use std::iter::repeat; #[allow(clippy::trivially_copy_pass_by_ref)] fn square_is_lower_64(x: &u32) -> bool { x * x < 64 } #[allow(clippy::maybe_infinite_iter)] #[deny(clippy::infinite_iter)] fn infinite_iters() { repeat(0_u8).collect::<Vec<_>>(); // infinite iter (0..8_u32).take_while(square_is_lower_64).cycle().count(); // infinite iter (0..8_u64).chain(0..).max(); // infinite iter (0_usize..) .chain([0usize, 1, 2].iter().cloned()) .skip_while(|x| *x != 42) .min(); // infinite iter (0..8_u32) .rev() .cycle() .map(|x| x + 1_u32) .for_each(|x| println!("{}", x)); // infinite iter (0..3_u32).flat_map(|x| x..).sum::<u32>(); // infinite iter (0_usize..).flat_map(|x| 0..x).product::<usize>(); // infinite iter (0_u64..).filter(|x| x % 2 == 0).last(); // infinite iter (0..42_u64).by_ref().last(); // not an infinite, because ranges are double-ended (0..).next(); // iterator is not exhausted } #[deny(clippy::maybe_infinite_iter)] fn potential_infinite_iters() { (0..).zip((0..).take_while(square_is_lower_64)).count(); // maybe infinite iter repeat(42).take_while(|x| *x == 42).chain(0..42).max(); // maybe infinite iter (1..) .scan(0, |state, x| { *state += x; Some(*state) }) .min(); // maybe infinite iter (0..).find(|x| *x == 24); // maybe infinite iter (0..).position(|x| x == 24); // maybe infinite iter (0..).any(|x| x == 24); // maybe infinite iter (0..).all(|x| x == 24); // maybe infinite iter (0..).zip(0..42).take_while(|&(x, _)| x != 42).count(); // not infinite repeat(42).take_while(|x| *x == 42).next(); // iterator is not exhausted } fn main() { infinite_iters(); potential_infinite_iters(); } mod finite_collect { use std::collections::HashSet; use std::iter::FromIterator; struct C; impl FromIterator<i32> for C { fn from_iter<I: IntoIterator<Item = i32>>(iter: I) -> Self { C } } fn check_collect() { let _: HashSet<i32> = (0..).collect(); // Infinite iter // Some data structures don't collect infinitely, such as `ArrayVec` let _: C = (0..).collect(); } }