mp_units::operator+

template<
    ReferenceOf<PO._quantity_spec_> auto R1,
    typename Rep1,
    std::derived_from<quantity_point> QP>
[[nodiscard]]
constexpr
QuantityPoint auto
operator+(
    quantity<R1, Rep1> const& q,
    QP const& qp)
requires requires { q + qp.quantity_ref_from(PO); };