testcase.cc:7:12: error: no viable conversion from 'tuple<typename __decay_and_strip<int>::__type, typename __decay_and_strip<int>::__type, typename __decay_and_strip<int>::__type>' to 'tuple<int16_t, int16_t, int16_t>'
    return std::make_tuple(0, 0, 0);
           ^~~~~~~~~~~~~~~~~~~~~~~~
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/6.1.1/../../../../include/c++/6.1.1/tuple:633:17: note: candidate constructor not viable: no known conversion from 'tuple<typename __decay_and_strip<int>::__type, typename __decay_and_strip<int>::__type, typename __decay_and_strip<int>::__type>' to 'const std::tuple<short, short, short> &' for 1st argument
      constexpr tuple(const tuple&) = default;
                ^
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/6.1.1/../../../../include/c++/6.1.1/tuple:635:17: note: candidate constructor not viable: no known conversion from 'tuple<typename __decay_and_strip<int>::__type, typename __decay_and_strip<int>::__type, typename __decay_and_strip<int>::__type>' to 'std::tuple<short, short, short> &&' for 1st argument
      constexpr tuple(tuple&&) = default; 
                ^
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/6.1.1/../../../../include/c++/6.1.1/tuple:614:19: note: candidate template ignored: disabled by 'enable_if' [with _UElements = <std::tuple<int, int, int>>]
        enable_if<_TMC<_UElements...>::template
                  ^
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/6.1.1/../../../../include/c++/6.1.1/tuple:644:19: note: candidate template ignored: disabled by 'enable_if' [with _UElements = <int, int, int>, _Dummy = void]
        enable_if<_TMC<_UElements...>::template
                  ^
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/6.1.1/../../../../include/c++/6.1.1/tuple:668:19: note: candidate template ignored: disabled by 'enable_if' [with _UElements = <int, int, int>, _Dummy = void]
        enable_if<_TMC<_UElements...>::template
                  ^
1 error generated.