SomeEnum = enum
{
    a,
    b,
    c,
    d,
}

foo = fn (arg: SomeEnum) SomeEnum
{
    return arg;
}

[export] main = fn [cc(c)] () s32
{
    >some_e: SomeEnum = .c;
    >a = foo(some_e);
    >b = foo(.d);
    if (a != .c) #trap();
    if (b != .d) #trap();
    return 0;
}