original.name="UnionType_Valid_3"
======
>>> main.whiley
type TYPE is null | int

function f(TYPE[] xs, TYPE p) -> int:
    int i = 0
    while i < |xs| where i >= 0:
        if xs[i] == p:
            return i
        i = i + 1
    return -1

public export method test() :
    assume f([null, 1, 2], null) == 0
    assume f([1, 2, null, 10], 10) == 3

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