variant TestVariant
{
    | Id { name : string; }
    | Pair { id1 : Id; id2 : Id; }

    public override ToString() : string
    {
        match (this)
        {
        | Id(name) => name
        | Pair(Id(name1), Id(name2)) => name1 + name2
        }
    }
}

1.n:13:3:13:8: [01;33mwarning [0m: matching is not exhaustive, example unmatched value: TestVariant.Pair (id1 = TestVariant.Id, id2 = Pair)