Defined in header
template <class T>
concept copyable =
copyable<T> specifies that
T is an movable object type that can also copied (that is, it supports copy construction and copy assignment).
It is intended that
copyable<T> also requires std::assignable_from<T&, const T> (assignment from const rvalue) and std::assignable_from<T&, T&> (assignment from non-const lvalue) to be satisfied.
 See also
| specifies that an object of a type can be moved and swapped |