Improve implementation of destructible

We did not apply this for old gcc compilers, but it turns out that they will fall over more complex ranges concepts later.

We can alleviate this by reusing `is_destructible` and generally clean the implementation up.

libcudacxx/include/cuda/std/detail/libcxx/include/__concepts/destructible.h

@@ -15,63 +15,50 @@
 #endif //__cuda_std__
 
 #include "../__concepts/__concept_macros.h"
+#include "../__type_traits/enable_if.h"
+#include "../__type_traits/is_destructible.h"
 #include "../__type_traits/is_object.h"
 #include "../__type_traits/is_nothrow_destructible.h"
+#include "../__type_traits/void_t.h"
+#include "../__utility/declval.h"
 
 #if defined(_LIBCUDACXX_USE_PRAGMA_GCC_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
 _LIBCUDACXX_BEGIN_NAMESPACE_STD
 
-#if _LIBCUDACXX_STD_VER > 11 && _GNUC_VER < 1100
-
-template<class _Tp>
-_LIBCUDACXX_CONCEPT destructible = is_nothrow_destructible_v<_Tp>;
-
-#else
-// [concept.destructible]
-#if _LIBCUDACXX_STD_VER > 17
-
-template<class _Tp>
-constexpr bool __destructible_impl = false;
-
-template<class _Tp>
-    requires requires(_Tp& __t) { { __t.~_Tp() } noexcept; }
-constexpr bool __destructible_impl<_Tp> = true;
-
-#elif _LIBCUDACXX_STD_VER > 11
+#if _LIBCUDACXX_STD_VER > 11
 
-template<class _Tp>
-_LIBCUDACXX_CONCEPT_FRAGMENT(
-  __destructible_impl_req_,
-  requires(_Tp& __t)(
-    requires(is_object_v<_Tp>),
-    requires(noexcept(__t.~_Tp()))
-  ));
+template<class _Tp, class = void, class = void>
+_LIBCUDACXX_INLINE_VAR constexpr bool __destructible_impl = false;
 
 template<class _Tp>
-constexpr bool __destructible_impl = _LIBCUDACXX_FRAGMENT(__destructible_impl_req_, _Tp);
-#endif // _LIBCUDACXX_STD_VER > 11
+_LIBCUDACXX_INLINE_VAR constexpr bool __destructible_impl<_Tp,
+                                   __enable_if_t<_LIBCUDACXX_TRAIT(is_object, _Tp)>,
+#if defined(_LIBCUDACXX_COMPILER_GCC)
+                                   __enable_if_t<_LIBCUDACXX_TRAIT(is_destructible, _Tp)>>
+#else // ^^^ defined(_LIBCUDACXX_COMPILER_GCC) ^^^ / vvv !_LIBCUDACXX_COMPILER_GCC vvv
+                                   __void_t<decltype(_CUDA_VSTD::declval<_Tp>().~_Tp())>>
+#endif // !_LIBCUDACXX_COMPILER_GCC
+                                   = noexcept(_CUDA_VSTD::declval<_Tp>().~_Tp());
 
-#if _LIBCUDACXX_STD_VER > 11
 template<class _Tp>
-constexpr bool __destructible = __destructible_impl<_Tp>;
+_LIBCUDACXX_INLINE_VAR constexpr bool __destructible = __destructible_impl<_Tp>;
 
 template<class _Tp>
-constexpr bool __destructible<_Tp&> = true;
+_LIBCUDACXX_INLINE_VAR constexpr bool __destructible<_Tp&> = true;
 
 template<class _Tp>
-constexpr bool __destructible<_Tp&&> = true;
+_LIBCUDACXX_INLINE_VAR constexpr bool __destructible<_Tp&&> = true;
 
 template<class _Tp, size_t _Nm>
-constexpr bool __destructible<_Tp[_Nm]> = __destructible<_Tp>;
+_LIBCUDACXX_INLINE_VAR constexpr bool __destructible<_Tp[_Nm]> = __destructible<_Tp>;
 
 template<class _Tp>
 _LIBCUDACXX_CONCEPT destructible = __destructible<_Tp>;
 
 #endif // _LIBCUDACXX_STD_VER > 11
-#endif // _GNUC_VER < 1100
 
 _LIBCUDACXX_END_NAMESPACE_STD