[Bug c++/81527] New: Missing inherited constructor by "using-declarations"

[tuwwcn at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81527

            Bug ID: 81527
           Summary: Missing inherited constructor by "using-declarations"
           Product: gcc
           Version: 6.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: tuwwcn at gmail dot com
  Target Milestone: ---

The below code is rejected by GCC 6.1.0(similar bug,
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70845), 6.3.0, 6.4.0, and 7.1.0,
but accepted by GCC 5.4.0.
I think the code is valid according to the language standard.

Building options: g++ test.cpp --std=c++14 (or g++ test.cpp --std=c++11)

test.cpp is as below:

/////////////////////////////////////////////
#include <utility>

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

int main() {
    std::pair<int, int> p{1, 2}; 
    A a(p);
}
///////////////////////////////////////////

Error Message produced by GCC 6.4.0(Building Option: g++ test.cpp --std=c++14,
other rejected versions show similar error message):

test.cpp: In function ‘int main()’:
test.cpp:9:10: error: no matching function for call to ‘A::A(std::pair<int,
int>&)’
     A a(p);
          ^
test.cpp:4:32: note: candidate: template<class _U1, class _U2, typename
std::enable_if<(_ConstructiblePair<_U1, _U2>() &&
_ImplicitlyConvertiblePair<_U1, _U2>()), bool>::type <anonymous> > constexpr
A::A(const int&, const int&)
     using std::pair<int, int>::pair;
                                ^~~~
test.cpp:4:32: note:   template argument deduction/substitution failed:
test.cpp:9:10: note:   candidate expects 2 arguments, 1 provided
     A a(p);
          ^
test.cpp:4:32: note: candidate: template<class _U1, class _U2, typename
std::enable_if<(_ConstructiblePair<_U1, _U2>() && (!
_ImplicitlyConvertiblePair<_U1, _U2>())), bool>::type <anonymous> > constexpr
A::A(const int&, const int&)
     using std::pair<int, int>::pair;
                                ^~~~
test.cpp:4:32: note:   template argument deduction/substitution failed:
test.cpp:9:10: note:   candidate expects 2 arguments, 1 provided
     A a(p);
          ^
test.cpp:4:32: note: candidate: template<class _U1, class _U2, typename
std::enable_if<(std::_PCC<((! std::is_same<int, _U1>::value) || (!
std::is_same<int, _U2>::value)), int, int>::_ConstructiblePair<_U1, _U2>() &&
std::_PCC<((! std::is_same<int, _U1>::value) || (! std::is_same<int,
_U2>::value)), int, int>::_ImplicitlyConvertiblePair<_U1, _U2>()), bool>::type
<anonymous> > constexpr A::A(const std::pair<_T1, _T2>&)
     using std::pair<int, int>::pair;
                                ^~~~
test.cpp:4:32: note:   template argument deduction/substitution failed:
In file included from
/home/tuweiwei/tools/gcc-6.4.0/include/c++/6.4.0/utility:70:0,
                 from test.cpp:1:
/home/tuweiwei/tools/gcc-6.4.0/include/c++/6.4.0/bits/stl_pair.h:275:18: error:
no type named ‘type’ in ‘struct std::enable_if<false, bool>’
      bool>::type=true>
                  ^~~~
/home/tuweiwei/tools/gcc-6.4.0/include/c++/6.4.0/bits/stl_pair.h:275:18: note:
invalid template non-type parameter
test.cpp:4:32: note: candidate: template<class _U1, class _U2, typename
std::enable_if<(std::_PCC<((! std::is_same<int, _U1>::value) || (!
std::is_same<int, _U2>::value)), int, int>::_ConstructiblePair<_U1, _U2>() &&
(! std::_PCC<((! std::is_same<int, _U1>::value) || (! std::is_same<int,
_U2>::value)), int, int>::_ImplicitlyConvertiblePair<_U1, _U2>())), bool>::type
<anonymous> > constexpr A::A(const std::pair<_T1, _T2>&)
     using std::pair<int, int>::pair;
                                ^~~~
test.cpp:4:32: note:   template argument deduction/substitution failed:
In file included from
/home/tuweiwei/tools/gcc-6.4.0/include/c++/6.4.0/utility:70:0,
                 from test.cpp:1:
/home/tuweiwei/tools/gcc-6.4.0/include/c++/6.4.0/bits/stl_pair.h:284:38: error:
no type named ‘type’ in ‘struct std::enable_if<false, bool>’
                          bool>::type=false>
                                      ^~~~~
/home/tuweiwei/tools/gcc-6.4.0/include/c++/6.4.0/bits/stl_pair.h:284:38: note:
invalid template non-type parameter
test.cpp:4:32: note: candidate: template<class _U1, typename
std::enable_if<_MoveCopyPair<true, _U1, int>(), bool>::type <anonymous> >
constexpr A::A(_U1&&, const int&)
     using std::pair<int, int>::pair;
                                ^~~~
test.cpp:4:32: note:   template argument deduction/substitution failed:
test.cpp:9:10: note:   candidate expects 2 arguments, 1 provided
     A a(p);
          ^
test.cpp:4:32: note: candidate: template<class _U1, typename
std::enable_if<_MoveCopyPair<false, _U1, int>(), bool>::type <anonymous> >
constexpr A::A(_U1&&, const int&)
     using std::pair<int, int>::pair;
                                ^~~~
test.cpp:4:32: note:   template argument deduction/substitution failed:
test.cpp:9:10: note:   candidate expects 2 arguments, 1 provided
     A a(p);
          ^
test.cpp:4:32: note: candidate: template<class _U2, typename
std::enable_if<_CopyMovePair<true, int, _U2>(), bool>::type <anonymous> >
constexpr A::A(const int&, _U2&&)
     using std::pair<int, int>::pair;
                                ^~~~
test.cpp:4:32: note:   template argument deduction/substitution failed:
test.cpp:9:10: note:   candidate expects 2 arguments, 1 provided
     A a(p);
          ^
test.cpp:4:32: note: candidate: template<class _U2, typename
std::enable_if<_CopyMovePair<false, int, _U2>(), bool>::type <anonymous> >
A::A(const int&, _U2&&)
     using std::pair<int, int>::pair;
                                ^~~~
test.cpp:4:32: note:   template argument deduction/substitution failed:
test.cpp:9:10: note:   candidate expects 2 arguments, 1 provided
     A a(p);
          ^
test.cpp:4:32: note: candidate: template<class _U1, class _U2, typename
std::enable_if<(_MoveConstructiblePair<_U1, _U2>() &&
_ImplicitlyMoveConvertiblePair<_U1, _U2>()), bool>::type <anonymous> >
constexpr A::A(_U1&&, _U2&&)
     using std::pair<int, int>::pair;
                                ^~~~
test.cpp:4:32: note:   template argument deduction/substitution failed:
test.cpp:9:10: note:   candidate expects 2 arguments, 1 provided
     A a(p);
          ^
test.cpp:4:32: note: candidate: template<class _U1, class _U2, typename
std::enable_if<(_MoveConstructiblePair<_U1, _U2>() && (!
_ImplicitlyMoveConvertiblePair<_U1, _U2>())), bool>::type <anonymous> >
constexpr A::A(_U1&&, _U2&&)
     using std::pair<int, int>::pair;
                                ^~~~
test.cpp:4:32: note:   template argument deduction/substitution failed:
test.cpp:9:10: note:   candidate expects 2 arguments, 1 provided
     A a(p);
          ^
test.cpp:4:32: note: candidate: template<class _U1, class _U2, typename
std::enable_if<(std::_PCC<((! std::is_same<int, _U1>::value) || (!
std::is_same<int, _U2>::value)), int, int>::_MoveConstructiblePair<_U1, _U2>()
&& std::_PCC<((! std::is_same<int, _U1>::value) || (! std::is_same<int,
_U2>::value)), int, int>::_ImplicitlyMoveConvertiblePair<_U1, _U2>()),
bool>::type <anonymous> > constexpr A::A(std::pair<_T1, _T2>&&)
     using std::pair<int, int>::pair;
                                ^~~~
test.cpp:4:32: note:   template argument deduction/substitution failed:
In file included from
/home/tuweiwei/tools/gcc-6.4.0/include/c++/6.4.0/utility:70:0,
                 from test.cpp:1:
/home/tuweiwei/tools/gcc-6.4.0/include/c++/6.4.0/bits/stl_pair.h:344:38: error:
no type named ‘type’ in ‘struct std::enable_if<false, bool>’
                          bool>::type=true>
                                      ^~~~
/home/tuweiwei/tools/gcc-6.4.0/include/c++/6.4.0/bits/stl_pair.h:344:38: note:
invalid template non-type parameter
test.cpp:4:32: note: candidate: template<class _U1, class _U2, typename
std::enable_if<(std::_PCC<((! std::is_same<int, _U1>::value) || (!
std::is_same<int, _U2>::value)), int, int>::_MoveConstructiblePair<_U1, _U2>()
&& (! std::_PCC<((! std::is_same<int, _U1>::value) || (! std::is_same<int,
_U2>::value)), int, int>::_ImplicitlyMoveConvertiblePair<_U1, _U2>())),
bool>::type <anonymous> > constexpr A::A(std::pair<_T1, _T2>&&)
     using std::pair<int, int>::pair;
                                ^~~~
test.cpp:4:32: note:   template argument deduction/substitution failed:
In file included from
/home/tuweiwei/tools/gcc-6.4.0/include/c++/6.4.0/utility:70:0,
                 from test.cpp:1:
/home/tuweiwei/tools/gcc-6.4.0/include/c++/6.4.0/bits/stl_pair.h:354:38: error:
no type named ‘type’ in ‘struct std::enable_if<false, bool>’
                          bool>::type=false>
                                      ^~~~~
/home/tuweiwei/tools/gcc-6.4.0/include/c++/6.4.0/bits/stl_pair.h:354:38: note:
invalid template non-type parameter
test.cpp:4:32: note: candidate: template<class ... _Args1, class ... _Args2>
A::A(std::piecewise_construct_t, std::tuple<_Args1 ...>, std::tuple<_Args2
...>)
     using std::pair<int, int>::pair;
                                ^~~~
test.cpp:4:32: note:   template argument deduction/substitution failed:
test.cpp:9:10: note:   candidate expects 3 arguments, 1 provided
     A a(p);
          ^
test.cpp:4:32: note: candidate: template<class ... _Args1, long unsigned int
..._Indexes1, class ... _Args2, long unsigned int ..._Indexes2>
A::A(std::tuple<_Args1 ...>&, std::tuple<_Args2 ...>&, std::_Index_tuple<_Ind2
...>, std::_Index_tuple<_Indexes2 ...>)
     using std::pair<int, int>::pair;
                                ^~~~
test.cpp:4:32: note:   template argument deduction/substitution failed:
test.cpp:9:10: note:   ‘std::pair<int, int>’ is not derived from
‘std::tuple<_Args1 ...>’
     A a(p);
          ^
test.cpp:3:8: note: candidate: constexpr A::A()
 struct A : public std::pair< int, int> {
        ^
test.cpp:3:8: note:   candidate expects 0 arguments, 1 provided
test.cpp:3:8: note: candidate: constexpr A::A(const A&)
test.cpp:3:8: note:   no known conversion for argument 1 from ‘std::pair<int,
int>’ to ‘const A&’
test.cpp:3:8: note: candidate: constexpr A::A(A&&)
test.cpp:3:8: note:   no known conversion for argument 1 from ‘std::pair<int,
int>’ to ‘A&&’