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

   1 // run-rustfix
   2 #![warn(clippy::iter_on_empty_collections)]
   3 #![allow(clippy::iter_next_slice, clippy::redundant_clone)]
   4
   5 fn array() {
   6     assert_eq!(std::iter::empty().next(), Option::<i32>::None);
   7     assert_eq!(std::iter::empty().next(), Option::<&mut i32>::None);
   8     assert_eq!(std::iter::empty().next(), Option::<&i32>::None);
   9     assert_eq!(std::iter::empty().next(), Option::<i32>::None);
  10     assert_eq!(std::iter::empty().next(), Option::<&mut i32>::None);
  11     assert_eq!(std::iter::empty().next(), Option::<&i32>::None);
  12
  13     // Don't trigger on non-iter methods
  14     let _: Option<String> = None.clone();
  15     let _: [String; 0] = [].clone();
  16
  17     // Don't trigger on match or if branches
  18     let _ = match 123 {
  19         123 => [].iter(),
  20         _ => ["test"].iter(),
  21     };
  22
  23     let _ = if false { ["test"].iter() } else { [].iter() };
  24 }
  25
  26 macro_rules! in_macros {
  27     () => {
  28         assert_eq!([].into_iter().next(), Option::<i32>::None);
  29         assert_eq!([].iter_mut().next(), Option::<&mut i32>::None);
  30         assert_eq!([].iter().next(), Option::<&i32>::None);
  31         assert_eq!(None.into_iter().next(), Option::<i32>::None);
  32         assert_eq!(None.iter_mut().next(), Option::<&mut i32>::None);
  33         assert_eq!(None.iter().next(), Option::<&i32>::None);
  34     };
  35 }
  36
  37 // Don't trigger on a `None` that isn't std's option
  38 mod custom_option {
  39     #[allow(unused)]
  40     enum CustomOption {
  41         Some(i32),
  42         None,
  43     }
  44
  45     impl CustomOption {
  46         fn iter(&self) {}
  47         fn iter_mut(&mut self) {}
  48         fn into_iter(self) {}
  49     }
  50     use CustomOption::*;
  51
  52     pub fn custom_option() {
  53         None.iter();
  54         None.iter_mut();
  55         None.into_iter();
  56     }
  57 }
  58
  59 fn main() {
  60     array();
  61     custom_option::custom_option();
  62     in_macros!();
  63 }