[Bug libstdc++/70845] [6/7 Regression] inherited piecewise_construct_t constructor from std::pair by "using-declarations" is missing

[tuwwcn at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70845

--- Comment #2 from Wei-Wei Tu <tuwwcn at gmail dot com> ---
(In reply to Jonathan Wakely from comment #1)
> Complete testcase (would it really have hurt to include the headers to make
> the testcase valid?)
> 
> #include <utility>
> #include <string>
> #include <tuple>
> 
> struct Test : public std::pair<int, std::string> {
>     using std::pair<int, std::string>::pair;
> };
> 
> Test p(std::piecewise_construct, std::forward_as_tuple(1),
> std::forward_as_tuple("abcd"));

#include <string>
#include <utility>
#include <tuple>

struct Test : public std::pair<int, std::string> {
    using std::pair<int, std::string>::pair;
};

int main() {
    Test p(std::piecewise_construct, std::forward_as_tuple(1),
std::forward_as_tuple("abcd"));
}

This is the test case