original.name="UnionType_Invalid_6"
======
>>> main.whiley
type IntList is {int | int[] op}

function f({int op} x) -> int:
    return x.op

public export method test():
    IntList x = {op: 1}
    x.op = 2
    x.op = [1, 2, 3]
    f(x)

---
E400 main.whiley 10,6