{"ast_node_type":"variable","tokens":[{"end":56,"kind":"keyword","start":0,"text":"let"}]}
                        let variant_index_relative_val =
                        let niche_start_val = ImmTy::from_uint(niche_start, tag_layout);
                            self.binary_op(mir::BinOp::Sub, &tag_val, &niche_start_val)?;