fixup! [libc++] Remove potential 0-sized array in __compressed_pair_padding

Author: serge-sans-paille

libcxx/include/__memory/compressed_pair.h

@@ -52,15 +52,11 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 
 #ifndef _LIBCPP_ABI_NO_COMPRESSED_PAIR_PADDING
 
-template <class _ToPad,
-          bool _Empty = ((is_empty<_ToPad>::value && !__libcpp_is_final<_ToPad>::value) ||
-                         is_reference<_ToPad>::value || sizeof(_ToPad) - __datasizeof_v<_ToPad> == 0)>
-class __compressed_pair_padding {
-  char __padding_[sizeof(_ToPad) - __datasizeof_v<_ToPad>];
-};
-
 template <class _ToPad>
-class __compressed_pair_padding<_ToPad, true> {};
+using __compressed_pair_padding =
+    __padding<((is_empty<_ToPad>::value && !__libcpp_is_final<_ToPad>::value) || is_reference<_ToPad>::value)
+                  ? 0
+                  : (sizeof(_ToPad) - __datasizeof_v<_ToPad>)>;
 
 #  define _LIBCPP_COMPRESSED_PAIR(T1, Initializer1, T2, Initializer2)                                                  \
     _LIBCPP_NO_UNIQUE_ADDRESS __attribute__((__aligned__(_LIBCPP_ALIGNOF(T2)))) T1 Initializer1;                       \