OK, thanks.
On Fri, 18 Jun 2021 at 16:13, Patrick Palka via Libstdc++
<libstd...@gcc.gnu.org> wrote:
>
> libstdc++-v3/ChangeLog:
>
> * include/std/concepts (convertible_to): Just use declval as per
> LWG 3557.
> ---
> libstdc++-v3/include/std/concepts | 4 +---
> 1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/libstdc++-v3/include/std/concepts
> b/libstdc++-v3/include/std/concepts
> index 4490f534412..7f5421f1475 100644
> --- a/libstdc++-v3/include/std/concepts
> +++ b/libstdc++-v3/include/std/concepts
> @@ -70,9 +70,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> /// [concept.convertible], concept convertible_to
> template<typename _From, typename _To>
> concept convertible_to = is_convertible_v<_From, _To>
> - && requires(add_rvalue_reference_t<_From> (&__f)()) {
> - static_cast<_To>(__f());
> - };
> + && requires { static_cast<_To>(std::declval<_From>()); };
>
> /// [concept.commonref], concept common_reference_with
> template<typename _Tp, typename _Up>
> --
> 2.32.0.93.g670b81a890
>
