[gcc r12-9346] libstdc++: Change class-key for duration and time_point to class

[Jonathan Wakely]

https://gcc.gnu.org/g:ffe86c4731532cdbbcb9ea0bf1a33bcd6968db49

commit r12-9346-gffe86c4731532cdbbcb9ea0bf1a33bcd6968db49
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri Dec 2 16:18:43 2022 +0000

    libstdc++: Change class-key for duration and time_point to class
    
    We define these with the 'struct' keyword, but the standard uses
    'class'. This results in warnings if users try to refer to them using
    elaborated type specifiers.
    
    libstdc++-v3/ChangeLog:
    
            * include/bits/chrono.h (duration, time_point): Change 'struct'
            to 'class'.
    
    (cherry picked from commit 7eec3114ebe8d4c55c64b4e47546d3d8f95eb09b)

Diff:
---
 libstdc++-v3/include/bits/chrono.h | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/libstdc++-v3/include/bits/chrono.h b/libstdc++-v3/include/bits/chrono.h
index 65e3e3183f7..36561d94bef 100644
--- a/libstdc++-v3/include/bits/chrono.h
+++ b/libstdc++-v3/include/bits/chrono.h
@@ -59,11 +59,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
     /// `chrono::duration` represents a distance between two points in time
     template<typename _Rep, typename _Period = ratio<1>>
-      struct duration;
+      class duration;
 
     /// `chrono::time_point` represents a point in time as measured by a clock
     template<typename _Clock, typename _Dur = typename _Clock::duration>
-      struct time_point;
+      class time_point;
     /// @}
   }
 
@@ -440,14 +440,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     /// @endcond
 
     template<typename _Rep, typename _Period>
-      struct duration
+      class duration
       {
 	static_assert(!__is_duration<_Rep>::value, "rep cannot be a duration");
 	static_assert(__is_ratio<_Period>::value,
 		      "period must be a specialization of ratio");
 	static_assert(_Period::num > 0, "period must be positive");
 
-      private:
 	template<typename _Rep2>
 	  using __is_float = treat_as_floating_point<_Rep2>;
 
@@ -853,11 +852,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 #undef _GLIBCXX_CHRONO_INT64_T
 
     template<typename _Clock, typename _Dur>
-      struct time_point
+      class time_point
       {
 	static_assert(__is_duration<_Dur>::value,
 	    "duration must be a specialization of std::chrono::duration");
 
+      public:
 	typedef _Clock						clock;
 	typedef _Dur						duration;
 	typedef typename duration::rep				rep;