| error[E0282]: type annotations needed | |
| --> $DIR/sort_by_key.rs:3:9 | |
| | | |
| LL | lst.sort_by_key(|&(v, _)| v.iter().sum()); | |
| | ^^^^^^^^^^^ --- help: consider specifying the type argument in the method call: `sum::<S>` | |
| | | | |
| | cannot infer type for type parameter `K` | |
| error: aborting due to previous error | |
| For more information about this error, try `rustc --explain E0282`. |