| #![crate_type = "lib"] |
| |
| // An example from #63908 of the linked-list cursor-like pattern of #46859/#48001, where the |
| // polonius alpha analysis shows the same imprecision as NLLs, unlike the datalog implementation. |
| |
| //@ ignore-compare-mode-polonius (explicit revisions) |
| //@ revisions: nll polonius legacy |
| //@ [nll] known-bug: #63908 |
| //@ [polonius] known-bug: #63908 |
| //@ [polonius] compile-flags: -Z polonius=next |
| //@ [legacy] check-pass |
| //@ [legacy] compile-flags: -Z polonius=legacy |
| |
| struct Node<T> { |
| value: T, |
| next: Option<Box<Self>>, |
| } |
| |
| type List<T> = Option<Box<Node<T>>>; |
| |
| fn remove_last_node_recursive<T>(node_ref: &mut List<T>) { |
| let next_ref = &mut node_ref.as_mut().unwrap().next; |
| |
| if next_ref.is_some() { |
| remove_last_node_recursive(next_ref); |
| } else { |
| *node_ref = None; |
| } |
| } |
| |
| // NLLs and polonius alpha fail here |
| fn remove_last_node_iterative<T>(mut node_ref: &mut List<T>) { |
| loop { |
| let next_ref = &mut node_ref.as_mut().unwrap().next; |
| |
| if next_ref.is_some() { |
| node_ref = next_ref; |
| } else { |
| break; |
| } |
| } |
| |
| *node_ref = None; |
| } |
