GB299 24.07.16.2 has-tuple-element helper concept needs convertible_to LWG 3323 #295
Description
has-tuple-element helper concept needs convertible_to
The exposition-only has-tuple-element concept (for elements_view) is defined as
template<class T, size_t N>
concept has-tuple-element = exposition only
requires(T t) {
typename tuple_size<T>::type;
requires N < tuple_size_v<T>;
typename tuple_element_t<N, T>;
{ get<N>(t) } -> const tuple_element_t<N, T>&;
};
However, the return type constraint for { get(t) } is no longer valid under the latest concepts changes
Proposed change:
Change to:
template<class T, size_t N>
concept has-tuple-element = exposition only
requires(T t) {
typename tuple_size<T>::type;
requires N < tuple_size_v<T>;
typename tuple_element_t<N, T>;
{ get<N>(t) } -> convertible_to<const tuple_element_t<N, T>&>;
};