Method can be confused for the standard trait method

Question

I have this warning, and I don't how to fix this warning.

warning: method `next` can be confused for the standard trait method `std::iter::Iterator::next`
  --> src/util/mod.rs:51:5
   |
51 | /     pub fn next(&mut self) -> Option<I::Item> {
52 | |         if self.iterator.peek().is_some() {
53 | |             self.prev = replace(&mut self.current, self.iterator.next());
54 | |             return self.current.clone();
...  |
59 | |         None
60 | |     }
   | |_____^
   |
   = help: consider implementing the trait `std::iter::Iterator` or choosing a less ambiguous method name
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#should_implement_trait
   = note: `#[warn(clippy::should_implement_trait)]` on by default

Here's the code I have right now - an iterator that's able to peek the previous item. next method is also in the snippet.

pub struct PrevPeekable<I>
where
    I: Iterator,
    <I as Iterator>::Item: Clone,
{
    /// Iterator that `PrevPeekable` wraps
    iterator: Peekable<I>,
    /// The item before the current item
    prev: Option<I::Item>,
    /// The current item
    current: Option<I::Item>,
    /// Keeps track of whether the iterator has reached the end or not
    finished: bool,
}

impl<I> PrevPeekable<I>
where
    I: Iterator,
    <I as Iterator>::Item: Clone,
{
        /// Returns the next item in the iterator
    pub fn next(&mut self) -> Option<I::Item> {
        if self.iterator.peek().is_some() {
            self.prev = replace(&mut self.current, self.iterator.next());
            return self.current.clone();
        } else if !self.finished {
            self.prev = replace(&mut self.current, self.iterator.next());
            self.finished = true;
        }
        None
    }
}

Thanks in advance.

Like the compiler says, either rename the `next` method to something else, or implement `Iterator` for your struct and move the code for the `next` method in this implementation. — Jmb, Jun 30 '23 at 12:47
That's not how you implement a trait, that [needs some code like `impl Iterator for Type { ... }`](https://doc.rust-lang.org/book/ch10-02-traits.html#implementing-a-trait-on-a-type) — cafce25, Jun 30 '23 at 13:02

score 4 · Accepted Answer · answered Jun 30 '23 at 13:06

You need to implement the Iterator trait and move your next code into this implementation:

use std::mem::replace;
use std::iter::Peekable;

pub struct PrevPeekable<I>
where
    I: Iterator,
    <I as Iterator>::Item: Clone,
{
    /// Iterator that `PrevPeekable` wraps
    iterator: Peekable<I>,
    /// The item before the current item
    prev: Option<I::Item>,
    /// The current item
    current: Option<I::Item>,
    /// Keeps track of whether the iterator has reached the end or not
    finished: bool,
}

impl<I> Iterator for PrevPeekable<I>
where
    I: Iterator,
    <I as Iterator>::Item: Clone,
{
    type Item = I::Item;

    /// Returns the next item in the iterator
    fn next(&mut self) -> Option<I::Item> {
        if self.iterator.peek().is_some() {
            self.prev = replace(&mut self.current, self.iterator.next());
            return self.current.clone();
        } else if !self.finished {
            self.prev = replace(&mut self.current, self.iterator.next());
            self.finished = true;
        }
        None
    }
}

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Method can be confused for the standard trait method

1 Answers1