123 lines
3.0 KiB
Rust
123 lines
3.0 KiB
Rust
//@ run-pass
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//@ edition:2024
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//@ compile-flags: -Z validate-mir -Zunstable-options
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#![feature(let_chains)]
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#![feature(if_let_rescope)]
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use std::cell::RefCell;
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use std::convert::TryInto;
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#[derive(Default)]
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struct DropOrderCollector(RefCell<Vec<u32>>);
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struct LoudDrop<'a>(&'a DropOrderCollector, u32);
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impl Drop for LoudDrop<'_> {
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fn drop(&mut self) {
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println!("{}", self.1);
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self.0.0.borrow_mut().push(self.1);
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}
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}
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impl DropOrderCollector {
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fn option_loud_drop(&self, n: u32) -> Option<LoudDrop> {
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Some(LoudDrop(self, n))
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}
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fn print(&self, n: u32) {
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println!("{}", n);
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self.0.borrow_mut().push(n)
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}
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fn assert_sorted(self) {
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assert!(
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self.0
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.into_inner()
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.into_iter()
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.enumerate()
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.all(|(idx, item)| idx + 1 == item.try_into().unwrap())
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);
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}
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fn if_let(&self) {
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if let None = self.option_loud_drop(1) {
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unreachable!();
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} else {
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self.print(2);
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}
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if let Some(_) = self.option_loud_drop(4) {
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self.print(3);
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}
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if let Some(_d) = self.option_loud_drop(6) {
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self.print(5);
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}
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}
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fn let_chain(&self) {
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// take the "then" branch
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if self.option_loud_drop(1).is_some() // 1
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&& self.option_loud_drop(2).is_some() // 2
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&& let Some(_d) = self.option_loud_drop(4)
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// 4
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{
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self.print(3); // 3
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}
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// take the "else" branch
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if self.option_loud_drop(5).is_some() // 1
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&& self.option_loud_drop(6).is_some() // 2
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&& let None = self.option_loud_drop(7)
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// 3
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{
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unreachable!();
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} else {
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self.print(8); // 4
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}
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// let exprs interspersed
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if self.option_loud_drop(9).is_some() // 1
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&& let Some(_d) = self.option_loud_drop(13) // 5
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&& self.option_loud_drop(10).is_some() // 2
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&& let Some(_e) = self.option_loud_drop(12)
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// 4
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{
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self.print(11); // 3
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}
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// let exprs first
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if let Some(_d) = self.option_loud_drop(18) // 5
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&& let Some(_e) = self.option_loud_drop(17) // 4
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&& self.option_loud_drop(14).is_some() // 1
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&& self.option_loud_drop(15).is_some()
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// 2
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{
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self.print(16); // 3
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}
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// let exprs last
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if self.option_loud_drop(19).is_some() // 1
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&& self.option_loud_drop(20).is_some() // 2
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&& let Some(_d) = self.option_loud_drop(23) // 5
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&& let Some(_e) = self.option_loud_drop(22)
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// 4
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{
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self.print(21); // 3
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}
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}
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}
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fn main() {
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println!("-- if let --");
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let collector = DropOrderCollector::default();
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collector.if_let();
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collector.assert_sorted();
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println!("-- let chain --");
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let collector = DropOrderCollector::default();
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collector.let_chain();
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collector.assert_sorted();
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}
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