False positive in use-some-for-output-vars when var in ref head ref

[anderseknert]

rule[arr[i]] contains value if {
    arr := [1, 2, 3]

    some i
    value := input.foo[i]
}

This currently reports i in the ref head as not being declared using some, while clearly it was. This seems to have something to do with the var being used in a nested ref, as rule[i] works as expected. Interestingly, making that change will instead have Regal correctly report input.foo[i] as a use-some-in-iteration violation... and that's somehow masked by i being in a nested ref. So two bugs really, but possibly related, so we'll see if there's a need for a separate issue for that later.