[libcxx-commits] [libcxx] Fix LWG issue4481 disallow chrono::duration<const T, P> (PR #207558)

[A. Jiang via libcxx-commits]

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@@ -164,6 +169,9 @@ template <class _ToDuration, class _Rep, class _Period, enable_if_t<__is_duratio
 
 template <class _Rep, class _Period>
 class duration {
+#if _LIBCPP_STD_VER >= 26
+  static_assert(is_same_v<_Rep, remove_cv_t<_Rep>>, "A duration representation cannot be cv-qualified");
+#endif
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frederick-vs-ja wrote:

Resolution LWG4481 should be applied to old modes. Also it's better to separately diagnose const- and volatile-qualifications.
```suggestion
  static_assert(!is_const<_Rep, remove_cv_t<_Rep>>::value, "A duration representation cannot be const-qualified");
  static_assert(is_volatile<_Rep, remove_cv_t<_Rep>>::value, "A duration representation cannot be volatile-qualified");
```

https://github.com/llvm/llvm-project/pull/207558