mp_units::quantity_point::operator‐=

template<
    auto R2,
    typename Rep2>
requires (implicitly_convertible(get_quantity_spec(R2), quantity_spec)) &&
            detail::ValuePreservingConversion<get_unit(R2), Rep2, unit, rep> &&
            requires(const quantity_type q) { quantity_from_origin_is_an_implementation_detail_ ‐= q; }
constexpr
quantity_point&
operator‐=(quantity<R2, Rep2> const& q) &;