`$stringify($vaexpr[0])` evaluates to `$vaexpr[0]`

Is this intended or a limitation of `$vaexpr`?
```c
module test;
import std::io;

fn int main(String[] args) {
  io::printn(@foo1(args)); // Prints "args"
  io::printn(@foo2(args)); // Prints "$vaexpr[0]"
  return 0;
}

macro @foo1(#expr) {
  return $stringify(#expr);
}

macro @foo2(...) {
  return $stringify($vaexpr[0]);
}
```