is a Cpp17UnaryTypeTrait
with a base characteristic of true_type
is a POD type,
A POD class is a class that is both a trivial class and a standard-layout class,
and has no non-static data members of type non-POD class (or array thereof).
A POD type is a scalar type, a POD class, an array of such a type,
or a cv-qualified version of one of these types.