void_t

template<class... T0toN>

using drama::void_t = typedef typename voider<T0toN...>::type

Define a void_t equivalent.

The c++ void_t type is only available from C++17, we want it from C++11. Here we define our own version in the drama namespace.

Based on https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n3911.pdf