Clippy lint · Pedantic · checked with Clippy 0.1.99

clippy::iter_not_returning_iterator: this method is named `iter` but its return type does not implement `Iterator`

What it meansDetects methods named iter or iter_mut that do not have a return type that implements Iterator. It is in the pedantic group and off by default.

What you see

warning: this method is named `iter` but its return type does not implement `Iterator`
 --> main.rs:6:5
  |
6 |     fn iter(&self) -> String {
  |     ^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#iter_not_returning_iterator
  = note: `-W clippy::iter-not-returning-iterator` implied by `-W clippy::pedantic`

Real output of Clippy 0.1.99 (Rust 1.99) on the example below. Names and line numbers in yours will differ.

Does it matter?

Methods named iter or iter_mut conventionally return an Iterator.

Stricter lints with some false positives. Off by default; opt in with clippy::pedantic.

How to fix it

Clippy does not fix this one automatically. Change the code by hand:

Flagged

// `String` does not implement `Iterator`
struct Data {}
impl Data {
    fn iter(&self) -> String {
        todo!()
    }
}

Write this instead

use std::str::Chars;
struct Data {}
impl Data {
    fn iter(&self) -> Chars<'static> {
        todo!()
    }
}

Turn it off, or on

It is off by default. To use it, set it to warn or deny:

Whole crate (Cargo.toml)

[lints.clippy]
iter_not_returning_iterator = "warn"

In code

#![warn(clippy::iter_not_returning_iterator)]

One run

cargo clippy -- -W clippy::iter-not-returning-iterator

The [lints] table needs Rust 1.74 or newer. In a workspace, put it under [workspace.lints.clippy] and add [lints] workspace = true to each member.

Pedanticgroup

allowdefault level

nofixed by cargo clippy --fix

1.57.0added in Rust

Clippy's own documentation

What it does

Detects methods named iter or iter_mut that do not have a return type that implements Iterator.

Why is this bad?

Methods named iter or iter_mut conventionally return an Iterator.

Example

// `String` does not implement `Iterator`
struct Data {}
impl Data {
    fn iter(&self) -> String {
        todo!()
    }
}

Use instead:

use std::str::Chars;
struct Data {}
impl Data {
    fn iter(&self) -> Chars<'static> {
        todo!()
    }
}

From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.

Up next

Also worth your time

Did this answer your question?