HelenOS sources

is_transparent    131 uspace/lib/cpp/include/__bits/functional/arithmetic_operations.hpp         struct is_transparent<T, void_t<typename T::is_transparent>>
is_transparent    136 uspace/lib/cpp/include/__bits/functional/arithmetic_operations.hpp         inline constexpr bool is_transparent_v = is_transparent<T>::value;
HelenOS homepage, sources at GitHub