original.name="ConstrainedInt_Valid_19"
======
>>> main.whiley


type a_nat is (int x) where x >= 0

type b_nat is (int x) where (2 * x) >= x

function f(a_nat x) -> b_nat:
    if x == 0:
        return 1
    else:
        return f(x - 1)

public export method test() :
    int x = 0
    x = f((a_nat) x)
    assume x == 1

---