original.name="UnionType_Valid_12"
======
>>> main.whiley
type MsgMode is {int op, int mode}
type IntList is {int op, bool[] rest} | MsgMode

function f(IntList y) -> IntList:
    return y

function g({int op, int mode} z) -> IntList:
    return z

public export method test() :
    IntList x = {op: 1, rest: [false]}
    assume f(x) == {op: 1, rest: [false]}
    MsgMode y = {op: 123, mode: 0}
    assume g(y) == {op: 123, mode: 0}

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