Why I'm getting this "Range Violation" error?

[rempas]

I have the following code:

```
import core.stdc.stdio;

void print(T)(string prompt, T args...) {
   size_t len = prompt.length;
   size_t i = 0;

   while (prompt[i] != '{' && i < len) {
     printf("%c", prompt[i]);
     i++;
   }
}

void main() {
   print("Hello, world!\n", 10);
}
```

When I execute it, I'm getting a range violation error. If I try 
to set "len" to be the length of the "prompt" minus 1, then it 
will work and it will print the "prompt" until the questionmark. 
So I cannot find where the error is...