Function one_of 

const fn one_of(
    id: &'static str,
    when: &'static [Condition],
    setting: &'static str,
    values: &'static [Value],
    strength: Strength,
    basis: Basis,
    reason: &'static str,
    source: &'static str,
) -> Rule

A choice of strength on basis: setting should be one of values, the first being the default.