{"ast_node_type":"other","tokens":[{"end":91,"kind":"keyword","start":0,"text":"//"}]}
        // First, we attempt to refine the `expr` for our span using the parent obligation.
    ) -> Result<&'tcx hir::Expr<'tcx>, &'tcx hir::Expr<'tcx>> {
        // If this cannot be done, then we are already stuck, so we stop early (hence the use