{"ast_node_type":"other","tokens":[{"end":84,"kind":"keyword","start":0,"text":"//"}]}
            // argument list and thus needs `::` between it and `FnOnce`. However in
            // Pedantically, `(T) -> U` in `FnOnce(T) -> U` is treated as a generic
            // today's Rust this type of path *semantically* cannot appear as a