{"ast_node_type":"other","tokens":[{"end":67,"kind":"keyword","start":0,"text":"assert!(opt_slice_ty.is_some()"}]}
                assert!(opt_slice_ty.is_some() || slice.is_none());
                // Note, though, that opt_slice_ty could be `Some(error_ty)`.
                (element_ty, opt_slice_ty, expected)