********** source program **********
fn f Int: x -> Int {
if ((x == 0))
return x;
else
return f(0 = (x - 1));

}
fn main () -> Int {
return f(0 = 2);

}
********** type checking **********
--- step exp Int --->
--- step exp Int --->
--- step exp Int --->
--- step exp Int --->
--- step exp Int --->
9: type error in call
expected: Int
actual: Tuple(0 = Int)
EXIT CODE: 255