2 // { dg-do compile { target c++20 } }
4 template <typename T, int _Extent = -1> struct span { span(T&&);};
5 template <typename T> span(T &&) -> span<T>;
6 template <typename et, int e = -1>
7 struct this_span : span<et, e> {
8 using span<et, e>::span;
10 template <typename T> this_span(T &&) -> this_span<T>;