$list = [1, 2, 3];

$opt_list = [1, null, 2, 3];

select
    ListIndexOf($list, 2),
    ListIndexOf($list, 100),
    ListIndexOf(Just($opt_list), 2),
    ListIndexOf(Just($opt_list), 200),
    ListIndexOf(Nothing(List<Int32>?), 2),
    ListIndexOf([], 'foo'),
    ListIndexOf(null, 1.0),
;