Function rustc_mir::transform::dest_prop::locals_used_as_array_index

pub(in transform::dest_prop) fn locals_used_as_array_index(
    body: &Body<'_>
) -> BitSet<Local>

PlaceElem::Index only stores a Local, so we can't replace that with a full Place.

Collect locals used as indices so we don't generate candidates that are impossible to apply later.