// error-pattern:unsatisfied precondition constraint (for example, even(y fn print_even(y: int) : even(y) { log(debug, y); } pure fn even(y: int) -> bool { true } fn main() { let mut y: int = 42; let mut x: int = 1; check (even(y)); loop { print_even(y); while true { while true { while true { y += x; } } } } }