compatible types for chains of different lengths

[Jon D via Digitalmars-d-learn]

I'd like to chain several ranges and operate on them. However, if 
the chains are different lengths, the data type is different. 
This makes it hard to use in a general way. There is likely an 
alternate way to do this that I'm missing.

A short example:

$ cat chain.d
import std.stdio;
import std.range;
import std.algorithm;

void main(string[] args)
{
     auto x1 = ["abc", "def", "ghi"];
     auto x2 = ["jkl", "mno", "pqr"];
     auto x3 = ["stu", "vwx", "yz"];
     auto chain1 = (args.length > 1) ? chain(x1, x2) : chain(x1);
     auto chain2 = (args.length > 1) ? chain(x1, x2, x3) : 
chain(x1, x2);
     chain1.joiner(", ").writeln;
     chain2.joiner(", ").writeln;
}
$ dmd chain.d
chain.d(10): Error: incompatible types for ((chain(x1, x2)) : 
(chain(x1))): 'Result' and 'string[]'
chain.d(11): Error: incompatible types for ((chain(x1, x2, x3)) : 
(chain(x1, x2))): 'Result' and 'Result'

Is there a different way to do this?

--Jon