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b99fe2b720
- linked-list cursor-like patterns - issue-46589 These are known-bugs for the polonius alpha, where they show the same imprecision as NLLs, but are supported by the old datalog implementation.
45 lines
1.1 KiB
Rust
45 lines
1.1 KiB
Rust
#![crate_type = "lib"]
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// An example from #63908 of the linked-list cursor-like pattern of #46859/#48001, where the
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// polonius alpha analysis shows the same imprecision as NLLs, unlike the datalog implementation.
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//@ ignore-compare-mode-polonius (explicit revisions)
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//@ revisions: nll polonius legacy
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//@ [nll] known-bug: #63908
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//@ [polonius] known-bug: #63908
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//@ [polonius] compile-flags: -Z polonius=next
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//@ [legacy] check-pass
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//@ [legacy] compile-flags: -Z polonius=legacy
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struct Node<T> {
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value: T,
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next: Option<Box<Self>>,
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}
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type List<T> = Option<Box<Node<T>>>;
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fn remove_last_node_recursive<T>(node_ref: &mut List<T>) {
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let next_ref = &mut node_ref.as_mut().unwrap().next;
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if next_ref.is_some() {
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remove_last_node_recursive(next_ref);
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} else {
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*node_ref = None;
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}
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}
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// NLLs and polonius alpha fail here
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fn remove_last_node_iterative<T>(mut node_ref: &mut List<T>) {
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loop {
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let next_ref = &mut node_ref.as_mut().unwrap().next;
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if next_ref.is_some() {
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node_ref = next_ref;
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} else {
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break;
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}
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}
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*node_ref = None;
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}
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