Unionize range types

[Freddy via Digitalmars-d-learn]

Is there any way I can Unionize range Types?
---
auto primeFactors(T)(T t, T div = 2)
{
    if (t % div == 0)
    {
        return t.only.chain(primeFactors(t / div, div));
    }
    if (div > t)
    {
        return [];
    }
    else
    {
        return primeFactors(t, div + 1);
    }
}

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