src/tools/clippy/tests/ui/while_let_on_iterator.fixed

   1 // run-rustfix
   2
   3 #![warn(clippy::while_let_on_iterator)]
   4 #![allow(clippy::never_loop, unreachable_code, unused_mut, dead_code)]
   5
   6 fn base() {
   7     let mut iter = 1..20;
   8     for x in iter {
   9         println!("{}", x);
  10     }
  11
  12     let mut iter = 1..20;
  13     for x in iter {
  14         println!("{}", x);
  15     }
  16
  17     let mut iter = 1..20;
  18     for _ in iter {}
  19
  20     let mut iter = 1..20;
  21     while let None = iter.next() {} // this is fine (if nonsensical)
  22
  23     let mut iter = 1..20;
  24     if let Some(x) = iter.next() {
  25         // also fine
  26         println!("{}", x)
  27     }
  28
  29     // the following shouldn't warn because it can't be written with a for loop
  30     let mut iter = 1u32..20;
  31     while let Some(_) = iter.next() {
  32         println!("next: {:?}", iter.next())
  33     }
  34
  35     // neither can this
  36     let mut iter = 1u32..20;
  37     while let Some(_) = iter.next() {
  38         println!("next: {:?}", iter.next());
  39     }
  40
  41     // or this
  42     let mut iter = 1u32..20;
  43     while let Some(_) = iter.next() {
  44         iter = 1..20;
  45     }
  46 }
  47
  48 // Issue #1188
  49 fn refutable() {
  50     let a = [42, 1337];
  51     let mut b = a.iter();
  52
  53     // consume all the 42s
  54     while let Some(&42) = b.next() {}
  55
  56     let a = [(1, 2, 3)];
  57     let mut b = a.iter();
  58
  59     while let Some(&(1, 2, 3)) = b.next() {}
  60
  61     let a = [Some(42)];
  62     let mut b = a.iter();
  63
  64     while let Some(&None) = b.next() {}
  65
  66     /* This gives “refutable pattern in `for` loop binding: `&_` not covered”
  67     for &42 in b {}
  68     for &(1, 2, 3) in b {}
  69     for &Option::None in b.next() {}
  70     // */
  71 }
  72
  73 fn refutable2() {
  74     // Issue 3780
  75     {
  76         let v = vec![1, 2, 3];
  77         let mut it = v.windows(2);
  78         while let Some([x, y]) = it.next() {
  79             println!("x: {}", x);
  80             println!("y: {}", y);
  81         }
  82
  83         let mut it = v.windows(2);
  84         while let Some([x, ..]) = it.next() {
  85             println!("x: {}", x);
  86         }
  87
  88         let mut it = v.windows(2);
  89         while let Some([.., y]) = it.next() {
  90             println!("y: {}", y);
  91         }
  92
  93         let mut it = v.windows(2);
  94         for [..] in it {}
  95
  96         let v = vec![[1], [2], [3]];
  97         let mut it = v.iter();
  98         while let Some([1]) = it.next() {}
  99
 100         let mut it = v.iter();
 101         for [_x] in it {}
 102     }
 103
 104     // binding
 105     {
 106         let v = vec![1, 2, 3];
 107         let mut it = v.iter();
 108         while let Some(x @ 1) = it.next() {
 109             println!("{}", x);
 110         }
 111
 112         let v = vec![[1], [2], [3]];
 113         let mut it = v.iter();
 114         for x @ [_] in it {
 115             println!("{:?}", x);
 116         }
 117     }
 118
 119     // false negative
 120     {
 121         let v = vec![1, 2, 3];
 122         let mut it = v.iter().map(Some);
 123         while let Some(Some(_) | None) = it.next() {
 124             println!("1");
 125         }
 126     }
 127 }
 128
 129 fn nested_loops() {
 130     let a = [42, 1337];
 131
 132     loop {
 133         let mut y = a.iter();
 134         for _ in y {
 135             // use a for loop here
 136         }
 137     }
 138 }
 139
 140 fn issue1121() {
 141     use std::collections::HashSet;
 142     let mut values = HashSet::new();
 143     values.insert(1);
 144
 145     while let Some(&value) = values.iter().next() {
 146         values.remove(&value);
 147     }
 148 }
 149
 150 fn issue2965() {
 151     // This should not cause an ICE
 152
 153     use std::collections::HashSet;
 154     let mut values = HashSet::new();
 155     values.insert(1);
 156
 157     while let Some(..) = values.iter().next() {}
 158 }
 159
 160 fn issue3670() {
 161     let array = [Some(0), None, Some(1)];
 162     let mut iter = array.iter();
 163
 164     while let Some(elem) = iter.next() {
 165         let _ = elem.or_else(|| *iter.next()?);
 166     }
 167 }
 168
 169 fn issue1654() {
 170     // should not lint if the iterator is generated on every iteration
 171     use std::collections::HashSet;
 172     let mut values = HashSet::new();
 173     values.insert(1);
 174
 175     while let Some(..) = values.iter().next() {
 176         values.remove(&1);
 177     }
 178
 179     while let Some(..) = values.iter().map(|x| x + 1).next() {}
 180
 181     let chars = "Hello, World!".char_indices();
 182     while let Some((i, ch)) = chars.clone().next() {
 183         println!("{}: {}", i, ch);
 184     }
 185 }
 186
 187 fn issue6491() {
 188     // Used in outer loop, needs &mut
 189     let mut it = 1..40;
 190     while let Some(n) = it.next() {
 191         for m in &mut it {
 192             if m % 10 == 0 {
 193                 break;
 194             }
 195             println!("doing something with m: {}", m);
 196         }
 197         println!("n still is {}", n);
 198     }
 199
 200     // This is fine, inner loop uses a new iterator.
 201     let mut it = 1..40;
 202     for n in it {
 203         let mut it = 1..40;
 204         for m in it {
 205             if m % 10 == 0 {
 206                 break;
 207             }
 208             println!("doing something with m: {}", m);
 209         }
 210
 211         // Weird binding shouldn't change anything.
 212         let (mut it, _) = (1..40, 0);
 213         for m in it {
 214             if m % 10 == 0 {
 215                 break;
 216             }
 217             println!("doing something with m: {}", m);
 218         }
 219
 220         // Used after the loop, needs &mut.
 221         let mut it = 1..40;
 222         for m in &mut it {
 223             if m % 10 == 0 {
 224                 break;
 225             }
 226             println!("doing something with m: {}", m);
 227         }
 228         println!("next item {}", it.next().unwrap());
 229
 230         println!("n still is {}", n);
 231     }
 232 }
 233
 234 fn issue6231() {
 235     // Closure in the outer loop, needs &mut
 236     let mut it = 1..40;
 237     let mut opt = Some(0);
 238     while let Some(n) = opt.take().or_else(|| it.next()) {
 239         for m in &mut it {
 240             if n % 10 == 0 {
 241                 break;
 242             }
 243             println!("doing something with m: {}", m);
 244         }
 245         println!("n still is {}", n);
 246     }
 247 }
 248
 249 fn issue1924() {
 250     struct S<T>(T);
 251     impl<T: Iterator<Item = u32>> S<T> {
 252         fn f(&mut self) -> Option<u32> {
 253             // Used as a field.
 254             for i in &mut self.0 {
 255                 if !(3..=7).contains(&i) {
 256                     return Some(i);
 257                 }
 258             }
 259             None
 260         }
 261
 262         fn f2(&mut self) -> Option<u32> {
 263             // Don't lint, self borrowed inside the loop
 264             while let Some(i) = self.0.next() {
 265                 if i == 1 {
 266                     return self.f();
 267                 }
 268             }
 269             None
 270         }
 271     }
 272     impl<T: Iterator<Item = u32>> S<(S<T>, Option<u32>)> {
 273         fn f3(&mut self) -> Option<u32> {
 274             // Don't lint, self borrowed inside the loop
 275             while let Some(i) = self.0.0.0.next() {
 276                 if i == 1 {
 277                     return self.0.0.f();
 278                 }
 279             }
 280             while let Some(i) = self.0.0.0.next() {
 281                 if i == 1 {
 282                     return self.f3();
 283                 }
 284             }
 285             // This one is fine, a different field is borrowed
 286             for i in &mut self.0.0.0 {
 287                 if i == 1 {
 288                     return self.0.1.take();
 289                 } else {
 290                     self.0.1 = Some(i);
 291                 }
 292             }
 293             None
 294         }
 295     }
 296
 297     struct S2<T>(T, u32);
 298     impl<T: Iterator<Item = u32>> Iterator for S2<T> {
 299         type Item = u32;
 300         fn next(&mut self) -> Option<u32> {
 301             self.0.next()
 302         }
 303     }
 304
 305     // Don't lint, field of the iterator is accessed in the loop
 306     let mut it = S2(1..40, 0);
 307     while let Some(n) = it.next() {
 308         if n == it.1 {
 309             break;
 310         }
 311     }
 312
 313     // Needs &mut, field of the iterator is accessed after the loop
 314     let mut it = S2(1..40, 0);
 315     for n in &mut it {
 316         if n == 0 {
 317             break;
 318         }
 319     }
 320     println!("iterator field {}", it.1);
 321 }
 322
 323 fn main() {
 324     let mut it = 0..20;
 325     for _ in it {
 326         println!("test");
 327     }
 328 }