return std::move(__out);
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_a_A(chrono::weekday __wd, typename _FormatContext::iterator __out,
+      template<typename _OutIter, typename _FormatContext>
+       _OutIter
+       _M_a_A(chrono::weekday __wd, _OutIter __out,
               _FormatContext& __ctx, bool __full) const
        {
          // %a Locale's abbreviated weekday name.
@@ -1172,9 +1171,9 @@ namespace __format
          return _M_write(std::move(__out), __loc, __str);
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_b_B(chrono::month __m, typename _FormatContext::iterator __out,
+      template<typename _OutIter, typename _FormatContext>
+       _OutIter
+       _M_b_B(chrono::month __m, _OutIter __out,
               _FormatContext& __ctx, bool __full) const
        {
          // %b Locale's abbreviated month name.
@@ -1202,9 +1201,9 @@ namespace __format
          return _M_write(std::move(__out), __loc, __str);
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_c(const _ChronoData<_CharT>& __t, typename _FormatContext::iterator __out,
+      template<typename _OutIter, typename _FormatContext>
+       _OutIter
+       _M_c(const _ChronoData<_CharT>& __t, _OutIter __out,
             _FormatContext& __ctx) const
        {
          // %c  Locale's date and time representation, for C-locale: %a %b %e %T %Y
@@ -1214,17 +1213,16 @@ namespace __format
          *__out = _S_space;
          __out = _M_b_B(__t._M_month, std::move(++__out), __ctx, false);
          *__out = _S_space;
-         __out = _M_d_e(__t._M_day, std::move(++__out), __ctx, 'e');
+         __out = _M_d_e(__t._M_day, std::move(++__out), 'e');
          *__out = _S_space;
-         __out = _M_R_X(__t, std::move(++__out), __ctx, true);
+         __out = _M_R_X(__t, std::move(++__out), true);
          *__out = _S_space;
-         return _M_C_y_Y(__t._M_year, std::move(++__out), __ctx, 'Y');
+         return _M_C_y_Y(__t._M_year, std::move(++__out), 'Y');
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_C_y_Y(chrono::year __y, typename _FormatContext::iterator __out,
-                _FormatContext& __ctx, _CharT __conv) const
+      template<typename _OutIter>
+       _OutIter
+       _M_C_y_Y(chrono::year __y, _OutIter __out, _CharT __conv) const
        {
          // %C  Year divided by 100 using floored division.
          // %EC Locale's alternative preresentation of the century (era name).
@@ -1273,10 +1271,9 @@ namespace __format
          return __out;
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_D_x(const _ChronoData<_CharT>& __t, typename _FormatContext::iterator __out,
-              _FormatContext&) const
+      template<typename _OutIter>
+       _OutIter
+       _M_D_x(const _ChronoData<_CharT>& __t, _OutIter __out) const
        {
          // %D  Equivalent to %m/%d/%y
          // %x  Locale's date rep, for C-locale: %m/%d/%y
@@ -1308,10 +1305,9 @@ namespace __format
          return std::move(__out);
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_d_e(chrono::day __d, typename _FormatContext::iterator __out,
-              _FormatContext& __ctx, _CharT __conv) const
+      template<typename _OutIter>
+       _OutIter
+       _M_d_e(chrono::day __d, _OutIter __out, _CharT __conv) const
        {
          // %d  The day of month as a decimal number.
          // %Od Locale's alternative representation.
@@ -1336,10 +1332,9 @@ namespace __format
          return std::move(__out);
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_F(const _ChronoData<_CharT>& __t, typename _FormatContext::iterator __out,
-            _FormatContext&) const
+      template<typename _OutIter>
+       _OutIter
+       _M_F(const _ChronoData<_CharT>& __t, _OutIter __out) const
        {
          auto __di = (unsigned)__t._M_day;
          auto __mi = (unsigned)__t._M_month;
@@ -1376,10 +1371,10 @@ namespace __format
          return std::move(__out);
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_g_G(const _ChronoData<_CharT>& __t, typename _FormatContext::iterator __out,
-            _FormatContext& __ctx, bool __full) const
+      template<typename _OutIter>
+       _OutIter
+       _M_g_G(const _ChronoData<_CharT>& __t, _OutIter __out,
+              bool __full) const
        {
          // %g last two decimal digits of the ISO week-based year.
          // %G ISO week-based year.
@@ -1389,13 +1384,12 @@ namespace __format
          __d -= (__t._M_weekday - Monday) - days(3);
          // ISO week-based year is the year that contains that Thursday:
          year __y = year_month_day(__d).year();
-         return _M_C_y_Y(__y, std::move(__out), __ctx, "yY"[__full]);
+         return _M_C_y_Y(__y, std::move(__out), "yY"[__full]);
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_H_I(chrono::hours __h, typename _FormatContext::iterator __out,
-              _FormatContext& __ctx, _CharT __conv) const
+      template<typename _OutIter>
+       _OutIter
+       _M_H_I(chrono::hours __h, _OutIter __out, _CharT __conv) const
        {
          // %H  The hour (24-hour clock) as a decimal number.
          // %OH Locale's alternative representation.
@@ -1416,10 +1410,9 @@ namespace __format
          return __format::__write(std::move(__out), _S_two_digits(__i));
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_j(const _ChronoData<_CharT>& __t, typename _FormatContext::iterator __out,
-            _FormatContext&) const
+      template<typename _OutIter>
+       _OutIter
+       _M_j(const _ChronoData<_CharT>& __t, _OutIter __out) const
        {
          if (_M_spec._M_time_only)
          {
@@ -1432,10 +1425,9 @@ namespace __format
                                __t._M_day_of_year.count());
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_m(chrono::month __m, typename _FormatContext::iterator __out,
-            _FormatContext& __ctx) const
+      template<typename _OutIter>
+       _OutIter
+       _M_m(chrono::month __m, _OutIter __out) const
        {
          // %m  month as a decimal number.
          // %Om Locale's alternative representation.
@@ -1446,10 +1438,9 @@ namespace __format
          return __format::__write(std::move(__out), _S_str_d2(__buf, __i));
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_M(chrono::minutes __m, typename _FormatContext::iterator __out,
-            _FormatContext& __ctx) const
+      template<typename _OutIter>
+       _OutIter
+       _M_M(chrono::minutes __m, _OutIter __out) const
        {
          // %M  The minute as a decimal number.
          // %OM Locale's alternative representation.
@@ -1458,10 +1449,9 @@ namespace __format
          return __format::__write(std::move(__out), _S_two_digits(__i));
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_p(chrono::hours __h, typename _FormatContext::iterator __out,
-            _FormatContext& __ctx) const
+      template<typename _OutIter, typename _FormatContext>
+       _OutIter
+       _M_p(chrono::hours __h, _OutIter __out, _FormatContext& __ctx) const
        {
          // %p The locale's equivalent of the AM/PM designations.
          auto __hi =  __h.count();
@@ -1475,27 +1465,26 @@ namespace __format
          return _M_write(std::move(__out), __loc, __ampm[__hi >= 12]);
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_q(__string_view __us, typename _FormatContext::iterator __out,
-            _FormatContext&) const
+      template<typename _OutIter>
+       _OutIter
+       _M_q(__string_view __us, _OutIter __out) const
        {
          // %q The duration's unit suffix
          return __format::__write(std::move(__out), __us);
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_Q(const _ChronoData<_CharT>& __t, typename _FormatContext::iterator __out,
-            _FormatContext& __ctx) const
+      template<typename _OutIter, typename _FormatContext>
+       _OutIter
+       _M_Q(const _ChronoData<_CharT>& __t, _OutIter __out,
+            _FormatContext&) const
        {
          // %Q The duration's numeric value.
          return std::vformat_to(std::move(__out), _S_empty_spec, __t._M_ereps);
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_r(const _ChronoData<_CharT>& __t, typename _FormatContext::iterator __out,
+      template<typename _OutIter, typename _FormatContext>
+       _OutIter
+       _M_r(const _ChronoData<_CharT>& __t, _OutIter __out,
             _FormatContext& __ctx) const
        {
          // %r Locale's 12-hour clock time, for C-locale: %I:%M:%S %p
@@ -1516,10 +1505,10 @@ namespace __format
          return _M_p(__t._M_hours, std::move(__out), __ctx);
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_R_X(const _ChronoData<_CharT>& __t, typename _FormatContext::iterator __out,
-              _FormatContext& __ctx, bool __secs) const
+      template<typename _OutIter>
+       _OutIter
+       _M_R_X(const _ChronoData<_CharT>& __t, _OutIter __out,
+              bool __secs) const
        {
          // %R  Equivalent to %H:%M
          // %X  Locale's time rep, for C-locale: %H:%M:%S (without subseconds)
@@ -1549,9 +1538,9 @@ namespace __format
          return __format::__write(std::move(__out), __sv);
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_S(const _ChronoData<_CharT>& __t, typename _FormatContext::iterator __out,
+      template<typename _OutIter, typename _FormatContext>
+       _OutIter
+       _M_S(const _ChronoData<_CharT>& __t, _OutIter __out,
             _FormatContext& __ctx, bool __subs = true) const
        {
          // %S  Seconds as a decimal number.
@@ -1565,10 +1554,9 @@ namespace __format
          return __out;
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_subsecs(const _ChronoData<_CharT>& __t,
-                  typename _FormatContext::iterator __out,
+      template<typename _OutIter, typename _FormatContext>
+       _OutIter
+       _M_subsecs(const _ChronoData<_CharT>& __t, _OutIter __out,
                   _FormatContext& __ctx) const
        {
          unsigned __prec = _M_spec._M_prec_kind != _WP_none
@@ -1628,20 +1616,19 @@ namespace __format
 
       // %t handled in _M_format
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_T(const _ChronoData<_CharT>& __t, typename _FormatContext::iterator __out,
+      template<typename _OutIter, typename _FormatContext>
+       _OutIter
+       _M_T(const _ChronoData<_CharT>& __t, _OutIter __out,
             _FormatContext& __ctx) const
        {
          // %T Equivalent to %H:%M:%S, with subseconds
-         __out = _M_R_X(__t, std::move(__out), __ctx, true);
+         __out = _M_R_X(__t, std::move(__out), true);
          return _M_subsecs(__t, std::move(__out), __ctx);
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_u_w(chrono::weekday __wd, typename _FormatContext::iterator __out,
-              _FormatContext& __ctx, _CharT __conv) const
+      template<typename _OutIter>
+       _OutIter
+       _M_u_w(chrono::weekday __wd, _OutIter __out, _CharT __conv) const
        {
          // %u  ISO weekday as a decimal number (1-7), where Monday is 1.
          // %Ou Locale's alternative numeric rep.
@@ -1653,10 +1640,10 @@ namespace __format
          return __format::__write(std::move(__out), _S_str_d1(__buf, __wdi));
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_U_V_W(const _ChronoData<_CharT>& __t, typename _FormatContext::iterator __out,
-                _FormatContext& __ctx, _CharT __conv) const
+      template<typename _OutIter>
+       _OutIter
+       _M_U_V_W(const _ChronoData<_CharT>& __t, _OutIter __out,
+                _CharT __conv) const
        {
          // %U  Week number of the year as a decimal number, from first Sunday.
          // %OU Locale's alternative numeric rep.
@@ -1686,10 +1673,9 @@ namespace __format
          return __format::__write(std::move(__out), __sv);
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_z(chrono::seconds __ts, typename _FormatContext::iterator __out,
-            _FormatContext&, bool __mod = false) const
+      template<typename _OutIter>
+       _OutIter
+       _M_z(chrono::seconds __ts, _OutIter __out, bool __mod = false) const
        {
          if (__ts == 0s)
            {
@@ -1711,10 +1697,9 @@ namespace __format
          return __format::__write(std::move(__out), __sv);
        }
 
-      template<typename _FormatContext>
-       typename _FormatContext::iterator
-       _M_Z(__string_view __abbrev, typename _FormatContext::iterator __out,
-            _FormatContext& __ctx) const
+      template<typename _OutIter>
+       _OutIter
+       _M_Z(__string_view __abbrev, _OutIter __out) const
        { return __format::__write(std::move(__out), __abbrev); }
 
       // %% handled in _M_format

diff --git a/libstdc++-v3/testsuite/std/time/format/empty_spec.cc b/libstdc++-v3/testsuite/std/time/format/empty_spec.cc
index 923df3d813cc0b5ee16d122482b47752d2d8ca19..ef1b19d688c7093160dc0546b7eabc012c696467 100644 (file)
--- a/libstdc++-v3/testsuite/std/time/format/empty_spec.cc
+++ b/libstdc++-v3/testsuite/std/time/format/empty_spec.cc
@@ -77,15 +77,18 @@ test_padding()
   VERIFY( res == WIDEN("==16 is not a valid month==") );
 }
 
-template<typename Ret = void>
+template<typename Ret = void, typename Under = long>
 struct Rep
 {
   using Return
     = std::conditional_t<std::is_void_v<Ret>, Rep, Ret>;
 
-  Rep(long v = 0) : val(v) {}
+  Rep(Under v = 0) : val(v) {}
 
-  operator long() const
+  template<typename ORet, typename OUnder>
+  Rep(Rep<ORet, OUnder> o) : val(o.val) {}
+
+  operator Under() const
   { return val; }
 
   Return
@@ -119,37 +122,43 @@ struct Rep
   operator<<(std::basic_ostream<CharT>& os, const Rep& t)
   { return os << t.val << WIDEN("[via <<]"); }
 
-  long val;
+  Under val;
+};
+
+template<typename Ret, typename Under1, typename Under2>
+struct std::common_type<Rep<Ret, Under1>, Rep<Ret, Under2>>
+{
+  using type = Rep<Ret, std::common_type_t<Under1, Under2>>;
 };
 
-template<typename Ret, typename Other>
+template<typename Ret, typename Under, typename Other>
   requires std::is_integral_v<Other>
-struct std::common_type<Rep<Ret>, Other>
+struct std::common_type<Rep<Ret, Under>, Other>
 {
-  using type = Rep<Ret>;
+  using type = Rep<Ret, std::common_type_t<Under, Other>>;
 };
 
-template<typename Ret, typename Other>
+template<typename Ret, typename Under, typename Other>
   requires std::is_integral_v<Other>
-struct std::common_type<Other, Rep<Ret>>
-  : std::common_type<Rep<Ret>, Other>
+struct std::common_type<Other, Rep<Ret, Under>>
+  : std::common_type<Rep<Ret, Under>, Other>
 { };
 
-template<typename Ret>
-struct std::numeric_limits<Rep<Ret>>
-  : std::numeric_limits<long>
+template<typename Ret, typename Under>
+struct std::numeric_limits<Rep<Ret, Under>>
+  : std::numeric_limits<Under>
 { };
 
-template<typename Ret, typename CharT>
-struct std::formatter<Rep<Ret>, CharT>
-  : std::formatter<long, CharT>
+template<typename Ret, typename Under, typename CharT>
+struct std::formatter<Rep<Ret, Under>, CharT>
+  : std::formatter<Under, CharT>
 {
   template<typename Out>
   typename std::basic_format_context<Out, CharT>::iterator
   format(const Rep<Ret>& t, std::basic_format_context<Out, CharT>& ctx) const
   {
     constexpr std::basic_string_view<CharT> suffix = WIDEN("[via format]");
-    auto out = std::formatter<long, CharT>::format(t.val, ctx);
+    auto out = std::formatter<Under, CharT>::format(t.val, ctx);
     return std::ranges::copy(suffix, out).out;
   }
 };