template<class LHS, class RHS>
concept assignable_from =
is_lvalue_reference_v<LHS> &&
common_reference_with<const remove_reference_t<LHS>&, const remove_reference_t<RHS>&> &&
requires(LHS lhs, RHS&& rhs) {
{ lhs = std::forward<RHS>(rhs) } -> same_as<LHS>;
};