libstdc++: Reorder constraints on std::span::span(Range&&) constructor.
authorJonathan Wakely <jwakely@redhat.com>
Mon, 1 Nov 2021 11:32:39 +0000 (11:32 +0000)
committerJonathan Wakely <jwakely@redhat.com>
Mon, 1 Nov 2021 21:01:31 +0000 (21:01 +0000)
In PR libstdc++/103013 Tim Song pointed out that we could reorder the
constraints of this constructor. That's worth doing just to reduce the
work the compiler has to do during overload resolution, even if it isn't
needed to make the code in the PR work.

libstdc++-v3/ChangeLog:

* include/std/span (span(Range&&)): Reorder constraints.

libstdc++-v3/include/std/span

index 61824de..0898ea8 100644 (file)
@@ -201,11 +201,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
        { }
 
       template<typename _Range>
-       requires ranges::contiguous_range<_Range> && ranges::sized_range<_Range>
-         && (ranges::borrowed_range<_Range> || is_const_v<element_type>)
-         && (!__detail::__is_span<remove_cvref_t<_Range>>)
+       requires (!__detail::__is_span<remove_cvref_t<_Range>>)
          && (!__detail::__is_std_array<remove_cvref_t<_Range>>)
          && (!is_array_v<remove_cvref_t<_Range>>)
+         && ranges::contiguous_range<_Range> && ranges::sized_range<_Range>
+         && (ranges::borrowed_range<_Range> || is_const_v<element_type>)
          && __is_compatible_ref<ranges::range_reference_t<_Range>>::value
        constexpr explicit(extent != dynamic_extent)
        span(_Range&& __range)