[libcxx-commits] [libcxx] [libc++] P3029R1: Better `mdspan`'s CTAD (PR #87873)

[Mark de Wever via libcxx-commits]

================
@@ -563,8 +602,13 @@ _LIBCPP_HIDE_FROM_ABI auto as_writable_bytes(span<_Tp, _Extent> __s) noexcept {
   return __s.__as_writable_bytes();
 }
 
+#  if _LIBCPP_STD_VER < 26
 template <contiguous_iterator _It, class _EndOrSize>
 span(_It, _EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>>;
+#  else
+template <contiguous_iterator _It, class _EndOrSize>
+span(_It, _EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>, __maybe_static_ext<_EndOrSize>>;
+#  endif
----------------
mordante wrote:

This order is more commonly used.
```suggestion
#  if _LIBCPP_STD_VER >= 26
template <contiguous_iterator _It, class _EndOrSize>
span(_It, _EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>, __maybe_static_ext<_EndOrSize>>;
#  else
template <contiguous_iterator _It, class _EndOrSize>
span(_It, _EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>>;
#  endif
```

https://github.com/llvm/llvm-project/pull/87873