src/tools/clippy/tests/ui/len_zero.rs

   1 #![warn(len_without_is_empty, len_zero)]
   2 #![allow(dead_code, unused)]
   3
   4 pub struct PubOne;
   5
   6 impl PubOne {
   7     pub fn len(self: &Self) -> isize {
   8         1
   9     }
  10 }
  11
  12 impl PubOne {
  13     // A second impl for this struct - the error span shouldn't mention this
  14     pub fn irrelevant(self: &Self) -> bool {
  15         false
  16     }
  17 }
  18
  19 // Identical to PubOne, but with an allow attribute on the impl complaining len
  20 pub struct PubAllowed;
  21
  22 #[allow(len_without_is_empty)]
  23 impl PubAllowed {
  24     pub fn len(self: &Self) -> isize {
  25         1
  26     }
  27 }
  28
  29 // No allow attribute on this impl block, but that doesn't matter - we only require one on the
  30 // impl containing len.
  31 impl PubAllowed {
  32     pub fn irrelevant(self: &Self) -> bool {
  33         false
  34     }
  35 }
  36
  37 struct NotPubOne;
  38
  39 impl NotPubOne {
  40     pub fn len(self: &Self) -> isize {
  41         // no error, len is pub but `NotPubOne` is not exported anyway
  42         1
  43     }
  44 }
  45
  46 struct One;
  47
  48 impl One {
  49     fn len(self: &Self) -> isize {
  50         // no error, len is private, see #1085
  51         1
  52     }
  53 }
  54
  55 pub trait PubTraitsToo {
  56     fn len(self: &Self) -> isize;
  57 }
  58
  59 impl PubTraitsToo for One {
  60     fn len(self: &Self) -> isize {
  61         0
  62     }
  63 }
  64
  65 trait TraitsToo {
  66     fn len(self: &Self) -> isize; // no error, len is private, see #1085
  67 }
  68
  69 impl TraitsToo for One {
  70     fn len(self: &Self) -> isize {
  71         0
  72     }
  73 }
  74
  75 struct HasPrivateIsEmpty;
  76
  77 impl HasPrivateIsEmpty {
  78     pub fn len(self: &Self) -> isize {
  79         1
  80     }
  81
  82     fn is_empty(self: &Self) -> bool {
  83         false
  84     }
  85 }
  86
  87 pub struct HasIsEmpty;
  88
  89 impl HasIsEmpty {
  90     pub fn len(self: &Self) -> isize {
  91         1
  92     }
  93
  94     fn is_empty(self: &Self) -> bool {
  95         false
  96     }
  97 }
  98
  99 struct Wither;
 100
 101 pub trait WithIsEmpty {
 102     fn len(self: &Self) -> isize;
 103     fn is_empty(self: &Self) -> bool;
 104 }
 105
 106 impl WithIsEmpty for Wither {
 107     fn len(self: &Self) -> isize {
 108         1
 109     }
 110
 111     fn is_empty(self: &Self) -> bool {
 112         false
 113     }
 114 }
 115
 116 pub struct HasWrongIsEmpty;
 117
 118 impl HasWrongIsEmpty {
 119     pub fn len(self: &Self) -> isize {
 120         1
 121     }
 122
 123     pub fn is_empty(self: &Self, x: u32) -> bool {
 124         false
 125     }
 126 }
 127
 128 pub trait Empty {
 129     fn is_empty(&self) -> bool;
 130 }
 131
 132 pub trait InheritingEmpty: Empty {
 133     //must not trigger LEN_WITHOUT_IS_EMPTY
 134     fn len(&self) -> isize;
 135 }
 136
 137 fn main() {
 138     let x = [1, 2];
 139     if x.len() == 0 {
 140         println!("This should not happen!");
 141     }
 142
 143     if "".len() == 0 {}
 144
 145     let y = One;
 146     if y.len() == 0 {
 147         //no error because One does not have .is_empty()
 148         println!("This should not happen either!");
 149     }
 150
 151     let z: &TraitsToo = &y;
 152     if z.len() > 0 {
 153         //no error, because TraitsToo has no .is_empty() method
 154         println!("Nor should this!");
 155     }
 156
 157     let has_is_empty = HasIsEmpty;
 158     if has_is_empty.len() == 0 {
 159         println!("Or this!");
 160     }
 161     if has_is_empty.len() != 0 {
 162         println!("Or this!");
 163     }
 164     if has_is_empty.len() > 0 {
 165         println!("Or this!");
 166     }
 167     if has_is_empty.len() < 1 {
 168         println!("Or this!");
 169     }
 170     if has_is_empty.len() >= 1 {
 171         println!("Or this!");
 172     }
 173     if has_is_empty.len() > 1 {
 174         // no error
 175         println!("This can happen.");
 176     }
 177     if has_is_empty.len() <= 1 {
 178         // no error
 179         println!("This can happen.");
 180     }
 181     if 0 == has_is_empty.len() {
 182         println!("Or this!");
 183     }
 184     if 0 != has_is_empty.len() {
 185         println!("Or this!");
 186     }
 187     if 0 < has_is_empty.len() {
 188         println!("Or this!");
 189     }
 190     if 1 <= has_is_empty.len() {
 191         println!("Or this!");
 192     }
 193     if 1 > has_is_empty.len() {
 194         println!("Or this!");
 195     }
 196     if 1 < has_is_empty.len() {
 197         // no error
 198         println!("This can happen.");
 199     }
 200     if 1 >= has_is_empty.len() {
 201         // no error
 202         println!("This can happen.");
 203     }
 204     assert!(!has_is_empty.is_empty());
 205
 206     let with_is_empty: &WithIsEmpty = &Wither;
 207     if with_is_empty.len() == 0 {
 208         println!("Or this!");
 209     }
 210     assert!(!with_is_empty.is_empty());
 211
 212     let has_wrong_is_empty = HasWrongIsEmpty;
 213     if has_wrong_is_empty.len() == 0 {
 214         //no error as HasWrongIsEmpty does not have .is_empty()
 215         println!("Or this!");
 216     }
 217 }
 218
 219 fn test_slice(b: &[u8]) {
 220     if b.len() != 0 {}
 221 }
 222
 223 // this used to ICE
 224 pub trait Foo: Sized {}
 225
 226 pub trait DependsOnFoo: Foo {
 227     fn len(&mut self) -> usize;
 228 }