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#![warn(clippy::iter_on_empty_collections)]
#![allow(clippy::iter_next_slice, clippy::redundant_clone)]
fn array() {
assert_eq!([].into_iter().next(), Option::<i32>::None);
//~^ iter_on_empty_collections
assert_eq!([].iter_mut().next(), Option::<&mut i32>::None);
//~^ iter_on_empty_collections
assert_eq!([].iter().next(), Option::<&i32>::None);
//~^ iter_on_empty_collections
assert_eq!(None.into_iter().next(), Option::<i32>::None);
//~^ iter_on_empty_collections
assert_eq!(None.iter_mut().next(), Option::<&mut i32>::None);
//~^ iter_on_empty_collections
assert_eq!(None.iter().next(), Option::<&i32>::None);
//~^ iter_on_empty_collections
// Don't trigger on non-iter methods
let _: Option<String> = None.clone();
let _: [String; 0] = [].clone();
// Don't trigger on match or if branches
let _ = match 123 {
123 => [].iter(),
_ => ["test"].iter(),
};
let _ = if false { ["test"].iter() } else { [].iter() };
let smth = Some(vec![1, 2, 3]);
// Don't trigger when the empty collection iter is relied upon for its concrete type
// But do trigger if it is just an iterator, despite being an argument to a method
for i in smth.as_ref().map_or([].iter(), |s| s.iter()).chain([].iter()) {
//~^ iter_on_empty_collections
println!("{i}");
}
// Same as above, but for empty collection iters with extra layers
for i in smth.as_ref().map_or({ [].iter() }, |s| s.iter()) {
println!("{y}", y = i + 1);
}
// Same as above, but for regular function calls
for i in Option::map_or(smth.as_ref(), [].iter(), |s| s.iter()) {
println!("{i}");
}
// Same as above, but when there are no predicates that mention the collection iter type.
let mut iter = [34, 228, 35].iter();
let _ = std::mem::replace(&mut iter, [].iter());
}
macro_rules! in_macros {
() => {
assert_eq!([].into_iter().next(), Option::<i32>::None);
assert_eq!([].iter_mut().next(), Option::<&mut i32>::None);
assert_eq!([].iter().next(), Option::<&i32>::None);
assert_eq!(None.into_iter().next(), Option::<i32>::None);
assert_eq!(None.iter_mut().next(), Option::<&mut i32>::None);
assert_eq!(None.iter().next(), Option::<&i32>::None);
};
}
// Don't trigger on a `None` that isn't std's option
mod custom_option {
#[allow(unused)]
enum CustomOption {
Some(i32),
None,
}
impl CustomOption {
fn iter(&self) {}
fn iter_mut(&mut self) {}
fn into_iter(self) {}
}
use CustomOption::*;
pub fn custom_option() {
None.iter();
None.iter_mut();
None.into_iter();
}
}
fn main() {
array();
custom_option::custom_option();
in_macros!();
}
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