[phobos] Preferred style for multivalue returns

[Lars Tandle Kyllingstad]

What follows may be a trivial design question, but it's not the first
time I've run into it, and I'm trying to figure out what is the "Phobos
style" for various things.

I want to add a function to the new std.process that waits for the first
child process to terminate, and returns its exit status AND process id,
but I'm having trouble deciding on a signature for it.

What do you find to be the preferred style for functions with multiple
return values?

        // Both of these are simple, but the choice between them
        // is kind of arbitrary (i.e. why should x be the "real"
        //  return value?)
        
        Pid waitAny(out int status);
        int waitAny(out Pid pid);
        
        
        // Introducing a completely new type just for this?
        
        struct WaitResult { Pid pid; int status; }
        WaitResult waitAny();
        
        
        // I personally find the following pretty elegant, but
        // perhaps a bit verbose?  And I don't see Tuple being
        // used much elsewhere in Phobos. (Why?)
        
        Tuple!(Pid, "pid", int, "status") waitAny();
        
        ...others?


-Lars