original.name="UnionType_Invalid_9"
js.execute.ignore=true
======
>>> main.whiley
type pos is (int p) where p > 0
type poslist is pos[]
type plt is pos | poslist
type nat is (int n) where n >= 0
type natlist is nat[]
type nlt is nat | natlist

function g(int y) -> nlt
requires y >= 0:
    return (nat) y

function f(int x) -> plt
requires x >= 0:
    return (plt) g(x)

public export method test():
   assume f(1) == 1
   assume f(0) == 0
---
E702 main.whiley 14,11:20
E717 main.whiley 14,4:20