Doolang currently does not allow you to mutate a primitive variable from another function.
Only support this as of now
fn Foo(x: Int) {
x = 123; // Only modifies Foo's local copy
print("inside Foo", x); // Print 123
}
fn main() {
let x: Int = 0;
Foo(x);
// x is still 0 here after Foo returns
print("out x", x); // Print 0
}