|
| 1 | +// run-pass |
| 2 | +// edition:2021 |
| 3 | +// check-run-results |
| 4 | +// |
| 5 | +// Drop order tests for let else |
| 6 | +// |
| 7 | +// Mostly this ensures two things: |
| 8 | +// 1. That let and let else temporary drop order is the same. |
| 9 | +// This is a specific design request: https://github.com/rust-lang/rust/pull/93628#issuecomment-1047140316 |
| 10 | +// 2. That the else block truly only runs after the |
| 11 | +// temporaries have dropped. |
| 12 | +// |
| 13 | +// We also print some nice tables for an overview by humans. |
| 14 | +// Changes in those tables are considered breakages, but the |
| 15 | +// important properties 1 and 2 are also enforced by the code. |
| 16 | +// This is important as it's easy to update the stdout file |
| 17 | +// with a --bless and miss the impact of that change. |
| 18 | + |
| 19 | +#![feature(let_else)] |
| 20 | +#![allow(irrefutable_let_patterns)] |
| 21 | + |
| 22 | +use std::cell::RefCell; |
| 23 | +use std::rc::Rc; |
| 24 | + |
| 25 | +#[derive(Clone)] |
| 26 | +struct DropAccountant(Rc<RefCell<Vec<Vec<String>>>>); |
| 27 | + |
| 28 | +impl DropAccountant { |
| 29 | + fn new() -> Self { |
| 30 | + Self(Default::default()) |
| 31 | + } |
| 32 | + fn build_droppy(&self, v: u32) -> Droppy<u32> { |
| 33 | + Droppy(self.clone(), v) |
| 34 | + } |
| 35 | + fn build_droppy_enum_none(&self, _v: u32) -> ((), DroppyEnum<u32>) { |
| 36 | + ((), DroppyEnum::None(self.clone())) |
| 37 | + } |
| 38 | + fn new_list(&self, s: impl ToString) { |
| 39 | + self.0.borrow_mut().push(vec![s.to_string()]); |
| 40 | + } |
| 41 | + fn push(&self, s: impl ToString) { |
| 42 | + let s = s.to_string(); |
| 43 | + let mut accounts = self.0.borrow_mut(); |
| 44 | + accounts.last_mut().unwrap().push(s); |
| 45 | + } |
| 46 | + fn print_table(&self) { |
| 47 | + println!(); |
| 48 | + |
| 49 | + let accounts = self.0.borrow(); |
| 50 | + let before_last = &accounts[accounts.len() - 2]; |
| 51 | + let last = &accounts[accounts.len() - 1]; |
| 52 | + let before_last = get_comma_list(before_last); |
| 53 | + let last = get_comma_list(last); |
| 54 | + const LINES: &[&str] = &[ |
| 55 | + "vanilla", |
| 56 | + "&", |
| 57 | + "&mut", |
| 58 | + "move", |
| 59 | + "fn(this)", |
| 60 | + "tuple", |
| 61 | + "array", |
| 62 | + "ref &", |
| 63 | + "ref mut &mut", |
| 64 | + ]; |
| 65 | + let max_len = LINES.iter().map(|v| v.len()).max().unwrap(); |
| 66 | + let max_len_before = before_last.iter().map(|v| v.len()).max().unwrap(); |
| 67 | + let max_len_last = last.iter().map(|v| v.len()).max().unwrap(); |
| 68 | + |
| 69 | + println!( |
| 70 | + "| {: <max_len$} | {: <max_len_before$} | {: <max_len_last$} |", |
| 71 | + "construct", before_last[0], last[0] |
| 72 | + ); |
| 73 | + println!("| {:-<max_len$} | {:-<max_len_before$} | {:-<max_len_last$} |", "", "", ""); |
| 74 | + |
| 75 | + for ((l, l_before), l_last) in |
| 76 | + LINES.iter().zip(before_last[1..].iter()).zip(last[1..].iter()) |
| 77 | + { |
| 78 | + println!( |
| 79 | + "| {: <max_len$} | {: <max_len_before$} | {: <max_len_last$} |", |
| 80 | + l, l_before, l_last, |
| 81 | + ); |
| 82 | + } |
| 83 | + } |
| 84 | + #[track_caller] |
| 85 | + fn assert_all_equal_to(&self, st: &str) { |
| 86 | + let accounts = self.0.borrow(); |
| 87 | + let last = &accounts[accounts.len() - 1]; |
| 88 | + let last = get_comma_list(last); |
| 89 | + for line in last[1..].iter() { |
| 90 | + assert_eq!(line.trim(), st.trim()); |
| 91 | + } |
| 92 | + } |
| 93 | + #[track_caller] |
| 94 | + fn assert_equality_last_two_lists(&self) { |
| 95 | + let accounts = self.0.borrow(); |
| 96 | + let last = &accounts[accounts.len() - 1]; |
| 97 | + let before_last = &accounts[accounts.len() - 2]; |
| 98 | + for (l, b) in last[1..].iter().zip(before_last[1..].iter()) { |
| 99 | + if !(l == b || l == "n/a" || b == "n/a") { |
| 100 | + panic!("not equal: '{last:?}' != '{before_last:?}'"); |
| 101 | + } |
| 102 | + } |
| 103 | + } |
| 104 | +} |
| 105 | + |
| 106 | +fn get_comma_list(sl: &[String]) -> Vec<String> { |
| 107 | + std::iter::once(sl[0].clone()) |
| 108 | + .chain(sl[1..].chunks(2).map(|c| c.join(","))) |
| 109 | + .collect::<Vec<String>>() |
| 110 | +} |
| 111 | + |
| 112 | +struct Droppy<T>(DropAccountant, T); |
| 113 | + |
| 114 | +impl<T> Drop for Droppy<T> { |
| 115 | + fn drop(&mut self) { |
| 116 | + self.0.push("drop"); |
| 117 | + } |
| 118 | +} |
| 119 | + |
| 120 | +#[allow(dead_code)] |
| 121 | +enum DroppyEnum<T> { |
| 122 | + Some(DropAccountant, T), |
| 123 | + None(DropAccountant), |
| 124 | +} |
| 125 | + |
| 126 | +impl<T> Drop for DroppyEnum<T> { |
| 127 | + fn drop(&mut self) { |
| 128 | + match self { |
| 129 | + DroppyEnum::Some(acc, _inner) => acc, |
| 130 | + DroppyEnum::None(acc) => acc, |
| 131 | + } |
| 132 | + .push("drop"); |
| 133 | + } |
| 134 | +} |
| 135 | + |
| 136 | +macro_rules! nestings_with { |
| 137 | + ($construct:ident, $binding:pat, $exp:expr) => { |
| 138 | + // vanilla: |
| 139 | + $construct!($binding, $exp.1); |
| 140 | + |
| 141 | + // &: |
| 142 | + $construct!(&$binding, &$exp.1); |
| 143 | + |
| 144 | + // &mut: |
| 145 | + $construct!(&mut $binding, &mut ($exp.1)); |
| 146 | + |
| 147 | + { |
| 148 | + // move: |
| 149 | + let w = $exp; |
| 150 | + $construct!( |
| 151 | + $binding, |
| 152 | + { |
| 153 | + let w = w; |
| 154 | + w |
| 155 | + } |
| 156 | + .1 |
| 157 | + ); |
| 158 | + } |
| 159 | + |
| 160 | + // fn(this): |
| 161 | + $construct!($binding, std::convert::identity($exp).1); |
| 162 | + }; |
| 163 | +} |
| 164 | + |
| 165 | +macro_rules! nestings { |
| 166 | + ($construct:ident, $binding:pat, $exp:expr) => { |
| 167 | + nestings_with!($construct, $binding, $exp); |
| 168 | + |
| 169 | + // tuple: |
| 170 | + $construct!(($binding, 77), ($exp.1, 77)); |
| 171 | + |
| 172 | + // array: |
| 173 | + $construct!([$binding], [$exp.1]); |
| 174 | + }; |
| 175 | +} |
| 176 | + |
| 177 | +macro_rules! let_else { |
| 178 | + ($acc:expr, $v:expr, $binding:pat, $build:ident) => { |
| 179 | + let acc = $acc; |
| 180 | + let v = $v; |
| 181 | + |
| 182 | + macro_rules! let_else_construct { |
| 183 | + ($arg:pat, $exp:expr) => { |
| 184 | + loop { |
| 185 | + let $arg = $exp else { |
| 186 | + acc.push("else"); |
| 187 | + break; |
| 188 | + }; |
| 189 | + acc.push("body"); |
| 190 | + break; |
| 191 | + } |
| 192 | + }; |
| 193 | + } |
| 194 | + nestings!(let_else_construct, $binding, acc.$build(v)); |
| 195 | + // ref &: |
| 196 | + let_else_construct!($binding, &acc.$build(v).1); |
| 197 | + |
| 198 | + // ref mut &mut: |
| 199 | + let_else_construct!($binding, &mut acc.$build(v).1); |
| 200 | + }; |
| 201 | +} |
| 202 | + |
| 203 | +macro_rules! let_ { |
| 204 | + ($acc:expr, $binding:tt) => { |
| 205 | + let acc = $acc; |
| 206 | + |
| 207 | + macro_rules! let_construct { |
| 208 | + ($arg:pat, $exp:expr) => {{ |
| 209 | + let $arg = $exp; |
| 210 | + acc.push("body"); |
| 211 | + }}; |
| 212 | + } |
| 213 | + let v = 0; |
| 214 | + { |
| 215 | + nestings_with!(let_construct, $binding, acc.build_droppy(v)); |
| 216 | + } |
| 217 | + acc.push("n/a"); |
| 218 | + acc.push("n/a"); |
| 219 | + acc.push("n/a"); |
| 220 | + acc.push("n/a"); |
| 221 | + |
| 222 | + // ref &: |
| 223 | + let_construct!($binding, &acc.build_droppy(v).1); |
| 224 | + |
| 225 | + // ref mut &mut: |
| 226 | + let_construct!($binding, &mut acc.build_droppy(v).1); |
| 227 | + }; |
| 228 | +} |
| 229 | + |
| 230 | +fn main() { |
| 231 | + let acc = DropAccountant::new(); |
| 232 | + |
| 233 | + println!(" --- matching cases ---"); |
| 234 | + |
| 235 | + // Ensure that let and let else have the same behaviour |
| 236 | + acc.new_list("let _"); |
| 237 | + let_!(&acc, _); |
| 238 | + acc.new_list("let else _"); |
| 239 | + let_else!(&acc, 0, _, build_droppy); |
| 240 | + acc.assert_equality_last_two_lists(); |
| 241 | + acc.print_table(); |
| 242 | + |
| 243 | + // Ensure that let and let else have the same behaviour |
| 244 | + acc.new_list("let _v"); |
| 245 | + let_!(&acc, _v); |
| 246 | + acc.new_list("let else _v"); |
| 247 | + let_else!(&acc, 0, _v, build_droppy); |
| 248 | + acc.assert_equality_last_two_lists(); |
| 249 | + acc.print_table(); |
| 250 | + |
| 251 | + println!(); |
| 252 | + |
| 253 | + println!(" --- mismatching cases ---"); |
| 254 | + |
| 255 | + acc.new_list("let else _ mismatch"); |
| 256 | + let_else!(&acc, 1, DroppyEnum::Some(_, _), build_droppy_enum_none); |
| 257 | + acc.new_list("let else _v mismatch"); |
| 258 | + let_else!(&acc, 1, DroppyEnum::Some(_, _v), build_droppy_enum_none); |
| 259 | + acc.print_table(); |
| 260 | + // This ensures that we always drop before visiting the else case |
| 261 | + acc.assert_all_equal_to("drop,else"); |
| 262 | + |
| 263 | + acc.new_list("let else 0 mismatch"); |
| 264 | + let_else!(&acc, 1, 0, build_droppy); |
| 265 | + acc.new_list("let else 0 mismatch"); |
| 266 | + let_else!(&acc, 1, 0, build_droppy); |
| 267 | + acc.print_table(); |
| 268 | + // This ensures that we always drop before visiting the else case |
| 269 | + acc.assert_all_equal_to("drop,else"); |
| 270 | +} |
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