********** source program **********
var Int : x = 1
fn identity (0 = Int: x) -> () {
return x;

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

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