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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