Uncalled functions hinder the compilation of fly programs

[lsig]

Fatal error: exception Failure("var lookup error: failed to find variable n\n")

Program:

fun fib(n: int) -> int {
if (n == 1) { return 1; }
else if (n == 0) { return 0; }
else { return fib(n); }
return 0;
}

fun main() -> int {
let s := 5;

print(s + 1);

return 0;

}