{"ast_node_type":"other","tokens":[{"end":96,"kind":"keyword","start":0,"text":"//"}]}
        //   "best effort" optimization and `{meta,pointee,}sized_constraint` may return `Some`,
        //   In this case, the builtin impl will have no nested subgoals. This is a
        //   even if the ADT is {meta,pointee,}sized for all possible args.