mp_units::get_common_reference

template<
    Reference R1,
    Reference R2,
    Reference... Rest>
[[nodiscard]]
consteval
Reference auto
get_common_reference(
    auto u1,
    auto u2,
    auto... rest)
requires (!(Unit<R1> && Unit<R2> && (... && Unit<Rest>))) && requires {
    get_common_quantity_spec(get_quantity_spec(r1), get_quantity_spec(r2), get_quantity_spec(rest)...);
    get_common_unit(get_unit(r1), get_unit(r2), get_unit(rest)...);
  };