{"ast_node_type":"variable","tokens":[{"end":85,"kind":"keyword","start":0,"text":"let"}]}
        let MemberConstraint { start_index, end_index, .. } = &self.constraints[pci];
    pub(crate) fn choice_regions(&self, pci: NllMemberConstraintIndex) -> &[ty::RegionVid] {
        &self.choice_regions[*start_index..*end_index]