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

}
fn main () -> Int {
return f(0 = 1);

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