{"ast_node_type":"other","tokens":[{"end":33,"kind":"keyword","start":0,"text":"ConstraintKind::RegSubReg"}]}
        ConstraintKind::RegSubReg
    let mut check = |c: &Constraint<'tcx>, cause: &SubregionOrigin<'tcx>, exact| match c.kind {
            if ((exact && c.sup == placeholder_region)