Idiomatic way to process const/immutable arrays as ranges

[Dicebot]

This question is so stupid I am just struck with trying to chose 
the "good" solution.

Consider this code:
string func(in string[] args)
{
    return args.join(" "); // compile error, args is not an input 
range
}

It is somewhat expected as you can hardly popFront on a const 
range. But then question is: how can I wrap const slice into a 
mutable range without copying data (using standard 
language/library solution)? Of course, I can do .dup.join, but 
there is no real need to do copy, even a shallow one.