[Bug c++/77797] Unable to use constexpr function as constexpr template parameter

[slavanap at yandex dot ru]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77797

--- Comment #4 from Vyacheslav <slavanap at yandex dot ru> ---
Okay. Got it.

Adding original error message below, so Google can lead to this bug report if
that happen to someone else.

prog.cc:74:125:   in constexpr expansion of 'Tools::generate_array<long
unsigned int, 19ul, long unsigned int (&)(long unsigned int),
std::integer_sequence<long unsigned int, 0ul, 1ul, 2ul, 3ul, 4ul, 5ul, 6ul,
7ul, 8ul, 9ul, 10ul, 11ul, 12ul, 13ul, 14ul, 15ul, 16ul, 17ul, 18ul> >((*
GeneratorUInt64Power10))'
prog.cc:58:48:   in constexpr expansion of 'Tools::generate_array_impl<long
unsigned int, 19ul, long unsigned int (&)(long unsigned int), {0ul, 1ul, 2ul,
3ul, 4ul, 5ul, 6ul, 7ul, 8ul, 9ul, 10ul, 11ul, 12ul, 13ul, 14ul, 15ul, 16ul,
17ul, 18ul}>((* & f), (std::integer_sequence<long unsigned int, 0ul, 1ul, 2ul,
3ul, 4ul, 5ul, 6ul, 7ul, 8ul, 9ul, 10ul, 11ul, 12ul, 13ul, 14ul, 15ul, 16ul,
17ul, 18ul>(), std::integer_sequence<long unsigned int, 0ul, 1ul, 2ul, 3ul,
4ul, 5ul, 6ul, 7ul, 8ul, 9ul, 10ul, 11ul, 12ul, 13ul, 14ul, 15ul, 16ul, 17ul,
18ul>()))'
prog.cc:53:17: error: expression 'GeneratorUInt64Power10' does not designate a
constexpr function
   return { { f(I) ... } };
                 ^