[Bug libstdc++/61795] [C++11] return type of std::pow(std::complex<float>, int) should be std::complex<double>

["kariya_mitsuru at hotmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61795

--- Comment #2 from Mitsuru Kariya <kariya_mitsuru at hotmail dot com> ---
I think that this behaviour is caused by r201253 (for PR57974, Comment 11).
DR844 was fixed by r136694 but reverted by r201253.

diff r135878 r136694
https://gcc.gnu.org/viewcvs/gcc/trunk/libstdc%2B%2B-v3/include/std/complex?r1=135878&r2=136694

diff r199924 r201253
https://gcc.gnu.org/viewcvs/gcc/trunk/libstdc%2B%2B-v3/include/std/complex?r1=199924&r2=201253


Moreover, I think that I mistook.

> Note that this problem does not occur in std::complex<double> and
> std::complex<long double> because there is no difference between
> C++03 and C++11.

This is not true.

In C++03, the 2nd argument of std::pow can cause implicit conversions.
(Because it is the trivial int type.)
However, I believe that it should cause no implicit conversion in C++11.
(I think so from C++11 standard text quoted above.)

Therefore, I think that the sample code below should be compiled successfully
in C++03 mode but should cause compilation error in C++11 mode.

===================================================================
#include <complex>

struct S {
  operator int() { return 1; }
};

int main()
{
  std::complex<double> d = std::pow(std::complex<double>(0), S());
}
===================================================================